Flow-limiting pneumatic modulator for a multidimensional gas chromatography system

Abstract

A flow restriction pneumatic modulator (FRPM) assembly for a multidimensional gas chromatography system includes a first inlet that receives a stream from a first chromatography column, a first channel having a flow resistor component and a first outlet, and a second channel having a second outlet that fluidly communicates with a downstream bypass line. The FRPM assembly also includes a second Y-shaped fluid connector having a second inlet that fluidly communicates with the first outlet, a third inlet that fluidly communicates with an auxiliary flow, and a third channel having a third outlet that fluidly communicates with a second chromatography column. The FRPM assembly also includes at least one flow control valve and can operate as an injector and a modulator to the second chromatography column. A method for chromatographically analyzing a fluid sample containing one or more target analytes in a multidimensional chromatography system is also provided.

Description

Technical Field

[0001] This PCT international application claims the benefit of U.S. Provisional Application No. 63 / 354,520, filed Jun. 22, 2022. The entire disclosure of the above application is incorporated herein by reference.

[0002] (Government Support) This invention was made with government support under Grant No. OH011082 awarded by the U.S. Centers for Disease Control and Prevention, Grant No. TR003812 awarded by the National Institutes of Health, and Grant No. FA8650-19-C-9101 awarded by the Office of the Director of National Intelligence (Intelligence Advanced Research Projects Activity). The U.S. government has certain rights in this invention.

[0003] The present disclosure relates to a flow-limiting air modulator for a multidimensional gas chromatography system and a method of performing multidimensional chromatography analysis with such a flow-limiting air modulator.

Background Art

[0004] This section provides background information related to the present disclosure that is not necessarily prior art.

[0005] Micro-gas chromatography (μGC) is performed on a miniaturized scale compared to conventional gas chromatography. μGC is a powerful portable vapor analysis method for applications such as environmental protection and monitoring, workplace hazard analysis, and biomedicine. To date, almost all μGC devices have been one-dimensional (1D) GC with relatively short columns (<10 m), and 1DGC limits the separation performance for complex mixtures that may require the separation of hundreds of diverse compounds for many field applications (e.g., those related to petroleum, food, metabolomics, or forensics). Therefore, the addition of a second column in two-dimensional (2D) GC, such as heart-cutting 2DGC or comprehensive 2DGC, is necessary to further enhance the separation ability and expand the range of compounds that can be analyzed by a single portable μGC device.

[0006] A multi-dimensional gas chromatography system includes at least two different chromatography columns in series. One particular type of μGC is comprehensive two-dimensional (2-D) gas chromatography (「GC×GC」) which is well-suited for the analysis and separation of complex mixtures of volatile and / or semi-volatile compounds. Generally, comprehensive 2-DGC utilizes two columns of different selectivities connected in series by an injector device. Typically, in GC×GC separation, the sample is introduced into the first chromatography column by injection. The target analyte species elutes from this first column and can be trapped by a downstream injector device or sampled periodically. In a 2-DGC device, the injector placed between the first and second dimension columns is an important component. The injector cuts a portion of the eluent from the first dimension GC column and injects this into the second dimension column for further analysis. When the injector performs the above operation periodically, the injector is generally also referred to as the 「modulator」 used in comprehensive 2-DGC.

[0007] The injector device or modulator device is arranged between the first column ( 1 D:first column) and the second column ( 2 D:second column), and functions to continuously capture, concentrate the compounds eluted from the first column, and re-inject them into the second column (as a continuous injector for the second column). Therefore, after collecting the elution species from the first column, a typical modulator periodically injects the collected content into the second column at predetermined regular intervals (for example, usually at intervals of 2 to 5 seconds). A very small part of such injected content can be separated in the second column and eluted into the downstream detector, and a very small part can be identified and / or measured in the detector.

[0008] Generally, there are two types of modulators, namely (1) thermal modulators, and (2) pneumatic modulators. Thermal modulators rely on trapping, which first cuts and supplements a part (for example, 2 seconds) of the eluent from the first - dimensional column, and then injects the trapped analyte into the second - dimensional column as a sharp peak by rapidly increasing the temperature. Furthermore, the thermal modulator needs to be cooled immediately to capture the subsequent eluent from the first - dimensional column. The main drawbacks of thermal modulators are that (1) high power is required for rapid temperature ramping, and (2) a rapid cooling mechanism (usually based on the Peltier effect or using liquid nitrogen or CO2) is needed, which makes the modulator bulky and difficult to operate. These increase the footprint of the modulator and are thus not suitable for the development of μGC. In addition, due to the thermal mass, the injection peak width is limited. Although a microfabricated thermal modulator using Peltier cooling has been demonstrated recently, it still consumes a lot of power, is difficult to manufacture and maintain, and cannot capture light compounds.

[0009] In contrast, pneumatic modulators rely on an auxiliary flow to control the injection of eluent from the first-dimensional column into the second-dimensional column. Pneumatic modulators use an external valve and an auxiliary flow to inject a portion of the eluent from the first-dimensional column into the second-dimensional column without rapid heating or cooling. Advantages of pneumatic modulators include (1) no need for rapid temperature increases and decreases, and (2) sharper injection peaks (e.g., peak width limited by the valve controlling the switching of the auxiliary flow). Several types of conventional pneumatic modulators are commonly used. The first is the stop-flow modulator, in which the flow in the first-dimensional ( 2 D:second-dimensional) column is temporarily stopped when separation in the second-dimensional 1 D:first-dimensional) column occurs. The stop-flow modulator (essentially a T-junction) can be microfabricated, but using the stop-flow mode significantly increases the first-dimensional ( 1 D) column separation time and causes further peak broadening. Airflow switching modulators such as Deans switches are also commonly used and are microfabricated for comprehensive 2DGC. Deans switches enable continuous first-dimensional ( 2 D) column separation associated with second-dimensional ( 1 D) column separation, but the flow rates in the first-dimensional ( 1 D) column and the second-dimensional ( 2 D) column need to be carefully adjusted to avoid backflow in the first-dimensional ( 1 D) column. Additionally, the concentration of the analyte in the second-dimensional ( 2 D) column is diluted by the auxiliary flow required to transfer the eluent from the first-dimensional ( 1 D) column to the second-dimensional ( 2 D) column. The differential flow modulator uses a 4-port valve or a 6-port valve so that the flow in the first-dimensional ( 1 D) column and the flow in the second-dimensional ( 2 D) column are independent, and thus a sharp second-dimensional ( 2D) Column injection and improved second dimension ( 2 D) For the separation of the column in the first dimension ( 1 D) High second dimension for the column ( 2 D) While enabling the flow rate ratio of the column, the accompanying first dimension ( 1 D) Column and second dimension ( 2 D) Enables the separation of the column. However, 4-port valves and 6-port valves are very bulky and heavy and are not suitable for μGC. Therefore, it would be desirable to develop a pneumatic modulator for a multidimensional gas chromatography system that is relatively light and small while providing excellent performance.

SUMMARY OF THE INVENTION

[0010] This section provides a general overview of the present disclosure and is not an all-inclusive disclosure of the full scope of the present disclosure or all of the features of the present disclosure.

[0011] In certain aspects, the present disclosure relates to a flow-restricted pneumatic modulator (FRPM) assembly for a multidimensional gas chromatography system. The FRPM assembly can include a first Y-shaped fluid connector. The first Y-shaped fluid connector has a first channel having a first inlet, a first outlet, and a second channel having a second outlet. The first inlet is configured to receive a stream from a first chromatography column. The first outlet is configured to be in fluid communication with a second chromatography column. The second outlet is configured to be in fluid communication with a downstream bypass line. The FRPM assembly also includes a first flow restrictor component disposed within the first channel, which has a first flow resistance to the stream. The second channel has a second flow resistance that is less than the first flow resistance. The FRPM assembly also has at least one flow control valve in fluid communication with the second outlet of the first Y-shaped fluid connector. The FRPM assembly further includes a second Y-shaped fluid connector having a second inlet and a third inlet connected to a third channel having a third outlet. The second inlet is configured to be in fluid communication with the first outlet of the first Y-shaped fluid connector and to receive a stream from a first chromatography column. The third inlet is configured to be in fluid communication with an auxiliary conduit upstream of the flow-restricted pneumatic modulator assembly, and the third outlet is configured to be in fluid communication with a second chromatography column. The flow-restricted pneumatic modulator assembly is configured to operate as an injector and a modulator to the second chromatography column.

[0012] In one aspect, the second channel includes a second flow restrictor component that exhibits the second flow resistance.

[0013] In one aspect, the FRPM assembly is formed on a substrate.

[0014] In one aspect, at least one flow control valve is a first flow control valve, and the flow restriction pneumatic modulator assembly further includes a second flow control valve that fluidly communicates with the third inlet of the second Y-shaped fluid connector upstream of the third inlet of the second Y-shaped fluid connector.

[0015] In a further aspect, the first flow control valve and the second flow control valve are each two-port valves each having an open position and a closed position.

[0016] In a further aspect, in a first operating mode of the FRPM assembly, the first flow control valve and the second flow control valve are closed to direct the stream through the first channel, the first flow resistor component, and the first outlet to the third channel and the third outlet, and are configured to direct the stream to the second chromatography column. In a second operating mode of the FRPM assembly, the first flow control valve and the second flow control valve are opened to direct the stream through the second channel and the second outlet and are configured to direct the stream to the bypass line. The auxiliary fluid from the auxiliary conduit flows through the first flow resistor component to minimize or prevent the fluid from flowing towards the second chromatography column through the first channel and the first outlet, and the first flow resistor component minimizes the disturbance caused by the auxiliary fluid flow in the stream within the first chromatography column.

[0017] In one aspect, at least one flow control valve comprises a three-way valve.

[0018] In certain aspects, the present disclosure also relates to a multidimensional gas chromatography apparatus. The multidimensional gas chromatography apparatus includes a first chromatography column that receives a fluid sample containing one or more target analytes. The multidimensional gas chromatography apparatus also includes a flow restriction pneumatic modulator (FRPM) assembly disposed downstream of the first chromatography column and in fluid communication with the first chromatography column, the FRPM assembly receiving a stream from the first chromatography column. The FRPM assembly includes a first inlet, a first channel having a first outlet, and a second channel having a second outlet, and a first flow restrictor component disposed within the first channel and having a first flow resistance to the stream, the second channel having a second flow resistance to the stream that is less than the first flow resistance, the first flow restrictor component; and a second Y-shaped fluid connector. The second Y-shaped fluid connector has a third channel having a second inlet, a third inlet, and a third outlet. The second inlet is in fluid communication with the first outlet of the first Y-shaped fluid connector and receives the stream from the first chromatography column. The FRPM assembly also includes at least one flow control valve. The multidimensional gas chromatography apparatus further includes an auxiliary fluid conduit disposed upstream of the FRPM assembly. The third inlet of the second Y-shaped fluid connector is in fluid communication with the auxiliary fluid conduit. The multidimensional gas chromatography apparatus also includes a second chromatography column disposed downstream of the FRPM assembly and in fluid communication with the third outlet of the second Y-shaped fluid connector. The FRPM assembly is configured to operate as an injector and a modulator to the second chromatography column. A bypass line is disposed downstream of the FRPM assembly and is in fluid communication with the second outlet of the first Y-shaped fluid connector. At least one flow control valve controls the flow of the stream to the bypass line. The multidimensional gas chromatography apparatus also includes at least one detector for detecting the presence of one or more target analytes eluted from the stream after passing through the second chromatography column.

[0019] In one aspect, at least one flow control valve is a second flow control valve that fluidly communicates with a second outlet of a first Y-shaped fluid connector. The multidimensional gas chromatography apparatus further includes a first flow control valve disposed upstream of the FRPM assembly that fluidly communicates with a third outlet of a second Y-shaped fluid connector.

[0020] In a further aspect, the first flow control valve and the second flow control valve are each two-port valves each having an open position and a closed position.

[0021] In a further aspect, in a first operating mode of the FRPM assembly, the first flow control valve and the second flow control valve direct the stream through a first channel, a first flow resistor component, a first outlet, a second inlet, and through a third channel to a third outlet and are closed to direct the stream to a second chromatography column. In a second operating mode of the FRPM assembly, the first flow control valve and the second flow control valve are opened to direct the stream through a second channel and a second outlet and are configured to direct the stream to a bypass line, and the first flow resistor component minimizes or prevents fluid from flowing through the first channel and the first outlet towards the second chromatography column.

[0022] In one aspect, at least one flow control valve comprises a three-way valve.

[0023] In one aspect, the FRPM assembly further includes a second flow resistor component disposed within a second channel of the first Y-shaped fluid connector, the second flow resistor component having a second flow resistance that is less than the first flow resistance.

[0024] In one aspect, the FRPM assembly is formed within a substrate.

[0025] In a further aspect, the substrate further comprises (i) a first chromatography column upstream of the FRPM assembly, (ii) a second chromatography column downstream of the FRPM assembly, or (iii) a first chromatography column upstream of the FRPM assembly and a second chromatography column downstream of the FRPM assembly.

[0026] In one aspect, at least one detector comprises a photoionization detector (PID).

[0027] In one aspect, the multidimensional gas chromatography apparatus further comprises a second detector disposed downstream of the first chromatography column and upstream of the first inlet of the FRPM assembly.

[0028] In one aspect, the first chromatography column is a first micro gas chromatography column, the second chromatography column is a second micro gas chromatography column, and the multidimensional gas chromatography apparatus is portable.

[0029] In certain aspects, the present disclosure also relates to a method for chromatographically analyzing a fluid sample containing one or more target analytes in a multidimensional chromatography system. The method includes separating one or more target analytes in the fluid sample within a first chromatography column and directing the stream exiting the first chromatography column toward a flow restriction pneumatic modulator (FRPM) assembly operating as an injector and a modulator to a downstream second chromatography column. The FRPM assembly includes a first y-shaped fluid connector having a first inlet, a first channel having a first outlet, and a second channel having a second outlet. The first y-shaped fluid connector also has a first flow resistor component disposed within the first channel that has a first flow resistance to the stream. The second channel has a second flow resistance to the stream that is less than the first flow resistance. The FRPM assembly also includes a second y-shaped fluid connector having a second inlet, a third inlet, and a third channel having a third outlet. The second inlet is in fluid communication with the first outlet of the first y-shaped fluid connector and receives the stream from the first chromatography column. The FRPM assembly also includes at least one flow control valve. The method further includes operating the FRPM assembly in a first operating mode for a first period, wherein at least one flow control valve is closed to selectively direct the stream through the first channel, through the first flow resistor component, through the first outlet to the second inlet, through the third channel and the third outlet to the second chromatography column. The method also includes operating the FRPM assembly in a second operating mode for a second period, wherein at least one flow control valve is opened to direct the stream through the second channel and the second outlet to a downstream bypass line.

[0030] In one aspect, at least one flow control valve includes a first flow control valve in fluid communication with a second outlet of a first Y-shaped fluid connector upstream of a bypass line, and a second flow control valve in fluid communication with a third inlet of a second Y-shaped fluid connector. The first flow control valve and the second flow control valve are each two-port valves having an open position and a closed position, respectively.

[0031] In one aspect, the first period is about 0.2 seconds or less.

[0032] In one aspect, in the first operating mode, the second chromatography column has a peak injection width of about 25 milliseconds or less.

[0033] In one aspect, the first flow rate of the stream in the first operating mode is about 0.5 mL / min or less, and the flow rate of the stream in the second operating mode is about 1 mL / min or more.

[0034] In one aspect, the multidimensional chromatography system further includes an auxiliary fluid conduit upstream of the FRPM assembly. At least one flow control valve includes a first flow control valve and a second flow control valve configured to receive auxiliary fluid from an auxiliary fluid conduit upstream of a third inlet of the second Y-shaped fluid connector. The auxiliary fluid conduit is in fluid communication with the second chromatography column such that, in the second operating mode, the auxiliary fluid flows through the first flow resistance component, minimizing or preventing fluid from flowing through the first channel and the first outlet toward the second chromatography column, and the first flow resistance component minimizes disturbances caused by the auxiliary fluid flow in the stream within the first chromatography column.

[0035] In one aspect, the stream entering the second chromatography column during the first operating mode has a first flow rate, and the auxiliary fluid entering the second chromatography column during the second operating mode has a second flow rate. The ratio of the second flow rate to the first flow rate is about 10:1 or more.

[0036] In one aspect, the method further includes operating the FRPM assembly in a first operating mode for a first period and repeating operating the FRPM assembly in a second operating mode for a second period.

[0037] In one aspect, the FRPM assembly has a duty cycle of from about 1% or more to about 50% or less.

[0038] In one aspect, the method further includes detecting one or more target analytes in a secondary stream exiting a second chromatography column.

[0039] In one aspect, the method further includes detecting one or more target analytes in a stream exiting a first chromatography column.

[0040] Further applicable areas will become apparent from the description provided herein. The description and specific examples in this summary are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure.

[0041] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to be illustrative of all possible implementations and are not intended to limit the scope of the present disclosure.

Brief Description of the Drawings

[0042]

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DETAILED DESCRIPTION OF THE INVENTION

[0043] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

[0044] Embodiment examples are provided so that this disclosure will be thorough and will fully convey the scope of this disclosure to those skilled in the art. To provide a complete understanding of the examples of this disclosure, many specific details are set forth, such as examples of particular compositions, components, devices, and methods. It will be apparent to those skilled in the art that specific details need not be employed, that the embodiment examples may be embodied in various forms, and that neither should be construed as limiting the scope of this disclosure. In some embodiment examples, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0045] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. The terms "comprises", "comprising", "including", and "having" are inclusive and thus specify the presence of stated features, elements, compositions, steps, integers, acts, and / or components, but do not preclude the presence of one or more other features, integers, steps, acts, elements, components, and / or groups thereof. The open-ended term "comprising" is to be understood as a non-limiting term used to describe and claim the various embodiments described herein, but in certain aspects, this term may alternatively be understood as a more restrictive, limiting term such as "consisting of" or "consisting essentially of". Thus, for any given embodiment listing compositions, materials, components, elements, features, integers, acts, and / or process steps, the present disclosure specifically includes embodiments consisting of, or consisting essentially of, such listed compositions, materials, components, elements, features, integers, acts, and / or process steps. In the case of "consisting of", alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, acts, and / or process steps, and in the case of "consisting essentially of", any additional compositions, materials, components, elements, features, integers, acts, and / or process steps that materially affect the basic and novel characteristics are excluded from such embodiments, but any compositions, materials, components, elements, features, integers, acts, and / or process steps that do not materially affect the basic and novel characteristics may be included in the embodiments.

[0046] The method steps, processes, and operations described in this specification should not be construed as necessarily requiring their execution in a particular order as specifically recited, unless the order of execution is specifically recited. It should also be understood that additional steps or alternative steps may be employed, unless otherwise indicated.

[0047] When an element, component, or layer is referred to as being "on," "engaged to," "connected to," or "coupled to" another element or layer, the element, component, or layer can be directly on, engaged to, connected to, or coupled to the other element, component, or layer. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening element or layer. Other terms used to describe the relationship between elements should be interpreted in the same manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the items listed in the associated list.

[0048] The terms "first", "second", "third", etc. may be used herein to describe various steps, elements, components, regions, layers, and / or sections, but these steps, elements, components, regions, layers, and / or sections are not to be limited by these terms unless otherwise indicated. These terms may be used only to distinguish one step, element, component, region, layer, or section from another. As used herein, the terms "first", "second", etc. and other numerical terms do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer, or section discussed below could be termed a second step, element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0049] Spatially or temporally relative terms such as "before", "after", "inner", "outer", "beneath", "below", "lower", "above", "upper", etc. may be used herein for ease of explanation to describe the relationship of one element or feature to another(s) as shown in the figures. Spatially or temporally relative terms may be intended to encompass various orientations of the device or system in use or operation in addition to the orientation shown in the figures.

[0050] Throughout this disclosure, numerical values are presented as approximate measurements or limitations of ranges to include minor deviations from a given value, and embodiments that approximately have the recited value, as well as embodiments that exactly have the recited value. Except as otherwise provided in the examples set forth at the end of the detailed description, all numerical values of parameters (e.g., quantities or conditions) in this specification, including those in the appended claims, are to be understood as being modified in all instances by the term "about" whether or not the term "about" actually appears before the numerical value. "About" indicates that the specified numerical value permits some inaccuracy (with respect to the exactness of the value, some approach to the value that is approximately or quite close, nearly). If the inaccuracy provided by "about" is not otherwise understood in the ordinary sense in the art, "about" as used herein indicates at least the variations that can result from the ordinary methods of measuring and using such parameters. For example, "about" can include variations of up to 5% or less, optionally 4% or less, optionally 3% or less, optionally 2% or less, optionally 1% or less, optionally 0.5% or less, and in certain embodiments, optionally 0.1% or less.

[0051] In addition, the disclosure of ranges includes disclosure of all values and subranges within the entire range, including the endpoints and subranges given for the range.

[0052] Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings.

[0053] In various aspects, the present disclosure provides a flow restrictor pneumatic modulator (FRPM) assembly for a multidimensional gas chromatography system. This type of FRPM assembly can, during operation, without interrupting the separation of the first dimension ( 1 D) column, provide a sharp injection into the second dimension ( 2 D) column of the multidimensional gas chromatography system and a high second dimension ( 2D) It can be a microfabricated chip-based FRPM that enables the flow rate of the column. In the provided FRPM assembly, a new type of pneumatic modulator is provided to cut the eluent from the first-dimensional column and then inject the eluent into the second-dimensional column. In certain embodiments, the multidimensional gas chromatography system has a first chromatography column, the first chromatography column is a first micro gas chromatography column, the second chromatography column is a second micro gas chromatography column, and the multidimensional gas chromatography device is portable. The term "microfluidic channel" can include one or more fluid flow paths having dimensions in the tens to hundreds of micrometers. As used herein, the term "fluid" is intended to broadly encompass gases, liquids, vapors, semi-fluid substances, and suspensions of solids in liquids or gases.

[0054] The multidimensional gas chromatography system 40 shown in FIG. 1 includes an FRPM assembly, or more specifically, a flow restriction pneumatic modulator (FRPM) assembly 50 outlined by the dashed box. The FRPM assembly 50 is outlined in dashed lines and includes a first Y-shaped fluid connector 60 having an inlet 62, a first channel 64 having a first outlet 66, and a second channel 68 having a second outlet 70, all of which are in fluid communication with each other. The inlet 62 is configured to connect to a first chromatography column 80 upstream of the FRPM assembly 50 and thus is in fluid communication with the first chromatography column 80. The first chromatography column 80 receives a sample fluid containing one or more target analytes to be analyzed and detected within the multidimensional gas chromatography system 40. The second outlet 70 is configured to connect to a downstream waste line or bypass line 84.

[0055] Accordingly, in this variant form, the FRPM assembly 50 can include a 1×2 first y-shaped fluid connector 60 that connects the first-dimensional column 80 to two downstream first channels 64 and 68 (marked as the “upper channel” and the “lower channel” in FIG. 1 respectively), as well as two flow control units 90, 92 (such as two-port valves that can be opened and closed). The FRPM assembly 50 also includes a second y-shaped fluid connector 72 whose overall contour is outlined by a dashed line, as will be further described below.

[0056] The FRPM assembly 50 also includes a first flow resistor component 96 disposed within the first or upper channel 64 of the y-shaped connector 60. The first flow resistor component 96 can be a short channel or column, but can have a cross-section that is much smaller than other fluid channels within the FRPM assembly 50. The second or lower channel 68 can have a second flow resistance to the stream that is less than the first flow resistance associated with the first flow resistor component 96. In a particular variant form, the FRPM assembly 50 can also include a second flow resistor component 98, “flow resistor 2”, disposed within the second or lower channel 68. The flow resistance of “flow resistor 1” 96 is much greater than the flow resistance of “flow resistor 2” 98, thus providing an asymmetric flow resistance to the flow rate-limiting pneumatic modulator 50.

[0057] The FRPM assembly 50 is outlined in dashed lines and also includes a second Y-shaped fluid connector 72 having a second inlet 74, a third inlet 76, a third channel 78, and a third outlet 79, all of which fluidly communicate with each other. Thus, the second Y-shaped fluid connector 72 is arranged in an orientation opposite to that of the first Y-shaped fluid connector 60. Thus, the first Y-shaped fluid connector 60 has a single inlet (the first inlet 62) and two outlets (the first outlet 66 and the second outlet 70). In that case, the second Y-shaped fluid connector 72 has two inlets (the second inlet 74 and the third inlet 76) and a single outlet (the third outlet 79) in the flow direction of the stream coming from the first chromatographic column 80 and proceeding towards the second chromatographic column 82 or the bypass line 84. Thus, the first outlet 66 of the first Y-shaped fluid connector 60 is connected to the second inlet 74 of the second Y-shaped fluid connector 72 and fluidly communicates with the second inlet 74. Thus, the second inlet 74 is configured to fluidly communicate with the first outlet 66 of the first Y-shaped fluid connector 60 and receive the stream from the first chromatographic column 80.

[0058] The multidimensional gas chromatographic system 40 can also include an auxiliary flow conduit 100 upstream of the FRPM assembly 50 that receives an inert carrier gas / auxiliary fluid. The third inlet 76 is configured to fluidly communicate with the auxiliary flow conduit 100, and thus the auxiliary fluid can pass through the second Y-shaped fluid connector 72. Any fluid stream passing through the second Y-shaped fluid connector 72 exits through the third channel 78 and the third outlet 79 and is directed towards the second chromatographic column 82.

[0059] The FRPM assembly 50 includes at least one flow control valve. For example, the FRPM assembly 50 of FIG. 1 has a first flow control valve 90 upstream of a second inlet 76 of a second Y-shaped fluid connector 72 that controls the auxiliary fluid flow into the second Y-shaped fluid connector 72. Also included is a second flow control valve 92 that fluidly communicates with a second outlet 70 of the first Y-shaped fluid connector 60 and is thus upstream of the second chromatography column 82. In certain variations, the first flow control valve 90 and the second flow control valve 92 are each two-port valves that each have an open position and a closed position. As further described herein, the FRPM assembly 50 is configured to operate as an injector and a modulator to the second chromatography column 82.

[0060] The second chromatography column 82 includes a detector 110 for detecting one or more target analytes processed within the second chromatography column 82. Although not shown in FIG. 1, other detectors may be included within the system including the downstream side of the first-dimensional chromatography column 80 to detect analytes eluted from the first-dimensional chromatography column 80.

[0061] The detector can be a photoionization detector (PID) such as a micro-photoionization detector (μPID). In certain variations, the detector can be a non-destructive on-column detector such as a capillary based optical ring resonator (CBORR) device, a Fabry-Perot interferometer based sensor, a chemoresistor sensor, an acoustic wave sensor, a thermal conductivity sensor, etc.

[0062] Furthermore, the multi-dimensional gas chromatography system 40 can have additional components known in the art, including, for example, a preconcentrator, additional columns, seals, valves, monitors (e.g., pressure monitors and temperature monitors), connectors, electrical wiring, gaskets, controllers, etc., but not shown.

[0063] In certain aspects, the present disclosure contemplates that the FRPM assembly and / or various components of a multidimensional gas chromatography apparatus are formed within a substrate such as a chip, board, base platform, etc. The substrate may be inorganic or organic, such as, by way of non-limiting example, silicon oxide, silicon, glass, polymer, etc. In certain variations, a multidimensional gas chromatography apparatus includes a substrate within which the FRPM assembly is formed, and one of the following configurations: (i) a first chromatography column upstream of the FRPM assembly, (ii) a second chromatography column downstream of the FRPM assembly, or (iii) a first chromatography column upstream of the FRPM assembly and a second chromatography column downstream of the FRPM assembly. Thus, the FRPM and the chromatography columns can be microfluidic structures, and multidimensional gas chromatography can be made portable.

[0064] As best seen in FIGS. 4A and 4B, a flow restrictor pneumatic modulator (FRPM) assembly 50 can have a first mode of operation as shown in FIG. 4A, in which both a first fluid flow control valve 90 and a second fluid flow control valve 92 are closed. When the first fluid flow control valve 90 and the second fluid flow control valve 92 are closed, a fluid sample / stream 120 eluted from upstream of the first chromatography column (80 shown in FIG. 1) passes through a first channel 64 and a first outlet 66, through a first flow resistor component 96 of a first y-shaped fluid connector 60, into a second inlet 74 of a second y-shaped fluid connector 72, and out of a third outlet 79. Thus, the fluid sample 120 is directed to the second chromatography column (82 shown in FIG. 1) in the first mode of operation.

[0065] As shown in FIG. 4B, the flow restriction pneumatic modulator (FRPM) assembly 50 also has a second operating mode, in which the first fluid flow control valve 90 and the second fluid flow control valve 92 are opened to direct the fluid sample 120 eluted from the upstream first chromatography column (80 shown in FIG. 1) through the second channel 68 and the second outlet 70 of the first y-shaped fluid connector 60. In this second operating mode, the fluid sample 120 is directed to the waste line or bypass line 84.

[0066] As shown in FIG. 4B, an auxiliary fluid 130 (e.g., carrier gas) exits from an auxiliary fluid conduit 100 (shown in FIG. 1) upstream of the FRPM assembly 50, where the first fluid flow control valve 90 is configured to receive the auxiliary fluid 130. The auxiliary fluid 130 flows to the secondary chromatography column 82 (of FIG. 1), through the first flow resistor component 96, through the first channel 64, through the second channel 68, exits from the first outlet 70, and then the auxiliary fluid 130 moves past the open second control valve 92 to the bypass line 84. Thus, a portion of the auxiliary flow 130 moving through the first channel 64, in the second operating mode, minimizes or prevents the fluid stream 120 from flowing through the first channel 64 and thus returning downstream to the second chromatography column 82 (shown in FIG. 1) through the second Y-shaped fluid connector 72. Thus, the first flow resistor component 96 serves to minimize or prevent the fluid sample 120 from moving in the direction towards the second Y-shaped fluid connector 72 (and thus into the second chromatography column 82 downstream of FIG. 1) by using a very small downward flow of the auxiliary fluid 130; in other words, the first flow resistor component 96 minimizes or prevents an excessive auxiliary fluid 130 from flowing downward towards the first channel 64. If the flow of the auxiliary fluid 130 towards the first channel 64 is not minimized, the flow and separation processes within the one-dimensional chromatography column 80 will be undesirably disrupted or perturbed. Thus, in the second operating mode, a portion of the auxiliary fluid 130 flows into, among other things, the two-dimensional column.

[0067] Thus, in the first operating mode of the flow-limiting pneumatic modulator 50, when both the first flow control valve 90 and the second flow control valve 92 are closed, the flow from the one-dimensional column and the eluent are diverted to the first or upper channel 64 and then diverted into the two-dimensional column. This fluid stream / flow experiences a high flow resistance having a total resistance that is the sum of the resistance from the one-dimensional column, the resistance from the first flow resistor 96, and the resistance from the two-dimensional column. As a result, the flow rate at which the eluent (fluid sample 120) is loaded from the one-dimensional column into the two-dimensional column is low.

[0068] However, in the second operating mode where both the first flow control valve 90 and the second flow control valve 92 are opened, there are two effects. First, the flow from the one-dimensional column is diverted to the second or lower channel 68 of the y-shaped fluid connector 60 because the auxiliary fluid flow 130 goes downward through the first or upper channel 64, preventing the one-dimensional flow 120 and the eluent / fluid sample 120 from going to the upper or first channel 64. Second, the flow within the one-dimensional column experiences a low flow resistance along with the total resistance contributed only from the one-dimensional column and an optional second flow resistor component (shown as the second flow resistor component 98 in FIG. 1 but not shown in FIGS. 4A and 4B). As a result, the flow rate within the one-dimensional column is even higher.

[0069] Based on the operating principle described above, an inclusive 2DGC incorporating a flow restriction pneumatic modulator (FRPM) assembly according to a particular aspect of the present disclosure can operate as follows. In a first mode of operation, both the first flow control valve 90 and the second flow control valve 92 are closed for a first period, also called the load time, which may be a short time. In a particular aspect, the first period is about 0.2 seconds or less, although other first periods are considered below. Then, in a second mode of operation, both the first flow control valve 90 and the second flow control valve 92 are switched to be opened for a second period. The second period in the second mode of operation is longer than the first period in the first mode of operation. The time or period during which both valves are open is the second period, which is called the two-dimensional separation time.

[0070] In this second mode of operation, as described above, the flow and eluent from the first dimension column go to the lower second channel 68 of the first Y-shaped fluid connector 60. This enables the separation of the analyte in the first dimension column to occur at a high flow rate (e.g., at a volumetric flow rate of about 1 to about 2 mL / min). During that time, a high auxiliary fluid flow acts as a carrier gas for two-dimensional column separation at a very high flow rate (e.g., about 5 mL / min). The even higher carrier gas flow rate sharpens the injection peak in the second dimension column. The peak width narrowing ratio is approximately determined by the carrier gas flow rate and the load flow rate for the second dimension column, as further explained below.

[0071] The sum of the first period (loading time) and the second period (separation time) is the modulation time. In one example, for instance, the first period or loading time can be about 0.2 seconds, and the second period or separation time can be about 1.8 seconds. In that case, the modulation time is 2 seconds. In certain embodiments, the modulation time or total operation time can be from about 0.005 seconds to about 50 seconds, optionally from about 0.2 seconds to about 50 seconds, and optionally from about 0.2 seconds to about 20 seconds. The operation sequence can optionally be 0.2 seconds, 1.8 seconds, 0.2 seconds, 1.8 seconds, or 2 seconds. In certain variations, the loading time can be in the range from about 0.2 seconds to about 50 seconds, optionally from about 0.2 seconds to about 20 seconds, from about 0.2 seconds to about 2 seconds.

[0072] The ratio of the first period to the modulation time is the duty cycle. In certain embodiments, methods and multidimensional chromatography systems using a flow-restricted air modulator can have a duty cycle from about 1% to about 100%, in certain embodiments optionally from about 10% to about 100%. In certain embodiments, the flow-restricted air modulator can have a duty cycle of about 50% or less, and the duty cycle is the sample / eluent loading time into the second chromatography column relative to the modulation time. In certain embodiments, the duty cycle (e.g., sample loading time relative to the modulation time) is from about 1% to about 50%, in certain embodiments optionally from about 10% to about 50% (e.g., 0.2 seconds of loading time within a 2-second modulation cycle to 1 second of loading time within a 2-second modulation cycle). Also, the duty cycle can vary throughout the operation of a gas chromatography (GC) system. For example, the duty cycle can vary from 10% of the first 100 seconds of GC operation to 50% of the remaining time of the GC operation.

[0073] The maximum modulation time for a flow-limiting pneumatic modulator within a multidimensional chromatography system can be about 50 seconds or less. In certain embodiments, the first period / loading time can be from 0.01% to 99.99% of the modulation time, and the second period / separation time can be from 99.99% to 0.01% of the modulation time. Thus, the range of the first period can be from about 0.005 seconds or more to about 49.995 seconds or less, and similarly, the second period can be from about 0.005 seconds or more to about 49.995 seconds or less. Also, the modulation time can vary throughout the operation of the GC system. For example, the modulation time can increase from 2 seconds within the first 100 seconds of the GC operation to 4 seconds within the remaining time of the GC operation.

[0074] In one example, the first period / loading time can be 20 seconds. This allows the flow and eluent from the first-dimensional column to be diverted at a low flow rate (e.g., a volumetric flow rate of 0.5 mL / min) to the first channel 64 within the first y-shaped fluid connector 60 and from the second inlet 74 to the third outlet 79 within the second y-shaped fluid connector 72. Thus, the eluent from the first-dimensional column can be injected into the second-dimensional column with an injection peak width of approximately 0.2 seconds. Thus, in certain variations, in the first operating mode, the second chromatography column has a peak injection width of about 0.2 seconds or less.

[0075] The injection peak width is determined by the first period / loading time and the ratio of the first-dimensional flow rate (the flow rate within the first chromatography column) to the second-dimensional flow rate (the flow rate within the second chromatography column). For example, if the loading time is 0.2 seconds, the first-dimensional flow rate is 1 mL / min, and the second-dimensional flow rate is 10 mL / min, the flow rate ratio is 10 (the value obtained by dividing 10 mL / min by 1 mL / min). The injection peak width is 0.2 seconds / 10 = 0.02 seconds. In certain variations, the injection peak can be from about 0.001 seconds or more to about 10 seconds or less.

[0076] In certain embodiments, the stream / fluid sample entering the second chromatography column during the first operating mode has a first flow rate, and the auxiliary fluid entering the second chromatography column during the second operating mode has a second flow rate. The ratio of the second flow rate to the first flow rate is, in certain embodiments, about 10:1 or greater. More specifically, the ratio of the carrier gas flow rate (5 mL / min) to the load flow rate (0.5 mL / min) is 10. Thus, the peak width is 0.02 seconds when a carrier gas of 5 mL / min is used (without considering other peak broadening and narrowing effects such as analyte diffusion and analyte plug compression). In the above example, the injection peak width is 0.2 seconds within the second chromatography column.

[0077] In various embodiments, the method of the present disclosure further includes repeating operating the flow-limiting pneumatic modulator in the first operating mode for a first period and operating the flow-limiting pneumatic modulator in the second operating mode for a second period. This can occur over many cycles.

[0078] In certain embodiments, the net effect is that the eluent from the first-dimensional column can be periodically injected into the second-dimensional column at a constant modulation time (e.g., in the above example, 1.8 seconds + 0.2 seconds = 2 seconds) with a duty cycle of 10% (the value obtained by dividing 0.2 seconds by 2 seconds). The first / injection flow rate is low (0.5 mL / min in the above example), and the auxiliary / carrier gas flow rate for the second-dimensional column is high (5 mL / min in the above example). The high ratio makes the injection peak width even sharper than the injection time (i.e., in the above example, the 0.2 injection time creates an injection peak width of 0.02 seconds).

[0079] In various aspects, a flow-limiting pneumatic modulator prepared in accordance with the present disclosure can provide various advantages to a multidimensional gas chromatography system. First, this modulator provides a slow injection time (or load time) from the first-dimensional column to the second-dimensional column due to the presence of the high flow resistance of the first flow resistor component 96. This makes the injection peak width even sharper (determined by the ratio of the carrier gas flow rate to the load flow rate for the second-dimensional column).

[0080] Second, a high auxiliary flow rate can be used to generate a very high carrier gas flow rate for the second-dimensional column without the concern that the high auxiliary flow can push the analyte within the first-dimensional column backward.

[0081] Third, this modulator provides lower consumption of the auxiliary flow because most of the auxiliary flow is used as the carrier gas for the second-dimensional column. Only a small portion of the auxiliary flow flows downward through the first channel 64 (as described above in the second operating mode shown in FIG. 4B). This portion of the flow would prevent the flow from the first-dimensional column from going to the first channel 64. The smaller this portion of the auxiliary flow, the less auxiliary flow is advantageously wasted.

[0082] Stopping for the first-dimensional separation is almost unnecessary. The effective flow rate is reduced from 1 mL / min (assuming 1 mL / min of the first-dimensional flow goes to the lower channel) to (1 mL / min × 90% + 0.5 mL / min × 10% = 0.95 mL / min) (assuming the load flow rate to the second-dimensional column is 0.5 mL / min and the duty cycle is 10%). As a result, the first-dimensional separation can be completed quickly.

[0083] In a specific deformation mode, the length of the upper first channel 64 of the Y-shaped fluid connector 60 is as short as possible. In a specific deformation mode, the upper limit of the length can be estimated to be the linear velocity of the flow (or analyte) in the upper first channel 64 that is 64 times the loading time. For example, if the velocity of the linear flow (or analyte) is 5 cm / second and the loading time is 0.2 seconds, the maximum length of the upper first channel 64 is 5 cm / second × 0.2 seconds = 1 cm. If the length of the upper first channel 64 is longer than the maximum length, there is not enough time for the eluent from the one-dimensional column to completely pass through to the two-dimensional column. As a result, when the auxiliary flow is introduced, a part of the eluent will be pushed in the reverse direction (i.e., from "2" to "1" in FIG. 1).

[0084] In one deformation mode, the experimental setup and parameters are shown in FIG. 2. In this example, a column (upper first channel) with a length of 3 cm and an inner diameter of 0.1 mm is used as the first resistor component. A column with a length of 0.5 m is used as the second flow resistor component, and the second flow resistor component has the same flow resistance as the two-dimensional column with exactly the same dimensions (length and inner diameter). When both the first flow control valve and the second flow control valve are opened, the flow rate in the one-dimensional column is approximately 1.8 mL / min. When both the first flow control valve and the second flow control valve are closed, the flow rate through the two-dimensional column (i.e., the loading flow rate) is approximately 0.85 mL / min. The carrier gas for the two-dimensional column is supplied by the auxiliary flow when the first flow control valve is opened, and it is 9 mL / min. Two detectors (Detector 1 and Detector 2) are used to monitor the eluents from the one-dimensional column and the two-dimensional column respectively.

[0085] The results are presented in FIGS. 3A - 3D. With a loading time of 0.1 s (FIG. 3A), the eluent from the first - dimension column cannot move through the 3 - cm long (ID: 0.1 mm) column to reach the second - dimension column. As a result, no peak appears in detector 2. However, when the loading time increases to 0.2 s, 0.3 s, and 0.4 s, the peak of the eluent appears in detector 2, which confirms the operation of the FRPM assembly. The peak width on the second - dimension column increases with the increase of the cut - off time or the loading time. For example, the peak width (full width at half maximum) of C6 is 0.045 s, 0.051 s, and 0.056 s for loading times of 0.2 s, 0.3 s, and 0.4 s, respectively.

[0086] In another experiment, the second - dimension column is removed and detector 2 is placed immediately after the junction between the 3 - cm (ID: 0.1 mm) column and the auxiliary flow channel. This enables testing the effect of the flow resistor without interference from the second - dimension column. Again, a mixture of C6, C7, and C8 is used. The loading time ranges from 0.1 s to 0.5 s. At a loading time or cut - off time of 0.1 s, no peak appears in detector 2. When the loading time is 0.2 s or more, a peak appears in detector 2. The peak width (full width at half maximum) of C6 is 0.038 s, 0.042 s, 0.049 s, and 0.057 s for loading times or cut - off times of 0.2 s, 0.3 s, 0.4 s, and 0.5 s, respectively. At a higher loading time (such as 0.5 s), the ratio of the loading time (0.5 s) to the peak width (0.057) approaches the ratio of the carrier - gas flow rate (9 mL / min) to the loading flow rate (0.85 mL / min). This is because at a higher loading time, the peak broadening caused by the internal volume of the detector can be ignored (in the experiment, a photo - ionization detector with an internal volume of approximately 2.3 microliters is used, and this internal volume corresponds to a sweep - out time of approximately 0.0023 mL / (9 mL / min)×60 s / min = 0.015 s).

[0087] In particular, the above-described FRPM assembly is not limited to use as an injector or modulator between the first-dimensional column and the second-dimensional column, and can be used in front of any column (including the first-dimensional column).

[0088] The design, manufacture, and characterization of this FRPM assembly are further described herein. In certain embodiments, an injection peak width of approximately 25 milliseconds (ms) is achieved with a second-dimensional ( 2 D) column / first-dimensional ( 1 D) column flow rate ratio greater than 10, without perturbing the first-dimensional ( 1 D) column. Subsequently, a flow-restricted pneumatic modulator, also referred to herein as a microfabricated chip-based flow-restricted pneumatic modulator (FRPM), is monolithically integrated with a 0.5 m 2 D column on a single chip. Finally, an all-in-one FRPM having a 10 mOV-1 1 D microfabricated column (μ-column) with built-in 0.5 mWAX (i.e., polyethylene glycol (PEG)) 2 D μ-column, and two through-flow microphotoionization detectors (μPIDs) was developed, the first of its kind automated comprehensive 2D μGC device. Rapid separation of 40 volatile organic compounds (VOCs) in 5 minutes was also demonstrated. 1 D μ-column and 2 D chromatograms obtained with two μPIDs at the ends of the 1 D μ-column were used to construct 2D contour plots, 2 D demonstrating improved peak capacity compared to conventional comprehensive 2DGC using only one vapor detector at the end of the 2 D column.

[0089] A block diagram of the FRPM is provided in FIGS. 4A - 4D along with the operation of the FRPM. The FRPM has an inlet for auxiliary flow (port 1), 1 D an inlet for eluent (port 2), 2 D an outlet connected to the column (port 3), and an outlet as a waste line (port 4), and 1 D and2 It is equipped with an internal flow resistor between it and D. The auxiliary flow and the waste / bypass line are controlled by two two-port valves. During loading in the first operating mode (Figure 4(A)), as described above, both valves are closed, 1 A part of the D eluent flows through the flow resistor component 2 and is loaded onto the D column. During 2 D separation in the second operating mode (Figure 4(B)), both valves are opened, and a high auxiliary flow is 2 for D separation 2 supplied simultaneously with the D carrier gas flow 1 and the D eluent 2 and a buffer flow that prevents the D eluent from entering the D column. At the same time, 1 D separation continues, 1 and the D eluent is diverted to the waste / bypass line. 2 After D separation, both valves are closed again, and a new modulation cycle begins. The manufacture of the FRPM is schematically shown in Figures 10A - 10F and Figures 11A and 11B.

[0090] Compared with the conventional pneumatic modulator described above, the FRPM modulator assembly has several advantages. First, a sharp 2 D injection and a rapid 2 D separation can use a high auxiliary flow rate. Second, the flow resistor limits the auxiliary flow wasted on the waste line (see Figures 12A - 12D). Third, again due to the flow resistor, 1 the influence of the auxiliary flow on the D flow and separation is minimized. As a result, 1 perturbations of the D flow (such as flow shocks during modulation switching and 1 D reverse flow, etc.) can be avoided, and a wide range of auxiliary flow rates and 1 D flow rates can be selected. This enables 1 detection immediately after the D outlet for directly monitoring D separation (further discussion continues). In contrast, a design without a flow resistor (e.g., a conventional Deans switch) 1 is 1Care must be taken to carefully balance D and the auxiliary flow, and it can still be subject to flow rate fluctuations during modulation. Fourth, 1 From the D outlet 2 The concentration (or density) of the eluent at the transfer junction from the D outlet to the D inlet is maintained. In contrast, the Deans switch relies on the auxiliary flow to push the eluent from 1 From D 2 To D, and as a result, dilutes the concentration of the eluent when a concentration-dependent vapor detector (e.g., PID) is used, 2 Reducing the D signal. Fifth, 1 D separation continues (different from stop-flow modulation), which 1 Promotes D separation, 1 Reducing the spread of the D peak. Sixth, the FRPM assembly prepared according to a particular aspect of the present disclosure is versatile and, as further discussed below, permanently closes the waste line valve, 1 By sharing the same pressure source / flow source for D and the auxiliary flow, it can operate in stop-flow mode. Seventh, the FRPM assembly prepared according to a particular aspect of the present disclosure can be easily microfabricated and can also be integrated with 2 The D column on a single chip.

[0091] Each FRPM chip has dimensions of 8 mm × 5 mm × 1 mm (length × width × thickness). Figure 4(C) shows a schematic diagram of the microfluidic channel inside the FRPM having a 2 mm long, 40 μm × 170 μm (width × depth) channel as a built-in flow resistor component. The width and depth of the flow resistor component can be adjusted to achieve various flow resistances. All other channels have a cross-section of 250 μm × 250 μm. The FRPM module was constructed by connecting the FRPM chip to two 2-port valves at the corresponding ports (Figure 4(D)).

[0092] Figures 12A-12D show the results of computational fluid dynamics (CFD, COMSOL Multiphysics®) for a flow resistor FRPM and an air modulator without a flow resistor (i.e., a 40 micrometer wide channel is replaced by a 250 micrometer wide channel). The entire simulation geometry includes a 10 m 250 micrometer wide column (not shown) attached to the FRPM module. The geometry of the FRPM is the same as that shown in FIGS. 1 and 16A-16D (without the flow resistor). In simulations using helium as the gas flow and silicon as the wall, the laminar flow module was used. An input pressure (13.8 kPa (2 psi)) was applied at the inlet of the 10 m column, an input pressure (3.79 kPa (0.55 psi) for the flow resistorless FPRM in FIGS. 12B and 12C) was applied at the inlet of port 1 in the FRPM module, and an input pressure of 2.76 kPa (0.4 psi) (FIGS. 12B and 12D) was applied to the FRPM with a flow resistor. A closed valve was simulated by simultaneously applying an extremely high viscosity (i.e., 10,000) to the short section of the inlet (port 1) and the waste line (port 4).

[0093] 2 During D loading, the velocity remains the same for the flow resistorless FRPM or the flow resistor FRPM (FIGS. 12A and 12B). This is because the additional flow resistance provided by the 40 μm narrow channel of the FRPM is negligible compared to the upstream 10 m column. This is consistent with the experimental results (FIG. 2). 2 During D separation, the flow resistorless FRPM requires a higher input pressure from port 1 (3.79 kPa (0.55 psi) vs. 2.76 kPa (0.4 psi)) to maintain the flow rate at port 3 the same as that of the flow resistor FRPM (see FIGS. 3C and 3D). The comparison between FIGS. 12C and 12D 2 During D separation, when the flow resistor FRPM is used, the auxiliary flow from port 1 deflects more flow 2 towards D (as the 2D carrier gas). Meanwhile, 1The D flow is diverted to the waste line by the buffer flow passing through the flow resistor, which 1 prevents the D flow from 2 entering D and 1 enables the D separation to continue without a major interruption.

[0094] Examples Analytical standard grades of hexane, heptane, octane, benzene, toluene, hexamethyldisilazane (HMDS), and 40 VOCs listed in Table 1 are purchased from Sigma-Aldrich (St. Louis, MO).

Table 1

[0095] N-type silicon wafers (P / N 1095, 100 mm diameter, 500 μm thick), P-type highly doped wafers (100 mm diameter, 0.001 - 0.005 Ω-cm, 400 μm thick), and Borofloat 33 glass (P / N 517) are purchased from University Wafer. Carbopack B (P / N 20273) and X (P / N 10437-U) are purchased from Sigma-Aldrich. Additional accessory materials are provided in Table 2.

Table 2

[0096] All materials are purchased and used without further purification or modification. Helium with 99.5% purity (P / N 49615He) is used as the carrier and auxiliary gas and is purchased from Leland Gas Technologies (South Plainfield, NJ).

[0097] Manufacture of Components According to the manufacturing process of FIGS. 10A - 10F, 10 m 1 D microcolumns (cross-section: 200 μm × 250 μm, width × depth), stand-alone FRPMs, integrated FRPMs, and 0.5 m 2A Dμ column was fabricated. The FRPM module / chip was microfabricated using the same process for the microcolumn (detailed in FIGS. 10A - 10F). The μ-column microfabrication process involves, first in FIG. 10A, exposing both the column and the inlet / outlet using a soft mask of photoresist. Next in FIG. 10B, an oxide hard mask is generated by DRIE (Deep Reactive Ion Etching). In FIG. 10C, a soft mask is generated by exposing only the inlet / outlet for DRIE up to 150 μm. In FIG. 10D, using DRIE over the entire pattern area, the inlet / outlet is etched to a depth of 400 μm and the column is etched to a depth of 250 μm. In FIG. 10E, the oxide mask is removed using BHF (Buffered Hydrofluoric Acid) and the column is sealed by anodic bonding to Pyrex glass. Finally, in FIG. 10F, a patterned metal heater (30 nm titanium / 320 nm platinum) is deposited on the back surface.

[0098] The stand-alone FRPM does not have a heater on the back surface of the chip, while the integrated FRPM and 2 The Dμ column was fabricated with a shared back heater. The manufacturing yield of the stand-alone FRPM is over about 95% (132 chips per 10.16 cm (4 inch) wafer), over about 90% for the integrated FRPM (12 chips per 10.16 cm (4 inch) wafer), and over about 50% for the 10 mμ column (2 chips per 10.16 cm (4 inch) wafer).

[0099] 0.5 m 2 The coating procedure for the integrated FRPM with a Dμ column (cross-section: 250 μm × 250 μm) is shown in FIGS. 11A and 11B. Before coating, 2 Both the Dμ column and the FRPM channels were deactivated by repeating the injection of HMDS at 120 °C for 1 hour eight times. During deactivation, the coating outlet was blocked with a rubber diaphragm. 2During the Dμ column coating, to ensure that the coating solution does not flow into the FRPM channel, only the coating outlet was opened and the FRPM outlet was blocked. A dummy 10mμ column was attached to the coating outlet as a flow resistor to control the coating flow rate. 2 The Dμ column was dynamically coated with PEG by injecting 15 μL of the solution and extruding it at a flow rate of 5 cm / min. PEG: A 2% (w / w) solution of CarboWAX 20M (1% w.r.t. CarboWAX) in dichloromethane having azobisisobutyronitrile as a cross-linking agent. The above coating was repeated twice.

[0100] Subsequently, the column was treated with HMDS after each coating and then baked out at 180 °C one hour before use. Finally, the guard column attached to the coating outlet was removed, and HYSOL (trademark) epoxy was applied to block the outlet. The 10mμ column was subjected to the same coating procedure with a 3% (w / w) solution of OV-1 in dichloromethane. The resistance of the integrated heater was measured to be 40 Ω for the integrated FRPM chip and 28 Ω for the 10mμ column. Both columns were wire-bonded to the PCB board to enable pulse-width modulation heating using a 24V peak voltage. The μPID chip was manufactured as described in the inventors' previous research. The μPID array was mounted on the PCB board as shown in Figure 8B.

[0101] A stainless steel preconcentrator was fabricated by cutting a 21.5 gauge stainless steel tube into 3.5 cm lengths. First, one end was plugged with glass wool. Subsequently, the tube was filled with 0.75 mg of Carboback B, followed by 0.75 mg of Carbopack X, and then the other end was also plugged with glass wool. After loading, two universal press-tite connectors were attached to both ends of the stainless steel tube and fixed using Hysol epoxy. Also, a very thin layer (approximately 0.2 mm) of epoxy was applied to the outer surface of the stainless steel tube body. The entire preconcentrator was placed in an oven at 120 °C and dried for 12 hours. Finally, KAPTON (trademark) tape was wrapped around the stainless steel tube, and then a 32 gauge nickel-chromium heating wire (resistance approximately 7 Ω) was wound to ensure electrical insulation between the stainless steel tube and the heating wire.

[0102] Setup and operation of a comprehensive 2D μGC system The comprehensive 2D μGC system includes a stainless steel preconcentrator, a 10 mOV-1 coated 1 D μ-column, an integrated FRPM and a 0.5 m 2 DWAX μ-column, and 1 D and 2 two through-flow μPIDs at each end of D, respectively. A plurality of components were interconnected using universal press-tite connectors and inert fused silica capillaries. A detailed circuit diagram is shown in Figure 8B along with a depiction of the apparatus. With both valves closed 2 at the end (port 3) of the D μPID 1 the D flow rate was calibrated. By opening both valves at the auxiliary inlet (port 1) and the waste line (port 4) 2 at the end of the D μPID 2 the D flow rate was calibrated. The analyte was stored in a TEDLAR (trademark) bag and 1 sampled into the preconcentrator prior to backflush injection into the D μ-column. During operation, the analyte was 1 separated by the D column and 1It flows through the DμPID and then enters the FRPM module for 2D comprehensive modulation and separation. The separation was carried out by an integrated back heater using programming that creates a temperature gradient in both dimensions. Helium (99.5% purity) was used as the carrier and auxiliary gas. The load time and modulation time were set by simultaneously controlling the ON and OFF states of the valves at the auxiliary inlet (port 3) and the waste line (port 4).

[0103] Segmented modulation is achieved by giving different load times and modulation times to different segments of the analysis. In the current study, modulation times of 1 s from 0 to 75 s, 2 s from 75 to 180 s, and 3 s from 180 to 350 s were used. The load time was kept at 0.4 s for all segments. The operation of the portable μGC was controlled by LabVIEW (trademark) software developed in-house.

[0104] Composition of the 2D chromatogram The 2D contour plots in Figures 28A - 28C are 2 using the conventional method employed in conventional comprehensive 2DGC that has only one detector at the exit of the D column (i.e., 1 there is no detector at the end of the D column). The 2D contour plots are generated by 2D interpolation of the original 2DGC data based on cubic splines. The interpolated values at the query grid points are based on cubic interpolation of the values at the adjacent grid points in each respective dimension.

[0105] The 2D contour plots in Figures 9F - 9J are 1 using the signals obtained from both the DμPID and 2 the DμPID. The conventional interpolation method based on cubic splines is first 2 performed using the DGC data. Then, the DGC data is employed to 1 correct the contour data along the 1 D direction, and 2 the peak shape along the D direction is maintained.

[0106] As shown in FIG. 5A, using the FRPM module 2 D injection was carried out at 10 mOV-1 1 D microcolumn and 2 a 20 cm guard column within D ( 2 not the D separation column) only. To measure and compare the eluent immediately before and after the FRPM, two perfusion μPIDs were used. Initial characterization was performed using non-modulated operation (chromatogram in FIG. 14A). All 1 D eluents were 1 moved to D with a slight delay between the eluent peaks detected by the D μPID and 2 the D μPID, and these delays increased for heavier compounds. These delays are 2 brought about by the 20 cm guard column within D. The comparison of the peak heights of C6 and C7 showed that 2 the D μPID was 2 about 2.4 times more sensitive than the D μPID. The relative peak heights for other compounds were also reduced in the D μPID compared to D due to the peak broadening brought about by the 20 cm guard column. 1 1 compared to D 2

[0107] Next, modulated operation was investigated. FIGS. 5B to 5D show the 1 D chromatogram and the modulated 2 D chromatogram using alkane and aromatic compounds. Since sharp 2 D injection is important to maximize the D peak capacity, 2 the 2 D injection peak width (defined as the full width at half maximum) for C6, C7, and C8 as a function of the flow rate ratio of 1 D to 2 D / 1 D) was examined (FIG. 6A). Generally, the injection peak width decreases as the 2 D / 2 D / 1 D flow rate ratio increases. However, the measured injection peak width is the ideal peak width ( 2 D / 1 is always wider than (defined as the load time divided by the D flow ratio). This broadening is caused by the 20 cm guard column, and the broadening with respect to the flow rate can be regarded as the Gorey plot of said column (Figure 6B). 2 The D injection peak width is also affected by the load time and is characterized at a fixed flow ratio of 13 in Figure 6C. The measured peak width increases linearly as the load time increases, and is also wider than the logical value in this case. The broadening effect decreases as the load time increases because the broadening from the guard column is no longer dominant (Figure 6D). As will be further described below in the situations of Figures 14A to 21B, for various load times 1 the maximum allowable without affecting the D flow and peak height (and peak area) 2 D / 1 the D flow ratio, and the comparison between the flow resistor equipped modulator and the flow resistorless modulator are explored. Based on these, a sharp injection peak of approximately 25 milliseconds can be 1 perturb the D flow 1 achieved at a load time of 0.25 seconds and a flow ratio greater than 10 without significantly slowing down the D separation or

[0108] Figures 13A to 21B provide additional characterization of the FRPM prepared according to certain aspects of the present disclosure regarding the maximum allowable 2 D / 1 D flow ratio, and the comparison between the flow resistor equipped modulator and the flow resistorless modulator, for various load times.

[0109] As described above, a sharp 2 D injection peak is generated 2 and a high flow ratio is desired to promote D separation. However, at an excessive flow ratio (i.e., a strong auxiliary flow), 1 the D flow is slowed down or even pushed backward, resulting in 1 a delay in the D retention time measured by the D μPID (see Figures 14A to 14D) and 1 1 ​It causes jittering of the D chromatogram (see FIGS. 15A to 15D). The delay in retention time lengthens the analysis time and reduces the peak capacity, and jittering makes it 1 almost impossible to perform D chromatogram analysis (such as peak fitting and peak identification). The flow resistor (i.e., narrow channel) in the FRPM significantly alleviates 1 the D retention time delay and jittering at high flow ratios.

[0110] FIGS. 14A to 14C show the 1 D peak delays of C6, C7, and C8 detected by D μPID with respect to the 1 flow ratio (FIG. 14A), load time (FIG. 14B), and modulation time (FIG. 14C). Experimental conditions: load time in (FIG. 14A) and (FIG. 14C) = 0.25 s. Load time in FIG. 14B = 0.1 to 0.5 s. Modulation time in FIGS. 14A and 14B = 2 s. Modulation time in FIG. 14C = 1 to 4 s. 2 D flow rate in FIG. 14A = 4 to 40 mL / min. FIGS. 14B and 14C have a 2 D flow rate of 16 mL / min. In all experiments, 1 D flow rate = 1.2 mL / min. Error bars are obtained from three measurements. The results are qualitatively consistent with the logical calculations shown in FIGS. 17A to 17C.

[0111] According to FIGS. 14A to 14C, no significant delay in the retention time of the D eluent was observed compared to the case without modulation. For example, the 1 D retention time for C7 was 120 s in the modulated operation (flow ratio 20) and 100 s in the non-modulated operation (see FIG. 13A). Further, according to FIGS. 15A to 15D, even at a flow ratio of 17 ( 1 D flow rate = 20 mL / min), the 2 D chromatogram still operates normally and smoothly. Jittering occurs when the flow ratio is 20 ( 1 D flow rate = 20 mL / min). 2It does not appear until the D flow rate exceeds 25 mL / min. In contrast, when the modulator was operated without a 40-μm-wide flow resistor (i.e., when the channel width of the flow resistor was 250 μm instead of 40 μm, see Figure 16A), 1 not only was the D retention time significantly delayed (e.g., the C7 retention time became 145 seconds at the same flow rate ratio of 20), but also 1 the D peak was strongly perturbed at low flow rate ratios ( 2 such as 9 at a D flow rate = 11 mL / min) (see Figures 16C and 16D).

[0112] Figures 15A to 15D show the 1 D chromatogram of C7 using the FRPM module and 2 an enlarged view of the D chromatogram. 2 D flow rates = 14 mL / min (Figure 15A), 25 mL / min (Figure 15B), 30.5 mL / min (Figure 15C), and 37 mL / min (Figure 15D). In all experiments, 1 D flow rate = 1.2 mL / min, load time = 0.25 seconds, and modulation time = 2 seconds. The black arrows indicate 1 the jittering at the D peak.

[0113] Figure 16A shows a schematic diagram of a microfabricated pneumatic modulator without a 40-μm-wide flow resistor. The flow resistor region has the same cross-section of 250 μm × 250 μm (width × depth) as all other channels. Figures 16B to 16D show the 1 D chromatogram of C7 and 2 an enlarged view of the D chromatogram. 2 D flow rates = 6 mL / min (Figure 16B), 11 mL / min (Figure 16C), and 20 mL / min (Figure 16D). In all experiments, 1 D flow rate = 1.2 mL / min, load time = 0.25 seconds, and modulation time = 2 seconds. The black arrows indicate 1 the jittering at the D peak.

[0114] 1 To better understand the delay in D retention time, first, during non-modulated operation (i.e., both valves in Figure 1A are closed),1 The velocity of the analyte in column D is V0, where V0 is the velocity of the analyte during the loading state under non-modulated operation when both valves are closed and the analyte is 1 moved from 2 D to 1 D. It is assumed that it is also the velocity of the analyte in column D when it is moved. 2 During the D separation stage, a high auxiliary flow is supplied when both valves are open. 1 The velocity of the analyte in column D is reduced to αV0, where α is between 0 and 1. Further, assuming that the modulation time is t and the duty cycle (the ratio of the load time to the modulation time) is m, 1 the effective velocity of the analyte in column D is V eff = V0×m + αV0×(1 - m) (1) as follows.

[0115] The retention time of the analyte is

Equation

[0116] There are several scenarios that can be studied. 1. Non-modulated operation. In this case, m = 1, and the 1 D retention time of the analyte is T = L / V0. 2. Stop-flow operation. In this case, α = 0 and m is between 0 and 1. As a result, 1 the D retention time is T = L / (mV0), which is significantly delayed compared to non-modulated operation. For example, when m = 0.25, 1 the D retention time becomes four times longer. 3. Modulated operation with the inventors' pneumatic modulator. In FIGS. 17A - 17C, 1 the D retention time delay is plotted against various α values (i.e., various flow ratios), load times, and modulation times. In all the following calculations, L = 10 m and V0 = 0.1 m / s are fixed.

[0117] In FIG. 17A, the hold-up time delay is calculated as a function of α from Equation (2). Higher α values correspond to lower flow ratios. Load time = 0.25 s, modulation time = 2 s, m = 0.125. In FIG. 17B, the hold-up time delay is calculated as a function of the load time. α = 0.8, modulation time = 2 s. In FIG. 17C, the hold-up time delay is calculated as a function of the modulation time. α = 0.8, load time = 0.25 s. In all calculations, L = 10 m and V0 = 0.1 m / s.

[0118] In FIGS. 18A-18E and FIGS. 19A and 19B, when determining the amount of mass moved from 1 D to 2 D, the peak areas (and heights) for various load times are examined. In FIGS. 17A-17C, it can be seen that when the load time is 0.1 s, 2 only small peaks appear in D. However, the peak height increases significantly when the load time exceeds 0.2 s. The peak height 1 changes depending on when loading from 2 D to 1 D occurs, so 2 the entire D peak area corresponding to the same analyte peak in D (for a given 1 D peak with multiple 2 D peaks present) is used to estimate the total mass transfer. As expected, FIG. 19A shows that 2 the D peak area is normalized by the corresponding 1 D peak area and increases linearly with the load time. In FIG. 19B, 2 the D peak area is further normalized by the load time. The load time has a threshold of about 0.2 s, and it is found that above about 0.2 s, the mass transfer is approximately the same regardless of the load time. However, below 0.2 s, the mass transfer decreases significantly. This threshold behavior is due to the flow resistance through the narrow channel when the two 2-port valves are switched from open to closed. 1It may be due to the minimum time required to re - establish the pressure pushing the D eluent. Similar threshold behavior is observed in a pneumatic modulator without a 40 - μm wide flow resistor (see FIGS. 20A - 20G and FIGS. 21A and 21B). The threshold drops to approximately 0.05 seconds. This is because it becomes easier (and faster) to re - establish the pressure pushing the D eluent when passing through a wider (250 - μm) channel. 1 It becomes easier (and faster) to re - establish the pressure pushing the D eluent.

[0119] Note that pneumatic modulator chips with flow resistor widths in the range of 20 μm to 250 μm have also been micro - fabricated and tested. A 40 - μm wide flow resistor provides optimal performance with respect to the maximum allowable 2 D / 1 D flow rate ratio ( 1 D peak strain and significant 1 D holding time delay without causing) and 2 D injection width.

[0120] FIGS. 18A - 18E show the 1 D chromatogram and 2 an enlarged view of the D chromatogram using the FRPM module. Loading times = 0.1 second (FIG. 18A), 0.2 second (FIG. 18B), 0.3 second (FIG. 18C), 0.4 second (FIG. 18D), and 0.5 second (FIG. 18E). In all experiments, modulation time = 1 second, 1 D flow rate = 1.2 mL / min, and 2 D flow rate = 16 mL / min.

[0121] FIG. 19A shows the 2 D and 1 peak area ratio between the C7 peaks in D. FIG. 19B shows the peak area ratio normalized by the loading time extracted from (FIG. 19A). Error bars are obtained from three measurements.

[0122] Figures 20A to 20G are the D chromatograms and 1 enlarged views of the D chronograms of C7 operated without a flow resistor at load times = 0.025 s (Figure 20A), 0.05 s (Figure 20B), 0.1 s (Figure 20C), 0.2 s (Figure 20D), 0.3 s (Figure 20E), 0.4 s (Figure 20F), and 0.5 s (Figure 20G). In all experiments, modulation time = 1 s, 2 D flow rate = 1.3 mL / min, and 1 D flow rate = 7.5 mL / min. The black arrows indicate the 2 dithering characteristics at the D peak. 1

[0123] Figure 21A shows the peak area ratio between the D and 2 D C7 peaks extracted from Figures 20A to 20G. Figure 21B shows the peak area ratio normalized by the load time extracted from Figure 21A. Error bars are obtained from three measurements. 1

[0124] In another variant, an alternative FRPM module design prepared according to certain aspects of the present disclosure replaces two two-way 2-port valves with a single three-way / 3-port valve (Figures 22A to 22C). 2 During D loading and 2 D separation, the 3-port valve directs the auxiliary flow to the normally open and normally closed ports of the 3-port valve, enabling performance similar to that of the 2-valve module (Figures 23A to 23D and Figures 24A to 24C). Compared to the 2-valve configuration, the single-valve FRPM module uses fewer components, is less expensive, and is easier to maintain. However, 1 the concentration (or density) of the eluent at the 2 transfer junction from the D outlet to the 1 D inlet decreases slightly due to the additional buffer flow added to the

[0125] Integrated FRPM and 2 D microcolumn module To further reduce the footprint and number of interconnections of the device, an FRPM of 0.5 m is achieved on a single chip with dimensions of 18 mm × 15 mm × 1 mm (length × width × thickness). 2 Integrated with a Dμ column (cross-section: 250 μm × 250 μm) (Figures 7A and 7B). 0.5 m 2 Due to the additional flow resistance of the Dμ column, the integrated module was re-evaluated in the same way as the stand-alone module (Figures 25A - 25C and Figures 26A - 26D). As shown in Figures 7C - 7E, at a flow rate ratio of 13, the integrated FRP module demonstrates performance similar to that of the stand-alone module with an additional peak broadening of approximately 20 m seconds due to the extra 0.5 m microcolumn.( 2 D( 2 The Dμ column alone was deactivated without a stationary phase coating).

[0126] Configuration and operation of an automated portable comprehensive 2DμGC The automated portable comprehensive 2DμGC device (Figures 8A and 8B) includes a 10 mOV-1 1 Dμ column (non-polar), an integrated FRPM, and a 0.5 mWAX 2 Dμ column (polar), 1 D outlet, and 2 Two through-flow μPIDs each at the D outlet, as well as accessories such as valves, preconcentrators, pumps, helium cartridges, and in-house control software. Miniaturized comprehensive 2DGC in subsystems has been investigated previously using μ columns and thermal / air modulators. However, these devices use desktop GC injectors and / or detectors and are thus not automated stand-alone systems for field applications. In this variant, the present disclosure provides an automated portable 2DμGC without using any desktop components at all.

[0127] This comprehensive 2DμGC differs from conventional comprehensive 2DGC in several aspects. First, conventional comprehensive 2 DGC 2 uses only one detector at the end of the D column. 1 D chromatograms2 Reconstructed based only on information from the D detector, which 1 results in errors in D retention time, 1 D peak broadening, and 1 the possibility of undersampling of the D peak. In contrast, the comprehensive 2D μGC according to certain aspects of the present disclosure 1 uses two flow-through μPIDs to monitor the D eluent and 2 the D eluent. This configuration 1 directly obtains a D chromatogram from the D μPID, 1 removing the need for reconstruction of the D chromatogram. As a result, 1 the D peak position (i.e., 1 the D retention time) is accurately determined, and the original 1 D peak width is maintained, which improves the separation performance (i.e., peak capacity). Second, due to the configuration of the two detectors, a new algorithm for generating 2D contour plots to improve separation performance was developed. Third, the modulation time is dynamically adjusted to fit various 1 D peak widths. For example, a short modulation time was used for the previous eluent with a sharper peak width (reducing the possibility of undersampling), and a longer modulation time was used for the subsequent eluent. 1

[0128] In FIGS. 9A - 9J, a comprehensive 2D μGC apparatus was used to separate 40 VOCs in approximately 5 minutes. FIG. 9A shows 1 the D μPID and 2 the D chromatogram and modulation 1 D chronogram obtained by the D μPID, respectively. 2 2 To visualize exemplary additional separations within D, two zooms are provided (FIGS. 9B - 9E). FIG. 9F presents a 2D contour plot generated using both the obtained 1 D chromatogram and 2 the D chromatogram (further described below). The 2D contour plot using the conventional method 2 ​​It depends only on the DμPID data and is plotted in FIGS. 28A - 28C. Additional 1 D information allows more peaks to be identified within the same segment (e.g., FIGS. 9G and 9I) compared to conventional 2D contour plots (e.g., FIGS. 28B and 28C). As a result, all 40 VOCs are separated using the method of the present invention compared to only 32 peaks using the conventional 2D contour plot method.

[0129] Using two detectors and the new method results in improved 1 D peak capacity and 1 accuracy of D peak retention time, significantly 1 for the D chromatogram configuration. 1 To evaluate the increase in D peak capacity, the D retention times and peak widths of benzene, C7, C8, and C9 are extracted from the conventional 2D contour plot and the new 2D contour plot and listed in Table 3. 1 These analytes from the new 2D contour plot all have sharper peak widths than those obtained from the conventional 2D contour plot, and these peak widths (and retention times) are very close to the direct measurements from the

Table 3

[0130] D chronogram. In particular, the C9 peak width is narrower in the new reconstruction compared to the measurement due to the co - elution of C9 within 1 D (FIG. 29). This suggests that this algorithm was able to reconstruct the true (i.e., non - co - eluted) peak for C9 by using 1 D data. The 1 D peak capacity of these analytes is calculated using the following formula, 1 D

Equation

[0131] 2 The D peak capacity can be estimated as follows assuming isothermal separation

Equation

[0132] In various aspects, the present disclosure 1 enables a high auxiliary flow rate without disturbing or blocking the D flow, and thus 1 maintains the D separation and 1 the D peak shape while enabling rapid 2Provide a new flow restriction pneumatic modulator (FRPM) for 2D comprehensive gas chromatography (GC) that enables D injection and separation. In the FRPM, the duty cycle (i.e., the sample loading time relative to the modulation time) ranges from 10% to 50% (e.g., a loading time of 0.2 to 1 second within a 2-second modulation cycle), and this duty cycle is lower compared to other valve-based differential flow modulators that use a high duty cycle of 80%. This low duty cycle does not affect this 2D μGC system due to the use of a concentration-dependent vapor sensor, 2 the D signal (i.e., 2 the sensitivity of the D detector) is, 2 reduced when the D detector (e.g., a flame ionization detector) is mass flow rate-dependent.

[0133] The integrated FRPM is also used when constructing an automated portable comprehensive 2D μGC. Rapid separation of approximately 40 VOCs in about 5 minutes was demonstrated. 2 More accurate 1 D peak reconstruction and increased peak capacity, resulting in 1 a D chromatogram and 2 a new algorithm for constructing a 2D contour plot incorporating both a D chromatogram and a D chromatogram was developed. Compared to 40 peaks separated by the new 2D contour plot (Figure 9F), 32 peaks were counted from the conventional 2D contour plot (Figure 28A), 1 29 peaks were counted from only the D chromatogram (Figure 9A), corresponding to an increase of 8 and 11 peaks respectively compared to comprehensive 2DGC and single-column 1DGC using conventional methods.

[0134] If desired, the FRPM (and thus the comprehensive 2D μGC) permanently closes the waste line / bypass line valve, 1By sharing the same pressure source / flow source for both D and the auxiliary flow, it can operate in the stop-flow mode. FIGS. 30A - 30D show the separation of the same 40 VOCs in FIGS. 9A - 9J using this mode. 1 Both the D separation time and peak width are significantly 1 increased by perturbations in the D flow. In certain operating paradigms, this can be a drawback, but the operational flexibility of the FRPM that enables the stop-flow mode is useful for other applications.

[0135] In various aspects, the present disclosure incorporates a flow-restricted pneumatic modular assembly that provides enhanced vapor separation capabilities compared to conventional 1DGC, and provides a two-dimensional (2D) gas chromatograph (GC) device that is useful for the analysis of very complex chemical samples. In certain aspects, 1 rapid 2 D injection and separation can be enabled without degrading the D separation rate and eluent peak profile. A microfabricated flow-restricted pneumatic modulator (FRPM) can be used in a portable comprehensive 2DGC. 2 D injection characteristics such as peak width and peak height of the injection were fully characterized by using through-microphotoionization detectors (μPIDs) at the inlet and outlet of the FRPM. An injection peak width of approximately 25 milliseconds can be achieved at a 2 D / 2 D flow rate ratio of more than 10. The FRPM is further integrated with a 0.5 m long 1 D μ-column on the same chip, and the performance of the FRPM was characterized. Finally, an integrated FRPM with a 10 m OV-1 2 D μ-column, a built-in 0.5 m polyethylene glycol (PEG) 1 D μ-column, and an automated portable comprehensive 2D μGC with two μPIDs are also provided. Rapid separation of approximately 40 volatile organic compounds in just about 5 minutes was demonstrated. A 2D contour plot was obtained with 2 D μ-columns and 1 D μ-columns at the ends of 2 the two μPIDs 1 D chronograms and 2It was configured using both D-chronograms.

[0136] In summary, the present disclosure provides the first automated portable comprehensive 2D μGC of its kind using an integrated flow restriction pneumatic modulator (FRPM). This small and versatile device provided a portable stand-alone separation of 40 VOCs in approximately 5 minutes with enhanced peak capacity compared to conventional 2DGC. The further integration of the 1 D μ-column and 2 both D μ-columns can further improve the compactness of the device and potentially enable a handheld device applicable to more field uses.

[0137] The foregoing description of the embodiments has been provided for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the disclosure. The individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in the selected embodiment even if not specifically shown or described. The same may be modified in many ways. Such modifications should not be regarded as a departure from the disclosure, and all such amendments are intended to be included within the scope of the disclosure.

Claims

1. A flow rate limiting pneumatic modulator assembly for a multi - dimensional gas chromatography system, a first y - shaped fluid connector having a first inlet, a first channel having a first outlet, and a second channel having a second outlet, wherein the first inlet is configured to receive a stream from a first chromatographic column, the first outlet is configured to be in fluid communication with a second chromatographic column, and the second outlet is configured to be in fluid communication with a downstream bypass line; a first y - shaped fluid connector, a first flow resistor component disposed within the first channel and having a first flow resistance to the stream, wherein the second channel has a second flow resistance that is less than the first flow resistance; a first flow resistor component, at least one flow control valve in fluid communication with the second outlet of the first y - shaped fluid connector, a second y - shaped fluid connector having a second inlet and a third inlet connected to a third channel having a third outlet, wherein the second inlet is in fluid communication with the first outlet of the first y - shaped fluid connector and is configured to receive the stream from the first chromatographic column, the third inlet is configured to be in fluid communication with an auxiliary conduit upstream of the flow rate limiting pneumatic modulator assembly, the third outlet is configured to be in fluid communication with the second chromatographic column, and the flow rate limiting pneumatic modulator assembly is configured to operate as an injector and a modulator to the second chromatographic column; a second y - shaped fluid connector comprising a flow rate limiting pneumatic modulator assembly.

2. The flow rate limiting pneumatic modulator assembly according to claim 1, wherein the second channel comprises a second flow resistor component indicating the second flow resistance.

3. The flow rate limiting pneumatic modulator assembly according to claim 1, formed on a substrate.

4. The at least one flow control valve is a first flow control valve, and the flow restriction pneumatic modulator assembly further comprises a second fluid control valve that fluidly communicates with the third inlet of the second Y-shaped fluid connector upstream of the third inlet of the second Y-shaped fluid connector. The flow restriction pneumatic modulator assembly according to claim 1.

5. The flow restriction pneumatic modulator assembly according to claim 4, wherein the first flow control valve and the second flow control valve are each two-port valves each having an open position and a closed position.

6. In a first operating mode of the flow restriction pneumatic modulator assembly, the first flow control valve and the second flow control valve are closed to direct the stream through the first channel, the first flow resistor component, and the first outlet to the third channel and the third outlet, and are configured to direct the stream to the second chromatography column. In a second operating mode of the flow restriction pneumatic modulator assembly, the first flow control valve and the second flow control valve are opened to direct the stream through the second channel and the second outlet, and are configured to direct the stream to the bypass line. The auxiliary fluid from the auxiliary conduit flows through the first flow resistor component to minimize or prevent fluid from flowing through the first channel and the first outlet towards the second chromatography column. The first flow resistor component minimizes the disturbance caused by the auxiliary fluid flow in the stream within the first chromatography column. The flow restriction pneumatic modulator assembly according to claim 4.

7. The flow restriction pneumatic modulator assembly according to claim 1, wherein the at least one flow control valve comprises a three-way valve.

8. A multidimensional gas chromatography apparatus, A first chromatography column that receives a fluid sample containing one or more target analytes, A flow restriction pneumatic modulator (FRPM) assembly disposed downstream of the first chromatography column and in fluid communication with the first chromatography column, the FRPM assembly receiving a stream from the first chromatography column, A first Y-shaped fluid connector having a first inlet, a first channel having a first outlet, and a second channel having a second outlet, A first flow resistor component disposed within the first channel, having a first flow resistance to the stream, wherein the second channel has a second flow resistance to the stream that is less than the first flow resistance. A second Y-shaped fluid connector having a second inlet, a third inlet, and a third channel having a third outlet, wherein the second inlet is in fluid communication with the first outlet of the first Y-shaped fluid connector and receives the stream from the first chromatography column. At least one flow control valve An FRPM assembly comprising An auxiliary fluid conduit disposed upstream of the FRPM assembly, wherein the third inlet of the second Y-shaped fluid connector is in fluid communication with the auxiliary fluid conduit. A second chromatography column disposed downstream of the FRPM assembly and in fluid communication with the third outlet of the second Y-shaped fluid connector, wherein the FRPM assembly is configured to operate as an injector and a modulator to the second chromatography column. A bypass line disposed downstream of the FRPM assembly and in fluid communication with the second outlet of the first Y-shaped fluid connector, wherein the at least one flow control valve controls the flow of the stream to the bypass line. At least one detector for detecting the presence of the one or more target analytes eluted from the stream after passing through the second chromatography column A multidimensional gas chromatography apparatus comprising

9. The multidimensional gas chromatography apparatus according to claim 8, wherein the at least one flow control valve is a second flow control valve in fluid communication with the second outlet of the first Y-shaped fluid connector, and the multidimensional gas chromatography apparatus further comprises a first flow control valve disposed upstream of the FRPM assembly and in fluid communication with the third outlet of the second Y-shaped fluid connector.

10. The multidimensional gas chromatography apparatus according to claim 9, wherein the first flow control valve and the second flow control valve are each two-port valves each having an open position and a closed position.

11. In a first operating mode of the FRPM assembly, the first flow control valve and the second flow control valve direct the stream through the first channel, the first flow resistor component, the first outlet, the second inlet, and through the third channel to the third outlet, and are closed to direct the stream to the second chromatography column. In a second operating mode of the FRPM assembly, the first flow control valve and the second flow control valve are opened to direct the stream through the second channel and the second outlet and are configured to direct the stream to the bypass line. The first flow resistor component minimizes or prevents fluid from flowing from the first channel and the first outlet towards the second chromatography column. The multidimensional gas chromatography apparatus according to claim 9.

12. The multidimensional gas chromatography apparatus according to claim 8, wherein the at least one flow control valve comprises a three-way valve.

13. The FRPM assembly further comprises a second flow resistor component disposed in the second channel of the first Y-shaped fluid connector, the second flow resistor component having a second flow resistance that is less than the first flow resistance. The multidimensional gas chromatography apparatus according to claim 8.

14. The multidimensional gas chromatography apparatus according to claim 8, further comprising a substrate, wherein the FRPM assembly is formed within the substrate.

15. The substrate is (i) the first chromatography column upstream of the FRPM assembly, (ii) the second chromatography column downstream of the FRPM assembly, or (iii) the first chromatography column upstream of the FRPM assembly and the second chromatography column downstream of the FRPM assembly The multidimensional gas chromatography apparatus according to claim 8, further comprising.

16. The multidimensional gas chromatography apparatus according to claim 8, wherein the at least one detector comprises a photoionization detector (PID).

17. The multi-dimensional gas chromatography apparatus according to claim 8, further comprising a second detector disposed downstream of the first chromatography column and upstream of the first inlet of the FRPM assembly.

18. The multi-dimensional gas chromatography apparatus according to claim 8, wherein the first chromatography column is a first micro gas chromatography column, the second chromatography column is a second micro gas chromatography column, and the multi-dimensional gas chromatography apparatus is portable.

19. A method for chromatographically analyzing a fluid sample containing one or more target analytes in a multi-dimensional chromatography system, comprising: separating the one or more target analytes in the fluid sample within a first chromatography column; directing the stream emerging from the first chromatography column towards a flow-restricted pneumatic modulator (FRPM) assembly operating as an injector and modulator to a downstream second chromatography column, the flow-restricted pneumatic modulator comprising: a first y-shaped fluid connector having a first inlet, a first channel having a first outlet, and a second channel having a second outlet; a first flow resistor component disposed within the first channel and having a first flow resistance to the stream, wherein the second channel has a second flow resistance to the stream that is less than the first flow resistance; a second y-shaped fluid connector having a second inlet, a third inlet, and a third channel having a third outlet, wherein the second inlet is in fluid communication with the first outlet of the first y-shaped fluid connector and receives the stream from the first chromatography column; at least one flow control valve; and directing; operating the FRPM assembly in a first operating mode for a first period, wherein the at least one flow control valve is closed to selectively direct the stream through the first channel, through the first flow resistor component, through the first outlet to the second inlet, through the third channel and the third outlet to the second chromatography column. Operating the FRPM assembly in a second operating mode for a second period, wherein the at least one flow control valve is opened to direct the stream through the second channel and the second outlet to a downstream bypass line A method comprising. **Claim 20** The method according to claim 19, comprising a first flow control valve in fluid communication with the second outlet of the first y-shaped fluid connector upstream of the bypass line, and a second flow control valve in fluid communication with the third inlet of the second y-shaped fluid connector, wherein the first flow control valve and the second flow control valve are each two-port valves having an open position and a closed position. **Claim 21** The method according to claim 19, wherein the first period is about 0.2 seconds or less. **Claim 22** The method according to claim 19, wherein in the first operating mode, the second chromatography column has a peak injection width of about 25 milliseconds or less. **Claim 23** The method according to claim 19, wherein a first flow rate of the stream in the first operating mode is about 0.5 mL / min or less, and a flow rate of the stream in the second operating mode is about 1 mL / min or more. **Claim 24** The multidimensional chromatography system further comprises an auxiliary fluid conduit upstream of the FRPM assembly, the at least one flow control valve comprising a first flow control valve and a second flow control valve configured to receive auxiliary fluid from the auxiliary fluid conduit upstream of the third inlet of the second y-shaped fluid connector, the auxiliary fluid conduit being in fluid communication with the second chromatography column, such that in the second operating mode, the auxiliary fluid flows through the first flow resistor component, minimizing or preventing fluid from flowing through the first channel and the first outlet towards the second chromatography column, and the first flow resistor component minimizing disturbances caused by the auxiliary fluid flow in the stream within the first chromatography column. **Claim 25** The stream entering the second chromatography column during the first mode of operation has a first flow rate, the auxiliary fluid entering the second chromatography column during the second mode of operation has a second flow rate, and the ratio of the second flow rate to the first flow rate is about 10:1 or greater, the method of claim 24.

26. The method of claim 19, further comprising repeating operating the FRPM assembly in the first mode of operation for a first period and operating the FRPM assembly in the second mode of operation for a second period.

27. The method of claim 26, wherein the FRPM assembly has a duty cycle of about 1% or more to about 50% or less.

28. The method of claim 19, further comprising detecting one or more target analytes in the secondary stream exiting the second chromatography column.

29. The method of claim 28, further comprising detecting one or more target analytes in the stream exiting the first chromatography column.

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