Method and system for carrier gas identification in gas chromatography

Abstract

SUMMARY OF THE INVENTION A method and system for carrier gas identification in gas chromatography is described herein. [Solution] In one aspect, a gas chromatography system includes a pneumatic system including an input flow path in fluid communication with a first output flow path and a second output flow path, a first flow sensor configured to generate a flow measurement signal corresponding to a first characteristic of the gas, a second flow sensor configured to generate a second flow measurement signal corresponding to a second characteristic of the gas that is different from the first gas characteristic, and a controller programmed to measure the first flow measurement signal for a flow rate of the gas through the pneumatic system, measure the second flow measurement signal for the flow rate of the gas through the pneumatic system, and identify the type of gas at the flow rate of the gas through the pneumatic system from the first and second flow measurement signals.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 056,832, filed July 27, 2020, the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] In gas chromatography, the composition of a sample is determined by passing the sample through a gas chromatography column. As a carrier gas transports the sample components from one end of the column to the other, time fluctuations can occur between the different molecular components of the sample. Based on this time fluctuation, the gas chromatography system can distinguish between the various components contained in the sample.

[0003] However, the time it takes for various sample components to pass through the column can depend on the composition of the carrier gas used to transport the sample through the column. Incorrect carrier gas identification can lead to performance issues. For example, if the carrier gas is not correctly identified, the carrier gas flow rate may not be properly controlled. This can lead to problems such as misidentification of the various components of the sample reaching the detector at the end of the column, poor peak shape, and poor separation of the sample components. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION A method and system for carrier gas identification in gas chromatography is described herein. [Means for solving the problem]

[0005] In one aspect, a gas chromatography system includes a pneumatic system including at least one input flow path in fluid communication with at least a first output flow path and a second output flow path; a first flow sensor disposed on the input flow path, the first flow sensor configured to generate a flow measurement signal corresponding to a first characteristic of the gas; a second flow sensor disposed on the first output flow path, the second flow sensor configured to generate a second flow measurement signal corresponding to a second characteristic of the gas different from the first gas characteristic; and a controller programmed to flow a gas through the pneumatic system, measure a first flow measurement signal of the flow of the gas through the pneumatic system from the first flow sensor, measure a second flow measurement signal of the flow of the gas through the pneumatic system from the second flow sensor, and identify a gas type of the flow of the gas through the pneumatic system from the first and second flow measurement signals.

[0006] This aspect can include various embodiments. In one embodiment, the microcontroller can be further configured to perform a calibration procedure, the calibration procedure including flowing a known type of gas through the pneumatic system, controlling a flow rate of the known type of gas via an external flow controller, and correlating the output of the first flow sensor and / or the second flow sensor, or both, to the controlled flow rate. In some cases, the gas chromatography system can further include at least one valve disposed along the input flow path, the first output flow path, and / or the second output flow path (i.e., the first output flow path, the second output flow path, or both), and the microcontroller can be further configured to cause the at least one valve to vary the flow rate through the pneumatic system.

[0007] In another embodiment, the properties of the gas may include viscosity and one or more of heat dissipation, thermal conductivity, and heat capacity.

[0008] In another embodiment, the microcontroller may be further configured to compare the identified gas type with a gas type entered by a user and generate an alert if the identified gas type does not match the gas type entered by the user.

[0009] In another embodiment, the microcontroller may be further configured to adjust one or more settings of the gas chromatography system based on the identified gas type.

[0010] In another embodiment, the gas chromatography system may include a third flow sensor disposed on the second output flow path, and the microcontroller may be further configured to generate a third flow measurement signal from the third flow sensor and identify a gas type of the flow rate of the gas through the pneumatic system from the first, second, and third flow measurement signals.

[0011] In another embodiment, the flow measurement signal is a flow rate of the expected configured gas. Optionally, the gas chromatography system may further include a third flow sensor disposed on the second output flow path, and the microcontroller may be further configured to generate a third flow rate from the third flow sensor for the expected configured gas type, sum the second flow rate and the third flow rate, compare the summed flow rate with the first flow rate, and determine whether the expected configured gas type corresponds to the type of gas flowing through the pneumatic system according to the comparison.

[0012] In some cases, the microcontroller may be further configured to determine that the assumed set gas type corresponds to the type of gas flowing through the pneumatic system based on a difference between the summed flow rate and a first flow rate that is less than a threshold value.

[0013] In some cases, the microcontroller may be further configured to identify a type of gas flowing through the pneumatic system based on a difference between the summed flow rate and the first flow rate by comparing the difference to an expected difference for one or more expected gas types.

[0014] In another embodiment, the gas chromatography system may further include an electric heater in fluid communication with the gas, and the controller may be further configured to cause the electric heater to heat a portion of the gas to a predetermined temperature, determine heater energy required to heat the portion of the gas to the predetermined temperature, and identify the type of gas flowing through the pneumatic system from the first and second flow measurement signals and the heater power required to heat the portion of the gas to the predetermined temperature.

[0015] In another embodiment, the gas chromatography system may further include an electric heater in fluid communication with the gas, and the controller is further configured to control the heater to heat the gas to a predetermined temperature, measure the heater energy required to heat the gas to the predetermined temperature, divide possible gas types into at least two groups based on physical properties, and determine which of the at least two groups the gas flowing through the pneumatic system belongs to from the required heater power.

[0016] In another aspect, a gas chromatography system includes a pneumatic system including at least one input flow path in fluid communication with at least a first output flow path and a second output flow path; a first flow sensor disposed on the input flow path, the first flow sensor configured to generate a flow measurement signal using a first property of the gas; a second flow sensor disposed on the first output flow path, the second flow sensor configured to generate a flow measurement signal using a second property of the gas, the second property being different from the first gas property; and flowing the gas through the pneumatic system to generate a first flow measurement signal from the first flow sensor and a second flow measurement signal from the second flow sensor. and a microcontroller programmed to generate a signal, vary the flow rate of gas through the input flow path and the first output flow path while maintaining a substantially constant flow rate of gas through the second output flow path, generate a third flow measurement signal from the first flow sensor, generate a fourth flow measurement signal from the second flow sensor, calculate a first change in the flow measurement signal by taking a difference between the first and third flow measurement signals, calculate a second change in the flow measurement signal by taking a difference between the second and fourth flow measurement signals, and identify the type of gas by comparing the first change in the flow measurement signal with the second change in the flow measurement signal.

[0017] This aspect can include various embodiments. In one embodiment, the microcontroller can be further configured to perform a calibration procedure. The calibration procedure includes flowing a known type of gas through the pneumatic system, controlling the flow rate of the known type of gas via an external flow controller, and correlating the output of the first flow sensor and / or the second flow sensor (i.e., the first flow sensor and / or the second flow sensor) to the controlled flow rate.

[0018] In another embodiment, the gas chromatography system can include at least one valve disposed along the input flow path, the first output flow path, the second output flow path, or any combination thereof, and the microcontroller can be further configured to utilize the valve to vary the flow rate through the pneumatic system.

[0019] In another embodiment, the microcontroller may be further configured to compare the identified gas type with the gas type entered by the user and generate an alert if the identified gas type does not match the gas type entered by the user.

[0020] In another embodiment, the gas chromatography system may further include an electric heater in fluid communication with the gas, and the microcontroller is further configured to control the heater to heat the gas to a temperature, measure the heater power required to heat the gas to the temperature, and identify the type of gas using the required heater power.

[0021] In another embodiment, the gas chromatography system may further include an electric heater in fluid communication with the gas, and the microcontroller is further configured to control the heater to heat the gas to a temperature, measure the heater power required to heat the gas to the temperature, divide possible gas types into at least two groups based on physical properties, and use the required heater power to determine which of these at least two groups the gas flowing through the pneumatic system belongs to.

[0022] In another embodiment, the flow measurement signal is a flow rate of a preset gas, and the microcontroller is further configured to identify the preset gas type as the type of gas flowing through the pneumatic system by a difference between the first change in the flow measurement signal and the second change in the flow measurement signal being substantially the same within a threshold value.

[0023] In another embodiment, the flow measurement signal is a set gas flow rate, and the microcontroller is further configured to identify the type of gas by using a difference between a first change in the flow measurement signal and a second change in the flow measurement signal and comparing the difference to an expected difference for each possible type of gas.

[0024] For a more complete understanding of the nature and desired objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters indicate corresponding parts throughout the several views. [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows a gas chromatography system according to one embodiment of the claimed invention. [Figure 2] 1 shows a pneumatic system according to one embodiment of the claimed invention; [Figure 3] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 4] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 5] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 6] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 7] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 8] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 9] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 10] 1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 11]1 illustrates a pneumatic system configuration for identifying gases in a gas chromatography system according to an embodiment of the claimed invention. [Figure 12] 1 illustrates a control system for a gas chromatography system according to one embodiment of the claimed invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] [Definition] The invention is most clearly understood with reference to the following definitions.

[0027] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0028] A "configured gas" can refer to a gas that is configured to flow in a gas chromatography system or a pneumatic system. For example, the system can calibrate system components (e.g., valves, flow amount, flow rate, etc.) in anticipation of the flow rate of the gas depending on different parameters or characteristics of the configured gas. The configured gas can be specified, for example, by a user interface such as a graphical user interface, a switch, a system estimate for the gas, etc.

[0029] "Actual gas" can refer to the gas flowing through a gas chromatography system or a pneumatic system. In some cases, the actual gas flowing through the system may differ from the programmed gas, especially if the programmed gas was incorrectly selected by the user or the system.

[0030] Unless otherwise stated or clear from the context, the term "about" as used herein is understood to mean within normal tolerances in the art, e.g., within two standard deviations of the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values ​​provided herein are modified by the term about.

[0031] The terms "comprise," "comprising," "containing," "having," and the like, as used in the specification and claims, may have the meaning ascribed to them under U.S. patent law, and may mean "include," "including," and the like.

[0032] Unless otherwise stated or clear from context, the term "or" as used herein is understood to be inclusive.

[0033] Ranges provided herein are understood to be shorthand for all values ​​within the range, e.g., ranges are understood to include any number, combination of numbers, etc. (including fractions thereof unless the context clearly dictates otherwise).

[0034] [Gas Chromatography System] The methods described herein can be performed by, and the systems described herein can be part of, a gas chromatography system. An exemplary gas chromatography system is shown in FIG. 1. A gas chromatography system can vaporize, separate, and detect components of a sample. This can be accomplished by injecting a sample into a gas chromatography ("GC") system and running the sample through a GC column, which separates the components or analytes of the sample and generates a signal representing the relative amount and / or identity of the analytes (i.e., the relative amount, identity, or both) as the analytes pass through a detector. As shown in FIG. 1, fluid flow through the system is shown as a single arrow, such as arrow 185, and electronic communication within the system is shown as a double arrow, such as arrow 175.

[0035] [Sample source] The sample source 105 can include any sample capable of transitioning to the gas phase by a gas chromatography system, for example, any solid, liquid, or gaseous substance that has a phase transition at temperatures up to about 450° C. Thus, a significant number of chemicals and biological agents are available as sample sources 105. In some cases, the sample source 105 can be stored in a vial or container, or the like, prior to source extraction.

[0036] [GC entrance] Gas chromatography system 100 may also include a GC inlet 120, such as the GC inlet shown in Figure 2. GC inlet 120 may further regulate sample and carrier gas transport to column 135 and other flow components of gas chromatography system 100. The GC inlet may also be part of a pneumatic system, such as pneumatic system 180.

[0037] An embodiment of a pneumatic system is shown in FIG. 2. Pneumatic system 200 can be an example of pneumatic system 180 in FIG. 1. A sample to be analyzed can be injected into the GC inlet of the pneumatic system. This typically occurs using an autosampler (liquid autosampler, headspace sampler, purge and trap, valve, etc.) or by manually measuring the amount of sample using a needle, syringe, or other sample probe or tubing that pierces the septum 275 of the pneumatic system and allows the sample to flow into the interior volume of inlet weld 215. Alternatively, a sampling device (such as a valve) can be connected to the GC inlet by other means (e.g., tubing, welding, etc.) to allow the sample to flow into the inlet without the use of a septum. If not already in a gaseous state, the sample injected into the GC inlet can be vaporized within the GC inlet before flowing into a GC column fluidly coupled to the GC inlet. The inlet can be heated to a temperature of up to about 450° C. to facilitate vaporization of the sample or to maintain the sample in a gaseous state.

[0038] Pneumatic system 200 can include multiple flow paths fluidly coupled to GC inlet weld 215. Some flow paths are input flow paths through which gas flows from an external source to the GC inlet, and some flow paths are output flow paths through which gas flows from the pneumatic system to an external sink, such as the ambient environment or other components of the GC system (e.g., a GC column, a detector, etc.).

[0039] The pneumatic system 200 can include a carrier gas supply line 205. The carrier gas supply line 205 is an input line and can connect a carrier supply port 210 to a GC inlet weld 215. For example, the pneumatic system 200 can receive a carrier gas from a gas source 110, such as a pressurized container of gas or a laboratory gas supply manifold, via the carrier supply port 210. The carrier gas can be an inert gas used to flow a sample through various components of a GC system, such as the GC inlet, GC column, and detector. Examples of carrier gases include helium, nitrogen, hydrogen, argon-methane mixtures, and the like.

[0040] The pneumatic system may also include a septum purge flowpath 225. The septum purge flowpath 225 is an output flowpath that can facilitate adjustment of pressure, sample volume, etc. within the pneumatic system 200. Carrier gas entering the GC inlet through the carrier gas supply flowpath may flow through the GC inlet septum after passing through the GC inlet septum. This allows gases generated from the inlet septum to be purged from the system to prevent contamination of the sample flowpath, such as the GC column and / or detector (i.e., the GC column, the detector, or both). The septum purge flowpath 225 may be connected to a purge vent. When opened, the purge vent can release contents, pressure, etc. from the septum purge flowpath to the ambient environment.

[0041] In some cases, the pneumatic system may also include a split channel 220, which is an output channel. When open, the split channel may release contents, pressure, etc., from the split channel 220 to the ambient environment. Additionally, the split channel 220 may adjust the volume and / or percentage (i.e., volume, percentage, or both) of the sample input to the inlet that is transported to a column (e.g., column 280) by allowing a portion of the carrier gas mixed with the sample to exit the GC inlet via the split channel 220 and be discarded, rather than passing through the GC column. This may reduce the amount of sample entering the column, avoiding column overload, which may result in poor peak shape. The split channel 220 may be connected to a split vent that can be routed to the ambient environment.

[0042] Pneumatic system 200 can also include a column flow path, which can include GC column 280. The column flow path can flow carrier gas and sample from within the pneumatic system at the GC inlet weld to the column being analyzed (e.g., column 280). In most cases, the column flow path is an output flow path, such as when flowing sample through a GC column or when flowing carrier gas through a GC column in standby mode. However, in some cases, such as when backflushing sample or contaminant components from the column via a split flow path, the column flow path can also be an input flow path. In the carrier gas discrimination examples described throughout this application, the column flow path can function as an output flow path.

[0043] Pneumatic system 200 can include various sensing devices and valves for monitoring and controlling parameters (e.g., flow rate, pressure, etc.) within the pneumatic system. For example, several flow paths of the pneumatic system (e.g., carrier gas flow path 205, septum purge flow path 225, split flow path 220, etc.) can include at least one valve (e.g., valve 230, valve 235, valve 240, etc.). Each valve can control whether the respective flow path is connected (e.g., open) or disconnected (e.g., closed) from other components of pneumatic system 200, a carrier gas source, or the ambient environment. Each valve can be a switching valve, a proportional valve, etc. In some cases, the column flow path of the pneumatic system does not include a valve.

[0044] Additionally, various sensors can be coupled to the flow paths within the pneumatic system 200. Flow sensors can be of various types known to those skilled in the art. A typical flow sensor used in a flow path of a pneumatic system requires knowledge of the type of gas flowing through the sensor to accurately determine the gas flow rate. For example, the flow sensor can be a thermal dispersion flow sensor, which measures flow rate by using the thermal conductivity of the gas to provide a heat source to heat the flowing gas and measures the temperature difference upstream and downstream of the heater. The temperature difference between the two sensors is proportional to the gas flow rate and the thermal conductivity of the gas. In another example, the flow sensor can be at least one pressure sensor upstream and / or downstream (i.e., upstream and / or downstream) of a flow restriction such as a frit, a tube, a channel in a manifold, or an orifice. Alternatively, the restriction can be a GC column. In one embodiment, the flow sensor can include one pressure sensor upstream of the restriction and open to ambient pressure downstream of the restriction. This type of flow sensor measures flow by using the viscosity of the gas and the internal dimensions and / or shape of the restriction (i.e., size and / or shape) to relate the pressure drop across the restriction to the flow rate of the gas. A temperature sensor can indicate the temperature of the gas to find the viscosity of the gas for use in calculating the flow rate from the pressure drop.

[0045] Other types of flow sensors that may be utilized include Coriolis, ultrasonic, and vortex shedding sensors.

[0046] The flow sensor can output a flow measurement signal indicative of the flow rate of the gas. This can be in the form of a raw voltage or current, or alternatively, a digital representation of a signal that can be related, either singly or jointly, to the flow rate of the gas via calibration data. This is referred to as the flow measurement signal (raw electrical output).

[0047] The flow measurement signal may also include the flow rate of the gas (e.g., mL / min) after converting the raw electrical output of the flow sensor to a flow rate using calibration information. This is referred to as the flow measurement signal (flow rate). When used alone, the flow measurement signal can refer to either the raw electrical output or the flow rate.

[0048] In the two examples shown, the flow measurement relies on gas properties such as thermal conductivity and viscosity. Therefore, to measure the flow rate of a gas, the type of gas must be known. The system can be calibrated for various gas types. For example, a calibration gas can be flowed through the system. The calibration gas can be of known composition, such as helium, hydrogen, nitrogen, or argon-methane, which are typical gases used in GC systems. The system can flow each gas through the flow sensor at a known flow rate measured by an independent flow sensor and obtain a flow measurement signal for each flow rate. The system can store these measurements corresponding to the calibration gas.

[0049] As an example, a flow sensor (e.g., flow sensor 245) can be coupled to carrier gas flow path 205 and can generate a flow measurement signal for the flow rate through carrier gas flow path 205 and / or other components of pneumatic system 200 (i.e., carrier gas flow path 205, pneumatic system 200, or both). A flow sensor (e.g., pressure sensor 250 coupled to frit 270) can be coupled to septum purge flow path 225. It can be assumed that the septum purge flow path is open to ambient pressure, or an additional pressure sensor (not shown) can be located downstream of frit 270. A flow sensor (e.g., pressure sensor 255 coupled to column 280) can be coupled to column flow path 290. In many cases, column 280 can be assumed to be open to atmospheric pressure or vacuum, depending on which detector 285 is fluidly connected to the outlet of column 280, or an additional pressure sensor (not shown) can be located downstream of column 280. The column temperature control device can indicate the temperature of the column, which can be further utilized to determine the viscosity of the flowing gas. In other cases, the column flow rate at the pressure measured from the pressure sensor 255 may be difficult or impossible to calculate due to unknown or changing conditions at the distal end (outlet) of the column, or if the column is a packed column rather than a capillary column. An advantage of some embodiments described herein is that the type of gas can be determined without requiring an accurate model of the column's flow rate. Furthermore, the flow sensors shown herein are merely examples, and other types or combinations of flow sensors can be used.

[0050] The flow paths of the pneumatic system may also include microchannels, flow restrictors, tubing, etc. The microchannels and flow restrictors can limit the flow rate of the gas through the corresponding flow path, as well as the pressure and flow rate of other components downstream and / or upstream (i.e., downstream and / or upstream). For example, the carrier supply flow path 205 can include a frit 265, and the septum purge flow path 225 can include a frit 270. In some cases, the valves 230, 235, 240, etc. can also function as flow restrictors, for example, if the valves are proportional valves. Additionally, other fluid components coupled to the column and / or column flow path (i.e., the column and / or column flow path) can function as restrictions that affect the flow rate through the column flow path.

[0051] A pneumatic system consisting of a sensor, proportional valve, and pneumatic restriction (along with an electronic closed-loop controller) can be used to control the gas flow into and out of the inlet. For example, a flow sensor 245 and proportional valve 235 can be used to control the flow rate into the inlet, with pressure sensor 255 measuring the resulting column pressure. Alternatively, pressure sensor 255 may be used in a closed-loop manner with the same valve 235 to control the pressure at the head of column 280. In this case, the pneumatic system effectively controls the flow out of the inlet (the column's flow rate) by controlling the pressure across the restriction (column), and the resulting flow rate at 205 is measured by flow sensor 245. In a similar manner (pressure across the restrictor), the septum purge paths (240, 250, 270) form flow controllers for additional paths out of the inlet. It is important to note that, based on the Ideal Gas Law, if the pressure in a pneumatic system is static, the sum of the actual flow rates into the inlets must equal the sum of the actual flow rates from the inlets. In some cases, split path 220 may or may not be included in the outlet flow rate determination by opening or closing split path 220 to the column (e.g., via valve 230). Additionally, in some cases, whether split path 220 is used in the outlet flow rate determination can be based on whether a flow sensor is coupled to split path 220.

[0052] The pneumatic system shown in FIG. 2 is one embodiment of a pneumatic system and represents what is known as a split / splitless ("SSL") inlet. In split mode, the inlet can open valve 230 to split the sample exiting the pneumatic system between the split and column flow paths. In splitless mode, valve 230 can be closed, and all sample injected into the inlet will exit through the column flow path. While preferred embodiments of the present invention have the inlet in splitless mode so that the flow rate of the unknown split path 220 is zero, it is understood that gas species can be optionally determined in split mode at lower split flow rates to minimize error in the summation equation "volume in = sum of volumes out." Several types of inlets exist, including a multi-mode inlet (MMI), a cool-on-column (COC) inlet, and a volatiles inlet (VI). These inlets can have different input and output flow paths and / or different combinations of valves and flow sensors on the flow paths (i.e., input and output flow paths, valves and flow sensors on the flow paths, or all three). For example, a COC inlet may not have a split flow path, but may have multiple flow paths (column flow, septum purge flow) all exiting the inlet and a flow sensor 245 for the inlet flow rate, allowing the comparison of all inlet flow rates to all outlet flow rates to be evaluated.

[0053] [column] Separation of sample components can occur in a column of a gas chromatography system, such as column 135 in Figure 1. Column 135 can contain a substance (e.g., a stationary phase) that does not vaporize and interacts differently with different sample components. The interactions can be physical in nature (e.g., adsorption, solvation, sieving, etc.) rather than chemical. An exemplary column can be a capillary tube (e.g., 5-100 m long, 0.1-0.5 mm diameter) with a suitable polymer film coating on its walls. The column can also contain particles that can interact with the sample, either directly or via a particle coating. In either case, as the sample components pass through the column, some components interact more strongly with the stationary phase than others and are retained for longer periods of time. Thus, the sample components are carried by a carrier gas to the detector end of column 135 at different exit times depending on their differences in interaction with the stationary phase. Furthermore, a GC system can have one or more columns connected in series or parallel. The column may also be connected to other gas flow sources at one or more points along the length of the column to vary the flow rate through the column.

[0054] [Column temperature control] Because interactions with the column are physical interactions, they can be regulated by controlling the temperature of the column 135 (e.g., via the column temperature control device 140). In some samples, some components can minimally interact with the column 135 at a given temperature, while other components can be held indefinitely at that same temperature. Thus, the column temperature control device 140 can control the column temperature in a controlled (and repeatable) manner while the sample components are moving through the column 135. Given the nature of the physical interactions, this temperature control can include increasing the temperature of the column 135 during sample elution. Once the last component has eluted from the column, the temperature can be returned to the starting temperature before the next sample is introduced. For some samples, the desired starting temperature may be below room temperature; for some samples, the desired starting temperature may be at or near room temperature; and for other samples, the desired starting column temperature may be above room temperature. In some cases, the column temperature control device may be a convection oven. In other cases, the column temperature control device may be a conduction heating device.

[0055] [Detector] The separated components of the sample can be received or identified by a detector 145. The detector 145 can provide a change in an electrical signal as some or all of the sample components elute from the column 135. Some detectors can distinguish between different molecules using the physical properties of the molecules. A typical type of detector is a thermal conductivity detector. A thermal conductivity detector monitors the thermal conductivity of a gas passing through the detector. A signal can be generated if the thermal conductivity of the sample component differs from that of the carrier gas. Other detectors rely on chemical reactions to produce new species that can provide an electrical signal. Some detectors rely on an ionization process in which the carrier gas is not ionized but the sample molecules are. Ionization can sometimes be measured as an electrical signal by collecting ions and monitoring the ion current. Some detectors can also convert sample molecules to an excited form, emitting photons. The photons can be detected using devices such as photomultipliers, which convert the photons into an electrical signal. Detectors can also include additional gases as reactants or sweep flow rates. Control of these gases can be achieved through electromechanical systems. In some embodiments, the GC system can include one or more detectors.

[0056] [Signal Processors and Data Analyzers] A signal processor 150 can receive and process the electrical signals generated by the detector 145. A data analyzer 155 can convert the gas chromatography signals received from the signal processor 150 into compound identification and calibrated amounts. The data analyzer can be on-board the GC system or external to the computer.

[0057] Input / Output Devices The input / output device 165 can receive input to and / or display output from the gas chromatography system (i.e., can receive input, display output, or both). The input / output device 165 can be analog switches or a keyboard and display or touch screen. Alternatively, setpoint entry and system monitoring can be accomplished via an external computer with appropriate software.

[0058] [Control System] The control system 160 can be an electronic device programmed to control the operation of the gas chromatography system to achieve a desired result. The control system 160 can be programmed to automatically execute the gas chromatography regimen without requiring input (from a feedback device or a user), or can incorporate such input. The principles of using feedback (such as from a temperature sensor) to regulate the operation of components are described, for example, in Karl Johan Astrom & Richard M. Murray, Feedback Systems: An Introduction for Scientists & Engineers, (2008).

[0059] The control system 160 can be a computing device such as a microcontroller (e.g., available under the trademark ARDUINO® or IOIO®), a general-purpose computer (e.g., a personal computer or PC), a workstation, a mainframe computer system, etc. An exemplary control system is shown in FIG. 12. The control system (“control unit”) 1200 can include a processor device (e.g., a central processing unit or “CPU”) 1202, a memory device 1204, a storage device 1206, a system bus 1210, and a communication interface 1212.

[0060] The processor 1202 may be any type of processing device for executing instructions and processing data.

[0061] Memory device 1204 may be any type of memory device, including any one or more of random access memory (“RAM”), read-only memory (“ROM”), flash memory, electrically erasable programmable read-only memory (“EEPROM”), etc.

[0062] The storage device 1206 can be any data storage device for reading from / writing to any removable and / or integrated optical, magnetic, and / or magneto-optical storage medium, etc. (e.g., hard disk, compact disc-read-only memory (“CD-ROM”), CD-ReWritable (“CDRW”), Digital Versatile Disc-ROM (“DVD-ROM”), DVD-RW, etc.). The storage device 1206 can also include a controller / interface for connecting to the system bus 1210. Thus, the memory device 1204 and the storage device 1206 are suitable for storing data and instructions of programmed processes for execution on the processor 1202.

[0063] The communication interface 1212 may be adapted and configured to communicate with any type of external device or other component of the gas chromatography system. For example, a double-lined arrow, such as arrow 175, in FIG. 1 indicates electronic communication between the control system 160 and another component of the gas chromatography system. The communication interface 1212 may further be adapted and configured to communicate with any system or network, such as one or more computing devices on a local area network ("LAN"), a wide area network ("WAN"), the Internet, etc. The communication interface 1212 may be directly connected to the system bus 1210 or may be connected via an appropriate interface.

[0064] Thus, control system 1200, by itself and / or in cooperation with one or more additional devices (i.e., by itself, in cooperation with one or more additional devices, or both), can execute processes, which may include algorithms, for controlling components of a gas chromatography system according to the claimed invention. Control system 1200 can be programmed or instructed to execute these processes according to any communication protocol and / or programming language (i.e., communication protocol and / or programming language) on any platform. Thus, processes can be embodied in data, as well as instructions, stored in memory device 1204 and / or storage device 1206 (i.e., memory device 1204 or storage device 1206, or both) or received by communication interface 1212 for execution on processor 1202.

[0065] [Carrier gas identification] Proper identification of the carrier gas entering a GC system is important to accurately identify the identity and / or relative quantity (i.e., identity and / or relative quantity) of analytes in a sample. As previously mentioned, the flow sensor in a pneumatic system may require knowledge of the type of carrier gas being used in order to properly control the flow rate of the gas through the system. Different carrier gases may have different viscosities, thermal conductivities, or other properties, which may produce different flow measurement signals (raw electrical outputs) for the same actual flow rate and / or require different flow sensor calibration data. Proper control of the flow rate of gas through a GC system requires knowledge of the type of gas being used.

[0066] As an example of the importance of maintaining an appropriate flow rate through a GC system, the flow rate through the column affects the analyte retention time, peak shape, and / or the column's separation ability (i.e., retention time, peak shape, and / or column separation ability). Therefore, an incorrect flow rate can result in analytes being improperly identified or quantified. Furthermore, when used in a split SSL inlet mode of operation, the relative flow rates through the column and split vent can affect the proportion of sample that enters the column for analysis. An incorrect split ratio can result in too much or too little sample entering the column, affecting the accuracy of analyte quantification.

[0067] In existing GC systems, a user is expected to input the type of carrier gas being used by the GC system, for example, using input / output device 165 of FIG. 1. This is prone to user error. A user may input the gas intended for use in an analysis into input / output device 165, but connect the wrong gas to carrier supply port 210. Alternatively, a user may connect the gas intended for use in an analysis to carrier supply port 210, but input the wrong gas into input / output device 165. Having the GC system identify the carrier gas being bled into the pneumatic system can eliminate these problems.

[0068] [Input / output flow measurement signal comparison] The methods described herein can identify carrier gas types by comparing flow measurement signals from multiple flow sensors that utilize different gas properties within a pneumatic system. In particular, the methods described herein can be implemented, in some cases, by hardware already relied upon by conventional gas chromatography systems (e.g., gas chromatography system 100 of FIG. 1), such that this hardware is reused or reconfigured to perform the methods described herein.

[0069] As mentioned above, gas laws such as the ideal gas law, when applied to a system at static pressure, constrain the actual (true) mass flow rate entering any point in the system to be the same as the actual (true) mass flow rate leaving that point, otherwise the pressure at that point will increase or decrease.

[0070] When applied to pneumatic systems with at least one input and two or more output streams, such as those found in the inlet section of a GC pneumatic system, the sum of all input flow rates must equal the sum of all output flow rates. This is similar to Kirchoff's law in electronic circuits, which states that the sum of all currents flowing into or out of a node must be equal. For a split / unsplit inlet with one input and three output streams, as shown in Figure 2, this means that carrier gas supply flow rate = column flow rate + septum purge flow rate + split flow rate.

[0071] Various types of flow sensors (measuring flow using thermal diffusivity, pressure across a restriction, etc.) will both have an error in the flow measurement signal (flow rate) if the actual gas differs from the set gas, but more importantly, the error will vary depending on the type of flow sensor. This discrepancy can be used to determine if the current gas is not the set gas, and in some cases, to determine the type of gas (among a variety of calibrated gases).

[0072] Alternatively, using the same principle, the error in the flow measurement signal (raw electrical output) can be used to determine if the current gas is not the calibrated gas, and in some cases, to determine the type of gas (among a variety of calibrated gases).

[0073] The gas chromatography system can sense a flow measurement signal or signals of a gas input to the pneumatic system on the input flow path, as well as at least one output flow measurement signal on the inlet output flow path, where the pneumatic system has at least two output flow paths. The output flow paths, with or without flow sensors, can be closed with substantially no flow passing through them (e.g., their value in the summation equation is zero). By monitoring the input and output flow measurement signals on the inlet flow path, the gas chromatography system can determine the type of gas flowing through the pneumatic system and / or determine whether the system is properly configured for the actual gas (i.e., determine the type of gas, or determine whether the system is properly configured for the gas, or both). In some cases, the system can further identify the actual gas type from the input and output flow measurement signals.

[0074] The pneumatic system flows gas through the input and output flow paths and records a flow measurement signal from the flow sensors. At least one flow sensor on the input flow path can be of a different type than at least one flow sensor on the output flow path. In other words, the flow sensor on the input flow path can generate a flow measurement signal using a different characteristic than at least one flow sensor on the output flow path. For example, the flow sensor on the input flow path can be a heat-dispersive flow sensor that measures flow using thermal conductivity, while the flow sensor on the output flow path can be a pressure-over-limiting flow sensor that measures flow using viscosity. In the case of a heat-dispersive flow sensor, gases with different thermal conductivities will generate different responses from the flow sensor for the same flow rate. Furthermore, in the case of a flow sensor configured with a pressure drop over a limit, gases with different viscosities will generate different responses from the flow sensor for the same flow rate. Other types of flow sensors that use different characteristics to measure flow rate are also contemplated.

[0075] The system can then compare the flow measurement signal from the flow sensor on the input flow path with the flow measurement signal from the flow sensor on the output flow path to identify the gas flowing through the pneumatic system. For flow measurement or calculation, the system can compare the flow measurement signal (flow rate) from the flow sensor on the input flow path with the flow measurement signal (flow rate) from the flow sensor on the output flow path to identify the gas flowing through the pneumatic system. Because at least one of the flow sensors on the input flow path measures flow using a different characteristic than one of the flow sensors on the output flow path, the GC system can identify the gas based on the difference in the flow sensor's response to gases with different characteristics based on whether the flow measurement signals from the flow sensors on the input and output flow paths match. Matching means that the flow measurement signals from the input and output flow paths, combined with knowledge of the output flow path that does not have a flow measurement signal, indicate that the same amount of gas is flowing out of the system as the gas flowing through it.

[0076] As an example, the viscosities of two commonly used carrier gases, nitrogen and helium, are similar. Therefore, depending on the sensor's resolution, the response of a viscosity-based flow sensor (e.g., a pressure sensor beyond its limits) may not be able to distinguish between these two gases for the same actual gas flow rate. However, nitrogen and helium have different thermal conductivities. The response of a thermal diffusion flow sensor to nitrogen and helium will be different. In this regard, if helium is flowing through a pneumatic system, the flow measurement signals of the thermal diffusion flow sensor in the input flow path and the viscosity-based flow sensor in the output flow path will match (e.g., show the same amount of helium entering the system as exiting the system) for helium as the designated gas, but will not match for nitrogen as the designated gas. Based on this comparison, it can be determined that helium is the gas flowing through the pneumatic system.

[0077] In determining a match between the input flow measurement signal and the output flow measurement signal, the pneumatic system can be configured for a gas. That is, a certain type of carrier gas can be assumed to be flowing through the pneumatic system (i.e., the preset gas). The carrier gas is one of the calibrated gases. The flow measurement signals can be compared using a lookup table, a formula, or other method that relies on calibration data for the preset carrier gas. If the flow measurement signals match (e.g., the flow measurement signal for the input flow path indicates that the flow rate entering the pneumatic system is the same as the flow rate leaving the inlet, as indicated by the flow measurement signal for the output flow path), the preset gas is correct. More specifically, the sum of the flow measurement signals (flow rates) on the input flow paths can be compared to the sum of the flow measurement signals (flow rates) on the output flow paths for the preset gas. If they match (e.g., are substantially the same within typical measurement error), the preset gas is the type of gas flowing through the pneumatic system.

[0078] If the flow measurement signals do not match, then the pneumatic system can be configured for a different gas and the process of comparing flow measurement signals can be repeated. Alternatively, the difference in the flow measurement signals of the input and output flow paths of the incorrectly configured gas can be used to identify the gas flowing through the pneumatic system.

[0079] As another example, a pneumatic system may not be configured for gas. In this case, the flow measurement signal of the input flow path can be compared to the flow measurement signal of the output flow path. A look-up table or formula that matches the flow measurement to a calibrated carrier gas can indicate the type of carrier gas flowing through the pneumatic system.

[0080] [Input / Output Flow Measurement with Bulkhead Purge Flow Off] In one embodiment, the gas chromatography system can monitor flow measurement signals from sensors in both the gas input flow path 335 and the column flow path 340. FIG. 3 illustrates a pneumatic system 300 configured to identify a carrier gas according to one embodiment of the claimed invention. The pneumatic system 300 can be configured to flow gas to an inlet through a gas supply port 305. The gas chromatography system can be configured to open (e.g., proportionally open) a valve 310 on the input flow path. Gas can flow through the valve 310 and a carrier gas supply flow sensor 315. The carrier gas supply flow sensor 315 can generate a flow measurement signal corresponding to a property (e.g., thermal conductivity, viscosity, etc.) of the gas entering the inlet.

[0081] The system can be further configured to close both the septum purge flow path and the split flow path. For example, the system can be configured to close valves 320 and 325. Thus, the system can limit the flow output of the pneumatic system through the column flow path. The column flow sensor 345 can generate a flow measurement signal corresponding to the properties (e.g., viscosity, thermal conductivity, etc.) of the flowing gas and representative of the gas exiting the inlet (e.g., via the column flow path). The carrier gas supply flow sensor 315 and the column flow sensor 345 can generate flow measurement signals using different properties (e.g., the carrier gas supply flow sensor 315 can be a thermal dispersion flow sensor, and the column flow sensor 345 can be a column pressure sensor 330 measuring the pressure beyond the column restriction 350, e.g., a viscosity-based flow sensor). The GC system can identify the type of carrier gas flowing through the inlet by comparing the flow measurement signals from the carrier gas supply sensor and the column flow sensor, as described above. In some cases, knowledge of the lack of gas flow in a closed flow path (e.g., the septum purge flow path or the split flow path) can also be taken into account when identifying the type of carrier gas.

[0082] Figure 4 illustrates a pneumatic system configured to identify a carrier gas, according to one embodiment of the claimed invention. Pneumatic system 400 can function similarly to pneumatic system 300 shown in Figure 3 and described above. However, in pneumatic system 300, valve 310 can be controlled and configured based on measurements received from second flow sensor 330, while valve 410 in pneumatic system 400 can be controlled and configured based on measurements received from carrier gas supply flow sensor 415. These closed-loop feedback systems are described in more detail below.

[0083] [Input / output flow rate comparison with column and septum purging on] In another embodiment, the gas chromatography system can monitor flow measurement signals from the gas input flow path, the column flow path, and the septum purge flow path. Figure 5 shows a pneumatic system 500 configured to identify a carrier gas, according to one embodiment of the claimed invention. The pneumatic system 500 can be configured to flow gas to an inlet through a gas supply port 505. The gas chromatography system can be configured such that a valve 510 on the input flow path 565 is open (e.g., proportionally open). The gas can flow through the valve 510 and a carrier gas supply flow sensor 515. The carrier gas supply flow sensor 515 can generate a flow measurement signal corresponding to a characteristic of the gas entering the pneumatic system 500.

[0084] The system can further be configured to close the output branch flow path 545. For example, the system can be configured to close the valve 525 on the split flow path 545, thereby restricting the flow rate of gas through the column flow path and the septum purge flow path (e.g., to the septum purge flow path via the open valve 520). The combination of the septum purge flow sensor 550 (e.g., pressure sensor 535 and restriction 555) and the column flow sensor 540 (e.g., pressure sensor 530 and column restriction 560) can generate a flow rate measurement signal of the gas exiting the inlet (e.g., via the column flow path and the septum purge flow path) that corresponds to other properties of the gas. At least one of the septum purge flow sensor 550 and the column flow sensor 540 can utilize different properties of the flowing gas to generate a flow rate measurement signal compared to other flow sensors in the pneumatic system. For example, the carrier gas supply flow sensor 515 can be a thermal dispersion flow sensor, while at least one of the septum purge flow sensor 550 and / or the column flow sensor 540 can be a viscosity-based flow sensor.

[0085] The system can sense flow measurement signals from flow sensors in the input and output flow paths. For example, a microcontroller in the system can receive sensed signals from the carrier gas supply flow sensor 515, the septum purge flow sensor 550, and the column flow sensor 540. In some cases, the microcontroller can be part of the control system 160 of FIG. 1. The system can then compare the flow measurement signal generated from the carrier gas supply flow sensor 515 with the flow measurement signals from the septum purge flow sensor 550 and the column flow sensor 540 (e.g., comparing the sum of the flow measurement signals (flow rate) of the septum purge and column flow sensors to the flow measurement signal (flow rate) of the carrier gas supply flow sensor). From this comparison, the system can determine whether the inlet is correctly configured for the flowing gas (e.g., if the sum of the flow measurement signals (flow rate) of the septum purge and column flow sensors is substantially equal to the flow measurement signal (flow rate) of the carrier gas supply flow sensor, the configured gas is flowing through the gas pneumatic system). Additionally or alternatively, the system can identify the type of gas being flowed from the comparison.

[0086] Figure 6 illustrates a pneumatic system 600 configured to identify a carrier gas, according to one embodiment of the claimed invention. Pneumatic system 600 may function similarly to pneumatic system 500 shown in Figure 5 and described above. However, whereas in pneumatic system 500, valve 510 may be controlled and configured based on measurements received from column flow sensor 540, valve 610 in pneumatic system 600 may be controlled and configured based on measurements received from carrier gas supply flow sensor 615. These closed-loop feedback systems are described in more detail below.

[0087] [Comparing input / output flow rates using delta measurement with column flow constant] The aforementioned gas type identification methods require the determination of a column flow measurement signal. While this may be sufficient for simple chromatography systems, in the case of packed columns or more complex systems, such as those described above (e.g., the outlet end of the column may be connected to a vacuum, a switching valve, another pressure regulator, etc.), the column flow measurement signal may be inaccurate, unknown to the gas chromatography system, and / or not easily modeled (i.e., not known, not easily modeled, or both). Furthermore, errors in the flow measurement signal of any of the flow sensors due to drift, thermal effects, etc., can cause errors in a direct comparison of the flow measurement signals, thus reducing the ability to identify the calibrated gas type.

[0088] An extension of the above method can be used to eliminate these drawbacks by utilizing a method that does not rely on the original value of the column flow rate and that nulls out any sensor errors that may have drifted in the flow measurement signal. This is accomplished by changing one or more of the controlled input or output flow rates and monitoring the resulting change in the flow measurement signal from the remaining paths. In this way, the original flow measurement signals (including those from the column flow path) can be effectively zeroed out because the gas type determination is based solely on the change in the flow measurement signal from each path (i.e., a delta measurement).

[0089] In one embodiment, the gas chromatography system can monitor step changes in flow measurement signals from both the gas input flow path and the septum purge flow path. FIG. 7 illustrates a pneumatic system 700 configured to identify a carrier gas, according to one embodiment of the claimed invention. The pneumatic system 700 can be configured to flow gas to an inlet through a gas supply port 705. The system 700 can be configured to open (e.g., proportionally open) a valve 710 on the input flow path 735, thereby allowing gas to flow through the valve 710 and a carrier gas supply flow sensor 715. Here, the carrier gas supply flow sensor can utilize a property (e.g., thermal dispersion) of the flowing gas to generate a flow measurement signal. The carrier gas supply flow sensor 715 can generate a first flow measurement signal.

[0090] System 700 can further be configured to close the split flow path. For example, the system can be configured to close valve 725. Thus, system 700 can limit the flow rate of gas through the column flow path and the septum purge flow path. A septum purge flow sensor 740 (e.g., pressure sensor 770 and restriction 745) can generate a second flow measurement signal, and optionally, a column flow sensor 750 (e.g., pressure sensor 730 and column restriction 755) can generate a flow measurement signal. These two flow measurement signals represent gas flowing out the inlet, with at least the septum purge flow sensor utilizing a gas property to measure a flow rate different from the flow rate of the carrier gas supply flow sensor (e.g., viscosity using pressure beyond the restriction to measure flow rate).

[0091] In some cases, the system can maintain a constant gas flow in a subset of the system's flow paths. For example, the system can maintain a constant flow rate in the column flow path. By keeping the flow rate in the column flow path constant, the system only requires flow measurement signals from flow paths experiencing variable flow rates. This is at least partially beneficial because the column flow path in the above example does not require a flow sensor. Rather, the system can monitor the column flow path for a constant flow rate, which can be indicated by monitoring the pressure in the flow path (e.g., via a pressure sensor).

[0092] System 700 can receive flow measurement signals from the input and output flow paths. The system's microcontroller can receive sense signals from a carrier gas supply flow sensor 715 and a septum purge flow sensor 740. Optionally, a column flow sensor 750 can maintain a constant flow rate through a column flow path 760. From these sense signals, the microcontroller can determine a flow measurement signal for the gas flowing through the pneumatic system.

[0093] The system 700 can then vary the flow rate of gas originating from the gas supply port 705 via changes to the flow rate through the septum purge flow path 765. Additionally, the system 700 can be configured to keep the flow rate through the column flow path substantially constant (e.g., approximately zero change) so that the flow rate experienced by the column flow path remains static as the flow rate at the gas supply port increases.

[0094] The system can then measure new flow measurement signals from the input and septum purge flow paths. The carrier gas supply flow sensor 715 can generate a third flow measurement signal, and the septum purge flow sensor 740 can generate a fourth flow measurement signal. A system microcontroller can receive sense signals from the carrier gas supply flow sensor 715 and the septum purge flow sensor 740. From these sense signals, the microcontroller can determine a flow measurement signal for gas flowing through the pneumatic system at the altered septum purge flow rate.

[0095] The system can then calculate the difference between a first set of flow measurement signals resulting from the original gas supply port flow rate and a second set of flow measurement signals resulting from the adjusted septum purge flow path gas flow rate. For example, the system can calculate a first change in the flow measurement signals by taking the difference between a first flow measurement signal resulting from the carrier gas supply flow sensor 715 and a third flow measurement signal resulting from the carrier gas supply flow sensor 715. Similarly, the system 700 can calculate a second change in the flow measurement signals by taking the difference between a second flow measurement signal resulting from the septum purge flow sensor 740 and a fourth flow measurement signal resulting from the septum purge flow sensor 740.

[0096] The system can then compare the first change in the flow measurement signal to the second change in the flow measurement signal. From this comparison, the system can determine whether the inlet is configured for the actual gas. If the change in the flow measurement signal (e.g., the delta from the comparison) is substantially the same (accounting for system calibration error), the actual gas is the configured gas type. Additionally, or alternatively, the system can identify the gas type of the actual gas. In some cases, a lookup table containing a set of equations can be stored (e.g., by the gas chromatography system or another remote system accessible to the gas chromatography system). The flow measurement signal values ​​can be input into these equations. This can be used to match delta values ​​between sensors and identify the gas type of the carrier gas.

[0097] The following table shows the experimental results of such a comparison. While the inlet was held at a fixed 10 psi column head pressure (i.e., no change in column flow rate), the septum purge flow rate setpoint (using the septum purge sensor) was changed from 3 mL / min to 13 mL / min (a 10 mL / min change), and the resulting first change in the flow measurement signal (flow rate) was measured by the carrier gas supply flow sensor (715 in Figure 7) on the input path. For each of the 16 table entries, the resulting change in the input path flow measurement signal (flow rate) is shown in both absolute error and percentage error terms. Along the diagonal, the configured gas is equal to the actual gas type, and the input path flow measurement signal (flow rate) errors are all within the flow calibration error range of less than 10%. All values ​​not along the diagonal are cases where the configured gas is not the same as the actual gas, and the error is large enough that it can be used to determine the correct calibrated gas type rather than just determining that the gas type is configured incorrectly. For example, when the setting is for helium and the error in the change in the first flow sensor measurement signal is 100 to 140%, it can be determined that the actual gas is hydrogen.

[0098] [Table 1]

[0099] [Comparing input / output flow using delta measurement with bulkhead purge flow turned off] In one embodiment, a gas chromatography system can monitor changes in flow measurement signals from the gas input flow path and the column flow path. Figure 8 illustrates a pneumatic system configured to identify a carrier gas, according to one embodiment of the claimed invention. Pneumatic system 800 can be configured to flow gas into input flow path 840 through gas supply port 805. Pneumatic system 800 can be configured to open valve 810 on the input flow path, thereby allowing gas to flow through valve 810 and carrier gas supply flow sensor 815. Here, carrier gas supply flow sensor 815 can generate a flow measurement signal corresponding to a characteristic of the flowing gas.

[0100] System 800 can be further configured to close split flow path 845 and septum purge flow path 850. For example, the system can be configured such that valves 820 and 825 are closed. Thus, system 800 can limit the flow rate output of gas through column flow path 855. Column flow sensor 860 (e.g., pressure sensor 830 and column restriction 865) can generate a flow rate measurement signal of the gas flowing out of the inlet that corresponds to another characteristic of the flowing gas different from the characteristic of carrier gas supply flow sensor 815.

[0101] The system 800 can measure flow measurement signals from the input and output flow paths. The carrier gas supply flow sensor 815 can generate a first flow measurement signal. The column flow sensor 860 can generate a second flow measurement signal. A microcontroller of the system can receive sensed signals from the carrier gas supply flow sensor 815 and the column flow sensor 860.

[0102] The system 800 can then change the flow rate of the gas originating from the gas supply port 805 via a change to the established gas flow rate setpoint of the column flow rate, as measured by the flow sensor 860. The system can then determine flow measurement signals from the input and column flow paths. The carrier gas supply flow sensor 815 can generate a third flow rate measurement signal, and the column flow sensor 860 can generate a fourth flow rate measurement signal. A microcontroller of the system can receive sensed signals (e.g., raw signals from the sensors) from the carrier gas supply flow sensor 815 and the column flow sensor 860.

[0103] The system can then calculate the difference between a first set of flow measurement signals resulting from the original gas delivery port flow rate and a second set of flow measurement signals resulting from the adjusted gas delivery port flow rate. For example, the gas chromatography system can calculate a first change in the flow measurement signals by taking the difference between a first flow measurement signal resulting from the carrier gas delivery flow sensor 815 and a third flow measurement signal resulting from the carrier gas delivery flow sensor 815. Similarly, the system can calculate a second change in the flow measurement signals by taking the difference between a second flow measurement signal resulting from the column flow sensor 860 and a fourth flow measurement signal resulting from the column flow sensor 860.

[0104] The system can then compare the first change in the flow measurement signal to the second change in the flow measurement signal. From this comparison, the gas chromatography system can determine whether the inlet is configured for the actual gas. If the change in the flow measurement signal (e.g., the delta from the comparison) is substantially the same (accounting for system calibration error), the actual gas is the configured gas type. Additionally, or alternatively, the system can identify the gas type of the actual gas. In some cases, a lookup table containing a series of equations can be stored (e.g., by the gas chromatography system or another remote system accessible to the gas chromatography system). The flow measurement signal values ​​can be input into these equations. These equations can be used to match delta values ​​between the sensors and identify the gas type of the actual gas.

[0105] Figure 9 shows a pneumatic system configured to identify a carrier gas, according to one embodiment of the claimed invention. System 900 can function similarly to system 800 shown in Figure 8 and described above. However, in system 900, valve 910 can be controlled and configured based on measurements received from carrier gas supply flow sensor 915, whereas the valve of system 800 can be controlled and configured based on measurements received from column flow sensor 860.

[0106] [Input / multiple output flow comparison using delta measurement with bulkhead purge flow constant] Similar to Figure 7, the column pressure, and therefore the flow rate, is held constant and the septum purge flow setpoint is changed. Figure 10 shows an embodiment that does the opposite: the septum purge pressure, and therefore the flow rate, is held constant while the column flow setpoint is changed.

[0107] In one embodiment, the gas chromatography system can monitor step changes in flow measurement signals from the gas input flow path 1040 and the column flow path 1045 while the septum purge flow path 1050 is open (e.g., to a fixed pressure and / or flow rate setpoint). FIG. 10 illustrates a pneumatic system configured to identify a carrier gas, according to one embodiment of the claimed invention. The pneumatic system 1000 can be configured to flow gas to the inlet through a gas supply port 1005. The system 1000 can be configured to open a valve 1010 on the input flow path 1040, thereby allowing gas to flow through the valve and a carrier gas supply flow sensor 1015, which can generate a flow measurement signal corresponding to the characteristics of the flowing gas.

[0108] System 1000 can be further configured to close split flow path 1055 (e.g., via valve 1025). Thus, system 1000 can restrict the flow rate output of gas through column flow path 1045 and septum purge flow path 1050. Optionally, septum purge flow sensor 1060 (e.g., pressure sensor 1035 and restriction 1065) can be maintained at a fixed flow rate setpoint, and column flow sensor 1070 (e.g., pressure sensor 1030 and column restriction 1075) can generate a flow measurement signal corresponding to another characteristic of the gas exiting the inlet and flowing. In some cases, a pressure sensor can be used to maintain a constant pressure in the septum purge flow path. At least the column flow sensor 1070 can generate a flow measurement signal using different characteristics than the carrier gas supply flow sensor 1015 (e.g., the column flow sensor 1070 can be viscosity-based using a pressure sensor 1030 that exceeds a limit 1075, while the carrier gas supply flow sensor 1015 can be a thermally dispersed flow sensor).

[0109] The system 1000 can measure flow measurement signals from the input and output flow paths. The carrier gas supply flow sensor 1015 can generate a first flow measurement signal, and the column flow sensor 1070 can generate a second flow measurement signal. A microcontroller of the system can receive sensed signals from the first flow sensor 1010, the septum purge flow sensor 1060 (optional), and the column flow sensor 1070.

[0110] The system 1000 can then vary the flow rate of the gas coming out of the gas supply port. The system 1000 can then measure flow measurement signals from the input, septum purge (optionally), and column flow paths. In some cases, the flow rate in the septum purge flow path can be kept constant, so no flow measurement signal is needed to identify the gas. The carrier gas supply flow sensor 1015 can generate a third flow measurement signal, and the column flow sensor 1070 can generate a fourth flow measurement signal. The system's microcontroller can receive sensing signals from the carrier gas supply flow sensor 1015, the septum purge flow sensor 1060 (optional), and the column flow sensor 1070.

[0111] The system 1000 can then calculate the difference between a first set of flow measurement signals generated during the original gas input flow rate and a second set of flow measurement signals generated during the adjusted gas input flow rate. For example, the system 1000 can calculate a first change in the flow measurement signals by taking the difference between a first flow measurement signal generated from the carrier gas supply flow sensor 1015 and a third flow measurement signal generated from the carrier gas supply flow sensor 1015. Similarly, the system 1000 can calculate a second change in the flow measurement signals by taking the difference between a second flow measurement signal generated from the column flow sensor 1070 and a fourth flow measurement signal generated from the column flow sensor 1070. From this comparison, the system 1000 can determine whether the preset gas is the actual gas. Additionally or alternatively, the system 1000 can identify the type of gas being flowed.

[0112] Figure 11 shows a pneumatic system configured to identify a carrier gas, according to one embodiment of the claimed invention. System 1100 can function in a manner similar to system 1000 shown in Figure 10 and described above. However, in system 1000, valve 1010 can be controlled and configured based on measurements received from carrier gas supply flow sensor 1015, while valve 1110 in system 1100 can be controlled and configured based on measurements received from column flow sensor 1130.

[0113] [Closed-loop feedback] In some cases, the gas chromatography system described above can control the flow rate through a flow path via a closed-loop system. Closed-loop control can be achieved by adjusting a valve in the system based on a flow measurement signal experienced upstream or downstream of the valve being adjusted. For example, valve 310 in FIG. 3 can adjust the flow rate of gas through the gas inlet flow path. Furthermore, the valve adjustment can be based on a flow measurement signal measured by either a column flow sensor or a carrier gas supply flow sensor. Similarly, a second valve on the septum purge flow path can be closed-loop controlled based on a downstream flow rate reading obtained by a septum purge flow sensor (e.g., as in FIG. 5).

[0114] These closed-loop control subsystems are particularly valuable for holding the flow rate setpoint of a particular gas constant while varying the flow rate setpoint of other gases. For example, in the flow measurement change comparison configurations of Figures 7-11, the flow rate of a gas through an input flow path can be adjusted to allow a change in flow rate to be experienced within the system. However, in some cases, it may be beneficial to isolate the gradual change experienced across a single output flow path rather than across multiple output flow paths. Thus, as in the example of Figure 10, the system can reconfigure valve 1020 according to a flow measurement signal obtained by a septum purge flow sensor or simply a septum purge pressure sensor to maintain a constant flow rate through the septum purge flow path as the gas input flow rate is adjusted. Thus, the column flow path may experience a flow rate change, as opposed to both the column and septum purge flow paths.

[0115] It is important to note two important aspects of the original flow setpoint and the second flow setpoint (e.g., delta measurement): First, both can be within the operating range of all flow sensors in the system (e.g., so that sensors do not saturate), and the change in flow setpoint can be large enough so that the calculated percentage error is not significantly affected by system noise.

[0116] It is also important to note that closed-loop control can depend on the gas preset for the system matching the actual gas flowing through the system. For example, a system can specify a flow rate setpoint for a preset gas. However, if the actual gas is not the preset gas, the specified flow rate setpoint may not match the actual flow rate of the gas based on the valve adjustment for the preset gas.

[0117] Furthermore, because the GC systems described herein operate in a split-free mode, the flow rates through the GC system are related to the total column flow rate and the septum purge flow rate (e.g., in some cases, the septum purge flow rate can be set to zero). Therefore, the maximum set point limit for the septum purge flow path (e.g., to avoid sensor saturation) can be 30 mL / min for all gases flowing (or 40 mL / min for a cool-on-column ("COC") inlet). Column flow rates are typically less than 10 mL / min for capillary columns and typically up to 60 mL / min for packed columns.

[0118] [Gas type classification based on thermal diffusivity] Gas chromatography pneumatic systems can be used to identify the type of gas in a system through the gas's thermal properties. For example, the flow sensor can be a thermal dispersion flow sensor, which can heat the gas using an electric heater. This heater can operate at a fixed voltage or current drive (e.g., varying the temperature) or at a fixed temperature (e.g., varying the power), depending on the flow rate and the gas in the sensor. When gas is flowing, the required power (fixed temperature heater) or resulting heater temperature (fixed heater drive) depends on both the thermal conductivity and heat capacity of the gas type. However, in the absence of flow, the required power or resulting heater temperature depends only on the thermal conductivity of the gas (e.g., the gas does not carry heat away, so the heat capacity of the gas is not a factor). Using either heater method, unknown carrier gases can be separated into groups with high thermal conductivity (e.g., a group containing helium and hydrogen) or low thermal conductivity (e.g., a group containing nitrogen and argon-methane). For example, for helium and hydrogen, fixed temperature heaters require more power and fixed voltage heaters operate at lower temperatures than for nitrogen and argon-methane. This division of gas types can be used in conjunction with flow sensors based on viscosity differences between gases to help identify the type of carrier gas being used or as a double check on the gas types identified in the previous discussion.

[0119] [repair] In some cases, the system can perform remediation procedures for the actual gas. For example, the system can identify that the actual gas does not match the system's currently configured gas. Thus, the system can generate and send a message to the user (e.g., via a display screen, wirelessly, etc.) corresponding to the incorrect configuration. In some cases, the system can terminate system operation, protecting the system from damage. In some cases, the system can automatically reconfigure to a different gas configuration.

[0120] [Setting variations] Exemplary embodiments of the present invention are described herein. However, those skilled in the art will appreciate that numerous gas chromatography systems and GC inlets can implement the described techniques. For example, while the above embodiments describe a particular flow sensor, the flow sensor can be coupled to either the carrier gas flow path, the septum purge flow path, the split flow path, or any other flow path in the gas chromatography system. Furthermore, the location where the flow sensor is coupled to a particular flow path can vary as well.

[0121] [Equivalent] While preferred embodiments of the present invention have been described using specific terminology, it is to be understood that such description is for purposes of example only, and that changes and modifications can be made without departing from the spirit or scope of the following claims.

[0122] [Incorporated by reference] The entire contents of all patents, published patent applications, and other references cited herein are hereby incorporated by reference. The claims as originally filed are as follows: Claim 1: a pneumatic system including at least one input fluid line in fluid communication with at least a first output fluid line and a second output fluid line; a first flow sensor disposed on the input flow path configured to generate a flow measurement signal corresponding to a first property of the gas; a second flow sensor disposed on the first output flow path configured to generate a second flow measurement signal corresponding to a second property of the gas that is different from the first gas property; a controller programmed to flow a gas through the pneumatic system, measure a first flow measurement signal of the flow rate of the gas through the pneumatic system from the first flow sensor, measure a second flow measurement signal of the flow rate of the gas through the pneumatic system from the second flow sensor, and identify a type of gas at the flow rate of the gas through the pneumatic system from the first and second flow measurement signals; A gas chromatography system comprising: Claim 2: the microcontroller is further configured to perform a calibration procedure; The calibration procedure comprises: flowing a known type of gas through said pneumatic system; controlling the flow rate of the known type of gas via an external flow controller; correlating the output of the first and / or second flow sensors, or both, to the controlled flow rate; 10. The gas chromatography system of claim 1, comprising: Claim 3: 10. The gas chromatography system of claim 1, further comprising at least one valve disposed along the input flow path, the first output flow path, and / or the second output flow path, wherein the microcontroller is further configured to cause the at least one valve to vary the flow rate through the pneumatic system. Claim 4: 4. The gas chromatography system of claim 3, wherein the at least one valve is disposed along the first output flow path and / or the second output flow path, and the at least one valve is substantially closed. Claim 5: The gas chromatography system of claim 1 , wherein the properties of the gas comprise viscosity and one or more of thermal dispersion, thermal conductivity, and heat capacity. Claim 6: The microcontroller comparing the identified type of gas with a set type of gas; The gas chromatography system of claim 1 , further configured to generate an alert if the identified gas type does not match the configured gas type. Claim 7: The gas chromatography system of claim 1 , wherein the microcontroller is further configured to adjust one or more settings of the gas chromatography system based on the identified gas type. Claim 8: a third flow sensor disposed on the second output flow path, and the microcontroller generating a third flow measurement signal from the third flow sensor; further configured to identify the type of gas in the flow rate of gas through the pneumatic system from the first, second, and third flow rate measurement signals. 10. The gas chromatography system of claim 1. Claim 9: The gas chromatography system of claim 1 , wherein the flow measurement signal is a preset gas flow rate. Claim 10: a third flow sensor disposed on the second output flow path, and the microcontroller generating a third flow rate from the third flow sensor for the assumed preset gas type; summing the second flow rate and the third flow rate; further configured to compare the summed flow rate with the first flow rate and determine whether the assumed preset gas type corresponds to the type of gas flowing through the pneumatic system according to the comparison. 10. The gas chromatography system of claim 9. Claim 11: The microcontroller and determining that the assumed preset gas type corresponds to the type of gas flowing through the pneumatic system based on a difference between the summed flow rate and the first flow rate being less than a threshold value. 11. The gas chromatography system of claim 10. Claim 12: The microcontroller further configured to identify the type of gas in the flow rate of gas through the pneumatic system based on the difference between the summed flow rate and the first flow rate and based on comparing the difference to an expected difference of one or more expected gas types. 11. The gas chromatography system of claim 10. Claim 13: an electric heater in fluid communication with the gas; controlling the electric heater to a predetermined voltage, current, or temperature to heat a portion of the gas; further configured to determine a heater energy for a given heater temperature or a resulting heater temperature for a given heater voltage or current; and identifying the type of gas is further based on either the heater energy or the resulting heater temperature. 10. The gas chromatography system of claim 1. Claim 14: an electric heater in fluid communication with the gas; controlling the electric heater to a predetermined temperature, voltage, or current; determining the heater energy for a given heater temperature or the resulting heater temperature for a given heater voltage or current; dividing said possible gas species into at least two groups based on physical properties; and further configured to determine, from the heater energy or the resulting heater temperature, which of these at least two groups the gas flowing through the pneumatic system belongs to. 10. The gas chromatography system of claim 1. Claim 15: 10. The gas chromatography system of claim 1, wherein the first flow sensor comprises a carrier gas supply flow sensor and the second flow sensor comprises either a column flow sensor or a septum purge flow sensor. Claim 16: a pneumatic system including at least one input fluid line in fluid communication with at least a first output fluid line and a second output fluid line; a first flow sensor disposed on the input flow path configured to generate a flow measurement signal using a first property of the gas; a second flow sensor disposed on the first output flow path, the second flow sensor configured to generate a flow measurement signal using a second property of the gas that is different from the first gas property; a microcontroller programmed to: flow a gas through the pneumatic system to generate a first flow measurement signal from the first flow sensor and a second flow measurement signal from the second flow sensor; vary the flow rate of the gas through the input flow path and the first output flow path while holding the flow rate of the gas through the second output flow path substantially constant; generate a third flow measurement signal from the first flow sensor and a fourth flow measurement signal from the second flow sensor; calculate a first change in the flow measurement signals by taking the difference between the first flow measurement signal and the third flow measurement signal; calculate a second change in the flow measurement signals by taking the difference between the second flow measurement signal and the fourth flow measurement signal; and identify a type of gas by comparing the first change in the flow measurement signals with the second change in the flow measurement signals; A gas chromatography system comprising: Claim 17: The microcontroller is further configured to perform a calibration procedure; The calibration procedure comprises: flowing a known type of gas through said pneumatic system; controlling the flow rate of the known type of gas via an external flow controller; correlating the output of the first and / or second flow sensors to the controlled flow rate; 17. The gas chromatography system of claim 16, comprising: Claim 18: 17. The gas chromatography system of claim 16, further comprising at least one valve disposed along the input flow path, the first output flow path, the second output flow path, or any combination, and wherein the microcontroller is further configured to utilize the valve to vary the flow rate through the pneumatic system. Claim 19: 20. The gas chromatography system of claim 18, wherein the at least one valve is disposed along the first output flow path and / or the second output flow path, and the at least one valve is substantially closed. Claim 20: The microcontroller comparing the identified type of gas with a set type of gas; configured to generate an alert if the identified gas type does not match the configured gas type. 17. The gas chromatography system of claim 16. Claim 21: further comprising an electric heater in fluid communication with the gas; The microcontroller controlling the electric heater to a predetermined voltage, current, or temperature to heat a portion of the gas; further configured to measure heater energy for a given heater temperature or a resulting heater temperature for a given heater voltage or current; the identification of the type of gas is further based on either the heater energy or the resulting heater temperature; 17. The gas chromatography system of claim 16. Claim 22: further comprising an electric heater in fluid communication with the gas; The microcontroller controlling the electric heater to a predetermined temperature, voltage, or current; determining the heater energy for a given heater temperature or the resulting heater temperature for a given heater voltage or current; dividing said possible gas species into at least two groups based on physical properties; and further configured to determine from the heater energy or the resulting heater temperature which of these at least two groups the gas flowing through the pneumatic system belongs to. 17. The gas chromatography system of claim 16. Claim 23: The flow measurement signal is a preset gas flow rate, and the microcontroller: 17. The gas chromatography system of claim 16, further configured to identify the set gas type as the gas type flowing through the pneumatic system when the difference between the first change in the flow measurement signal and the second change in the flow measurement signal is substantially the same within a threshold value. Claim 24: The flow measurement signal is a preset gas flow rate, and the microcontroller: further configured to use the difference between the first change in the flow measurement signal and the second change in the flow measurement signal to identify the gas type by comparing the difference to the difference expected for each calibrated gas type. 17. The gas chromatography system of claim 16. Claim 25: 17. The gas chromatography system of claim 16, further comprising a third flow or pressure sensor disposed on the second output flow path. Claim 26: 17. The gas chromatography system of claim 16, wherein the properties of the gas comprise viscosity and one or more of thermal dispersion, thermal conductivity, and heat capacity. Claim 27: 17. The gas chromatography system of claim 16, wherein the first flow sensor comprises a carrier gas supply flow sensor and the second flow sensor comprises either a column flow sensor or a septum purge flow sensor.

Claims

1. a pneumatic system including at least one input flow path in fluid communication with at least a first output flow path and a second output flow path; a first flow sensor disposed on the input flow path configured to generate a flow measurement signal corresponding to a first property of the gas; a second flow sensor disposed on the first output flow path configured to generate a second flow measurement signal corresponding to a second property of the gas that is different from the first property of the gas; a controller programmed to: flow a gas through the pneumatic system; measure a flow measurement signal from the first flow sensor corresponding to a first characteristic of the gas flow rate of the gas through the pneumatic system; measure a second flow measurement signal from the second flow sensor corresponding to a second characteristic of the gas flow rate of the gas through the pneumatic system; and identify a type of gas in the gas flow through the pneumatic system from the flow measurement signal corresponding to the first characteristic of the gas and the second flow measurement signal; A gas chromatography system comprising:

2. the controller is further configured to perform a calibration procedure; The calibration procedure comprises: flowing a known type of gas through said pneumatic system; controlling the flow rate of the known type of gas via an external flow controller; correlating the output of the first and / or second flow sensors, or both, to the controlled flow rate; The gas chromatography system of claim 1 , comprising:

3. 10. The gas chromatography system of claim 1, further comprising at least one valve disposed along the input flow path, the first output flow path, and / or the second output flow path, and wherein the controller is further configured to cause the at least one valve to vary a flow rate through the pneumatic system.

4. The gas chromatography system of claim 3 , wherein the at least one valve is disposed along the first output flow path and / or the second output flow path, and the at least one valve is substantially closed.

5. The gas chromatography system of claim 1 , wherein the properties of the gas comprise viscosity and one or more of thermal dispersion, thermal conductivity, and heat capacity.

6. The controller comparing the identified type of gas with a set type of gas; The gas chromatography system of claim 1 , further configured to generate an alert if the identified gas type does not match the configured gas type.

7. The gas chromatography system of claim 1 , wherein the controller is further configured to adjust one or more settings of the gas chromatography system based on the identified gas type.

8. a third flow sensor disposed on the second output flow path, the controller generating a third flow measurement signal from the third flow sensor; further configured to identify the type of gas in the gas flow through the pneumatic system from the first, second, and third flow measurement signals. The gas chromatography system of claim 1 .

9. The gas chromatography system of claim 1 , wherein the flow measurement signal is a set gas flow rate.

10. a third flow sensor disposed on the second output flow path, the controller generating a third flow rate from the third flow sensor for the set gas type; summing the second flow rate and the third flow rate; further configured to compare the summed flow rate with the first flow rate and determine whether the preset gas type corresponds to the type of gas flowing through the pneumatic system according to the comparison.

10. The gas chromatography system of claim 9.

11. The controller and determining that the set gas type corresponds to the type of gas flowing through the pneumatic system based on a difference between the summed flow rate and the first flow rate being less than a threshold value. The gas chromatography system of claim 10.

12. The controller further configured to identify a type of gas in the gas flow through the pneumatic system based on a difference between the summed flow rate and the first flow rate and based on comparing the difference to an expected difference of one or more expected gas types. The gas chromatography system of claim 10.

13. an electric heater in fluid communication with the gas; controlling the electric heater to a predetermined voltage, current, or temperature to heat a portion of the gas; further configured to determine a heater energy for a given heater temperature or a resulting heater temperature for a given heater voltage or current; and identifying the type of gas is further based on either the heater energy or the resulting heater temperature. The gas chromatography system of claim 1 .

14. an electric heater in fluid communication with the gas; controlling the electric heater to a predetermined temperature, voltage, or current; determining the heater energy for a given heater temperature or the resulting heater temperature for a given heater voltage or current; dividing the possible gas species into at least two groups based on physical properties; and determining from the heater energy or the resulting heater temperature which of these at least two groups the gas flowing through the pneumatic system belongs to. The gas chromatography system of claim 1 .

15. 10. The gas chromatography system of claim 1, wherein the first flow sensor comprises a carrier gas supply flow sensor and the second flow sensor comprises either a column flow sensor or a septum purge flow sensor.

16. a pneumatic system including at least one input flow path in fluid communication with at least a first output flow path and a second output flow path; a first flow sensor disposed in the input flow path configured to generate a flow measurement signal using a first property of the gas; a second flow sensor disposed on the first output flow path configured to generate a flow measurement signal using a second property of the gas that is different from the first property of the gas; a microcontroller programmed to: flow gas through the pneumatic system to generate a first flow measurement signal from the first flow sensor and a second flow measurement signal from the second flow sensor; vary the flow rate of gas through the input flow path and the first output flow path while maintaining a substantially constant flow rate of gas through the second output flow path; generate a third flow measurement signal from the first flow sensor and a fourth flow measurement signal from the second flow sensor; calculate a first change in the flow measurement signal by taking the difference between the first flow measurement signal and the third flow measurement signal; calculate a second change in the flow measurement signal by taking the difference between the second flow measurement signal and the fourth flow measurement signal; and identify the type of gas by comparing the first change in the flow measurement signal with the second change in the flow measurement signal; A gas chromatography system comprising:

17. The microcontroller is further configured to perform a calibration procedure; The calibration procedure comprises: flowing a known type of gas through said pneumatic system; controlling the flow rate of the known type of gas via an external flow controller; correlating the output of the first and / or second flow sensors to the controlled flow rate; and 17. The gas chromatography system of claim 16, comprising:

18. 17. The gas chromatography system of claim 16, further comprising at least one valve disposed along the input flow path, the first output flow path, the second output flow path, or any combination, wherein the microcontroller is further configured to utilize the valve to vary a flow rate through the pneumatic system.

19. 20. The gas chromatography system of claim 18, wherein the at least one valve is disposed along the first output flow path and / or the second output flow path, and the at least one valve is substantially closed.

20. The microcontroller comparing the identified type of gas with a set type of gas; configured to generate an alert if the identified gas type does not match the configured gas type.

17. The gas chromatography system of claim 16.

21. further comprising an electric heater in fluid communication with the gas; The microcontroller controlling the electric heater to a predetermined voltage, current, or temperature to heat a portion of the gas; further configured to measure heater energy for a given heater temperature or a resulting heater temperature for a given heater voltage or current; the identification of the type of gas is further based on either the heater energy or the resulting heater temperature; 17. The gas chromatography system of claim 16.

22. further comprising an electric heater in fluid communication with the gas; The microcontroller controlling the electric heater to a predetermined temperature, voltage, or current; determining the heater energy for a given heater temperature or the resulting heater temperature for a given heater voltage or current; dividing the possible gas species into at least two groups based on physical properties; and further configured to determine from the heater energy or the resulting heater temperature which of these at least two groups the gas flowing through the pneumatic system belongs to.

17. The gas chromatography system of claim 16.

23. The flow measurement signal is a preset gas flow rate, and the microcontroller:

17. The gas chromatography system of claim 16, further configured to identify the set gas type as the gas type flowing through the pneumatic system when a difference between the first change in the flow measurement signal and the second change in the flow measurement signal is substantially the same within a threshold value.

24. The flow measurement signal is a preset gas flow rate, and the microcontroller: and further configured to use a difference between the first change in the flow measurement signal and the second change in the flow measurement signal to identify the gas type by comparing the difference to an expected difference for each calibrated gas type.

17. The gas chromatography system of claim 16.

25. 17. The gas chromatography system of claim 16, further comprising a third flow or pressure sensor disposed on the second output flow path.

26. 17. The gas chromatography system of claim 16, wherein the properties of the gas comprise viscosity and one or more of thermal dispersion, thermal conductivity, and heat capacity.

27. 17. The gas chromatography system of claim 16, wherein the first flow sensor comprises a carrier gas supply flow sensor and the second flow sensor comprises either a column flow sensor or a septum purge flow sensor.

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