Sample injector for gas chromatograph

Abstract

A sample injector for a gas chromatograph is described, the sample injector comprising: a body defining a sample chamber configured to receive a sample; and a plurality of heating elements, wherein the plurality of heating elements are used for heating the main body. Each heating element of the plurality of heating elements is configured to be controlled independently of each other heating element of the plurality of heating elements. Also described is a method of heating a sample injector for a gas chromatograph, the method comprising providing a plurality of heating elements configured to heat a body of the sample injector; and controlling each of the plurality of heating elements independently of each other of the plurality of heating elements.

Description

Technical Field

[0001] This invention relates to gas chromatography, and more specifically, to a sample injector for a gas chromatograph (GC) and a method of operating the same. Background Technology

[0002] The injector is used to introduce the sample into the chromatographic column within the gas chromatograph. A syringe is used to introduce the sample into the internal cavity of the injector. A heating element is used to heat the injector to heat and vaporize the sample, which can then be transferred to the analytical column located in the gas chromatograph column oven for chromatographic separation.

[0003] An appropriate temperature profile (temperature profile) along the injector is crucial for the precision and accuracy of the analysis, as it determines the proper introduction, vaporization, and transport of the sample. The injector's temperature profile, especially at its extremes, is highly sensitive to external conditions. In particular, the area of ​​the injector in contact with or adjacent to the column oven may become overheated due to the oven's heat when the column oven is at a high temperature, or become undercooled when the column oven is kept at a low temperature.

[0004] Cold spots in the injector can cause sample discrimination (i.e., incomplete transport). Conversely, overheated areas can affect the integrity of the internal surfaces and may lead to sample degradation or adsorption.

[0005] A heating element with a single control may not be able to properly manage the injector's temperature profile, especially when the column oven is performing temperature cycling.

[0006] A gas chromatography column oven assembly is described in US2003 / 0037592A1, the entire contents of which are incorporated herein by reference. An injection port for a gas chromatograph is described in US9632064B2, the entire contents of which are incorporated herein by reference.

[0007] EP1719958A1 addresses the cold spot problem. It discloses a direct heating tube that directly heats a fluid during fluid passage, characterized in that a second heating tube, connected to a first heating tube, is disposed outside the first heating tube in the desired portion to be heated.

[0008] Existing systems may offer limited control options and may not be able to compensate for overheating and / or account for environmental changes. Existing systems may also lack the ability to change the injector temperature profile during different operational phases.

[0009] The present invention aims to provide an improved sample injector for a gas chromatograph, and a method for heating the sample injector for a gas chromatograph to overcome the formation of undesirable cold spots or hot spots. Another object is to provide a sample injector in which the temperature of different regions of the injector can be modified throughout its operation or at specified operational stages to optimize injection performance and to allow the operation of the injector to be customized according to the type of sample to be analyzed. Summary of the Invention

[0010] According to a first aspect of this disclosure, a sample injector for a gas chromatograph is provided, the sample injector comprising: The body, which defines a sample chamber configured to receive a sample; and Multiple heating elements are used to heat the main body; Each of the plurality of heating elements is configured to be controlled independently of each of the other heating elements.

[0011] The sample injector may further include one or more of the following features: The body may include multiple regions, and the multiple heating elements may be configured such that each of the multiple heating elements is configured to heat a different region within the multiple regions. The sample injector may be configured to heat one of the multiple regions to a temperature different from one or more other regions within the multiple regions during at least one operational phase of the sample injector. The body may be an elongated tube defining a longitudinal axis, having an inlet end and a downstream end along the longitudinal axis away from the inlet end; wherein the multiple regions include an inlet region disposed at or near the inlet end of the body and a downstream region disposed at or near the downstream end of the body. The multiple heating elements may include an inlet heating element disposed to heat the inlet region. The multiple heating elements may include a downstream heating element disposed to heat the downstream region.

[0012] The plurality of regions may include an intermediate region disposed between the inlet region and the downstream region; and the plurality of heating elements may include one or more intermediate heating elements disposed to heat the intermediate region.

[0013] The sample injector can be configured to change the temperature of at least one of the plurality of regions during at least one operating phase of the sample injector. The sample injector may include multiple phases, and changing the temperature of at least one of the plurality of regions during at least one operating phase of the sample injector may include setting a setpoint temperature for the region during each of the plurality of phases.

[0014] The multiple heating elements can be arranged in series along the main body.

[0015] Each of the plurality of heating elements may be arranged adjacent to or around the corresponding area of ​​the plurality of regions.

[0016] Each of the plurality of heating elements may include a heatable coil arranged around the body; wherein, optionally, the coil density of one or more of the plurality of heating elements varies along the length of the body.

[0017] The sample injector may further include a plurality of housings, each of which is arranged around one of the plurality of heating elements and a corresponding region of the plurality of regions; wherein optionally, the plurality of housings are arranged in series along the body.

[0018] The sample injector may include a controller configured to independently control each of the plurality of heating elements based on a parameter indicating the temperature of the region in which the heating element is configured to be heated.

[0019] The sample injector may include multiple temperature sensors, each of which is arranged adjacent to one of the multiple regions.

[0020] The parameters indicating the temperature of this area include one or more of the following: The current in the heating element; The temperature of the heating element measured using the corresponding temperature sensor among multiple temperature sensors; and The temperature of the area is measured using the corresponding temperature sensor among multiple temperature sensors.

[0021] Each of the plurality of heating elements can be configured to be energized independently of each of the other heating elements.

[0022] According to a second aspect of this disclosure, a gas chromatograph assembly including a sample injector according to this disclosure is provided.

[0023] According to a third aspect of this disclosure, a method for heating a sample injector for a gas chromatograph is provided, the method comprising: Provided multiple heating elements configured to heat the body of the sample injector; and Each of the plurality of heating elements is controlled independently of each of the other heating elements.

[0024] The method may further include one or more of the following features: The body may include multiple regions, wherein each of the multiple heating elements is configured to heat a different region within the multiple regions. The method may include changing the temperature of at least one of the multiple regions during at least one operational phase of the sample injector. Operation of the sample injector may include multiple phases, and changing the temperature of at least one of the multiple regions during at least one operational phase of the sample injector may include setting a setpoint temperature for the region during each of the multiple phases.

[0025] The method may include heating one of the plurality of regions to a temperature different from that of one or more other regions of the plurality of regions during at least one operating phase of the sample injector.

[0026] The method may include measuring a first parameter indicating the temperature of a first region among a plurality of heating elements, and controlling a first heating element among the plurality of heating elements to heat the first region to one or more temperature setpoints; wherein measuring the parameter indicating the temperature of the first region may optionally include measuring the current in the first heating element, measuring the temperature of the first heating element using a temperature sensor, and / or measuring the temperature of the first region using a temperature sensor. The first region may be an inlet region of the body, and the first heating element is an inlet heating element. The method may include controlling the inlet heating element to heat the inlet region during the sample introduction phase when the sample is introduced into the sample injector.

[0027] The method may include one of the following: i) Selectively control the inlet heating element to heat the inlet region to the following temperature during the injection phase: The high temperature set point at which the sample can be completely evaporated; and / or Low temperature set point; or ii) Control the inlet heating element to maintain the temperature of the inlet region at the low-temperature set point throughout the operation of the sample injector.

[0028] The method may include: i) Controlling the inlet heating element to heat the inlet region to a high-temperature setpoint where the sample can be completely evaporated during the sample introduction phase into the sample injector; and ii) Control the inlet heating element so that the temperature of the inlet region decreases from the high-temperature setpoint to the low-temperature setpoint. Step ii) may occur either immediately after the evaporation phase in which the sample is evaporated and transported by the carrier gas to the gas chromatography column, or after a predetermined period of time after the completion of the evaporation phase.

[0029] The method may include measuring a second parameter indicating the temperature of a second region among the plurality of heating elements; and independently controlling a second heating element among the plurality of heating elements to heat the second region to one or more temperature setpoints; wherein measuring the parameter indicating the temperature of the second region may optionally include measuring the current in the second heating element, measuring the temperature of the second heating element using a sensor, measuring the temperature of the second region using a sensor, and / or measuring the column oven temperature using a sensor. The second region may be a downstream region of the body, and the second heating element may be a downstream heating element. Optionally, the second heating element may be maintained at a high temperature setpoint at which the sample can be completely vaporized throughout the operation of the sample injector.

[0030] The method may include measuring a third parameter indicating the temperature of a third region among the plurality of regions, and independently controlling a third heating element among the plurality of heating elements to heat the third region to one or more temperature setpoints; wherein measuring the parameter indicating the temperature of the third region may optionally include measuring the current in the third heating element, measuring the temperature of the third heating element using a sensor, and / or measuring the temperature of the third region using a sensor.

[0031] The third region may be the middle region of the main body, and the third heating element may be an intermediate heating element; optionally, the third heating element may be maintained at a high temperature set point at which the sample can be completely evaporated throughout the operation of the sample injector.

[0032] The method may include initially controlling the plurality of heating elements to heat each of the plurality of regions to a low-temperature setpoint; and after the sample has been introduced into the sample injector, controlling the plurality of heating elements to heat each of the plurality of regions to a high-temperature setpoint where the sample can be completely evaporated, until the sample has evaporated. The method may further include, during the gas chromatograph run phase following sample evaporation, controlling an intermediate heating element among the plurality of heating elements to heat an intermediate region among the plurality of regions to a high-temperature setpoint; and / or, during the gas chromatograph run phase, controlling an inlet heating element among the plurality of heating elements such that the inlet region among the plurality of regions is not heated. The method may further include measuring a parameter indicating the column oven temperature of the gas chromatograph, and, depending on the measured parameter, performing one of the following: during the gas chromatograph run phase following sample evaporation, controlling a downstream heating element among the plurality of heating elements to heat a downstream region among the plurality of regions to a high-temperature setpoint; or, during the gas chromatograph run phase, controlling a downstream heating element among the plurality of heating elements such that the downstream region among the plurality of regions is not heated.

[0033] Controlling each of the plurality of heating elements may include dynamically controlling each heating element, for example, in response to one or more external temperature changes.

[0034] In any of the methods disclosed herein, the sample injector may be any sample injector according to this disclosure. Attached Figure Description

[0035] Embodiments of this disclosure will now be described by way of example only, with reference to the following non-limiting drawings, in which: Figure 1 It is a schematic diagram of a gas chromatograph including a sample injector according to the present disclosure; Figure 2 This is a schematic cross-sectional view showing a first sample injector according to the present disclosure; Figure 3 It is shown Figure 2 A schematic cross-sectional view of the sample injector in use; and Figure 4 This is a schematic diagram showing a second sample injector according to the present disclosure; Figure 5 Is with Figure 4 A schematic cross-sectional view of a sample injector of the same type shown. Detailed Implementation

[0036] Figure 1 A schematic diagram of a gas chromatograph 40 including a sample injector 1 according to the present disclosure is shown. The sample injector 1 is fluidly connected via a tubing 42 to a gas chromatography (GC) column 43 disposed within a column oven 41. The tubing 42 is fluidly coupled to or forms part of the gas chromatography column 43 of the gas chromatograph 40. A controller 44 is provided for controlling the sample injector 1 and / or the gas chromatograph 40.

[0037] To perform scientific analysis within column 43, material sample 45 (typically in liquid form) is injected into sample injector 1 along with a carrier gas (also known as the mobile phase). The sample is heated by sample injector 1 and injected into column 43 of column oven 41, which separates sample 45 into its individual components. These individual components then flow out through outlet port 46 for analysis, such as by mass spectrometry.

[0038] Figure 2 and Figure 3 A schematic diagram of a first sample injector according to a non-limiting embodiment of the present disclosure is shown. The sample injector may be, for example, a programmed temperature vaporization (PTV) injector.

[0039] The sample injector 1 includes a body 10 that defines a sample chamber 11 configured to receive a sample. Figure 2As shown, the main body 10 may be in the form of an elongated tube defining a longitudinal axis 15. The main body 10 has an inlet end 12 and a downstream end 13, with the downstream end 13 located away from the inlet end 12 along the longitudinal axis 15.

[0040] A septum 50 may be disposed at the inlet end 12 of the body 10 for receiving a sample, for example, by delivering a liquid sample to the sample chamber 11 by passing a syringe needle through the septum 50. A liner 11a may be disposed within the sample chamber 11, and the sample is contained within the liner 11a during use. The downstream end 13 of the injector may include an injection portion 14 for being contained within the gas chromatograph 40 during use, for example... Figure 2 and Figure 3 The example shown.

[0041] like Figure 2 As shown, the body 10 of the sample injector 1 may include multiple regions, including an inlet region 20a arranged near the inlet end 12 of the body, a downstream region 20c arranged near the downstream end 13 of the body, and an intermediate region 20b arranged between the inlet region 20a and the downstream region 20c.

[0042] The sample injector 1 includes a plurality of heating elements for heating the body 10. Each of these heating elements is configured to be controlled independently of each of the other heating elements. For example, each of the heating elements can be configured to be energized independently of each of the other heating elements. Figure 2 In the embodiment shown, the sample injector 1 includes three heating elements.

[0043] The plurality of heating elements can be configured such that each of the plurality of heating elements is configured to heat a different area of ​​the plurality of regions, for example by arranging them around or adjacent to corresponding areas of the plurality of regions.

[0044] like Figure 2 and Figure 3 As shown, the plurality of heating elements may include an inlet heating element 30a arranged to heat the inlet region 20a, a downstream heating element 30c arranged to heat the downstream region 20c, and an intermediate heating element 30b arranged to heat the intermediate region 20b. Figure 2 As shown, the plurality of heating elements can be arranged in series along the main body 10 (i.e., in series along the direction aligned with the longitudinal axis 15 of the main body 10).

[0045] exist Figure 2 and Figure 3 In this embodiment, each of the heating elements is a heatable coil arranged around the body 10. In this embodiment, the coil density of the heating elements is uniform along the longitudinal length of the body 10.

[0046] Sample injector 1 may include controller 44 (see Figure 1 The controller is configured to independently control each of the plurality of heating elements. For example... Figure 2 As shown, multiple temperature sensors can be provided. Each of these multiple temperature sensors 31a, 31b, 31c can be configured to be arranged adjacent to or in contact with a corresponding area of ​​the multiple regions, such that the controller 44 can be configured to monitor the temperature of each of the multiple regions 20a, 20b, 20c respectively. The controller 44 can be configured to control the current applied to each of the heating elements 30a, 30b, 30c based on the input of the corresponding temperature sensor arranged adjacent to each region. The temperature sensor may be a thermocouple.

[0047] In another embodiment, the gas chromatograph includes a sample injector 1 according to the present disclosure. Figure 3 It shows Figure 2 The sample injector 1 is used as part of the gas chromatograph 40. During use, the injection section 14 of the injector 1 is housed within the column oven of the gas chromatograph 40. The sample can be transferred from the injector 1 to the gas chromatographic column 43, the upper part of which is arranged within the injection section 14 of the main body. Figure 3 As shown, a forced air cooling device 3 can be installed around the injector body 1 to further control the temperature of the injector 1.

[0048] Figure 4 and Figure 5 A schematic diagram of a second sample injector 101 according to another non-limiting embodiment of this disclosure is shown. The differences between the second sample injector and the first sample injector will be described below. All other features of this additional embodiment may be as described above. The second sample injector may be a split / splitless (SSL) injector.

[0049] like Figure 4 and Figure 5 As shown, the sample injector 101 may include multiple housings and multiple temperature sensors. Each of the multiple heating elements 130a, 130b, 130c of the sample injector 101 may include a cylindrical or columnar resistor arranged adjacent to and extending along the area of ​​the body 10 to be heated by the heating element. Each of the multiple housings 132a, 132b, 132c may be in the form of a generally tubular block including an internal cavity, arranged around the body 110 of the injector (e.g., ...). Figure 4 and Figure 5The embodiment shown is configured to house heating elements 130a, 130b, and 130c, regions 20a, 20b, and 20c within the body 10 to be heated by the heating elements, and one of the multiple temperature sensors 131a, 131b, and 131c, all substantially enclosed by a housing. The multiple housings and the multiple heating elements may be arranged in series along the body 10. The arrangement and configuration of the multiple heating elements and / or the multiple temperature sensors may be as described above.

[0050] This disclosure also provides a method for heating a sample injector for a gas chromatograph, the method comprising providing a plurality of heating elements configured to heat the body of the sample injector; and controlling each of the plurality of heating elements independently of each of the other heating elements. The sample injector may be any sample injector 1, 101 according to this disclosure.

[0051] The method may include measuring parameters indicating the temperature of a first region of the indicating bodies 10, 110, and controlling a first heating element among the plurality of heating elements to heat the first region to one or more temperature setpoints. Measuring parameters indicating the temperature of the first region may include measuring the current in the first heating element, measuring the temperature of the first heating element using temperature sensors 31a, 131a, and / or measuring the temperature of the first region using first temperature sensors 31a, 131a. The temperature sensors may be any temperature sensors described herein.

[0052] The first region may be the inlet region 20a of the main body 10, and the first heating element may be the inlet heating element 30a, 130a. The method may further include controlling the inlet heating elements 30a, 130a to heat the inlet region during the sample injection phase when the sample is injected into the sample injector.

[0053] The method may further include measuring a second parameter indicating the temperature of a second region of the body, and independently controlling a second heating element among the plurality of heating elements to heat the second region to one or more temperature setpoints. The parameter for measuring the temperature of the second region may include measuring the current in the second heating element, measuring the temperature of the second heating element using second temperature sensors 31c and 131c, measuring the temperature of the second region using second temperature sensors 31c and 131c, and / or measuring the temperature of the column oven using sensors. The second region may be a downstream region 20c of the body 10, and the second heating element may be a downstream heating element 30c or 130c.

[0054] The method may further include measuring a third parameter indicating the temperature of a third region of the indicating bodies 10 and 110, and independently controlling a third heating element among the plurality of heating elements to heat the third region to one or more temperature setpoints. Measuring the parameter indicating the temperature of the third region may include measuring the current in the third heating element, measuring the temperature of the third heating element using third temperature sensors 31b and 131b, and / or measuring the temperature of the third region using third temperature sensors 31b and 131b. The third region may be an intermediate region 20c of the body 10, and the third heating element may be an intermediate heating element 30c or 130c.

[0055] In use, as external conditions change, the plurality of heating elements can be controlled to maintain a predetermined temperature profile in one or more regions of the bodies 10, 110. For example, when the temperature of the gas chromatograph column oven rises and there is heat transfer from the gas chromatograph column oven to an adjacent region (i.e., downstream region 20c) of the injector, the corresponding heating element can be controlled to lower its temperature, thereby maintaining the temperature setpoint in that region of the body 10. Optionally, the heating elements can be controlled at least in part based on the output of a sensor configured to measure the internal temperature of the column oven.

[0056] These multiple heating elements can also be controlled according to a time program, in which a temperature setpoint is set for each heating element in each of the multiple operating stages of the sample injectors 1 and 101. The operating stages of the sample injectors can be as follows: - "Standby" phase: During this phase, the gas chromatography system is idle, and some operating parameters may differ from the sample injection and analysis setpoints. - The "Ready" stage is where the method parameters for the gas chromatography system are set. Once these parameters are met, the gas chromatography system is ready for operation.

[0057] - The "sample introduction" stage, in which the sample is physically introduced into the sample injector.

[0058] - The "evaporation" stage, in which the sample is evaporated and transported by the carrier gas into the gas chromatography column. The "injection" stage and the "evaporation" stage can be separate sequential stages. Alternatively, the "injection" stage and the "evaporation" stage can overlap or be performed simultaneously.

[0059] - The "GC run" phase, in which the sample undergoes chromatographic separation through the column. This phase is defined herein with reference to the temperature setting of the heating element. Those skilled in the art will understand that chromatographic separation of the sample can begin during the evaporation phase.

[0060] - The "post-run" phase, during which the gas chromatography system is restoring its initial operating parameters.

[0061] In any embodiment of this disclosure, one or more of the plurality of heating elements may be controlled during each operating phase to heat a corresponding region of the body to one or more temperature setpoints (i.e., target temperatures). These one or more temperature setpoints may vary between samples. The temperature setpoints may be set based on the following: - For high-temperature setpoints, the temperature is at or above the predetermined temperature; or - For low temperature setpoints, the temperature is at or below the predetermined temperature.

[0062] The predetermined temperature can be determined based on the composition of the sample mixture, solvent, or injector components. For example, it can be the boiling point temperature or a temperature suitable for complete evaporation of one of the sample, sample components, or solvents used in combination with the sample for injection into the injector. For example, a “low temperature setpoint” can be defined as a setpoint below the boiling point of the solvent or below the boiling point of the sample mixture. In hot needle technology, the low temperature setpoint can be selected as a temperature that minimizes the degassing of siloxanes in the septum, such as a temperature setpoint at or below 100 degrees Celsius. A “high temperature setpoint” can be defined as a temperature sufficient to allow complete evaporation of the sample. A high temperature setpoint can be a temperature high enough within a reasonable time frame to allow complete evaporation of the sample. A high temperature setpoint can be higher than the boiling point of the solvent or the boiling point of the sample mixture. If some components of the sample can be completely evaporated below their boiling point within a reasonable time frame, the high temperature setpoint can be lower than the boiling points of those components. A reasonable time frame can be a period of time that will not significantly prolong the normal operating time of the gas chromatograph and / or will not affect the required separation efficiency for analyzing the sample, as will be understood by those skilled in the art. This is typically in the order of several minutes, such as less than 5 minutes, less than 3 minutes, less than 1 minute, or 1 to 3 minutes. For the injectors described herein with PTV or SSL injectors, this is typically 1 to 3 minutes.

[0063] The following provides non-limiting examples of how the sample injector of this disclosure can be controlled during use.

[0064] In the first example, the sample injector is a PTV injector, such as... Figure 2 and Figure 3 The embodiment shown is described below. The injector operates in a programmed temperature mode, controlling the plurality of heating elements during each operation phase as shown in Table 1 below to heat the corresponding region of the body 10 to one or more temperature setpoints. In the following text, "T setpoint" means "temperature setpoint".

[0065] As shown in Table 1, each of the plurality of heating elements can be controlled during the sample injection phase, so that regions 20a, 20b, and 20c of the body 10 are maintained at a low temperature setpoint to avoid any evaporation during sample injection (thus avoiding sample discrimination). In sample 45 (see...) Figure 1 After the sample is injected into injectors 1 and 101, the intermediate heating element among the multiple heating elements can be heated to a high temperature set point to completely evaporate the sample and allow it to be transferred to the analytical column during the sample evaporation stage.

[0066] Once sample 45 has been transferred to column 43, inlet region 20a can be cooled or allowed to cool, for example by not heating inlet heating elements 30a, 130a, in order to protect the septum from degradation caused by high temperature (thereby reducing the release of siloxanes that may be present in the septum 40 material into the analytical system).

[0067] Table 1: Temperature setpoints for the inlet, middle, and downstream regions of the PTV injector

[0068] The downstream region 20c of injectors 1 and 101 can also be cooled, or allowed to be cooled, for example by not heating the downstream heating elements 30c and 130c, in order to protect the adjacent part of the GC column 43 (a part of which is housed inside the injector) from overheating, since this part of the injector is also indirectly heated by the GC column oven 41.

[0069] During the GC run, the middle region of the injector can be kept at a high temperature to bake the liner 11a of the sample chamber 11 (i.e., heating the liner 11a in the absence of sample 45 to remove residue), thereby reducing the carryover effect (contamination from residue of previous run samples) and without affecting the inlet region 20a and septum 50, and / or downstream region 20c and the upper part of the GC column 43.

[0070] Variations of the temperature setpoint shown in the first example are illustrated in Table 1A below.

[0071] Table 1A: Temperature setpoints for the inlet, middle, and downstream regions of the PTV injector

[0072] For example, as shown in Table 1A, the GC run phase may include an initial GC run phase and a final GC run phase. Throughout the sample injector operation, the GC column oven may be at a low temperature, except during the final GC run phase, during which the GC column oven temperature may be at a high temperature. In any embodiment of the invention, the power level supplied to each of the plurality of heating elements during each phase may correspond to the temperature setpoint of the corresponding region of the injector (e.g., when setting a high temperature setpoint for a region, a corresponding high heating power level may be provided to the heating element). At any phase in any embodiment, when the GC column oven temperature is high, a high temperature setpoint may be achieved by providing low power to the corresponding heating element. Using a low power setting can compensate for the heating effect from the high-temperature GC column oven, thereby avoiding overheating of the relevant region. Therefore, in the example shown in Table 1A, during the final GC run phase, the temperature setpoint of the downstream region 20c may be high, but low power may be provided to the downstream region heating element to achieve the downstream region temperature setpoint and avoid overheating of the downstream region.

[0073] In embodiments where sample injectors 1 and 101 are SSL injectors, the plurality of regions may include an inlet region 20a, and the plurality of heating elements may include inlet heating elements 30a and 130a arranged to heat the inlet region 20a. In such embodiments, sample injectors 1 and 101 may be operated according to either a "cold needle technique" or a "hot needle technique" to introduce a sample into injectors 1 and 101. In the cold needle technique, sample 45 is introduced into injectors 1 and 101 in liquid form, and evaporates once sample 45 enters the sample chamber. For this technique, the temperature of the syringe needle used to introduce sample 45 into injectors 1 and 101 must be maintained below the solvent boiling point temperature during the introduction of sample 45 into injectors 1 and 101; therefore, the inlet region 20a of injectors 1 and 101 must be maintained at a low temperature. In the hot needle technique, the inlet region 20a of the injector is heated to a sufficiently high temperature set point to achieve complete evaporation of the sample, and the sample is injected into the injector in the form of a hot spray (i.e., the injection and evaporation phases overlap or occur simultaneously).

[0074] In the second and third examples described below, the sample injector is an SSL injector, for example... Figure 4 and Figure 5 The sample injector 101 in the illustrated embodiment. A plurality of heating elements 130a, 130b, 130c are configured and controlled to heat corresponding regions 20a, 20b, 20c of the body 10 to one or more temperature setpoints during each operation phase, as described below.

[0075] In the second example, the sample injector 101 can be operated using cold needle technology, wherein the temperature setpoint of each of the plurality of regions of the body 10 is maintained throughout the process as follows: -Inlet area 20a-Low temperature setpoint; -Middle area 20b-High temperature setpoint; and -Downstream region 20°C -High temperature setpoint.

[0076] In a variant of the second example, the temperature setpoint of the downstream region can vary during the GC operation phase. For example, the downstream heating element can be dynamically controlled in response to external temperature changes, such as the GC column oven temperature. The temperature setpoint of the downstream region can be high or low, or the downstream region can be unheated, thereby minimizing cold spots and / or overheating in the downstream region.

[0077] In the third example, the sample injector 101 can be operated using hot needle technology, wherein the temperature setpoint of each of the plurality of regions can be maintained at a high temperature setpoint, or it can be controlled according to the timing mode shown in Table 2 below.

[0078] Table 2: Temperature setpoints for the inlet, middle, and downstream regions of the SSL injector using a heated needle injection system

[0079] In both technologies, the intermediate heating element 130b and the downstream heating element 130c can be maintained at a high temperature setpoint throughout the process.

[0080] In hot needle technology, during the sample introduction / evaporation phase, inlet heating elements 30a and 130a heat the inlet region 20a to a sufficiently high temperature setpoint to achieve complete sample evaporation. Therefore, the sample introduction and evaporation phases can overlap or occur simultaneously. The inlet heating elements 30a and 130a can heat the inlet region 20a to the high temperature setpoint for a predetermined time period until sample transfer is complete. This predetermined time period can be approximately in the range of 0.5–5 minutes.

[0081] Since the inlet heating elements 30a and 130a can be controlled (e.g., via the sample injector or the controller 44 of the gas chromatograph (see...) Figure 1 The inlet region 20a can be selectively heated to either a high-temperature or low-temperature setpoint, thus allowing the same sample injector to be selectively used for either cold or hot needle techniques. Since the temperature setpoint of the inlet region 20a can be lowered shortly after the injection phase, the sample injectors 1, 101 of this disclosure also avoid the disadvantages of continuous heating of the inlet region 20a found in hot needle injectors. Sustained high temperatures in the inlet region 20a can lead to degradation of the septum 50 material, potentially causing siloxane contamination of the system from the septum material.

[0082] Although embodiments of this disclosure have been described above and illustrated in the accompanying drawings, these are merely examples and are not intended to be limiting. Those skilled in the art will understand that alternatives are possible within the scope of this disclosure. For example, the sample injector, gas chromatograph, and method of this disclosure may include any combination of the following features.

[0083] In any embodiment, each of the plurality of heating elements can be controlled such that the temperature profile of the sample injector is variable both spatially and temporally. Spatially varying the temperature profile may include individually controlling each of the plurality of heating elements and configuring them to heat different regions within a plurality of regions of the sample injector. Temporally varying the temperature profile may include making the temperature of each heating element variable during sample injector operation. For example, a setpoint temperature may be set for each region of the sample injector at each stage of sample injector operation, and the heating elements may be individually controlled to heat the corresponding region to the setpoint temperature at each stage. The temperature setpoint for each region may be the same at each stage, or it may vary during at least one of the plurality of stages.

[0084] In any embodiment, each of the plurality of heating elements can be controlled such that its temperature varies over time. For example, for each of the plurality of operating stages of the sample injector, the temperature of each heating element can be set to a selected setpoint. This can be achieved by independently controlling each of the plurality of heating elements during each stage.

[0085] In any embodiment, each of the plurality of heating elements can be dynamically controlled during sample injector operation. For example, each of the plurality of heating elements can be dynamically controlled in response to changes in external temperature. Dynamic control of the heating elements may include modifying the temperature setpoint during injector use, for example, in response to changes in column oven temperature, and / or may include increasing or decreasing the power of the heating element. Dynamic control of the heating elements may include increasing or decreasing the temperature of the heating element (e.g., by increasing or decreasing the power of the heating element) to achieve a desired temperature setpoint for a corresponding region, for example, in response to changes in column oven temperature. External temperature changes may include, for example, the temperature of a GC column oven or room temperature. One or more sensors may be provided to measure external temperature changes. By dynamically controlling the heating elements, the sample injector and method of the present invention can minimize the possibility of so-called cold spots and / or overheated regions in the sample injector.

[0086] The body of the sample injector may be generally elongated and define a longitudinal axis. The plurality of heating elements may be arranged in series along the body such that the heating elements do not overlap along the longitudinal axis of the body. Alternatively, the ends of one or more heating elements may overlap with the ends of adjacent heating elements.

[0087] In the illustrated example, the sample injector includes three heating elements. In any embodiment of this disclosure, the sample injector may include two or more heating elements, or at least three heating elements. For example, the sample injector may include only one inlet heating element and one downstream heating element. Alternatively, the sample injector may include one inlet heating element, one downstream heating element, and one or more intermediate heating elements; that is, the plurality of regions may include any number of intermediate regions, each intermediate region being provided with a corresponding heating element from the plurality of heating elements.

[0088] The inlet region can be the portion of the organism that is furthest from the gas chromatograph during use. The downstream region can be the portion of the organism that is closest to the gas chromatograph during use. The intermediate region can be defined as any portion of the organism located between the inlet region and the downstream region.

[0089] In embodiments of this disclosure, each of the plurality of heating elements is configured to heat a single corresponding region within the plurality of regions (i.e., a region different from the region heated by any other heating element in the plurality of heating elements). Each of the plurality of heating elements is configured such that the temperature of each heating element can be controlled independently of the temperatures of any and all other heating elements in the plurality of heating elements. However, in use, any two or more of the plurality of heating elements can be controlled to have the same temperature.

[0090] The heating element may be in the form of a heating coil arranged around the body of the injector, such that the area of ​​the body to be heated is located inside the coil that heats that area; alternatively, each of the plurality of heating elements may be in the form of a resistor arranged adjacent to the corresponding area of ​​the body to be heated. The resistor may be cylindrical or cylindrical.

[0091] In any embodiment where the heating element is a heatable coil, the coil density of the heatable coil may be uniform, or alternatively, the coil density of one or more heating elements may vary along the length of the body (e.g., in a direction generally aligned with the longitudinal axis of the body). For example, the coil density of the inlet heating element may be higher than that of the downstream heating element to provide a higher heating quantity to compensate for the relatively low ambient temperature in the inlet region, since the inlet region is located at the furthest point from the column oven.

[0092] The heating element can be made of a metallic material, such as a metal alloy, for example, an Fe-Cr-Al alloy. The body can be made of stainless steel and may include a glass or metal liner arranged to line the sample chamber.

[0093] Each of the plurality of heating elements may have a uniform length (e.g., length relative to the longitudinal axis of the body). Alternatively, one or more of the plurality of heating elements may have a length different from one or more of the other heating elements. For example, the plurality of heating elements may include: - An inlet heating element that extends longitudinally along approximately one-quarter of the body of the injector; - One or more intermediate heating elements, which may extend longitudinally about halfway along the body of the injector; and / or - Downstream heating element, which extends longitudinally along approximately one-quarter of the body of the injector.

[0094] In any embodiment, the sample can be a liquid, solid, or gaseous sample. The sample can be a mixture of samples. In use, the sample is typically combined with a liquid solvent for injection into a sample injector.

[0095] The sample injector may include a controller configured to measure a parameter indicating the temperature of a region within the plurality of regions of the body, and to derive the temperature of that region based on the parameter. This parameter may be, for example, a current applied to a corresponding heating element, an input from a temperature sensor located adjacent to that region of the body, or an input from a temperature sensor located adjacent to the heating element. The controller may control the heating element corresponding to that region based on the derived temperature, for example, by controlling the current applied to the heating element.

[0096] Each temperature sensor may be arranged outside the body and adjacent to (optionally in contact with) the corresponding area of ​​the body (i.e. the area where the temperature is determined based on the sensor).

[0097] The sample injectors in the illustrated embodiments are described as PTV or SSL injectors. These injector types are merely examples and are not limiting. Any type of injector can be used in any embodiment, particularly in conjunction with any of the control methods or procedures described above. For example, a multi-mode injector can be used.

[0098] These multiple heating elements are heated by an electric current flowing through them and regulated by voltage control. In direct heating techniques, the correlation between the heating element current and temperature for each element can be obtained through calibration. In this case, the temperature is not directly measured but derived from the current used. Alternatively, the temperature of each heating element can be controlled by measuring the temperature of a corresponding area of ​​the body using a temperature sensor. The injector heater is heated by current circulation, but the control of the current is based on temperature feedback measured by a temperature sensor.

[0099] A forced air cooling device can be installed around the injector body to further control the injector temperature.

[0100] The high-temperature setpoint can be in the range of 180 to 350 degrees Celsius. For example, for the SSL injector, the high-temperature setpoint can be between 180 and 320 degrees Celsius, and / or for the PTV injector, the high-temperature setpoint can be between 280 and 350 degrees Celsius.

[0101] The low temperature setpoint can be below 100 degrees Celsius.

[0102] The sample injector may be configured to heat one of the plurality of heating elements to a temperature different from that of one or more other heating elements during at least one phase of operation of the sample injector. The sample injector may include a controller configured to control the heating elements in such a manner.

[0103] As described herein, each of the plurality of heating elements is configured to heat a different area within the plurality of regions. The terms “corresponding area” and “corresponding heating element” as used herein refer to the area to which a particular heating element is configured to heat, and conversely, the heating element that heats a particular area. Heating elements may be configured to heat corresponding areas within the plurality of regions by arranging heating elements around or adjacent to corresponding areas.

[0104] As used herein, unless otherwise stated, references to heating a region “during” a particular operational phase mean heating that region throughout the entire phase.

[0105] The sample injector may include a septum disposed at the inlet end of the body for receiving the sample passing through it. A septum cap may be disposed at the inlet end for connecting the sample chamber to a sample purge line, a split line, a carrier gas inlet, and / or similar connections. The downstream end of the sample injector may include an injection section that is housed within a column oven during use.

[0106] Any embodiment of the sample injector according to the present invention may be provided as part of a gas chromatograph. Any sample injector of this disclosure may be configured to perform methods according to the present disclosure; for example, the sample injector may include a controller configured to control a heating element according to the methods of the present disclosure.

[0107] In any embodiment, the gas chromatograph or sample injector may include a controller configured to perform the methods described herein.

[0108] By independently controlling the temperature of multiple heating elements, each arranged to heat a corresponding area of ​​the injector body, the temperature of each area of ​​the body can be controlled more precisely, allowing for different heating of different areas. This avoids, for example, cold spots and overheated areas in the body, and thus also avoids cold spots and overheated areas in the sample chamber defined by the body.

[0109] Individual control of the heating element means that the temperature of each distinct region of the body, and therefore the temperature of the sample chamber defined by the body, can be precisely controlled and varied between regions. This allows the controller to compensate for temperature variations and ensure that the temperature is as uniform as possible to avoid cold spots or overheated areas. For example, the upstream end of the injector can be set to a lower temperature to avoid heating the septum. Independent temperature control of the downstream end also prevents overheating of the top portion of the analytical column in the column oven, which is heated jointly by the injector and the column oven.

[0110] By using a heating element in the form of a heating coil, the contact between the heating element and the main body can be improved, thereby improving the heat transfer efficiency of the heating element to the main body.

[0111] By providing a housing that surrounds one or more of these heating elements, more uniform heating can be provided due to the quality and thermal conductivity of the housing material. For example, the housing can be a block of metal, such as aluminum.

[0112] The SSL injector in the gas chromatograph provides multiple independently controlled heating elements, allowing a single injector to simultaneously provide both cold and hot needle injections without requiring injection type changes when switching between these methods. This reduces downtime during column oven use and the number of devices required to perform these methods. Furthermore, this invention avoids the drawbacks of hot needle injectors, which typically maintain continuous heating in the inlet region, leading to septum degradation and siloxane contamination of the system, because the top portion of the injector cools immediately after the injection phase due to solvent evaporation from the needle.

Claims

1. A sample injector for a gas chromatograph, comprising: The main body defines a sample chamber configured to receive a sample; and Multiple heating elements, the multiple heating elements being used to heat the main body; Each of the plurality of heating elements is configured to be controlled independently of each of the other heating elements.

2. The sample injector according to any of the preceding claims, wherein: The main body includes multiple regions; and The plurality of heating elements are configured such that each of the plurality of heating elements is configured to heat a different region within the plurality of regions.

3. The sample injector of claim 2, wherein the sample injector is configured to heat one of the plurality of regions to a temperature different from that of one or more other regions of the plurality of regions during at least one operating phase of the sample injector.

4. The sample injector according to any one of claims 2 to 3, wherein: The body is an elongated tube defining a longitudinal axis, the body having an inlet end and a downstream end, the downstream end being located away from the inlet end along the longitudinal axis; The plurality of regions include an entrance region located at or near the entrance end of the body and a downstream region located at or near the downstream end of the body.

5. The sample injector of claim 4, wherein the plurality of heating elements includes an inlet heating element arranged to heat the inlet region.

6. The sample injector according to claim 4 or claim 5, wherein the plurality of heating elements includes a downstream heating element arranged to heat the downstream region.

7. The sample injector according to any one of claims 4 to 6, wherein: The plurality of regions includes an intermediate region arranged between the entrance region and the downstream region; and The plurality of heating elements includes one or more intermediate heating elements, which are arranged to heat the intermediate region.

8. The sample injector according to any one of claims 2 to 7, wherein the sample injector is configured to change the temperature of at least one of the plurality of regions during at least one operating phase of the sample injector, such that the temperature of the region changes over time during the operation of the sample injector. Optionally, the operation of the sample injector includes multiple stages, and changing the temperature of at least one of the multiple regions during at least one operation stage of the sample injector includes setting a setpoint temperature for the region during each of the multiple stages.

9. The sample injector according to any of the preceding claims, wherein the plurality of heating elements are arranged in series along the body.

10. The sample injector according to any one of claims 2 to 9, wherein each of the plurality of heating elements is arranged adjacent to or around a corresponding region of the plurality of regions.

11. The sample injector of claim 10, wherein each of the plurality of heating elements comprises a heatable coil arranged around the body; Optionally, the coil density of one or more of the plurality of heating elements varies along the length of the body.

12. The sample injector of claim 10, further comprising a plurality of housings, each of the plurality of housings being arranged around one of the plurality of heating elements and a corresponding region of the plurality of regions; Optionally, the plurality of outer shells are arranged in series along the main body.

13. The sample injector according to any one of claims 2 to 12, the sample injector further comprising a controller configured to independently control each of the plurality of heating elements based on a parameter indicating the temperature of the region in which the heating element is configured to be heated.

14. The sample injector according to any one of claims 2 to 13, the sample injector further comprising a plurality of temperature sensors, each of the plurality of temperature sensors being arranged in a region adjacent to the plurality of regions.

15. The sample injector according to claim 14, which is dependent on claim 13, wherein the parameter indicating the temperature of the region includes one or more of the following: The current in the heating element; The temperature of the heating element is measured using the corresponding temperature sensor among the plurality of temperature sensors; and The temperature of the area is measured using the corresponding temperature sensor among the plurality of temperature sensors.

16. The sample injector according to any of the preceding claims, wherein each of the plurality of heating elements is configured to be energized independently of each of the other heating elements.

17. A method for heating a sample injector for a gas chromatograph, the method comprising: A plurality of heating elements are provided, the plurality of heating elements being configured to heat the body of the sample injector; as well as Each of the plurality of heating elements is controlled independently of each of the other heating elements.

18. The method of claim 17, wherein the body comprises a plurality of regions, and Each of the plurality of heating elements is configured to heat a different region within the plurality of regions.

19. The method of claim 18, the method further comprising changing the temperature of at least one of the plurality of regions during at least one operating phase of the sample injector, such that the temperature of the region varies over time during the operation of the sample injector; Optionally, the operation of the sample injector includes multiple stages, and changing the temperature of at least one of the multiple regions during at least one operation stage of the sample injector includes setting a setpoint temperature for the region during each of the multiple stages.

20. The method of claim 18 or claim 19, the method further comprising heating one of the plurality of regions to a temperature different from that of one or more other regions of the plurality of regions during at least one operating phase of the sample injector.

21. The method according to any one of claims 18 to 20, the method further comprising: A first parameter is measured to indicate the temperature of the first region among the plurality of regions; as well as Control the first heating element among the plurality of heating elements to heat the first region to one or more temperature setpoints; The parameters used to measure the temperature of the first region may optionally include measuring the current in the first heating element, measuring the temperature of the first heating element using a temperature sensor, and / or measuring the temperature of the first region using a temperature sensor.

22. The method of claim 21, wherein the first region is the inlet region of the body, and the first heating element is an inlet heating element.

23. The method of claim 22, the method further comprising controlling the inlet heating element to heat the inlet region during the sample introduction phase when the sample is introduced into the sample injector.

24. The method of claim 23, wherein the method further comprises one of the following: i) Selectively control the inlet heating element to heat the inlet region to the following temperature during the sample introduction phase: The high-temperature setpoint at which the sample can be completely evaporated; or Low temperature set point; or ii) Control the inlet heating element to maintain the temperature of the inlet region at the low temperature set point throughout the operation of the sample injector.

25. The method of claim 23, further comprising: i) Control the inlet heating element to heat the inlet region to a high temperature setpoint where the sample can be completely evaporated during the sample introduction phase when the sample is introduced into the sample injector; as well as ii) Control the inlet heating element to reduce the temperature of the inlet region from the high temperature setpoint to the low temperature setpoint.

26. The method of claim 25, wherein step ii) occurs in one of the following: Immediately after the evaporation stage, when the sample is evaporated and transported by carrier gas to the gas chromatography column; or After a predetermined time period following the completion of the evaporation phase.

27. The method according to any one of claims 18 to 26, the method further comprising: A second parameter is measured to indicate the temperature of a second region among the plurality of regions; as well as The second heating element among the plurality of heating elements is independently controlled to heat the second region to one or more temperature setpoints; The parameters used to measure the temperature of the second region may optionally include measuring the current in the second heating element, measuring the temperature of the second heating element using a sensor, measuring the temperature of the second region using a sensor, and / or measuring the temperature of the column oven using a sensor.

28. The method of claim 27, wherein the second region is a downstream region of the body, and the second heating element is a downstream heating element; Optionally, the second heating element is maintained at a high temperature setpoint at which the sample can be completely evaporated throughout the operation of the sample injector.

29. The method according to any one of claims 27 to 28, the method further comprising: A third parameter is measured to indicate the temperature of a third region among the plurality of regions; as well as The third heating element among the plurality of heating elements is independently controlled to heat the third region to one or more temperature setpoints; The parameters used to measure the temperature of the third region may optionally include measuring the current in the third heating element, measuring the temperature of the third heating element using a sensor, and / or measuring the temperature of the third region using a sensor.

30. The method of claim 29, wherein the third region is the middle region of the body, and the third heating element is an intermediate heating element; Optionally, the third heating element is maintained at a high temperature setpoint at which the sample can be completely evaporated throughout the operation of the sample injector.

31. The method according to any one of claims 18 to 30, the method further comprising: Initially, the plurality of heating elements are controlled to heat each of the plurality of regions to a low temperature setpoint; as well as After the sample has been introduced into the sample injector, the plurality of heating elements are controlled to heat each of the plurality of regions to a high temperature setpoint where the sample can be completely evaporated, until the sample has evaporated.

32. The method according to claim 31, further comprising: During the gas chromatograph operation phase after the sample evaporation, the intermediate heating element among the plurality of heating elements is controlled to heat the intermediate region among the plurality of regions to a high temperature setpoint. and / or During the operation of the gas chromatograph, the inlet heating element among the plurality of heating elements is controlled so that the inlet region among the plurality of regions is not heated.

33. The method of claim 31 or claim 32, further comprising measuring a parameter indicating the column oven temperature of the gas chromatograph, and performing one of the following actions depending on the measured parameter: During the gas chromatograph operation phase after sample evaporation, the downstream heating element among the plurality of heating elements is controlled to heat the downstream region of the plurality of regions to a high temperature setpoint; or During the operation of the gas chromatograph, the downstream heating element among the plurality of heating elements is controlled such that the downstream region among the plurality of regions is not heated.

34. The method according to any one of claims 17 to 33, wherein controlling each of the plurality of heating elements comprises dynamically controlling each heating element in response to one or more external temperature changes.

35. The method according to any one of claims 17 to 34, wherein the sample injector is the sample injector according to any one of claims 1 to 16.

36. A gas chromatograph assembly comprising a sample injector according to any one of claims 1 to 16.

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