Automatic Leak Detection

Abstract

It is an object of the present invention to provide a method for detecting leaks in a gas chromatograph system. A gas chromatography system has a closed exhaust path. Gas is flowed through a column of the gas chromatography system at a first flow rate to cause a first pressure change from a first pressure, the first change defining a first pressure differential. A first duration of the first pressure difference and / or the first pressure change is measured. The closed exhaust path is opened and a second flow rate through the exhaust path is set. Gas is flowed through the column at a third flow rate and through the exhaust path at a second flow rate to cause a second pressure change in the gas chromatography system from a second pressure, the second change defining a second pressure difference. A second duration of the second pressure difference and / or the second pressure change is measured. The presence or absence of a leak in the gas chromatography system is determined based on the first pressure difference and / or the first duration, the second pressure difference and / or the second duration.

Description

[Technical Field]

[0001] The present disclosure relates generally to methods and systems for automatically detecting leaks, particularly in gas chromatography systems. The systems and methods may be suitable for use in conjunction with mass spectrometry (MS), for example, in a GC-MS instrument. [Background technology]

[0002] A gas chromatograph (GC) is an instrument used to separate and analyze components in a sample. Figures 1 and 2 show exemplary gas chromatographs 100, 200 capable of split-mode and splitless-mode injection.

[0003] During operation, carrier gas is supplied to the column inlet (sometimes referred to herein as an injector or inlet) 105 of the GC 100, 200. The column inlet may be a split / splitless (SSL) inlet or a programmable temperature vaporizing (PTV) inlet. The PTV inlet may also be operable in split and / or splitless mode. The column inlet 105 is covered by a septum, and a septum purge path 104 provides carrier gas flow across the septum via an input path 103. The sample is introduced into the carrier gas in the column inlet 105 via a syringe through the septum. The sample then flows via the carrier gas into the column 101, which connects to the column vent / detector. The sample / carrier gas mixture may also be exhausted to a split vent (not shown) via split path 102. The split path 102 and input path 103 may include charcoal traps 117, 118.

[0004] In split mode operation, split path 102 is open (i.e., valve 110 is open) so that carrier gas passes through column 101, septum purge path 104, and split path 102 and exits inlet 105. In splitless mode, split path 102 is closed (i.e., valve 110 is closed) so that carrier gas does not pass through split path 102 and exit column inlet 105. In both cases, the flow rate of carrier gas entering column inlet 105 is equal to the sum of the flow rates exiting column inlet 105.

[0005] The gas chromatograph 100 shown in Figure 1 operates using forward pressure regulation, in which a pressure sensor 107 is used to measure the head pressure of the inlet 105 / column 101 and control the column flow via valve 111. Figure 2 shows a gas chromatograph 200 operating using backpressure regulation, in which the column head pressure / flow is controlled via an outlet valve (not shown).

[0006] In the GC system 100 shown in FIG. 1, the septum purge flow rate and the split vent flow rate can be measured by flow sensors 108 and 109, respectively. Flow sensors 108 and 109 can include pressure sensors 113, 115 and flow restrictors 114, 116. Alternatively, flow sensors 108 and 109 can be mass flow sensors or other types of flow sensors. In the GC system 200 shown in FIG. 2, only the septum purge rate can be measured by flow sensor 108 with a restrictor, and the flow through split flow path 102 can be measured using pressure sensor 107. The flow through gas inlet path 103 can be measured using flow sensor 201.

[0007] The tightness of the GC pneumatic system is important for accurate analysis of the components in the sample. It is essential that the injector 105 and column connections are leak-free.

[0008] Leak detectors can be used to detect leaks. However, they are expensive and not very stable when measuring small flow rates. Therefore, their ability to detect very small leaks (e.g., at flow rates typical of capillary columns or even smaller) is very limited.

[0009] Another method for verifying whether there is a leak requires the user to set an empirical decompression time for a certain pressure drop. The presence of a leak can then be detected by comparing the measured time with a threshold time set by the user. However, calculating this threshold time based on theoretical parameters is practically impossible, since some of the parameters (e.g., the volume of the column inlet (injector), including the liner and charcoal trap) can be difficult to determine with sufficient accuracy. Furthermore, some of the relationships required for the calculation are very complex.

[0010] U.S. Patent No. 5,938,817 describes an anomaly detector that monitors the gas flow rate into the vaporization chamber. If there is a gas leak in the septum, more carrier gas is required to maintain a constant pressure in the vaporization chamber, so as the gas leak increases, the monitored gas flow rate at the gas inlet increases. The anomaly detector sends a warning signal when the monitored flow rate reaches a predetermined threshold. However, when operating in split mode, it is impossible to determine whether there is a leak or whether the increase in the monitored gas flow rate is due to the split flow. As a result, U.S. Patent No. 5,938,817 describes monitoring the voltage applied to the coil controlling the opening of the split port valve and sending a warning signal when the voltage is below a threshold. However, this is an inaccurate method of measuring split flow due to variations in the valve and valve operating conditions.

[0011] U.S. Patent No. 7,559,227 describes detecting a flow disruption based on the difference between input and output flows. If the difference exceeds a certain error threshold, a leak can be inferred. However, it is difficult to detect small differences between two flow rates, which can be very large. That is, it is difficult to measure small flow rate fluctuations with a wide range flow sensor.

[0012] Therefore, a method and system that overcomes these problems is desirable. Summary of the Invention

[0013] Against this background, there is provided a method and a system for detecting leaks in a gas chromatographic system as set out in the independent claims. Further aspects of the invention are set out in the description and claims.

[0014] The present disclosure relates to determining the air tightness of a gas chromatography system, and in particular to determining the air tightness of injectors and column fittings. The disclosure involves using a gas flow path within a gas chromatography system to create a controlled leak. The time it takes for a particular pressure change as gas flows through the column and gas flow path is then compared to the time it takes for the same pressure change when gas flows through the column alone. This is used to determine whether there is a leak in the system.

[0015] The above methods may be implemented as a computer program comprising instructions for operating a computer or computer system, and the computer program may be stored on a non-transitory computer-readable medium.

[0016] A computer system may include a processor, such as a central processing unit (CPU). The processor may execute logic in the form of a software program. A computer system may include memory, including volatile and non-volatile storage media. Different parts of the system may be connected using a network (e.g., wireless and wired networks). A computer system may include one or more interfaces. A computer system may include a suitable operating system, such as, for example, UNIX (including Linux), Windows (RTM), etc.

[0017] The above methods may be implemented in a system comprising a gas chromatography apparatus and a controller configured to operate the gas chromatography apparatus.

[0018] It should be noted that any feature described herein may be used with any specific aspect or embodiment of the invention. Moreover, any combination of features of any specific device, structure, or method is also provided, even if the combination is not explicitly disclosed.

[0019] The present invention will now be described with reference to the accompanying drawings which show different embodiments thereof, the drawings being provided purely by way of example and not by way of limitation. The invention may be put into practice in many ways and preferred embodiments may now be described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0020] [Figure 1] 1 illustrates a gas chromatography system capable of operating in split and splitless modes. [Figure 2] 1 illustrates a gas chromatography system capable of operating in split and splitless modes. [Figure 3]1 shows a gas chromatography system with an on-column inlet. [Figure 4] 1 shows a flowchart method for detecting leaks. [Figure 5] 1 shows a flowchart method for determining whether there is a leak. [Figure 6] 1 shows a flowchart method for detecting leaks.

[0021] It should be noted that the figures are shown in schematic form for simplicity and are not necessarily drawn to scale, and similar features are given the same reference numerals. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present disclosure provides a method for detecting leaks in a gas chromatography (GC) system 100, 200, 300. The method involves generating a controlled leak in the GC system 100, 200, 300 while gas is flowing through the column 101. The controlled leak can then be used as a criterion for determining whether there is a leak, instead of requiring the user to set an empirical value. That is, the leak can be detected automatically. Furthermore, the leak can be detected at any time except when the gas chromatograph is in its "run" state, because detecting it at any time would interfere with the user's analysis. Because changes in oven temperature alter column flow, it is preferable to detect leaks when the oven is isothermal (e.g., when the gas chromatograph is idle). That is, it is preferable to have a stable oven temperature during the leak check. Thus, the leak check can be performed, for example, during the equilibration time before an injection or at the end of a sample analysis.

[0023] An exemplary GC system 300 suitable for use in this method is shown in Figure 3. GC 300 includes an on-column inlet 105 and is similar to GCs 100 and 200 described above, but does not include a split flow path 102 or a septum purge path 104. Instead, GC system 300 includes a vacuum path 119, which can be opened or closed via a valve 120. While this path 119 is shown in Figure 3 as exiting at a location corresponding to the location of septum purge path 104 in Figures 1 and 2, vacuum path 119 can be located anywhere on injector 105.

[0024] The GC system 100, 200, 300 may include a controller configured to operate the GC system 100, 200, 300 according to the methods disclosed herein. The GC system 100, 200, 300 may also be used in combination with a mass spectrometer.

[0025] The depressurization rate of the GC systems 100, 200, and 300 can be expressed as follows:

[0026]

number

[0027]

number

[0028]

number

[0029] When one or more exhaust paths 102, 104, 119 are open, then:

[0030]

number

[0031] The depressurization time can be measured both with and without a controlled / generated leak from the exhaust paths 102, 104, 119. The generated leak can be on the same order of magnitude as the column flow, but is not limited to this example.

[0032] Depressurization time can be measured both with and without a controlled / generated leak, which can be as large as the column flow, but is not limited to this example.

[0033] If the pressure change is the same for measurements with and without the generated leak (i.e., ΔP1 = ΔP2), then

[0034]

number

[0035]

number

[0036] Based on equation (6), it can be determined whether the system 100, 200, 300 has a leak, for example, based on the depressurization time. This determination is explained in more detail with reference to FIGS. 4 and 5 and Table 1.

[0037] Alternatively, if the decompression time is kept constant (i.e., t1 = t2), then we can derive

[0038]

number

[0039] In this case, the pressure change can be measured both with and without a leak occurring. Based on equation (7), for example, it can be determined based on the pressure change whether there is a leak in the system 100, 200, 300. This determination is explained in more detail with reference to FIG. 2.

[0040] Alternatively, neither the pressure change nor the decompression time may be kept constant. In this case, it can be derived as follows:

[0041]

number

[0042] The leak flow rate can be determined based on the determined values ​​of ΔP1, ΔP2, t1, and / or t2 using equations (3) and (4). For example, by assuming the constant K is the same for all measurements, equations (3) and (4) can be rearranged to the following equation:

[0043]

number

[0044] Equation (9) can be simplified if ΔP1=ΔP2 and t1=t2.

[0045] Flow rates are measured in standard cubic centimeters per minute (sccm), or cm, at standard pressure and temperature. 3 For example, when operating in split mode, the carrier gas flow into the column inlet 105 may be measured as 106 sccm, and the flows from the column inlet 105 via the split path 102, the septum purge path 104, and the column 101 may be 100 sccm, 5 sccm, and 1 sccm, respectively.

[0046] In splitless mode, the flow of carrier gas into column inlet 105 is much lower, for example, 6 sccm, and then the flows out of column inlet 105 via septum purge path 104 and column 101 may be 5 sccm and 1 sccm, respectively. Alternatively, the septum purge path may also be closed in splitless mode. In this case, the flow of carrier gas into inlet 105 is equal to the flow of gas through column 101, for example, 1 sccm.

[0047] The characteristics of column 101, such as its length, inner diameter, and thickness of its stationary phase, affect the flow through column 101. Generally, shorter columns provide relatively high flow at low pressures. The internal volume of injector 105 affects how quickly the pressure drops when the input gas is turned off or the input gas set pressure is reduced (e.g., by closing or partially closing valve 111, respectively). However, split path 102 and septum purge path 104 may have restrictors 114, 116 and valves 110, 112 that control the restrictors 114, 116, thereby allowing flow through these paths to be controlled independently of the internal volume. Similarly, pressure reduction path 119 may have restrictor 116 and valve 120 that controls restrictor 116.

[0048] Accordingly, a method is provided, in a gas chromatography system (100, 200, 300) having at least one closed exhaust path (102, 104, 119), comprising the steps of flowing gas at a first flow rate through a column (101) of the gas chromatography system (100, 200, 300) to cause a first pressure change from the first pressure that defines a first pressure differential, and measuring a first duration of the first pressure difference and / or the first pressure change; opening the at least one closed exhaust path (102, 104, 119) and setting a respective second flow rate through each of the at least one open exhaust path (102, 104, 119); causing a second pressure change from the second pressure within the gas chromatography system 100, 200, 300 by flowing gas at a third flow rate through the ram 101 and flowing gas at a respective second flow rate through each of the at least one open exhaust paths 102, 104, 119, defining a second pressure differential, and measuring the second pressure differential and / or a second duration of the second pressure change; and determining whether there is a leak within the gas chromatography system 100, 200, 300 based on the measured first pressure difference and / or first duration and the measured second pressure difference and / or second duration.

[0049] This method provides for automatic leak detection in the gas chromatography system 100, 200, 300. Furthermore, leaks can be detected at any time (although detecting leaks whenever the gas chromatograph is in its "run" state is not preferred as it would interfere with the user's analysis). Because column flow changes when the oven temperature changes, it is preferable to detect leaks when the oven is isothermal (e.g., when the gas chromatograph is idle). That is, it is preferable to have a stable oven temperature during leak testing. Therefore, a leak check can be performed, for example, during the equilibration time before injection or at the end of a sample analysis.

[0050] The determining step may include determining that there is a leak in the gas chromatography system 100, 200, 300 if the first pressure differential and / or the first duration differs by more than a threshold amount from an expected value established based on the respective second pressure differential and / or second duration.

[0051] Alternatively or additionally, the determining step may include determining that there is a leak in the gas chromatography system 100, 200, 300 if the amount of gas indicated by the second duration differs from an expected value established from the amount of gas indicated by the first duration by more than a threshold amount, and / or if the amount of gas indicated by the first duration differs from an expected value established from the amount of gas indicated by the second duration by more than a threshold amount.

[0052] Alternatively or additionally, the determining step may include determining that there is a leak based on a difference between an expected flow rate and a sum of the first flow rate and at least one second flow rate that is greater than a threshold amount, the expected flow rate being established based on the first duration and the second duration.

[0053] If ΔP1=ΔP2, then a leak may be determined to exist if:

[0054]

number

[0055] If:

[0056]

number

[0057]

number

[0058] Flowing the gas through the column 101 can include flowing the gas through the column 101 and at least one open exhaust path 102 , 104 , 119 .

[0059] The step of opening at least one exhaust path 102, 104, 119 may include opening multiple exhaust paths 102, 104, 119.

[0060] Preferably, one or more of the respective second flow rates may be a multiple of the first flow rate, and / or the third flow rate may be a multiple of the first flow rate. In some embodiments, this may mean that one or more of the second flow rates are equal to the first flow rate and / or the third flow rate is equal to the first flow rate (i.e., the multiple is 1). The multiple may be an integer multiple. Having one or more respective second flow rates and / or third flow rates be a multiple of the first flow rate may simplify determining whether there is a leak (e.g., by simplifying any calculations).

[0061] In other embodiments, one or more of the respective second flow rates may not be a multiple of the first flow rate, and / or the third flow rate may not be a multiple of the first flow rate.

[0062] Preferably, at least one exhaust path 102, 104, 119 can be one or more of the septum purge path 104, the split path 102, and the reduced pressure path 119. Having the exhaust path 102, 104, 119 be the septum purge path 104 or the split path 102 means that leak detection can be performed on standard GC systems 100, 200, 300 that include one or both of these paths, such as GC systems 100, 200, 300 that include an SSL or PTV inlet, without having to install additional paths to perform leak testing. Having the exhaust path 102, 104, 119 be the reduced pressure path 119 means that leak testing can be performed on GC systems 100, 200, 300 that do not include a split path 102 or a septum purge path 104, such as an on-column inlet 105. Furthermore, the reduced pressure path 119 can exit at any point on the inlet 105 and can therefore be installed wherever is most convenient for the user.

[0063] In some cases, the first pressure may be equal to the second pressure, the first pressure differential may be equal to the second pressure differential, and / or the first duration may be equal to the second duration, which may simplify determining whether there is a leak (e.g., by simplifying any calculations).

[0064] In a preferred embodiment, there is the further step of pressurizing the gas chromatography system 100, 200, 300 at a first pressure and a second pressure by opening the gas inlets.

[0065] In another preferred embodiment, the method includes the step of closing the gas inlet before the steps of measuring the first duration and measuring the second duration.

[0066] In another embodiment, before measuring the first pressure difference and / or the first duration, there is a further step of calibrating the column 101 by determining parameters of the column 101. The parameters may include the length and inner diameter of the column 101. The parameters may further include the stationary phase of the column 101. Calibrating the column 101 means that the flow through the column 101 can be more accurately determined as the column 101 depressurizes.

[0067] Preferably, the gas chromatography systems 100, 200, 300 include a mass spectrometer, so that molecules separated by the gas chromatograph can be provided to the mass spectrometer for detection and analysis.

[0068] Following a determination that there is a leak, the method may further include logging a record of the determination via the gas chromatography system 100, 200, 300 and providing an indication to a user that a leak has been detected. Thus, the user may be readily aware that a leak has been detected and may take steps to correct the leak. In another embodiment, following a determination that there is no leak, the method may further include logging a record of the determination via the gas chromatography system 100, 200, 300 and providing an indication to a user that there is no leak in the system 100, 200, 300. Thus, the user may be readily aware that the gas chromatography system 100, 200, 300 is operating normally.

[0069] In some cases, following a determination that there is no leak, the method may include the further steps of determining a first parameter related to a first pressure difference and first duration and / or a second pressure difference and second duration, flowing gas through column 101 at a further flow rate to cause a further pressure change from the further pressure defining a further pressure difference, and measuring the further pressure difference and / or the further duration of the pressure change, and determining whether there is a leak based on the first parameter, the further pressure difference, and the further duration. Thus, the parameters known to be indicative of no leak can be used to later determine whether system 100, 200, 300 is still leak-free.

[0070] In such a case, determining whether there is a leak may include determining that there is a leak if the measured further duration differs from an expected value established based on the further pressure differential and the first parameter. Alternatively or additionally, the determining may include determining that there is a leak if the measured further pressure differential differs from an expected value based on the further duration and the first parameter.

[0071] In another example in such a case, the step of determining whether there is a leak may instead include determining a further parameter related to a further pressure differential and a further duration, and determining that there is a leak if the further parameter differs from the first parameter by more than a threshold amount. The further parameter may be a constant related to the further pressure differential and the further duration. In the absence of changes to the system 100, 200, 300 that would change this constant (e.g., a change in the injector liner changing the internal volume), the further parameter may be compared to the first parameter known to be indicative of a leak-free system 100, 200, 300.

[0072] In yet a further example in such a case, the first parameter may represent a pressure drop per time increment, and the determining step may further include determining an additional parameter representing the pressure drop per time increment based on the additional pressure difference and the additional duration, and determining that there is a leak if the additional parameter is greater than the first parameter.

[0073] In these embodiments, it can be determined at a later time whether there is a leak without having to repeat the measuring step again.

[0074] Also provided are systems 100, 200, 300 comprising a gas chromatography apparatus and a controller configured to operate the gas chromatography apparatus according to the above-described methods.

[0075] There is also a non-transitory storage medium that stores machine-executable instructions that, when executed, cause a computing device to perform the steps of the above-described method.

[0076] 4, a flowchart of a method for detecting leaks in a gas chromatography system 100, 200, 300 is shown. In step 401, one or more exhaust paths 102, 104, 119 of the system 100, 200, 300 are closed. For example, all exhaust paths 102, 104, 119 may be closed so that gas can flow from the injector 105 only through the column 101 (i.e., zero flow through closed exhaust paths 102, 104, 119). Alternatively, if the GC 100, 200, etc. has at least two output paths 102, 104, 119, one output path 102, 104, 119 may be left open in step 201 so that gas can flow from the column 101 and the open output path 102, 104, 119.

[0077] The exhaust pathways may also be referred to herein as output pathways 102, 104, 119 and may include a split pathway (sometimes referred to as a split flow path) 102, a septum purge pathway 104, a vacuum pathway 119, or another output pathway 102, 104, 119. In other words, the exhaust / output pathways 102, 104, 119 include a gas pathway exiting the injector 105 that may be closed (i.e., does not include the column 101).

[0078] The gas inlet path 103 may also be closed or partially closed in step 401, for example, by closing or partially closing valve 111. The gas inlet path 103 and exhaust paths 102, 104, 119 may be closed manually or by the GC system 100, 200, 300. With the gas input path 103 closed, the injector 105 depressurizes as gas flows out of the injector 105 through an open gas path (e.g., column path 101 when all exhaust paths 102, 104, 119 are closed) at a first flow rate. When the gas input path 103 is partially closed, the flow out of the injector 105 must be greater than the flow through the gas input path 103 to ensure the injector 105 depressurizes. Partially closing the gas input path 103 means increased depressurization time, which can make the system more sensitive to determining whether there is a leak by reducing the relative error in later steps of the measurement. Generally, at low flow rates it is preferable to completely close the gas inlet path 103, but at high flow rates partially closing the gas inlet path 103 may have benefits associated with increasing the depressurization time.

[0079] In step 402, the duration for the pressure in the system 100, 200, 300 to change from a first pressure by a first pressure difference can be measured. Alternatively or additionally, the first pressure difference can be determined, for example, by calculating the difference between the first pressure and a second pressure measured after one or more exhaust paths 102, 104, 119 are closed. The first pressure can be the injector pressure before closing the exhaust paths 102, 104, 119 and the gas inlet path 103. The pressure difference should be small enough so that the relationship between pressure and flow rate in the column can be approximated as linear, as in equation (6). The duration of the pressure change can be measured manually or by the GC system 100, 200, 300. Step 403 includes opening the gas inlet and repressurizing the GC system 100, 200, 300. The system can be repressurized at the first pressure or at a different pressure.

[0080] Step 403 also includes opening at least one of the closed exhaust paths 102, 104, 119 or channels to create a controlled (known) leak. For example, valve 110, valve 112, and / or valve 120 may be opened to allow gas to flow out of the injector via split path 102, septum purge path 104, and / or reduced pressure path 119, respectively. GC systems 100, 200, 300 may have controllers configured to open and close valves 110, 111, 112, 120. Alternatively, additional exhaust paths 102, 104, 119 may be provided to implement the leak that may be opened in step 403.

[0081] The flow through at least one open exhaust path 102, 104, 119 can be set to a multiple of the first flow rate. For example, if one exhaust path 102, 104, 119 is opened, the total flow rate out of the column inlet 105 can be twice the first flow rate. That is, the flow through the column 101 and one exhaust path 102, 104, 119 can both be equal to the first flow rate (i.e., the multiplier can be 1). Alternatively, the flow through at least one exhaust channel can be set to twice the first flow rate so that the total flow rate out of the column inlet 105 is three times the first flow rate. In another example, if two exhaust paths 102, 104, 119 are opened, the total flow rate out of the injector 105 can be three times the total flow rate of the first flow rate (i.e., the multiplier can be 2). In other words, each of the at least one open exhaust path 102, 104, 119 may be set to a multiple of the first flow rate.

[0082] Alternatively, the flow rate of one or more exhaust paths 102, 104, 119 can be set to a second flow rate that is different from the first flow rate. In this example, if two or more exhaust paths 102, 104, 119 are opened, the flow rate of each exhaust path 102, 104, 119 can be set to the second flow rate, or the flow rates of each exhaust path 102, 104, 119 can be different. For example, the first exhaust path 102, 104, 119 can have a flow rate equal to the first flow rate, and the second exhaust path 102, 104, 119 can have a flow rate equal to the second flow rate. In another example, each of the open exhaust channels and columns can have different flow rates.

[0083] Before or after at least one exhaust path 102, 104, 119 is opened, the gas inlet path 103 is closed, thereby depressurizing the injector 105 as gas flows through the previously opened gas path (e.g., column 101) and the open at least one exhaust path 102, 104, 119. In this step, the flow through the column 101 can be set to a third flow rate, which can be a multiple of the first flow rate or can be a different flow rate. In step 404, the time it takes for the pressure of the GC system 100, 200, 300 to change from the second pressure by a second pressure differential can be measured. Alternatively or additionally, the second pressure differential can be determined. The second pressure can be the same as the first pressure or can be a different pressure.

[0084] In step 405, it is determined whether there is a leak in the GC system 100, 200, 300. This determination may be based on the first depressurization duration in step 402 and the second depressurization duration in step 404. Alternatively, the determination may be based on the first pressure change in step 402 and the second pressure change in step 404. In another embodiment, the determination may be based on a combination of at least one depressurization duration and at least one pressure difference.

[0085] The determination may be based on a direct comparison of the decompression times. For example, if the first pressure difference is equal to the second pressure difference (i.e., ΔP1 = ΔP2), then the decompression time t2 is shorter than t1 (due to the increased flow rate caused by the controlled leak), consistent with equation (6), and the system 100, 200, 300 is leak-free. Otherwise, a true leak exists. This determination is explained in more detail with reference to FIG. 5. The first pressure difference may be considered equal to the second pressure difference if the difference between the values ​​is less than 5%, less than 2%, or less than 1%. Other thresholds greater than 5% may also be used (e.g., 10%, 20%, or 50%).

[0086] Similarly, a determination may be based on a direct comparison of pressure changes, for example, if the depressurization time t2 is equal to or within a threshold tolerance range of t1 (e.g., 50%, 20%, 10%, 5%, 2%, or 1%) and the pressure change ΔP2 is greater than ΔP1, consistent with equation (7), then the system 100, 200, 300 may be determined to be leak-free.

[0087] Alternatively, the determination may be made indirectly based on the depressurization time. For example, an expected value for t2 may be established based on t1 and the expected value of t2 compared to the determined value of t2. The expected value may be established based on Equation (6). For example, if t1 is measured to be 10 seconds for a first gas flow rate through the column, then one of the exhaust paths 102, 104, 119 is opened and the flow rate is set to the first flow rate, the expected value for t2 may be 5 seconds. If the measured value of t2 differs from the expected value, it may be determined that there is a leak in the system. In some embodiments, the difference between the measured and expected values ​​may be used to identify the general area of ​​the leak. For example, if t2 is greater than the expected value, it may be determined that there is a leak in the inlet 105 or an open gas path (e.g., column 101). In another embodiment, if t2 is less than the expected value, it may be determined that there is a leak in one or more of the open exhaust paths 102, 104, 119. If the difference between the measured and expected values ​​of t2 is less than 10% of the expected value, it can be determined that the measured value of t2 does not differ from the expected value. Other thresholds greater than or less than 10% (e.g., 1%, 2%, 5%, 20%, or 50%) can also be used.

[0088] Similarly, a determination can be made indirectly based on a pressure change. For example, an expected value of ΔP2 can be established based on ΔP1 and the expected value of ΔP2 compared to the determined value of ΔP2. The expected value can be established based on Equation (7). For example, if ΔP1 is measured to be 10 kPa for a first gas flow rate through column 101, then one of exhaust paths 102, 104, 119 is opened and the flow rate is set to the first flow rate, the expected value of ΔP2 can be 20 kPa based on Equation (7). If the measured value of ΔP2 differs from the expected value, it can be determined that there is a leak in the system. Furthermore, if ΔP2 is less than the expected value, it can be determined that there is a leak in inlet 105 or an open gas path (e.g., column 101). If ΔP2 is greater than the expected value, it can be determined that there is a leak in one or more of the open exhaust paths 102, 104, 119. ΔP2 can only be determined to differ from the expected value if the difference between the values ​​is less than 10% of the expected value. Other thresholds greater than or less than 10% (eg, 1%, 2%, 5%, 20%, or 50%) can also be used.

[0089] In another example, an expected value for t1 can be established based on t2 and the expected value of t1 compared to the measured value of t1. The expected value for t1 can be established based on equation (6). For example, t2 can be measured as 6 seconds when one exhaust path 102, 104, 119 is open and the flow through the column and the open exhaust path 102, 104, 119 are both equal to a first flow rate. An expected value for t1 for gas flowing through the column only at the first flow rate can be 12 seconds. If the measured value of t1 differs from the expected value, it can be determined that there is a leak in the system. As described above, the nature of the difference from the expected value (greater or less) can be used to determine where the leak is located.

[0090] Similarly, an expected value for ΔP1 can be established based on ΔP2 and the expected value of ΔP1 compared to the determined value of ΔP1. The expected value can be established based on Equation (7). For example, if ΔP2 is measured to be 10 kPa when the flow through the column is equal to the open exhaust channel, the expected value for ΔP1 can be 5 kPa when the exhaust channel is closed. If the measured value of ΔP1 differs from the expected value, it can be determined that there is a leak in the system. As described above, the nature of the difference (greater or smaller) from the expected value can be used to determine where the leak is located. ΔP1 can only be determined to differ from the expected value if the difference between the values ​​is less than 10% of the expected value. Other thresholds greater or less than 10% (e.g., 1%, 2%, 5%, 20%, or 50%) can also be used.

[0091] Alternatively or additionally, a leak can be determined by calculating the total flow rate out of the injector 105 based on the first and second durations using equation (8) and subtracting the sum of the flow rates through the column 101 and the open exhaust paths 102, 104, 119. If there is a difference between these values ​​that exceeds a threshold, a leak can be determined to exist. The threshold can be between 0.01 and 0.1 mL / min. In other embodiments, the threshold can be 0, such that any difference between the values ​​registers as a leak. This method is described in further detail in connection with Tables 1 and 2.

[0092] The determination may also or instead be based on the amount of gas indicated by the depressurization time. In the absence of leaks, the volume of gas passing through the column 101 during a first duration at a first flow rate should be equal to the volume of gas passing through the column 101 and one or more open exhaust paths 102, 104, 119 during a second duration. Equal may mean, for example, that the difference in the gas volumes is less than 5% of at least one of the gas volumes. Other thresholds for equality may be used, such as thresholds greater than 5% (e.g., 10%, 20%, or 50%) or less than 5% (e.g., 2% or 1%).

[0093] Instead, if the volume of gas indicated by the second duration differs from an expectation (e.g., an expected value) established by the volume of gas indicated by the first duration, a leak may be determined to exist. A leak may be determined to exist only if the difference between the volume of gas indicated by the second duration and the expectation is greater than a threshold. The threshold may be between 0.01 mL and 0.1 mL, or may be 0, as described above.

[0094] The presence of a leak may also be determined based on a combination of the above-described determination methods. For example, a leak may be determined to exist only if two or more of the above methods indicate the presence of a leak. In another embodiment, if one or more methods indicate the absence of a leak, a leak may be determined to exist. For example, if one method indicates the presence of a leak but one or more methods indicate the absence of a leak, a leak may be determined to exist but not exist, or vice versa.

[0095] Steps 401-405 may be performed in a different order, for example, steps 403 and 404 may be performed before steps 401 and 402, such that the second duration may be determined before the first duration.

[0096] An example of how a leak may be determined based on a comparison of durations is shown in Figure 5. In step 501:

[0097]

number

[0098]

number

[0099]

number

[0100]

number

[0101]

number

[0102]

number

[0103]

number

[0104]

number

[0105] The location of the leak can be determined based on the relationship between t1 and t2, for example, if t2 is

[0106]

number

[0107]

number

[0108] For example, F1 can be the flow through the column path 101, and F2 can be equal to the sum of the flow through the column path 101 and at least one exhaust path 102, 104, 119. If the flow is doubled by opening one of the output paths 102, 104, 119 (e.g., septum purge path 104) and the flow through the output paths 102, 104, 119 is set to the same flow rate as the flow through the column 101, then F2 = 2F1. Then, from equation (6), it can be seen that the depressurization time should be half of the depressurization time when gas flows only through the column 101 (i.e., t2 = 0.5t1). If the depressurization duration is not shortened accordingly, then it means that the flow out of the injector was higher than the measured column flow, i.e., there is a leak in the GC system 100, 200, 300. If the decompression duration is reduced beyond 0.5t1, doing so will cause leaks in the open exhaust paths 102, 104, 119.

[0109] The example described in Figure 5 assumes that the first pressure differential and the second pressure differential are equal (which may mean that the difference in values ​​is less than a threshold value). However, if neither the duration nor the pressure differential are equal, a leak may be determined to exist, similar to the method described above, if:

[0110]

number

[0111] Alternatively, if the durations are equal and the first and second pressure differentials are not equal, a leak may be determined based on a comparison of the pressure differentials.

[0112]

number

[0113]

number

[0114]

number

[0115]

number

[0116]

number

[0117]

number

[0118]

number

[0119]

number

[0120] As discussed above in connection with FIG. 5, the location of the leak may be determined based on the relationship between ΔP1 and ΔP2, for example, if ΔP2 is

[0121]

number

[0122]

number

[0123] Similar to the method described above, if the duration and pressure difference are not equal, a leak may be determined to exist if:

[0124]

number

[0125] Similar to the method described above, a leak can also be determined to exist based on a comparison of the values ​​of ΔP1t2 and ΔP2t1. This may be appropriate when neither the duration nor the pressure difference is held constant. The comparison can be performed using equation (9), e.g.,

[0126]

number

[0127] Following a determination that a leak exists, the gas chromatography system 100, 200, 300 may log the presence of the leak. For example, the GC system 100, 200, 300 may record the time that the leak was determined to exist and / or record the calculated leak rate. The leak rate may be determined as described below with reference to Table 1. The GC system 100 may additionally or alternatively send an indication to the user that the presence of a leak has been detected. For example, the GC system 100, 200, 300 may include a warning device. The warning device may include a light that illuminates when the presence of a leak is detected or a display configured to display a warning. Other warning devices that alert the user to the presence of a leak are also possible. Logging the detected leak and / or alerting the user to the detected leak may allow the user to investigate the presence of an otherwise unknown leak.

[0128] In the above examples, it was assumed that the pressure drop was small enough that the relationship between flow and pressure in column 101 could be considered linear. As the pressure drop increases, this relationship can no longer be assumed to be linear, and more complex nonlinear flow and pressure equations must be applied to avoid precision errors that could mask leaks.

[0129] Following a determination that no leak is present, the measurements of ΔP1, ΔP2, t1, and t2 can be used to later determine whether a leak is present, and the measurements can be stored in memory for this purpose.

[0130] For example, if the pressure difference and duration are known, it is possible to solve equations (3) and (4) for K. For example, the value

[0131]

number

[0132] That is, in one embodiment, following step 405 / 503, gas may be flowed through the GC system 100, 200, 300 (e.g., column 101, or column 101 and one or more open exhaust paths 102, 104, 119) at an additional flow rate, causing an additional pressure change from the additional pressure due to an additional pressure differential (ΔP3). An additional duration (t3) of the additional pressure change and / or the additional pressure differential may then be measured. The measurement may then be used to determine whether there is a leak. The additional flow rate may be a multiple of the first, second, and / or third flow rate. Similarly, the additional pressure differential may be the same as the first and / or second pressure differential. Similarly, the additional pressure may be the same as the first and / or second pressure.

[0133] For example, the determination may be made indirectly based on the decompression time and pressure difference. For example, an expected value for t3 may be established based on equation (3) using the measured value of ΔP3 and the determined value of K, or based on equation (4) if one or more exhaust paths 102, 104, 119 are open. If the expected value for t3 differs from the measured value of t3, it may be determined that there is a leak in the system. If the difference between the measured and expected values ​​of t3 is less than 10% of the expected value, it may be determined that the measured value of t3 does not differ from the expected value (i.e., no leak may be determined). Other thresholds greater than or less than 10% (e.g., 1%, 2%, 5%, 20%, or 50%) may also be used.

[0134] Similarly, an expected value for ΔP3 can be established based on equation (3) or (4) using the measured value of t3 and the determined value of K. If the expected value of ΔP3 differs from the measured value of ΔP3, it can be determined that there is a leak in the system. If the difference between the measured and expected value of ΔP3 is less than 10% of the expected value, it can be determined that there is no leak. Other thresholds greater than or less than 10% (e.g., 1%, 2%, 5%, 20%, or 50%) can also be used.

[0135] In further embodiments, equation (3) or (4) may be used to determine a second value of K based on measurements of t3 and ΔP3. If the determined second value of K differs from the initial value of K by more than a threshold value (e.g., by 1%, 2%, 5%, 10%, 20%, or 50% of either or both of the determined K values), a leak may be determined to exist.

[0136] In another example, the initial value of K when there is no leak can be used to determine the leak flow rate. For example, the column flow rate and the flow rate through any open exhaust paths 102, 104, 119 can be calculated using equations (3) or (4) as F based on t and ΔP. leaks may be known so that it can be determined.

[0137] In yet another example, measurements of ΔP1 and t1 or ΔP2 and t2 can be used to determine a first value representing the pressure drop per time increment. Following step 405 / 503, gas can be flowed through the system 100, 200, 300 to cause a further pressure change as described above. A further duration of the further pressure change and a further pressure difference can then be measured. A second value representing the pressure drop per time increment can then be determined based on the measured further duration and further pressure difference. If the second value indicates an increase in pressure drop per time increment greater than a threshold value (e.g., 5% of the first value), it can be determined that there is a leak. The values ​​may also be referred to as parameters, and vice versa.

[0138] As discussed above in connection with FIG. 2, the presence of a leak may be determined based on a combination of the above-described determination methods. For example, a leak may be determined to exist only if two or more of the above methods indicate the presence of a leak. In another example, if one or more methods indicate the absence of a leak, a leak may be determined to exist. For example, if one method indicates the presence of a leak but one or more methods indicate the absence of a leak, a leak may be determined not to exist, or vice versa.

[0139] 6 shows a flow chart method for detecting leaks, which is similar to the more general method described with reference to FIG.

[0140] In step 601, theoretical column parameters are set, or the column is calibrated. Calibrating the column includes determining the column parameters, which may be at least the column length and inner diameter. Calibrating the column may also include determining the thickness of the stationary phase. The length and inner diameter may be used to determine the flow through the column 101 for each pressure measurement.

[0141] A leak check is initiated following step 601. In step 602, the GC system 100, 200, 300 is equilibrated at a first pressure and the gas flow from the column 101 is set.

[0142] In step 603, the output path valves 110, 112, 120 are closed so that only gas exits the column 101. This may include closing the split path valve 110, the septum purge valve 112, and / or the pressure reducing valve 120. The gas may exit the column at a preset flow rate, or may be set to exit the column at a third flow rate. The third flow rate may be a multiple of the preset flow rate, or may be a different flow rate.

[0143] In step 604, the gas inlet is closed. Closing the gas inlet may include closing a valve in the GC system 100, 200, 300, such as valve 111. Step 604 also includes measuring the time it takes for the pressure in the GC system 100, 200, 300 to reach a second pressure. If the pressure drop is too large, the relationship between flow and duration can no longer be considered linear, so the second pressure must be close to the first pressure. That is, if the pressure drop is too large, doubling the initial flow rate (e.g., by opening one of the exhaust paths 102, 104, 119) will not halve the duration of the pressure drop.

[0144] Steps 602-604 may be performed in a different order, for example, the output paths 102, 104, 119 may be closed before equilibrating the system, or the gas inlet may be closed before closing the output paths 102, 104, 119.

[0145] In step 605, the injector 105 may be repressurized at a first pressure by opening the gas inlet (e.g., by opening valve 111). However, as described with reference to FIG. 4, the column inlet 105 may be repressurized at a different pressure. Step 605 may also include setting a column flow. The column flow may be equal to the column flow measured in step 602.

[0146] At least one of the exhaust paths 102, 104, 119 is opened in step 606 (e.g., septum purge valve 112 or split valve 110 is opened). The flow through the open exhaust paths 102, 104, 119 is also set in this step, which may be achieved using a flow restrictor such as restrictor 114 or 116. The set flow may be equal to the column flow measured in step 602 and / or step 605. Alternatively, the flow may be set to a different flow rate, as described with reference to FIG. 4.

[0147] Some of steps 605 and 606 may be performed in a different order, for example, the column flow may be measured after opening the exhaust paths 102, 104, 119, and / or the flow rate through at least one open exhaust path 102, 104, 119 may be set before measuring the column flow.

[0148] In step 607, the gas inlet valve (e.g., valve 111) is closed or partially closed and the time it takes for the GC system 100, 200, 300 to drop a predetermined amount from the pressure set in step 605 (which may be the first pressure or a different pressure) is measured.

[0149] It can then be determined whether there is a leak in the GC system 100, 200, 300 based on the duration measured in steps 605 and 607, as described with reference to FIGS.

[0150] The following tables (Tables 1 and 2) show results from initial experiments demonstrating the ability of the described method and system to detect leaks. In these experiments, the flows through the column and exhaust paths 102, 104, 119 were set to be equal. However, as noted above, the flows through the output paths 102, 104, 119 may or may not be a multiple of the flows through the columns.

[0151] [Table 1]

[0152] [Table 2]

[0153] Duration t1 represents the time it takes for the pressure to drop from P1 to P2 when gas flows at a first velocity only through column 101. Duration t2 represents the time it takes for the same pressure to drop when gas flows at a first velocity through column 101 and the exhaust path.

[0154] In Tests 1, 1b, and 2, the exhaust path 102, 104, 119 was the septum purge path 104. In Tests 3 and 3b, a split path 102 was used due to the higher flow rate. However, another exhaust path 102, 104, 119 could be opened instead of or in addition to the path used in these tests.

[0155] As shown in Tests 1, 2, 3, and 3b, the duration t2 is half the duration t1 in the conditions of these tests, as expected. However, Test 1b shows that if the pressure drop is too large, the relationship between flow and duration is not linear (doubling the initial flow does not halve the duration).

[0156] Table 1 contains the theoretical leak rate calculated using equation (9), the decompression time and pressure difference in Table 1. Since the system was expected to be leak-free, the F leaks The calculated value of should be approximately 0. This was the case for Test 1. Tests 1b, 2, 3, and 3b suggest a leak, but this is due to the precision of the time measurement, which was done with a stopwatch and is only in seconds. Higher resolution time measurement and automation of the procedure in the firmware of the GC system 100, 200, 300 should provide the expected results. However, even when measuring to the nearest second using a stopwatch, the F in Table 1 leaks Note that the calculated value of is close to 0. leaks The negative values ​​of are hypothesized to be due to the fact that in some cases there are no actual leaks in these tests.

[0157] As a further test of the method, an uncontrolled leak was simulated by restricting the flow through purge path 104 using flow restrictor 116, and the results are shown in Table 2. Thus, in these experiments, an uncontrolled leak was known, but in reality, an uncontrolled leak is not known. Tests 4a and 5a in Table 2, in which no artificial leak was simulated, are included for reference.

[0158] In Tests 4b-4f and Tests 5b-5e, the artificial leak flow rate was set in 0.5 mL / min increments. Because the gas chromatograph hardware used did not allow the purge flow to be set below 0.5 mL / min, it was not possible to test smaller simulated leaks in these experiments. A simulated (artificial) leak differs from a controlled leak through the exhaust path. In particular, a controlled leak is used as a reference to determine whether a leak exists, whereas a simulated leak is used to verify that an uncontrolled leak (in this case, an artificial leak) can be detected. This verification was performed by calculating the simulated leak rate.

[0159] Using Test 4b as an example, duration t2 represents the time it takes for the GC system pressure to drop from 41.6 kPa to 36.6 kPa when the flow through column 101 was equal to 5.52 mL / min and the flow through the exhaust path was set to 5.60 mL / min. That is, the total set flow from column inlet 105 was 11.12 mL / min. Additionally, there was an artificial leak of 0.5 L / min.

[0160] In general, the simulated leak rate can be determined via equation (9). Because the first and second pressure differentials in each of the tests in Tables 1, 2, and 3 are equal, equation (9) can be simplified to:

[0161]

number

[0162] In Table 2, the determined simulated leakage F leaks is found to be within the same order of magnitude as the artificial leak setting.

[0163] In Tests 5a-5e, the initial pressure of the GC systems 100, 200, and 300 was increased to 150 kPa, and the pressure drop was increased to at least 10 kPa because the columns were much longer than in the other tests. When the pressure parameters of Tests 4a-4d were used, the flow through the columns in Tests 5a-5e was much lower than in Tests 4a-4d due to differences in column geometry. Therefore, the pressure and pressure drop were increased to better detect the presence of simulated leaks.

[0164] Tests 4e, 4f, and 5e show that when the pressure drop is too large, the relationship between duration and flow rate is not linear; therefore, although the presence of a leak is still determined, the calculated flow rate of the simulated leak is less accurate. In particular, the decompression of inlet 105 becomes slower when the pressure drop is too large. This nonlinearity is the reason for the negative values ​​of the simulated leak flow rates determined in Tests 4e and 4f.

[0165] These initial experiments were performed with limited precision to confirm the feasibility of the method. Further experiments using different conditions and more accurate measurement methods, such as writing firmware routines that can perform measurements automatically, are necessary to evaluate the sensitivity that can be achieved by the method. The precision of the results in Tables 1 and 2 can be improved by implementing fully automated measurements in firmware to perform the measurement steps.

[0166] As shown by the above test, it is possible to determine whether a leak exists based on an empirical measurement of a first duration of time versus pressure change when gas flows only through the column. That is, a second measurement of a first duration of time versus the same pressure change when gas flows only through the column can be used to determine whether a leak exists in the GC system 100, 200, 300. For example, the second measurement can be directly compared to the empirical measurement. In another example, the second measurement can be used to calculate a leak rate, as described above with reference to Tables 1 and 2. As described in connection with FIG. 4, a combination of methods can be used to determine whether a leak exists.

[0167] The advantage of obtaining empirical measurements for specific column parameters is that the measurements can be used across many GC systems that use the same column parameters, i.e., the user does not need to calculate threshold decompression times based on theoretical parameters that are difficult to calculate with sufficient accuracy.

[0168] Thus, while there are advantages associated with determining whether there is a leak based on a first duration during which gas flows only through column 101 and a second duration during which gas flows through column 101 and at least one open exhaust path 102, 104, 119, there may also be advantages associated with determining the presence of a leak based on two measurements of the first duration.

[0169] The methods described herein may be implemented using computer system configurations including handheld devices, microprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, etc. Embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing devices linked through a network.

[0170] Certain embodiments may also be embodied as computer-readable code on a non-transitory computer-readable medium. The computer-readable medium is any data storage device that can store data, which can then be read by a computer system. Examples of computer-readable media include hard drives, network attached storage (NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tape, and other optical or non-optical data storage devices. The computer-readable medium can also be distributed over network-coupled computer systems, resulting in distributed storage and execution of the computer-readable code.

[0171] Although embodiments according to the present disclosure have been described with reference to particular types of equipment and applications (particularly gas chromatographs), and the embodiments, as discussed herein, have particular advantages in such cases, the approaches according to the present disclosure may be applied to other types of equipment and / or applications. The specific calibration details of the GC systems 100, 200, 300, while potentially advantageous (particularly in view of known calibration constraints and capabilities), may be significantly modified to arrive at a device with similar or identical operation. Each feature disclosed herein, unless otherwise specified, may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless otherwise specified, each disclosed feature is merely an example of a generic series of equivalent or similar features. All aspects and / or features disclosed herein may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. In particular, preferred features of the present disclosure are applicable to all aspects and embodiments of the present disclosure and may be used in any combination. Likewise, features described in non-essential combinations may be used separately (but not in combination).

[0172] There is an implicit "about" before temperatures, concentrations, times, pressures, flow rates, cross-sectional areas, voltages, currents, etc. discussed in the present teachings, and thus it is understood that very small, minor deviations are within the scope of the present teachings. Furthermore, values ​​referred to as "equal" may actually differ by less than a threshold amount. The threshold amount may be, for example, 5%. The threshold may also be greater than 5% (e.g., 10%, 20%, or 50%) or less than 5% (e.g., 2% or 1%). 2% or 1%.

[0173] As used herein, including in the claims, the singular forms of terms herein are to be construed as including the plural, and vice versa, unless the context otherwise indicates. For example, in the claims, references to the singular, including "a" or "an" (e.g., an ion packet), mean "one or more" (e.g., one or more ion packets), unless the context otherwise indicates.

[0174] Throughout the specification and claims of this disclosure, words such as "comprise," "including," "having," and "contain," as well as variations of words such as "comprising" and "comprises" or the like, mean "including, but not limited to," and are not intended to exclude other elements. Also, the use of "or" is inclusive, so that the phrase "A or B" is true when "A" is true, when "B" is true, or when both "A" and "B" are true.

[0175] The use of any and all examples or exemplary language (such as "for instance," "such as," "for example," and similar language) provided herein is intended merely to better illustrate the invention and does not pose a limitation on the scope of the disclosure unless specifically claimed. No language in the specification should be construed as indicating any element not claimed as essential to the practice of the disclosure.

[0176] The terms "first" and "second" may be reversed without changing the scope of the invention. That is, an element referred to as a "first" element (e.g., t1) may instead be referred to as a "second" element (e.g., t2), and an element referred to as a "second" element (e.g., t2) may instead be considered a "first" element (e.g., t1).

[0177] Any steps described herein may be performed in any order, or simultaneously, unless otherwise stated or otherwise required by context. Furthermore, if a step is described as being performed after another step, this does not exclude intervening steps from being performed.

[0178] Furthermore, unless otherwise understood or stated, implicitly or explicitly, it is understood that for any given component or embodiment described herein, any of the possible candidates or alternatives listed for that component may be used generally, either individually or in combination with one another. Furthermore, unless otherwise understood or stated, implicitly or explicitly, it is understood that any listing of such candidates or alternatives is merely exemplary and not limiting.

[0179] In this detailed description of various embodiments, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, those skilled in the art will understand that these various embodiments may be practiced without or with these specific details. Furthermore, those skilled in the art will readily understand that the specific order in which the methods are presented and performed is illustrative, and it is contemplated that the order may be changed and still remain within the scope of the various embodiments disclosed herein.

[0180] All literature and similar materials cited in this application, including but not limited to patents, patent applications, articles, books, papers, and Internet web pages, are expressly incorporated by reference in their entirety for any purpose. Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which the various embodiments described herein belong.

Claims

1. A method for detecting leaks in a gas chromatography system, comprising: In a gas chromatography system having at least one closed exhaust path, flowing gas at a first flow rate through a column of the gas chromatography system to cause a first pressure change from a first pressure, the first pressure change defining a first pressure differential, and measuring the first pressure differential and / or a first duration of the first pressure change; opening at least one closed exhaust path and setting a respective second flow rate through each of the at least one open exhaust path; causing a second pressure change from a second pressure in the gas chromatography system by flowing the gas through the column at a third flow rate and flowing the gas through each of the at least one open exhaust path at the respective second flow rate, the second pressure change defining a second pressure differential, and measuring the second pressure differential and / or a second duration of the second pressure change; determining whether there is a leak in the gas chromatography system based on the measured first pressure differential and / or first duration and the measured second pressure differential and / or second duration.

2. 2. The method of claim 1, wherein the determining step includes determining that there is a leak in the gas chromatography system if the first pressure differential and / or the first duration differs from an expected value established based on the second pressure differential and / or the second duration by more than a threshold amount.

3. 2. The method of claim 1, wherein the determining step includes determining that there is a leak in the gas chromatography system if the amount of gas indicated by the second duration differs from an established expectation from the amount of gas indicated by the first duration by more than a threshold amount and / or if the amount of gas indicated by the first duration differs from an established expectation from the amount of gas indicated by the second duration by more than a threshold amount.

4. 2. The method of claim 1, wherein the determining step includes determining that there is a leak based on a difference between an expected flow rate and a sum of the first flow rate and the second flow rate for each of the at least one open exhaust path that is greater than a threshold amount, the expected flow rate being established based on the first duration and the second duration.

5. The method of claim 1 , wherein flowing a gas through the column comprises flowing a gas through the column and at least one open exhaust path.

6. The method of claim 1 , wherein the step of opening at least one exhaust path comprises opening a plurality of exhaust paths.

7. The method of claim 1 , wherein one or more of the respective second flow rates is a multiple of the first flow rate and / or the third flow rate is a multiple of the first flow rate.

8. The method of claim 1 , wherein the at least one closed exhaust path is one or more of a septum purge path, a split path, and a vacuum path.

9. 2. The method of claim 1, wherein the first pressure is equal to the second pressure, the first pressure difference is equal to the second pressure difference, and / or the first duration is equal to the second duration.

10. The method of claim 1 , further comprising pressurizing the gas chromatography system at the first pressure and the second pressure by opening a gas inlet.

11. The method of claim 10 , further comprising the step of closing the gas inlet before the step of measuring the first duration and the step of measuring the second duration.

12. 2. The method of claim 1, further comprising, prior to measuring the first pressure difference and / or the first duration, calibrating the column by determining parameters of the column, the parameters including a length and an inner diameter of the column.

13. The method of claim 1 , wherein the gas chromatography system includes a mass spectrometer.

14. 10. The method of claim 1, further comprising the step of, following a determination that there is a leak, logging a record of the determination via the gas chromatography system and providing an indication to a user that a leak has been detected.

15. Following the determination that there was no leak, determining first parameters related to the first pressure differential and the first duration and / or the second pressure differential and the second duration; flowing gas through the column at a further flow rate to cause a further pressure change from a further pressure, defining a further pressure differential, and measuring a further duration of the further pressure differential and / or the further pressure change; The method of claim 1 , further comprising: determining whether there is a leak based on the first parameter, the additional pressure differential, and the additional duration.

16. The step of determining whether there is a leak comprises: the measured further duration differs from an expected value established based on the further pressure differential and the first parameter; and / or 16. The method of claim 15, comprising determining that there is a leak if the measured further pressure differential differs from an expected value based on the further duration and the first parameter.

17. The step of determining whether there is a leak comprises: determining further parameters relating to said further pressure differential and said further duration; and determining that there is a leak if the further parameter differs from the first parameter by more than a threshold amount.

18. The first parameter represents a pressure drop per time increment, and the determining step comprises: determining an additional parameter representative of a pressure drop per time increment based on the additional pressure difference and the additional time duration; and determining that there is a leak if the additional parameter is greater than the first parameter.

19. 1. A system comprising: a gas chromatography apparatus; and a controller configured to operate the gas chromatography apparatus, In a gas chromatography system having at least one closed exhaust path, flowing gas at a first flow rate through a column of the gas chromatography system to cause a first pressure change from a first pressure, the first pressure change defining a first pressure differential, and measuring a first duration of the first pressure differential and / or the first pressure change; opening the at least one closed exhaust path and setting a respective second flow rate through each of the at least one open exhaust path; causing a second pressure change from a second pressure within the gas chromatography system by flowing the gas at a third flow rate through the column and flowing the gas at the respective second flow rate through each of the at least one open exhaust path, the second pressure change defining a second pressure differential, and measuring a second duration of the second pressure differential and / or the second pressure change; and operating the gas chromatography apparatus to determine whether there is a leak in the gas chromatography system based on the measured first pressure differential and / or first duration and the measured second pressure differential and / or second duration.

20. A non-transitory storage medium storing machine-executable instructions that, when executed, cause a computing device to perform the steps of: In a gas chromatography system having at least one closed exhaust path, flowing gas at a first flow rate through a column of the gas chromatography system to cause a first pressure change from a first pressure, the first pressure change defining a first pressure differential, and measuring the first pressure differential and / or a first duration of the first pressure change; opening at least one closed exhaust path and setting a respective second flow rate through each of the at least one open exhaust path; causing a second pressure change from a second pressure in the gas chromatography system by flowing the gas through the column at a third flow rate and flowing the gas through each of the at least one open exhaust path at the respective second flow rate, the second pressure change defining a second pressure differential, and measuring the second pressure differential and / or a second duration of the second pressure change; and determining whether there is a leak in the gas chromatography system based on the measured first pressure differential and / or first duration and the measured second pressure differential and / or second duration.

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