A GC-DID-MSD tandem analytical instrument and its detection and control method

Abstract

This invention relates to the field of trace analysis technology and discloses a GC-DID-MSD tandem analytical instrument and its detection and control method. The instrument includes: a gas chromatography injection module, a chromatographic separation capillary column, a DID detection unit, a damped capillary column, and an MSD detection unit connected in series. The gas chromatography injection module is connected to the chromatographic separation capillary column and is used to introduce the sample carried by the carrier gas He1 into the chromatographic separation capillary column to obtain the separated components. The chromatographic separation capillary column is connected to the DID detection unit and is used to sequentially deliver the separated components to the DID detection unit for detection. The output of the DID detection unit is connected to the damped capillary column. The damped capillary column is connected to the MSD detection unit. The MSD detection unit is used for mass spectrometry detection of the damped gas. This invention simplifies the detection process and avoids errors caused by multiple injections.

Description

Technical Field

[0001] This invention relates to the field of trace analysis technology, and more specifically, to a GC-DID-MSD tandem analytical instrument and its detection and control method. Background Technology

[0002] In the field of trace analysis, mass spectrometry detectors (MSD) excel in qualitative analysis, with quantitative detection limits reaching the ppm level; while discharge helium ionization detectors (DID) are renowned for their superior quantitative capabilities, with detection limits approaching the ppb level. It is noteworthy that both MSD and DID are universal detectors, providing excellent responses to almost all compounds—an advantage unmatched by most other detectors. However, the combined use of these two detectors has not yet been successfully implemented.

[0003] For the qualitative analysis of small molecule compounds, gas chromatography-mass spectrometry (GC-MS, also known as GC-MSD) is currently the most mature technology. This is mainly due to its mass spectrometry database of over 300,000 spectra, each containing rich molecular fragment information available for manual interpretation. Therefore, GC-MSD has become the preferred tool for the qualitative analysis of small molecule compounds. However, mass spectrometry data does not perform as well as expected when used for quantitative analysis: due to the significant differences in mass spectrometry responses among different compounds (sometimes up to 10 times or even higher), the reliability of quantitative results for mixtures is significantly affected.

[0004] Therefore, it is necessary to design a GC-DID-MSD tandem analytical instrument and its detection and control method to solve the problems existing in the current technology. Summary of the Invention

[0005] In view of this, the present invention proposes a GC-DID-MSD tandem analytical instrument and its detection and control method, aiming to solve the problem that the two detectors cannot be used in combination in the prior art, and cannot simultaneously achieve accurate characterization and accurate quantification of trace components.

[0006] In one aspect, the present invention proposes a GC-DID-MSD tandem analytical instrument, comprising: The gas chromatography injection module, chromatographic separation capillary column, DID detection unit, damped capillary column, and MSD detection unit are connected in series sequentially; among them... The gas chromatography injection module is connected to the chromatographic separation capillary column and is used to introduce the sample carried by the carrier gas He1 into the chromatographic separation capillary column to obtain the separated components. The chromatographic separation capillary column is connected to the DID detection unit and is used to sequentially deliver the separated components to the DID detection unit for detection. The output of the DID detection unit is connected to the damping capillary column, and is used to combine the gas after DID detection with the discharge gas He2 before entering the damping capillary column. The damping capillary column is connected to the MSD detection unit and is used to limit the gas flow rate entering the MSD detection unit. The MSD detection unit is used to perform mass spectrometry detection on the damped gas. The signals from both the DID detection unit and the MSD detection unit are connected to the chromatography workstation for synchronous acquisition and analysis.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: By connecting the DID detection unit and the MSD detection unit in series and combining the damping capillary column to adjust and limit the gas flow rate, the present invention retains the advantages of the DID discharge ionization detector in terms of high sensitivity and wide linear range for permanent gases and weakly polar electronegative substances, while also utilizing the qualitative capabilities of the mass spectrometer detector to solve the problem that it is difficult to distinguish target components in complex matrices by relying solely on DID retention time for qualitative analysis. It can simultaneously achieve accurate quantification and reliable qualitative analysis of target components, significantly improving the accuracy and reliability of the detection results. At the same time, the entire instrument can complete the synchronous detection of dual detectors with only one injection, eliminating the need for secondary injection analysis, simplifying the detection process, and avoiding errors caused by multiple injections. It is suitable for the precise analysis and detection of trace permanent gases and low-boiling-point components.

[0008] In another aspect, the present invention also proposes a detection and control method for a GC-DID-MSD tandem analytical instrument, comprising the following steps: Select the injection conditions, and control the gas chromatography injection module under the injection conditions so that the carrier gas He1 carries the sample to be tested into the chromatographic separation capillary column for component separation, so as to obtain the chromatographic elution sequence of single components flowing out sequentially. Based on the chromatographic elution sequence, each single component is sequentially introduced into the DID detection unit for detection, and the discharge gas He2 of the DID detection unit is combined with the single component at the detection outlet to form a mixed gas flow. The mixed airflow is introduced into the damping capillary column, which limits the total gas flow rate entering the MSD detection unit so that the gas flow rate entering the MSD detection unit is attenuated to a preset range. Under the premise of meeting the MSD detection flow conditions, the gas treated by the damped capillary column is introduced into the MSD detection unit for mass spectrometry detection to obtain the mass spectrometry signal of the corresponding component. The signals from the DID detection unit and the MSD detection unit are acquired synchronously, and data matching processing is performed based on the time correspondence to obtain the target component identification results and peak feature analysis results.

[0009] Furthermore, the injection conditions include the injection port temperature, carrier gas He1 flow rate, split ratio, and sample injection volume.

[0010] Furthermore, when each individual component is sequentially introduced into the DID detection unit for detection based on the chromatographic elution sequence, the process includes: A single-component time window control signal is generated based on the peak elution time information of the chromatographic separation capillary column, and the sampling triggering of the DID detection unit is time-controlled according to the time window control signal. The chromatographic elution sequence is monitored in real time using a chromatography workstation, and the peak start time and peak end time of each individual component are extracted to form the entry time interval of each component. The detection sampling period of the DID detection unit is controlled based on the single component entry time interval, so that the detection sampling corresponds to the single component outflow process on the time axis. During the detection sampling period, the discharge state of the DID detection unit and the detection response channel are controlled to be in a stable working mode, so that the corresponding DID response signal is generated after the single component enters the detection area in sequence. The DID detection unit continuously detects single components and outputs the detection signal to the chromatography workstation to form a DID detection sequence corresponding to the chromatographic elution sequence.

[0011] Furthermore, when limiting the total gas flow rate entering the MSD detection unit through the damping capillary column, the following methods are included: The rated injection flow range and the stable operating threshold of the vacuum system of the MSD detection unit are obtained, and the initial flow control quantity is determined based on the rated injection flow range and the stable operating threshold of the vacuum system. The outlet gas flow rate of the DID detection unit and the inlet flow rate of the discharge gas He2 are obtained, and the flow rates of the two gases are superimposed to calculate the theoretical flow rate value of the mixed gas. A flow deviation value is generated based on the deviation relationship between the theoretical flow rate of the mixed gas and the initial flow control value; The inlet flow distribution ratio and outlet back pressure control parameters of the gas entering the damping capillary column are adjusted based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column. The flow rate of the mixed gas is controlled by adjusting the flow resistance conditions, so that the total flow rate of the gas entering the MSD detection unit is stabilized within the target flow rate range.

[0012] Furthermore, when determining the initial flow control quantity based on the rated injection flow range and the stable operating threshold of the vacuum system, the following steps are included: Based on the stable operating threshold of the vacuum system, the boundary constraints of the target flow range are corrected to obtain the stable operating flow range; An intermediate flow rate value is selected within the stable operating flow rate range as the initial flow control value.

[0013] Further, when correcting the boundary constraints of the target flow range based on the stable operating threshold of the vacuum system to obtain the stable operating flow range, the following steps are included: Acquire vacuum response data of the MSD detection unit vacuum system under different sample flow rates, and establish the correspondence between flow rate and vacuum degree; The allowable range of vacuum degree variation is determined based on the stable operating threshold of the vacuum system, and flow rate sub-intervals that meet the vacuum stability conditions are selected based on the allowable range of vacuum degree variation. The upper limit flow value of the flow sub-interval is truncated by a threshold, and the truncated flow sub-interval is integrated to obtain a continuous and stable flow interval. The continuous stable flow range is taken as the stable working flow range.

[0014] Further, when adjusting the inlet flow distribution ratio and outlet back pressure control parameters of the gas entering the damping capillary column based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column, the following steps are included: Obtain the flow deviation value, and determine the flow adjustment direction and adjustment level based on the sign of the flow deviation value; When the flow deviation is positive, the inlet flow distribution ratio into the damping capillary column is reduced according to the preset first inlet flow adjustment step, and the outlet back pressure control parameter is increased according to the preset first back pressure adjustment step. When the flow deviation value is negative, the inlet flow distribution ratio entering the damping capillary column is increased according to the preset second inlet flow adjustment step size, and the outlet back pressure control parameter is decreased according to the preset second back pressure adjustment step size.

[0015] Furthermore, the preset first inlet flow rate adjustment step, the preset first back pressure adjustment step, the preset second inlet flow rate adjustment step, and the preset second back pressure adjustment step are set in stages according to the absolute value of the flow rate deviation value.

[0016] It is understandable that the above-mentioned GC-DID-MSD tandem analytical instrument and its detection and control method have the same beneficial effects, and will not be elaborated further here. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural block diagram of the GC-DID-MSD tandem analytical instrument provided in an embodiment of the present invention; Figure 2 A flowchart of the detection and control method for the GC-DID-MSD tandem analytical instrument provided in an embodiment of the present invention.

[0019] In the diagram: 100, Gas chromatography injection module; 200, Chromatographic separation capillary column; 300, DID detection unit; 400, Damped capillary column; 500, MSD detection unit. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] See Figure 1 As shown in some embodiments of this application, this embodiment provides a GC-DID-MSD tandem analysis instrument, including: The gas chromatography injection module 100, the chromatographic separation capillary column 200, the DID detection unit 300, the damping capillary column 400, and the MSD detection unit 500 are connected in series sequentially; among them, The gas chromatography injection module 100 is connected to the chromatographic separation capillary column 200 and is used to introduce the sample carried by the carrier gas He1 into the chromatographic separation capillary column 200 to obtain the separated components. The chromatographic separation capillary column 200 is connected to the DID detection unit 300, which is used to sequentially deliver the separated components to the DID detection unit 300 for detection; The output of the DID detection unit 300 is connected to the damping capillary column 400, which is used to combine the gas after DID detection with the discharge gas He2 and then enter the damping capillary column 400. The damping capillary column 400 is connected to the MSD detection unit 500 and is used to limit the gas flow rate entering the MSD detection unit 500. The MSD detection unit 500 is used for mass spectrometry detection of damped gas. The signals from both the DID detection unit 300 and the MSD detection unit 500 are connected to the chromatography workstation for synchronous acquisition and analysis.

[0023] It is understood that this embodiment, by connecting the DID detection unit 300 and the MSD detection unit 500 in series and combining the damping capillary column 400 to regulate the gas flow rate, retains the advantages of the DID discharge ionization detector in terms of high sensitivity and wide linear range for permanent gases and weakly polar electronegative substances. At the same time, it utilizes the qualitative capabilities of the mass spectrometer detector to solve the problem that it is difficult to distinguish target components in complex matrices by relying solely on DID retention time for qualitative analysis. It can simultaneously achieve accurate quantification and reliable qualitative analysis of target components, significantly improving the accuracy and reliability of the detection results. In addition, the entire instrument can complete the synchronous detection of dual detectors with only one injection, eliminating the need for secondary injection analysis, simplifying the detection process, and avoiding errors caused by multiple injections. It is suitable for the precise analysis and detection of trace permanent gases and low-boiling-point components.

[0024] See Figure 2 As shown in some embodiments of this application, this embodiment provides a detection and control method for a GC-DID-MSD tandem analytical instrument, including the following steps: S100: Select the injection conditions, and control the gas chromatography injection module under the injection conditions so that the carrier gas He1 carries the sample to be tested into the chromatographic separation capillary column for component separation, so as to obtain the chromatographic elution sequence of single components flowing out sequentially. S200: Based on the chromatographic elution sequence, each single component is sequentially introduced into the DID detection unit for detection, and the discharge gas He2 of the DID detection unit is combined with the single component at the detection outlet to form a mixed gas flow. S300: The mixed airflow is introduced into the damping capillary column, and the total flow rate of the gas entering the MSD detection unit is limited by the damping capillary column; S400: Under the premise of meeting the MSD detection flow conditions, the gas treated by the damped capillary column is introduced into the MSD detection unit for mass spectrometry detection to obtain the mass spectrometry signal of the corresponding component. S500: Controls the synchronous acquisition of signals from the DID detection unit and the MSD detection unit, and performs data matching processing based on the time correspondence to obtain target component identification results and peak feature analysis results.

[0025] It is understandable that meeting the MSD detection flow rate conditions means that the total gas flow rate entering the MSD detection unit 500 is within its rated injection flow rate range, and that the vacuum level of the MSD vacuum system can be maintained at the stable operating threshold. This will prevent the vacuum system from being overloaded due to excessive injection flow rate, which would affect the ion source ionization efficiency, mass spectrometry signal stability, and the service life of the vacuum system. This ensures that the mass spectrometry detection process can operate continuously and stably, and obtain accurate and reliable mass spectrometry qualitative data.

[0026] It is understandable that controlling the synchronous acquisition of signals from the DID detection unit 300 and the MSD detection unit 500, and performing data matching processing based on time correspondence to obtain target component identification results and peak characteristic analysis results, means firstly, matching the retention time and response signal obtained from DID detection with the retention time and mass spectrum information obtained from MSD detection one by one according to a unified acquisition time axis, so that the DID quantitative response signal and the MSD mass spectrometry qualitative signal of the same single component are matched one by one; then, using the MSD mass spectrum database to search and match each component, and combining the chromatographic retention time information to complete the accurate qualitative identification of the target component; finally, extracting the DID response peak area or peak height of each target component from the matched signal, and combining it with the pre-established quantitative calibration curve to complete the accurate quantification of the target component, and finally outputting the qualitative identification result and quantitative result of the target component simultaneously.

[0027] Specifically, the injection conditions include the injection port temperature, the He1 carrier gas flow rate, the split ratio, and the sample injection volume.

[0028] It is understandable that the injection port temperature refers to the operating temperature of the injection port of the gas chromatography injection module 100. Its setting must ensure that the sample to be tested can be completely vaporized while avoiding thermal decomposition. It is typically set not lower than the boiling point temperature of the highest boiling point component in the sample and not higher than the sample decomposition temperature, to ensure that all components can be smoothly vaporized and expelled with the carrier gas into the chromatographic separation capillary column 200. The carrier gas He1 flow rate needs to be adjusted according to the specifications, inner diameter, column capacity, and expected separation effect of the chromatographic separation capillary column 200 to ensure good baseline separation of each component and avoid peak overlap interfering with subsequent detection matching. The split ratio is determined based on the concentration range of the target component in the sample. For higher concentrations, the split ratio is appropriately increased to avoid column overload and peak distortion. For lower concentrations, the split ratio can be reduced or even splitless injection can be used to ensure sufficient response intensity for the target component. The sample injection volume needs to be determined in conjunction with the split ratio and the linear range of the detector to ensure that the response signal of the target component is within the linear range of the DID and MSD detectors, avoiding overload and quantitative errors.

[0029] Specifically, when each single component is sequentially introduced into the DID detection unit 300 for detection based on the chromatographic elution sequence, the process includes: A single-component time window control signal is generated based on the peak elution time information of the chromatographic separation capillary column 200, and the sampling triggering of the DID detection unit 300 is time-controlled according to the time window control signal. The chromatographic elution sequence is monitored in real time using a chromatography workstation, and the peak start time and peak end time of each individual component are extracted to form the entry time interval of each component. The detection sampling period of the DID detection unit 300 is controlled based on the single component entry time interval, so that the detection sampling corresponds to the single component outflow process on the time axis. During the detection sampling period, the discharge state of the DID detection unit 300 and the detection response channel are controlled to be in a stable working mode, so that the corresponding DID response signal is generated after the single component enters the detection area in sequence. The DID detection unit 300 continuously detects single components and outputs the detection signal to the chromatography workstation to form a DID detection sequence corresponding to the chromatographic elution sequence.

[0030] It is understandable that by controlling sampling through timing, it is possible to ensure that the outflow process of a single component is fully collected, avoiding the omission of key peak information, while reducing invalid sampling during non-peak periods, reducing data storage redundancy, improving the efficiency of subsequent data processing, and also helping to maintain the stability of the DID discharge state, extend the life of the detector, and ensure the stability and repeatability of the response signal.

[0031] Specifically, when limiting the total gas flow rate entering the MSD detection unit 500 via the damping capillary column 400, the following is included: Obtain the rated injection flow range and the stable operating threshold of the vacuum system for the MSD detection unit 500, and determine the initial flow control quantity based on the rated injection flow range and the stable operating threshold of the vacuum system; The outlet gas flow rate of the DID detection unit 300 and the introduction flow rate of the discharge gas He2 are obtained, and the flow rates of the two gases are superimposed to calculate the theoretical flow rate value of the mixed gas. The flow deviation value is generated based on the deviation relationship between the theoretical flow rate of the mixed gas and the initial flow control value. The inlet flow distribution ratio and outlet back pressure control parameters of the gas entering the damping capillary column 400 are adjusted based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column 400. The flow rate of the mixed gas is controlled by adjusting the flow resistance conditions, so that the total flow rate of the gas entering the MSD detection unit 500 is stabilized within the target flow rate range.

[0032] It is understandable that the rated injection flow rate range refers to the flow rate interval between the maximum and minimum injection flow rates that allow the MSD detection unit 500 to operate continuously and stably while ensuring detection accuracy. Within this range, the ion source ionization efficiency of the MSD detection unit 500 is stable, the mass analyzer operates normally, and the intensity and signal-to-noise ratio of the mass spectrometry signal meet the qualitative detection requirements. Signal distortion or abnormal equipment operation will not occur due to flow rates exceeding the range. The stable operating threshold of the vacuum system refers to the maximum inlet flow rate threshold at which the vacuum system can maintain normal operation without the vacuum level dropping beyond the allowable range due to excessive load. Once the injection flow rate exceeds this threshold, the vacuum system load will continuously increase, and the vacuum level will decrease, which will not only affect the mass spectrometry detection performance but may also damage the vacuum system components.

[0033] Understandably, the specific steps for obtaining the outlet gas flow rate of the DID detection unit 300 and the inlet flow rate of the discharge gas He2, and then calculating the theoretical flow rate of the mixed gas by superimposing the flow rates of the two gases, are as follows: First, the flow rate of the gas flowing out of the DID outlet is sampled and detected in real time, while the flow rate of the introduced discharge gas He2 is collected in real time. The two flow rate values ​​collected at the same time are summed to obtain the theoretical total flow rate of the mixed gas flow before entering the damping capillary column 400 at that moment. Subsequently, the difference between this theoretical total flow rate and the predetermined target control flow rate value is calculated to obtain the aforementioned flow deviation value, which is used for subsequent flow regulation and control.

[0034] Specifically, when determining the initial flow control quantity based on the rated injection flow range and the stable operating threshold of the vacuum system, the following should be included: Based on the stable operating threshold of the vacuum system, the boundary constraints of the target flow range are corrected to obtain the stable operating flow range; Within the stable operating flow range, select the intermediate flow value as the initial flow control value.

[0035] It is understandable that the target flow range refers to the flow control range preset in combination with the rated injection flow requirements of the MSD detection unit. When initially setting it, the upper and lower limits of the rated injection flow range should be used as the initial boundaries of the target flow range.

[0036] Specifically, when correcting the boundary constraints of the target flow range based on the stable operating threshold of the vacuum system to obtain the stable operating flow range, the following steps are taken: Acquire vacuum response data of the MSD detection unit 500 vacuum system under different injection flow rates, and establish the correspondence between flow rate and vacuum degree; The allowable range of vacuum degree variation is determined based on the stable operating threshold of the vacuum system, and flow rate sub-intervals that meet the vacuum stability conditions are selected based on the allowable range of vacuum degree variation. Threshold truncation is performed on the upper limit flow value of the flow sub-interval, and interval integration is performed on the truncated flow sub-interval to obtain a continuous and stable flow interval. The continuous and stable flow range is taken as the stable working flow range.

[0037] Understandably, determining the allowable range of vacuum variation based on the stable operating threshold of the vacuum system, and then selecting flow rate sub-intervals that meet the vacuum stability conditions based on this allowable range, means taking the minimum vacuum level required for normal operation of the vacuum system as the lower limit of the allowable range and the initial vacuum level as the upper limit. All flow rate points in the flow rate-vacuum level correspondence that meet the allowable vacuum level range are extracted. These flow rate points constitute the sub-intervals that meet the vacuum stability conditions. If no flow rate points meet the conditions, it indicates that the current total injection flow rate exceeds the maximum capacity of the vacuum system, requiring adjustment of the flow parameters of the DID discharge gas He2 to reduce the total mixed gas flow rate before re-selection. Threshold truncation is performed on the upper limit flow rate values ​​of the flow rate sub-intervals. Specifically, the portion exceeding the stable operating threshold of the vacuum system is directly removed, retaining only the flow rate range below the threshold to prevent excessive flow exceeding the vacuum system's capacity. Then, all the dispersed flow rate sub-intervals obtained after truncation are merged to obtain a continuous flow rate interval. This interval is the stable operating flow rate interval that simultaneously meets the MSD rated injection requirements and the stable operation requirements of the vacuum system.

[0038] Understandably, threshold truncation of the upper limit flow rate of the flow rate sub-interval and interval integration of the truncated flow rate sub-intervals to obtain a continuous stable flow rate interval means merging and connecting the endpoints of the dispersed and adjacent sub-intervals. If there are gaps between multiple dispersed sub-intervals, their independent interval ranges are retained. The continuous interval with the largest total length among all retained intervals is the final stable working flow rate interval. If all sub-intervals are discontinuous after truncation, it means that the current parameter combination cannot meet the vacuum stability requirements. It is necessary to readjust the upstream DID discharge gas flow rate and injection parameters, reduce the total injection flow rate, and recalculate and screen.

[0039] Specifically, adjusting the inlet flow distribution ratio and outlet back pressure control parameters of the damping capillary column 400 based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column 400 includes: Obtain the flow deviation value, and determine the direction and adjustment level of flow adjustment based on the sign of the flow deviation value; When the flow deviation is positive, the inlet flow distribution ratio into the damping capillary column 400 is reduced according to the preset first inlet flow adjustment step size, and the outlet back pressure control parameter is increased according to the preset first back pressure adjustment step size. When the flow deviation is negative, the inlet flow distribution ratio into the damping capillary column 400 is increased according to the preset second inlet flow adjustment step, and the outlet back pressure control parameter is decreased according to the preset second back pressure adjustment step.

[0040] Specifically, the preset first inlet flow rate adjustment step, the preset first back pressure adjustment step, the preset second inlet flow rate adjustment step, and the preset second back pressure adjustment step are set in stages according to the absolute value of the flow rate deviation.

[0041] Understandably, the larger the absolute value of the flow deviation, the greater the deviation between the actual total flow and the target control quantity. Therefore, a larger adjustment step size is needed to accelerate the adjustment convergence speed and prevent the flow from being in a deviated state for a long time, which would affect the stable operation of the MSD detection unit 500. Conversely, when the absolute value of the flow deviation is small, it means that the current flow is close to the target control range. At this time, a smaller adjustment step size can be used to avoid over-adjustment and flow oscillation, thus improving the stability of flow control. Through the coordinated control of inlet flow distribution ratio adjustment and outlet back pressure adjustment, the effective flow resistance of the damping capillary column 400 can be precisely changed, achieving stable control of the total flow entering the MSD detection unit 500, while retaining sufficient target components to enter the mass spectrometry detection unit, ensuring the accuracy of qualitative identification.

[0042] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A GC-DID-MSD tandem analytical instrument, characterized in that, include: The gas chromatography injection module, chromatographic separation capillary column, DID detection unit, damped capillary column, and MSD detection unit are connected in series sequentially; among them... The gas chromatography injection module is connected to the chromatographic separation capillary column and is used to introduce the sample carried by the carrier gas He1 into the chromatographic separation capillary column to obtain the separated components. The chromatographic separation capillary column is connected to the DID detection unit and is used to sequentially deliver the separated components to the DID detection unit for detection. The output of the DID detection unit is connected to the damping capillary column, and is used to combine the gas after DID detection with the discharge gas He2 before entering the damping capillary column. The damping capillary column is connected to the MSD detection unit and is used to limit the gas flow rate entering the MSD detection unit. The MSD detection unit is used to perform mass spectrometry detection on the damped gas. The signals from both the DID detection unit and the MSD detection unit are connected to the chromatography workstation for synchronous acquisition and analysis.

2. A detection and control method for a GC-DID-MSD tandem analytical instrument, applied in the GC-DID-MSD tandem analytical instrument as described in claim 1, characterized in that, include: Select the injection conditions, and control the gas chromatography injection module under the injection conditions so that the carrier gas He1 carries the sample to be tested into the chromatographic separation capillary column for component separation, so as to obtain the chromatographic elution sequence of single components flowing out sequentially. Based on the chromatographic elution sequence, each single component is sequentially introduced into the DID detection unit for detection, and the discharge gas He2 of the DID detection unit is combined with the single component at the detection outlet to form a mixed gas flow. The mixed airflow is introduced into the damping capillary column, which limits the total gas flow rate entering the MSD detection unit so that the gas flow rate entering the MSD detection unit is attenuated to a preset range. Under the premise of meeting the MSD detection flow conditions, the gas treated by the damped capillary column is introduced into the MSD detection unit for mass spectrometry detection to obtain the mass spectrometry signal of the corresponding component. The signals from the DID detection unit and the MSD detection unit are acquired synchronously, and data matching processing is performed based on the time correspondence to obtain the target component identification results and peak feature analysis results.

3. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 2, characterized in that, The injection conditions include the injection port temperature, carrier gas He1 flow rate, split ratio, and sample injection volume.

4. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 3, characterized in that, When each single component is sequentially introduced into the DID detection unit for detection based on the chromatographic elution sequence, the following is included: A single-component time window control signal is generated based on the peak elution time information of the chromatographic separation capillary column, and the sampling triggering of the DID detection unit is time-controlled according to the time window control signal. The chromatographic elution sequence is monitored in real time using a chromatography workstation, and the peak start time and peak end time of each individual component are extracted to form the entry time interval of each component. The detection sampling period of the DID detection unit is controlled based on the single component entry time interval, so that the detection sampling corresponds to the single component outflow process on the time axis. During the detection sampling period, the discharge state of the DID detection unit and the detection response channel are controlled to be in a stable working mode, so that the corresponding DID response signal is generated after the single component enters the detection area in sequence. The DID detection unit continuously detects single components and outputs the detection signal to the chromatography workstation to form a DID detection sequence corresponding to the chromatographic elution sequence.

5. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 4, characterized in that, When limiting the total gas flow rate entering the MSD detection unit through the damping capillary column, the following is included: The rated injection flow range and the stable operating threshold of the vacuum system of the MSD detection unit are obtained, and the initial flow control quantity is determined based on the rated injection flow range and the stable operating threshold of the vacuum system. The outlet gas flow rate of the DID detection unit and the inlet flow rate of the discharge gas He2 are obtained, and the flow rates of the two gases are superimposed to calculate the theoretical flow rate value of the mixed gas. A flow deviation value is generated based on the deviation relationship between the theoretical flow rate of the mixed gas and the initial flow control value; The inlet flow distribution ratio and outlet back pressure control parameters of the gas entering the damping capillary column are adjusted based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column. The flow rate of the mixed gas is controlled by adjusting the flow resistance conditions, so that the total flow rate of the gas entering the MSD detection unit is stabilized within the target flow rate range.

6. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 5, characterized in that, When determining the initial flow control quantity based on the rated injection flow range and the stable operating threshold of the vacuum system, the following are included: Based on the stable operating threshold of the vacuum system, the boundary constraints of the target flow range are corrected to obtain the stable operating flow range; An intermediate flow rate value is selected within the stable operating flow rate range as the initial flow control value.

7. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 6, characterized in that, When the target flow range is corrected by boundary constraints based on the stable operating threshold of the vacuum system to obtain the stable operating flow range, the following steps are taken: Acquire vacuum response data of the MSD detection unit vacuum system under different sample flow rates, and establish the correspondence between flow rate and vacuum degree; The allowable range of vacuum degree variation is determined based on the stable operating threshold of the vacuum system, and flow rate sub-intervals that meet the vacuum stability conditions are selected based on the allowable range of vacuum degree variation. The upper limit flow value of the flow sub-interval is truncated by a threshold, and the truncated flow sub-interval is integrated to obtain a continuous and stable flow interval. The continuous stable flow range is taken as the stable working flow range.

8. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 7, characterized in that, When adjusting the inlet flow distribution ratio and outlet back pressure control parameters of the gas entering the damping capillary column based on the flow deviation value to change the flow resistance conditions of the gas in the damping capillary column, the following methods are included: Obtain the flow deviation value, and determine the flow adjustment direction and adjustment level based on the sign of the flow deviation value; When the flow deviation is positive, the inlet flow distribution ratio into the damping capillary column is reduced according to the preset first inlet flow adjustment step, and the outlet back pressure control parameter is increased according to the preset first back pressure adjustment step. When the flow deviation value is negative, the inlet flow distribution ratio entering the damping capillary column is increased according to the preset second inlet flow adjustment step size, and the outlet back pressure control parameter is decreased according to the preset second back pressure adjustment step size.

9. The detection and control method for the GC-DID-MSD tandem analytical instrument according to claim 8, characterized in that, The preset first inlet flow rate adjustment step, preset first back pressure adjustment step, preset second inlet flow rate adjustment step, and preset second back pressure adjustment step are set in stages according to the absolute value of the flow rate deviation.

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