Chromatographic analysis device and method

Abstract

The invention relates to a chromatographic technology, and particularly provides a chromatographic analysis device and method.The chromatographic analysis device comprises an enrichment module, a first chromatographic column, a first detector and an analysis module; the two ends of the enrichment module are connected with a first switching module, when the first switching module is switched to a sampling state, sample gas sequentially passes through the first switching module and the enrichment module and enters the second detector, and when the first switching module is switched to a sample injection state, carrier gas sequentially passes through the first switching module, the enrichment module and the first chromatographic column and enters the first detector; a port of the first switching module is connected with a second detector, and the response time of the second detector is not longer than that of the first detector; the judgment module is used for judging whether the output value of the second detector exceeds a threshold value or not; and the controller is used for stopping sampling when the judgment result is yes. The method has the advantages of good data reliability and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to chromatography, in particular to a chromatographic analysis device and method. BACKGROUND

[0002] The pre-concentrator of the VOCs online monitoring system generally adopts the technical scheme of low-temperature trapping of enrichment tubes and high-temperature desorption, but the enrichment tubes have a certain trapping upper limit. When the VOCs in the ambient air exceed a certain concentration, the enrichment tube will be penetrated, that is, the measured substances in the sample gas cannot be trapped in the enrichment tube and are directly discharged, thereby directly causing the concentration measurement value to be inaccurate (low). The penetration of the enrichment tube is related to the enrichment temperature, the amount of filler, the sampling volume, the sample concentration, etc. Under normal circumstances, people will determine the amount of enrichment filler, the sampling volume, etc. in advance according to the general concentration range of the sample to be measured and the enrichment temperature condition. In actual testing, the sample concentration fluctuation range is relatively large or the enrichment temperature changes, which may cause sample penetration, but the accurate determination of whether each group of samples is penetrated or not is not performed.

[0003] In addition, in order to accurately quantify, two chromatographic columns with different polarities may be used in the sample separation stage, and the mass spectrometry detector can also quantify by extracting different fragment ions between the co-flow components, but there are still some isomers (such as 2,3-dimethylbutane and 2-methylpentane; m-, p-xylene, etc.) with similar retention times and the same fragment ion types, which cannot be effectively excluded from each other by extracting ions (especially for low-concentration ambient air). SUMMARY

[0004] To solve the above problems in the prior art, the present application provides a chromatographic analysis device.

[0005] The purpose of the present application is achieved by the following technical solutions: A chromatographic analysis device, comprising an enrichment module, a first chromatographic column, a first detector and an analysis module; the chromatographic analysis device further comprises: A first switching module, two ends of the enrichment module are connected to the first switching module, when the first switching module is switched to a sampling state, sample gas passes through the first switching module and the enrichment module in sequence and enters the second detector, when it is switched to a sample injection state, carrier gas passes through the first switching module, the enrichment module and the first chromatographic column in sequence and enters the first detector; A second detector, a port of the first switching module is connected to the second detector, the response time of the second detector is not higher than that of the first detector; A judgment module, the judgment module is used to judge whether the output value of the second detector exceeds a threshold value; A controller, the controller is used to stop sampling when the judgment result is yes.

[0006] The application also aims at providing a chromatographic analysis method.

[0007] The chromatographic analysis method comprises the following steps: A1. The first switching module is switched to a sampling state, sample gas passes through the first switching module and the enrichment module in sequence, and enters a second detector, the response time of the second detector being not higher than that of the first detector; A2. The judging module judges whether the output value of the second detector exceeds a threshold value or not; If the result is yes, sampling is stopped; If the result is no, normal sampling is carried out; A3. When the first switching module is switched to an injection state, carrier gas passes through the first switching module, the enrichment module and the first chromatographic column in sequence, and enters the first detector; A4. The analyzing module outputs the concentration of components in the sample gas.

[0008] Compared with the prior art, the application has the beneficial effects that: 1. The second detector is used to monitor the exhaust gas of each sample group after being captured by the enrichment module in real time, so that the breakthrough of each sample group after enrichment is avoided (or the sampling is stopped immediately when the breakthrough moment is recognized), and the measurement accuracy of the sample concentration is improved; When the ambient air sample encounters a sudden high concentration value exceeding the enrichment upper limit of the enrichment tube, the application can monitor and trigger the stop of sampling in real time, use the current sampling volume for calculation, avoid the loss of the current data, and improve the detection upper limit of high concentration to a certain extent; 2. The application sets secondary separation (the second switching module, the empty column, the different stationary phase chromatographic column and the third switching module), selectively separates the components that cannot be completely separated by the conventional chromatographic column again, selectively improves the separation degree between the components with similar retention times (or co-eluted components), improves the accuracy of the concentration measurement of the co-eluted components, significantly reduces the cost (avoids adding a complete set of chromatographic column), has strong scalability, and does not significantly increase the separation time of the whole chromatograph. BRIEF DESCRIPTION OF DRAWINGS

[0009] The disclosure of the application will become more apparent with reference to the accompanying drawings. It is easy for those skilled in the art to understand that the drawings are only used to illustrate the technical solutions of the application, and are not intended to limit the protection scope of the application. In the drawings: Figure 1 is a structural schematic view of a chromatographic analysis device according to the application. DETAILED DESCRIPTION

[0010] Figure 1The alternative embodiments of the present application described in the following description and illustrated in the accompanying drawings are presented by way of example only. The novel methods and systems described herein can be implemented in various ways, and are not limited to the embodiments described herein. The present application is directed to overcoming one or more of the limitations set forth above. Numerous alternative embodiments of the present application will be apparent to those skilled in the art in view of the following detailed description.

[0011] Embodiment 1

[0012] A chromatographic analysis device according to one embodiment of the present application is shown in Figure 1 The device includes: The enrichment module 31, the first chromatographic column 11, the first detector 21 and the analysis module are all prior art in the field.

[0013] The enrichment module 31 is connected to the first switching module 41 at both ends. When the first switching module 41 is switched to the sampling state, the sample gas passes through the first switching module 41 and the enrichment module 31 in turn, and enters the second detector 22. When the first switching module 41 is switched to the injection state, the carrier gas passes through the first switching module 41, the enrichment module 31 and the first chromatographic column 11 in turn, and enters the first detector 21.

[0014] The port of the first switching module 41 is connected to the second detector 22. The response time of the second detector 22 is not higher than that of the first detector 21, thereby providing high sensitivity and fast response.

[0015] The judging module is used to judge whether the output value of the second detector 22 exceeds a threshold value.

[0016] The controller is used to stop sampling when the result of the judgment is yes. The specific stopping method is prior art in the field.

[0017] In order to meet the requirements of different separation degrees, the chromatographic analysis device further includes: The empty column 12 and the plurality of different stationary phase chromatographic columns 13-15 are connected in parallel, and the input end is connected to the second switching module 42, and the output end is connected to the third switching module 43.

[0018] When the second switching module 42 is switched, the outlet of the first chromatographic column 11 is selectively connected to any one of the empty column 12 and the plurality of different stationary phase chromatographic columns 13-15.

[0019] When the third switching module 43 is switched, the first detector 21 is selectively connected to any one of the empty column 12 and the plurality of different stationary phase chromatographic columns 13-15.

[0020] When the separation degree of the components separated by the first chromatographic column 11 meets the requirement, the controller controls the second switching module 42 and the third switching module 43 to select the empty column 12.

[0021] When the co-eluted components are separated by the first chromatographic column 11, the corresponding stationary phase chromatographic column is selected according to the physicochemical properties of the co-eluted components and the switching of the second switching module 42 and the third switching module 43.

[0022] When the output result of the judging module is yes, the analysis module outputs the component concentration C=C0·V0 / (V1-V2) in the sample gas, C0 is the output value of the first detector 21 when the judging result is no and the first switching module 41 is switched to the sampling state, V0 is the normal sampling volume, V1 is the sampling volume when the judging result is yes, and V2 is the volume between the first switching module 41 and the second detector 22.

[0023] The chromatographic analysis method of the embodiment of the present application, i.e., the working method of the chromatographic analysis device of the present embodiment, comprises the following steps: A1. The first switching module 41 is switched to the sampling state, and the sample gas sequentially passes through the first switching module 41 and the enrichment module 31, enters the second detector 22, and the response time of the second detector 22 is not higher than that of the first detector 21.

[0024] A2. The judging module judges whether the output value of the second detector 22 exceeds the threshold value.

[0025] If the result is yes, the sampling is stopped.

[0026] If the result is no, the normal sampling is performed.

[0027] A3. When the first switching module 41 is switched to the sampling state, the carrier gas sequentially passes through the first switching module 41, the enrichment module 31 and the first chromatographic column 11, and enters the first detector 21.

[0028] A4. The analysis module outputs the concentration of the components in the sample gas.

[0029] When the judging result is yes, the analysis module outputs the component concentration C=C0·V0 / (V1-V2) in the sample gas.

[0030] C0 is the output value of the first detector 21 when the judging result is no and the first switching module 41 is switched to the sampling state, V0 is the normal sampling volume, V1 is the sampling volume when the judging result is yes, and V2 is the volume between the first switching module 41 and the second detector 22.

[0031] In order to meet the requirements of different separation degrees, when the separation degree of the component separated by the first chromatographic column 11 meets the requirements, the controller controls the switching of the second switching module 42 and the third switching module 43, so that the component separated by the first chromatographic column 11 passes through the second switching module 42, the empty column 12 and the third switching module 43 in turn, and enters the first detector 21.

[0032] When the co-flow component is separated by the first chromatographic column 11, the controller controls the switching of the second switching module 42 and the third switching module 43 according to the physical and chemical properties of the co-flow component, so that the component separated by the first chromatographic column 11 passes through the second switching module 42, the selected chromatographic column and the third switching module 43 in turn, and enters the first detector 21.

[0033] Embodiment 2

[0034] Application example of the chromatographic analysis device and method of embodiment 1 of the present application.

[0035] In this application example, as shown in Figure 1 The first switching module 41 adopts a two-position multi-way valve, and the second switching module 42 and the third switching module 43 adopt multi-channel direction selection valves. The first detector 21 adopts an FID, and the second detector 22 adopts a PID. The enrichment module 31 adopts an enrichment tube with a temperature control function.

[0036] The chromatographic columns 13-15 adopt different stationary phases and temperatures, wherein the empty column 12 maintains a high temperature condition T0 (such as 100℃), and the remaining conventional chromatographic columns 13-15 maintain different low temperature conditions T1, T2, T3, etc. The temperature of each chromatographic column can be adjusted.

[0037] The carrier gas, the sample gas, both ends of the first chromatographic column 11 and the second detector 22 are communicated with the port of the first switching module 41.

[0038] The output end of the first chromatographic column 11 is connected to the second switching module 42, one end of the empty column 12 and the different stationary phase chromatographic columns 13-15 is connected to the second switching module 42, and the other end is connected to the third switching module 43. The first detector 21 is communicated with the third switching module 43.

[0039] The chromatographic analysis method of the embodiment of the present application, that is, the working method of the chromatographic analysis device of the present embodiment, includes the following steps: A1. The first switching module 41 is switched to a sampling state, the sample gas passes through the first switching module 41 and the enrichment module 31 in turn, and enters the second detector 22, and the response time of the second detector 22 is not higher than that of the first detector 21.

[0040] A2. The judging module judges whether the output value of the second detector 22 exceeds a threshold value.

[0041] If the result is yes, stop sampling.

[0042] If the result is no, normal sampling.

[0043] A3. When the first switching module 41 switches to the sampling state, the carrier gas sequentially passes through the first switching module 41, the enrichment module 31 and the first chromatographic column 11, and enters the first detector 21.

[0044] A4. When the result of the judgment is no, the analysis module outputs the concentration Co of the component in the sample gas.

[0045] When the result of the judgment is yes, the analysis module outputs the concentration C of the component in the sample gas, C=C0·V0 / (V1-V2).

[0046] Co is the output value of the first detector 21 when the result of the judgment is no and the first switching module 41 switches to the sampling state, V0 is the normal sampling volume, V1 is the sampling volume when the result of the judgment is yes, and V2 is the volume between the first switching module 41 and the second detector 22.

[0047] The formula for calculating the separation degree R between two components is the difference between the retention times of the adjacent two peaks divided by the average peak width of the two peaks. It is generally considered that when R≥1, the two peaks are well separated; when R<1, it is considered that there is a certain overlap or co-elution between the two peaks. The valve time and other parameters of the corresponding components can be set in advance according to the needs in the method. In the above process, when the separation degree of the components separated by the first chromatographic column 11 meets the requirements, such as R≥1, the controller controls the switching of the second switching module 42 and the third switching module 43, so that the components separated by the first chromatographic column 11 sequentially pass through the second switching module 42, the empty column 12 and the third switching module 43, and enter the first detector 21.

[0048] When the first chromatographic column 11 separates co-eluted components (such as R<1), the controller controls the switching of the second switching module 42 and the third switching module 43 according to the physicochemical properties of the co-eluted components (according to the principle of similar compatibility, a chromatographic column with a polarity close to that of the co-eluted components is selected and the temperature is appropriately reduced to improve the separation degree), so that the components separated by the first chromatographic column 11 sequentially pass through the second switching module 42, the selected chromatographic column and the third switching module 43, and enter the first detector 21.

[0049] For example, when detecting 57 PAMS gases in ambient air with the device, the first chromatographic column 11 can be a DB-1 chromatographic column, the first detector 21 can use an FID detector, and the second detector 22 can be a PID detector. Assuming that the signal intensity of the PID detector when detecting zero gas blank (or nitrogen blank) is 10 (i.e., the background threshold is 10), when the signal intensity output value of the PID is > 10, the enrichment module stops sampling; when the signal intensity output value is always ≤ 10, the enrichment module normally samples until the set volume (such as 900 mL). Among the 57 PAMS monitoring factors, the separation degree of some factors such as 2-methylhexane and 2,3-dimethylpentane in the first chromatographic column 11 can be < 1, but the separation degree in the DB-624 chromatographic column is > 1, so the chromatographic column 13 can be selected as a DB-624 chromatographic column (if necessary, the chromatographic column 13 can also be set to a low temperature such as 10°C to further improve the separation degree), and the related parameters such as the valve time of 2-methylhexane and 2,3-dimethylpentane are set in advance in the method, while the empty column 12 selects a certain length according to the actual situation to appropriately prolong the peak time of the substances after the co-flowing components, so as to prevent the peak overlap with the substances in the chromatographic column 13.

Claims

1. A chromatographic apparatus comprising an enrichment module, a first chromatographic column, a first detector and an analysis module; characterised in that, The chromatographic analysis device further comprises: A first switching module, two ends of the enrichment module are connected to the first switching module, when the first switching module is switched to a sampling state, sample gas passes through the first switching module and the enrichment module in sequence and enters a second detector, when the first switching module is switched to a sample injection state, carrier gas passes through the first switching module, the enrichment module and the first chromatographic column in sequence and enters the first detector; The second detector is connected to a port of the first switching module, and a response time of the second detector is not higher than that of the first detector; A judging module is configured to judge whether an output value of the second detector exceeds a threshold value; A controller is configured to stop sampling when the judging result is yes.

2. The chromatographic device of claim 1, wherein, The chromatographic analysis device further comprises: An empty column and a plurality of different stationary phase chromatographic columns are connected in parallel, an input end is connected to a second switching module, and an output end is connected to a third switching module; The second switching module is configured to selectively connect an outlet of the first chromatographic column to any one of the empty column and the plurality of different stationary phase chromatographic columns when the second switching module is switched; The third switching module is configured to selectively connect the first detector to any one of the empty column and the plurality of different stationary phase chromatographic columns when the third switching module is switched.

3. The chromatographic apparatus of claim 2, wherein, When the separation degree of components separated by the first chromatographic column meets a requirement, the controller controls the second switching module and the third switching module to select the empty column; When the first chromatographic column separates co-eluted components, a corresponding stationary phase chromatographic column is selected according to the physicochemical properties of the co-eluted components and the switching of the second switching module and the third switching module.

4. The chromatographic device of claim 2, wherein, The first switching module is a two-position multi-way valve, and the second switching module and the third switching module are multi-channel directional valves.

5. The chromatographic device of claim 1, wherein, When the judging module outputs a result of yes, the analysis module outputs a component concentration C=C0·V0 / (V1-V2) in sample gas, C0 is an output value of the first detector when the judging result is no and the first switching module is switched to the sample injection state, V0 is a normal sampling volume, V1 is a sampling volume when the judging result is yes, and V2 is a volume between the first switching module and the second detector.

6. The chromatographic device of claim 1, wherein, The first detector is a PID or a mass spectrometer, and the second detector is a PID.

7. A chromatographic analysis method, comprising the following steps: A1. The first switching module is switched to a sampling state, sample gas passes through the first switching module and the enrichment module in sequence and enters the second detector, and a response time of the second detector is not higher than that of the first detector; A2. The judging module judges whether an output value of the second detector exceeds a threshold value; If the result is yes, sampling is stopped; If the result is no, normal sampling is performed; A3. When the first switching module is switched to a sample injection state, carrier gas passes through the first switching module, the enrichment module and the first chromatographic column in sequence and enters the first detector; A4. The analysis module outputs a component concentration in sample gas.

8. The chromatographic method according to claim 7, characterized in that, When the judging result is yes, the analysis module outputs a component concentration C=C0·V0 / (V1-V2) in sample gas. C0 is the output value of the first detector when the judgment result is no and the first switching module switches to the sampling state, V0 is a normal sampling volume, V1 is a sampling volume when the judgment result is yes, and V2 is a volume between the first switching module and the second detector.

9. The chromatographic method of claim 7, wherein, When the separation degree of the components separated by the first chromatographic column meets the requirements, the controller controls the switching of the second switching module and the third switching module, so that the components separated by the first chromatographic column pass through the second switching module, the empty column and the third switching module in sequence, and enter the first detector. When the co-eluted components are separated by the first chromatographic column, the controller controls the switching of the second switching module and the third switching module according to the physicochemical properties of the co-eluted components, so that the components separated by the first chromatographic column pass through the second switching module, the selected chromatographic column and the third switching module in sequence, and enter the first detector.

10. The chromatographic method of claim 7, wherein, The first detector adopts a PID or a mass spectrometer, and the second detector adopts a PID.

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