Pans analysis apparatus and method based on chromatographic techniques

Abstract

The present application relates to chromatography technology, and specifically provides a PANs analysis device and method based on chromatography technology, the analysis device comprising a detector, a chromatographic column and a first quantitative ring, all of which are connected to ports of a multi-way valve; one end of a first pipeline is selectively connected to air and a standard gas, and the other end is connected to a first port of the multi-way valve; one end of a second pipeline is connected to the chromatographic column, and the other end is connected to a second port of the multi-way valve; a second quantitative ring is arranged on the first pipeline; under switching of a flow path switching unit, the second port is connected to the chromatographic column through the second pipeline, or is sequentially connected to the chromatographic column through the second pipeline, the second quantitative ring and the second pipeline, and the first port is connected to the air or the standard gas through the first pipeline. The present application has the advantages of accurate measurement and the like, and is applied in air detection.

Description

TECHNICAL FIELD

[0001] The present application relates to chromatography technology, in particular to a PANs analysis device and method based on chromatography technology. BACKGROUND

[0002] Peroxyacetyl nitrate (PAN) is the most important photochemical secondary pollutant besides ozone, which is not directly emitted by natural sources and anthropogenic sources, but only comes from photochemical reactions, and is an important indicator of atmospheric photochemical pollution. At present, long-term online continuous monitoring of such pollutants has been carried out in monitoring stations all over the country.

[0003] At present, the mainstream PANs analysis method is a detection method combining gas chromatography and ECD detector. The internal standard method is often used in quantitative gas chromatography, and a PANs calibrator is equipped to calibrate the PANs analyzer, and the calibration period is generally one week or two weeks. The disadvantages of this method are:

[0004] 1. The online monitoring instrument of gas chromatography generally has the problem of long test period. Only one group of data can be measured in a test period. A test period includes several steps such as pre-pumping, sampling, sampling, and back blowing, each step is carried out separately, so that the analysis period of the test is longer.

[0005] Calibration and measurement are carried out separately. The instrument needs to change the sample gas measurement mode to calibration state during calibration. The PAN standard gas has a certain stabilization time from synthesis to reaching the target concentration. Therefore, the PAN analyzer in the prior art will lose a long time of measurement data during each calibration.

[0006] 2. The internal standard method has problems such as poor mixing of internal standards in samples, reaction between internal standards and sample components, variable purity of internal standards, etc. SUMMARY

[0007] In order to solve the above problems in the prior art, the present application provides a PANs analysis device based on chromatography technology.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] The PANS analysis device based on chromatography technology comprises a detector, a chromatographic column and a first quantitative ring, wherein the detector, the chromatographic column and the first quantitative ring are connected to the ports of a multi-way valve; the analysis device further comprises:

[0010] A first pipeline and a second pipeline, one end of the first pipeline is selectively connected to air and standard gas, the other end is connected to the first port of the multi-way valve, one end of the second pipeline is connected to the chromatographic column, the other end is connected to the second port of the multi-way valve;

[0011] a second quantitative ring, disposed on the first pipe;

[0012] a flow path switching unit, under switching of which the second port is communicated with the chromatographic column through the second pipe, or is communicated with the chromatographic column through the second pipe, the second quantitative ring and the second pipe in sequence, and the first port is connected with the air or the standard gas through the first pipe;

[0013] when the multi-way valve is switched to the first state, the air or the standard gas passes through the first pipe, the second quantitative ring and the multi-way valve in sequence, when switched to the second state, the carrier gas passes through the multi-way valve, the first quantitative ring, the second port, the second pipe, the chromatographic column and the detector in sequence, and when switched to the third state, the carrier gas passes through the multi-way valve, the first quantitative ring, the second port, the second pipe, the second quantitative ring, the second pipe, the chromatographic column and the detector in sequence.

[0014] The purpose of the present application is also to provide a PANs analysis method based on chromatographic technology, and the purpose is achieved by the following technical scheme:

[0015] The PANs analysis method based on chromatographic technology comprises the following stages in each detection cycle:

[0016] a sample gas collection stage, in which the multi-way valve is switched to the first state, the flow path switching unit is switched, and the sample gas passes through the first pipe, the first port of the multi-way valve, the first quantitative ring and the multi-way valve in sequence;

[0017] a sample gas injection stage, in which the multi-way valve is switched to the second state, the flow path switching unit is switched, and the carrier gas passes through the multi-way valve, the first quantitative ring, the second port of the multi-way valve, the second pipe, the multi-way valve, the chromatographic column and the detector in sequence;

[0018] Meanwhile, the standard gas passes through the first pipe, the second quantitative ring and the first port in sequence;

[0019] a standard gas analysis stage, in which the multi-way valve is switched to the third state, the flow path switching unit is switched, and the carrier gas passes through the multi-way valve, the first quantitative ring, the second port, the second pipe, the second quantitative ring, the second pipe, the multi-way valve, the chromatographic column and the detector in sequence.

[0020] Compared with the prior art, the present application has the beneficial effects that:

[0021] 1. The detection cycle is short;

[0022] In each detection cycle, the sample gas injection and the standard gas sampling are performed at the same time, so that the entire detection cycle is shortened;

[0023] 2. The accuracy is good;

[0024] The new concentration calculation method is used, and the detection accuracy is improved.

[0025] The linkage of the EPC and the sensor makes the sample gas or standard gas pressure entering the chromatographic column the same, and improves the detection accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0026] The disclosure of the present application will become more fully understood from the detailed description given herein below, and the accompanying drawings. It is understood that these drawings are only for purposes of illustrating the present application and are not intended to limit the present application. In the drawings:

[0027] Figure 1 is a structural schematic diagram of an analysis device according to an embodiment of the present application in a first state;

[0028] Figure 2 is a structural schematic diagram of an analysis device according to an embodiment of the present application in a second state;

[0029] Figure 3 is a structural schematic diagram of an analysis device according to an embodiment of the present application in a third state. DETAILED DESCRIPTION

[0030] Figures 1-3 The following description describes optional specific embodiments of the present application to teach those skilled in the art how to implement and reproduce the present application. Some conventional aspects have been simplified or omitted in order to explain the present application. Those skilled in the art should understand that variations or substitutions derived from these specific embodiments will be within the scope of the present application. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present application. Thus, the present application is not limited to the following optional specific embodiments, but is only defined by the claims and their equivalents.

[0031] Example 1.

[0032] The PANs analysis device based on chromatographic technology according to the embodiments of the present application, as shown in Figure 1 includes:

[0033] A detector 51, a chromatographic column 42 and a first quantitative ring 31, all of which are connected to a port of a multi-way valve 11, and these devices and the connection manner are all prior art in the field.

[0034] One end of a first pipe 21 is selectively connected to air and standard gas, and the other end is connected to a first port of the multi-way valve 11, one end of a second pipe 22 is connected to the chromatographic column 42, and the other end is connected to a second port of the multi-way valve 11.

[0035] A second quantitative ring 32 is arranged on the first pipe 21.

[0036] In the switching of the flow path switching unit, the second port is connected to the chromatographic column 42 through the second pipe 22, or is connected to the chromatographic column 42 through the second pipe 22, the second constant volume ring 32 and the second pipe 22 in sequence, and the first port is connected to the air or standard gas through the first pipe 21.

[0037] When the multi-way valve 11 is switched to the first state, the air or standard gas is connected to the first pipe 21, the second constant volume ring 32 and the multi-way valve 11 in sequence, when switched to the second state, the carrier gas is connected to the multi-way valve 11, the first constant volume ring 31, the second port, the second pipe 22, the chromatographic column 42 and the detector 51 in sequence, and when switched to the third state, the carrier gas is connected to the multi-way valve 11, the first constant volume ring 31, the second port, the second pipe 22, the second constant volume ring 32, the second pipe 22, the chromatographic column 42 and the detector 51 in sequence.

[0038] In order to realize the flow path switching, further, the flow path switching unit comprises:

[0039] The first switching module is used for selectively connecting the second port to the second pipe 22 or the first pipe 21.

[0040] The second switching module is used for selectively connecting one end of the second constant volume ring 32 to the first pipe 21 or the first switching module.

[0041] The third switching module is used for selectively connecting the other end of the second constant volume ring 32 to the first pipe 21 or the second pipe 22.

[0042] In order to improve the detection accuracy, further, the analysis device further comprises:

[0043] The sensor 81 is used for obtaining the pressure in the second pipe 22 upstream of the chromatographic column 42.

[0044] The carrier gas enters the multi-way valve 11 through the EPC 71.

[0045] The controller is used for adjusting the EPC 71 so that the output value of the sensor 81 is unchanged.

[0046] In order to improve the detection accuracy, further, the analysis unit processes the output signal of the detector 51 to obtain the concentration C of PANs in the sample gas sample :

[0047] C sample =(K1×A sample / A std )×K2×C std +b,

[0048] K1=A 2average / A 1average ;

[0049] K2=Astd current / A std ref ;

[0050] b=(1 / n)×Σ[C std cert -(A std i / A std ref )×C std cert ];

[0051] A sample is the peak area of the sample gas PANs, A std is the peak area of the standard gas PANs, C std is the concentration of the standard gas PANs, A 2average is the average value of the peak area of the standard gas in the continuous test of the second quantitative ring 32 for M times, A 1average is the average value of the peak area of the standard gas in the continuous test of the first quantitative ring 31 for M times, M is an integer greater than 2, A std current is the peak area of the standard gas actually measured in the current period, A std ref is the peak area of the standard gas in the reference, n is the number of data points of the test standard gas, Σ is the summation of i from 1 to n, C std cert is the concentration of the test standard gas, A std i is the peak area of the standard gas measured in the i-th calibration.

[0052] The PANs analysis method based on chromatographic technology in the embodiment of the application includes the following stages in each detection period:

[0053] The sample gas collection stage, as shown in FIG. 3, the multi-way valve 11 is switched to the first state, the flow path switching unit is switched, and the sample gas sequentially passes through the first pipeline 21, the first port of the multi-way valve 11, the first quantitative ring 31 and the multi-way valve 11. Figure 1 The sample gas injection stage, as shown in FIG. 4, the multi-way valve 11 is switched to the second state, the flow path switching unit is switched, and the carrier gas sequentially passes through the multi-way valve 11, the first quantitative ring 31, the second port of the multi-way valve 11, the second pipeline 22, the multi-way valve 11, the chromatographic column 42 and the detector 51.

[0054] Figure 2 At the same time, the standard gas sequentially passes through the first pipeline 21, the second quantitative ring 32 and the first port.

[0055] The standard gas analysis stage, as shown in FIG. 5, the multi-way valve 11 is switched to the third state, the flow path switching unit is switched, and the carrier gas sequentially passes through the multi-way valve 11, the first quantitative ring 31, the second port, the second pipeline 22, the second quantitative ring 32, the second pipeline 22, the multi-way valve 11, the chromatographic column 42 and the detector 51.

[0056] The purge stage, as shown in FIG. 6, the multi-way valve 11 is switched to the fourth state, the flow path switching unit is switched, and the carrier gas sequentially passes through the multi-way valve 11, the first quantitative ring 31, the second port, the second pipeline 22, the second quantitative ring 32, the second pipeline 22, the multi-way valve 11, the chromatographic column 42 and the detector 51. Figure 3

[0057] Figure 1 ​​​As shown, the multi-way valve 11 switches to the first state, the flow path switching unit switches, and the gas sequentially passes through the first pipe 21, the first port of the multi-way valve 11, the first quantitative ring 31, and the multi-way valve 11.

[0058] In the attached drawings Figures 1-3 , the blue color represents the flow direction, and the red color represents the flow path disconnection.

[0059] To improve the detection accuracy, further, the EPC 71 of the carrier gas flow path is adjusted during the sample gas injection stage and the standard gas analysis stage, so that the gas pressure in the second pipe 22 upstream of the chromatographic column 42 is equal.

[0060] To improve the detection accuracy, further, the analysis unit processes the output signal of the detector 51 to obtain the PANs concentration C sample in the sample gas.

[0061] C sample =(K1×A sample / A std )×K2×C std +b,

[0062] K1=A 2average / A 1average ;

[0063] K2=A std current / A std ref ;

[0064] b=(1 / n)×Σ[C std cert -(A std i / A std ref )×C std cert ];

[0065] A sample is the peak area of the sample gas PANs, A std is the peak area of the standard gas PANs, C std is the PANs standard gas concentration, A 2average is the average value of the peak area of the standard gas tested M times in succession by the second quantitative ring 32, A 1average is the average value of the peak area of the standard gas tested M times in succession by the first quantitative ring 31, M is an integer greater than 2, A std current is the peak area of the standard gas actually measured in the current period, A std ref is the reference standard gas peak area, n is the number of test standard gas data points, Σ is the summation of i from 1 to n, C std cert is the test standard gas concentration, A std i is the peak area of the standard gas measured in the i-th calibration.

[0066] In the sample gas collection stage and the purging stage, the gas passes through the first pipe 21, the second dosing ring 32, the first port of the multi-way valve, the first dosing ring 31 and the multi-way valve 11 in sequence.

[0067] Embodiment 2.

[0068] Application example of the PANs analysis device and method based on chromatographic technology according to embodiment 1 of the present application.

[0069] In this application example, as shown in Figure 1 , the carrier gas is connected to the port of the multi-way valve 11 through the EPC 71. The two ends of the first dosing ring 31, one end of the chromatographic column 42 and one end of the pre-column 41 are respectively connected to the ports of the multi-way valve 11, the other end of the chromatographic column 42 is connected to the detector 51, and the other end of the pre-column 41 is connected to the pressure sensor 81, the second pipe 22 and the second port of the multi-way valve 11 in sequence.

[0070] The air and the standard gas are connected to the first pipe 21, the second dosing ring 32 and the first port of the multi-way valve 11 in sequence through the two-position three-way electromagnetic valve 61.

[0071] The flow path switching unit includes a plurality of two-position three-way electromagnetic valves, which are respectively arranged on the first pipe 21 and the second pipe 22, so that when switched, the second port is connected to the pre-column 41 through the second pipe 22, or is connected to the pre-column 41 in sequence through the second pipe 22, the second dosing ring 32 and the second pipe 22, and the first port is connected to the air or the standard gas through the first pipe 21 and the second dosing ring 32.

[0072] The analysis unit is used to obtain the concentration C sample of the PANs in the air according to the output signal of the detector 51.

[0073] C sample = (K1×A sample / A std )×K2×C std +b,

[0074] K1=A 2average / A 1average ;

[0075] K2=A std current / A std ref ;

[0076] b=(1 / n)×Σ[C std cert -(A std i / A std ref )×C std cert ];

[0077] A sample is the peak area of the sample gas PANs, and A stdis the peak area of the standard gas PANs, A std is the concentration of the standard gas PANs, A 2average is the average of the peak area of the standard gas tested 3 times continuously by the second quantitative ring 32, A 1average is the average of the peak area of the standard gas tested 3 times continuously by the first quantitative ring 31, A std current is the peak area of the standard gas measured in the current cycle, A std ref is the peak area of the standard gas, n is the number of data points of the standard gas tested, and Σ is the summation of i from 1 to n, C std cert is the concentration of the standard gas tested, A std i is the peak area of the standard gas measured in the i-th calibration.

[0078] The PANs analysis method based on chromatographic technology of the embodiment of the application, i.e. the working method of the analysis device of the embodiment, in each detection cycle, the analysis method comprises the following stages:

[0079] The sample gas collection stage, as shown in Figure 1 , the multi-way valve 11 is switched to the first state, the flow path switching unit is switched, and the sample gas passes through the two-position three-way electromagnetic valve 61, the first pipeline 21, the second quantitative ring 32 (forward passing), the first port of the multi-way valve 11, the first quantitative ring 31 and the multi-way valve 11 in turn, and is then emptied.

[0080] The sample gas injection stage, as shown in Figure 2 , the multi-way valve 11 is switched to the second state, the flow path switching unit is switched, and the carrier gas passes through the EPC 71, the multi-way valve 11, the first quantitative ring 31 (reverse passing), the second port of the multi-way valve 11, the second pipeline 22, the pre-column 41, the multi-way valve 11, the chromatographic column 42 and the detector 51 in turn.

[0081] At the same time, the standard gas passes through the two-position three-way electromagnetic valve 61, the first pipeline 21, the second quantitative ring 32 and the first port in turn, and is then emptied.

[0082] The standard gas analysis stage, as shown in Figure 3 , the multi-way valve 11 is switched to the third state, the flow path switching unit is switched, and the carrier gas passes through the EPC 71, the multi-way valve 11, the first quantitative ring 31, the second port, the second pipeline 22, the second quantitative ring 32, the second pipeline 22, the pre-column 41, the multi-way valve 11, the chromatographic column 42 and the detector 51 in turn.

[0083] In the sample gas injection stage and the standard gas analysis stage, the EPC 71 of the carrier gas flow path is adjusted so that the gas pressure in the second pipeline 22 upstream of the chromatographic column 42 is equal.

[0084] The purge stage, as shown in Figure 1As shown, the multi-way valve 11 is switched to the first state, the flow path switching unit is switched, and the gas (air) sequentially passes through the two-position three-way electromagnetic valve 61, the first pipe 21, the second dosing ring 32, the first port, the first dosing ring 31 and the multi-way valve 11.

[0085] The analysis unit processes the output signal of the detector 51 to obtain the concentration C of PANs in the sample gas sample :

[0086] C sample =(K1×A sample / A std )×K2×C std +b,

[0087] K1=A 2average / A 1average ;

[0088] K2=A std current / A std ref ;

[0089] b=(1 / n)×Σ[C std cert -(A std i / A std ref )×C std cert ];

[0090] A sample is the peak area of PANs in the sample gas, A std is the peak area of PANs in the standard gas, C std is the concentration of PANs in the standard gas, A 2average is the average value of the peak area of the standard gas tested 3 times in succession by the second dosing ring 32, A 1average is the average value of the peak area of the standard gas tested 3 times in succession by the first dosing ring 31, A std current is the peak area of the standard gas actually measured in the current period, A std ref is the reference peak area of the standard gas, n is the number of data points of the standard gas tested, Σ is the summation of i from 1 to n, C std cert is the concentration of the standard gas tested, A std i is the peak area of the standard gas measured in the i-th calibration.

[0091] The measured parameters of the embodiment are as follows:

[0092] The 4ppb PAN standard gas is synthesized online, sequentially passes through the first dosing ring 31 and the second dosing ring 32, and 3 sets of stable peak areas are continuously recorded, as shown in Table 1.

[0093] Table 1 is 3 sets of stable peak areas and K1.

[0094] .

[0095] Normal continuous internal standard test, A std ref is the average of the peak areas of the previous ten second quantitative ring 32 tests.

[0096] Ten groups of second quantitative ring 32 test 4ppb PAN standard gas peak areas are recorded continuously, and A std ref， As shown in Table 2.

[0097] Table 2 is the peak area and A std ref .

[0098] .

[0099] The sample gas internal standard test is recorded twice continuously, as shown in Table 3.

[0100] Table 3 is the A sample , A std of the sample gas and the standard gas.

[0101] .

[0102] Sample gas 1 concentration calculation:

[0103] b=(1 / n)·Σ[C std -(A stdi / A stdref )·C std ]= (1 / 1) ·Σ[4-(2324.83 / 2319.02)·4]=-0.01ppb.

[0104] K2= A std current / A std ref =2324.83 / 2319.02=1.0025.

[0105] C sample =(K1·A sample / A std )·K2·C std +b.

[0106] =(0.9133·1214.39 / 2324.83) ·1.0025·4-0.01.

[0107] =1.903ppb.

[0108] Sample gas 2 concentration calculation:

[0109] At this time, A std ref The first group of peak areas involved in the calculation in the b parameter are replaced by the internal standard peak area in the sample gas measurement 1, A std ref The value is corrected to 2319.94.

[0110] b=(1 / n)·Σ[Cstd - (A stdi / A stdref ) · C std ].

[0111] = (1 / 2) · [[4-(2324.83 / 2319.94) · 4] + [4-(2317.66 / 2319.94) · 4]].

[0112] b = -0.0023 ppb.

[0113] At this time, A std ref1 in K2 is calculated by the first group of peak areas participating in the calculation, A std ref1 which is corrected to 2319.94.

[0114] K2 = A std current / A std ref1 = 2317.66 / 2319.94 = 0.999.

[0115] C sample = (K1 · A sample / A std ) · K2 · C std +b.

[0116] = (0.9133 · 1246.84 / 2317.66) · 0.999 · 4-0.0023.

[0117] = 1.9611 ppb.

Claims

1. A method for PANs analysis based on chromatographic techniques, characterized in that, In each detection cycle, the analysis method comprises the following stages: a sample gas collection stage, the multi-way valve is switched to a first state, the flow path switching unit is switched, and the sample gas sequentially passes through a first conduit, a first port of the multi-way valve, a first dosing ring, and the multi-way valve; a sample gas injection stage, the multi-way valve is switched to a second state, the flow path switching unit is switched, and the carrier gas sequentially passes through the multi-way valve, the first dosing ring, a second port of the multi-way valve, a second conduit, the multi-way valve, a chromatographic column, and a detector; simultaneously, the standard gas sequentially passes through the first conduit, a second dosing ring, and the first port; a standard gas analysis stage, the multi-way valve is switched to a third state, the flow path switching unit is switched, and the carrier gas sequentially passes through the multi-way valve, the first dosing ring, the second port, the second conduit, the second dosing ring, the second conduit, the multi-way valve, the chromatographic column, and the detector; the detector, the chromatographic column, and the first dosing ring are connected to the ports of the multi-way valve; one end of the first conduit is selectively connected to air and the standard gas, and the other end is connected to the first port of the multi-way valve; one end of the second conduit is connected to the chromatographic column, and the other end is connected to the second port of the multi-way valve; the second dosing ring is arranged on the first conduit; under the switching of the flow path switching unit, the second port is connected to the chromatographic column through the second conduit, or sequentially connected to the chromatographic column through the second conduit, the second dosing ring, and the second conduit, and the first port is connected to the air or the standard gas through the first conduit.

2. The analysis method according to claim 1, characterized in that, The analysis method comprises the following stages: a purge stage, the multi-way valve is switched to a first state, the flow path switching unit is switched, and the cleaning gas sequentially passes through a first conduit, a first port of the multi-way valve, a first dosing ring, and the multi-way valve.

3. The analysis method of claim 1, wherein, In the sample gas injection stage and the standard gas analysis stage, the EPC of the carrier gas flow path is adjusted so that the gas pressure in the second conduit upstream of the chromatographic column is equal.

4. The analysis method of claim 1, wherein, The analysis unit processes the output signal of the detector to obtain the concentration C of PANs in the sample gas sample : C sample = (K1 x A sample / A std ) x K2 x C std + b, K1 = A 2average / A 1average ; K2 = A std current / A std ref ; b = (1 / n) x Σ[C std cert - (A std i / A std ref ) x C std cert ]; A sample is the peak area of the sample gas PANs, A std is the peak area of the calibration gas PANs, C std is the calibration gas PANs concentration, A 2average is the average of the calibration gas peak areas from M consecutive tests of the second quantification loop, A 1average is the average of the calibration gas peak areas from M consecutive tests of the first quantification loop, M is an integer greater than 2, A std current is the current cycle measured calibration gas peak area, A std ref is the reference calibration gas peak area, n is the number of test calibration gas data points, Σ is the summation from i = 1 to n, C std cert is the test calibration gas concentration, A std i is the measured calibration gas peak area from the i-th calibration.

5. The analysis method of claim 2, wherein, In the sample gas collection stage and the purge stage, the gas sequentially passes through the first conduit, a second dosing ring, a first port of the multi-way valve, a first dosing ring, and the multi-way valve.

6. The analysis method of claim 1, wherein, The flow path switching unit comprises: a first switching module for selectively connecting the second port to the second conduit or the first conduit; a second switching module for selectively connecting one end of the second dosing ring to the first conduit or the first switching module; a third switching module for selectively connecting the other end of the second dosing ring to the first conduit or the second conduit.

7. The analysis method of claim 1, wherein, In the second state and the third state, the second conduit sequentially connects a pre-column, the multi-way valve, the chromatographic column, and the detector.

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