A method for determining the SO2 content in a gas sample

Abstract

The application belongs to the field of detection and analysis, and particularly relates to a method for determining the content of SO2 in a gas sample, comprising: detecting the gas sample by using an ion mobility spectrometer to obtain a spectrum; in the ion mobility spectrometer, the outlet of a dopant tank is in communication with a carrier gas channel, the carrier gas is air, the dopant tank comprises hexachloroethane dopant and is kept at 30-45 DEG C; in the spectrum, the retention time when the intensity of the dopant peak is equal to that of the SO2 peak is determined as the termination retention time; all the spectra from the peak of SO2 to the termination retention time are obtained, in each detection spectrum, the integral area of the region where the peak height of SO2 is higher than that of the dopant is calculated, the sum of the integral areas of all the detection spectra is calculated as an index value; and the content of SO2 in the gas sample is calculated according to the index value. The method for determining the content of SO2 in the gas sample has high accuracy, good repeatability and high precision.

Description

Technical Field

[0001] This invention belongs to the field of detection and analysis, and specifically relates to a method for determining the SO2 content in a gas sample. Background Technology

[0002] Ion mobility spectrometry is one of the earliest and most widely used trace chemical substance detection technologies. It can be used in normal temperature and pressure environments and has the advantages of small equipment size, low power consumption, and high portability. It has a wide range of applications in experimental testing, chemical engineering, and security inspection.

[0003] Based on the principle of ion migration, charged ions generate an electrical signal when they reach the signal receiving disk. The more ions that reach the ion receiving area, the stronger the signal. Based on this basic principle, ion migration equipment can be used for quantitative analysis.

[0004] In actual measurement, signal intensity is affected by a variety of factors. For example, when the ionization source is a vacuum UV lamp, lamp attenuation will lead to a weakening of the sample ion signal intensity. Unstable sample molecule concentration will also cause changes in the sample ion signal intensity. Changes in the voltage applied to the electrode ring of the ion migration tube and the flow rate of the carrier gas will also affect the signal intensity of the reagent ions. In addition, when the sample peak position is close to the RIP (reacting ion peak), the RIP peak and the sample peak will partially overlap. On the one hand, this makes it impossible to accurately reflect the actual peak intensity value of the sample. On the other hand, the two peaks are stuck together, resulting in inaccurate peak area statistics.

[0005] In response to the above situation, the following three problems urgently need to be solved: 1. The RIP peak and the peak of the sample to be tested are close in position, which makes it impossible to accurately calculate the peak area; 2. The equipment is affected by external environmental factors, which causes the peak intensity of the sample to fluctuate by 20%-30% for the same concentration, affecting the accuracy of detection; 3. The ionization source has a limited lifespan, and the ionization efficiency decreases with the use of the equipment, resulting in changes in signal intensity. Summary of the Invention

[0006] One objective of this invention is to improve the accuracy of SO2 content determination in gas samples; another objective of this invention is to improve the repeatability of SO2 content determination in gas samples; and yet another objective of this invention is to improve the precision of SO2 content determination in gas samples.

[0007] To achieve the above objectives, the present invention relates to a method for determining the SO2 content in a gas sample, comprising the following steps:

[0008] The gas sample is detected using an ion mobility spectrometer to obtain a detection spectrum. The ion mobility spectrometer includes a carrier gas channel and a dopant container. The outlet of the dopant container is connected to the interior of the carrier gas channel. The carrier gas introduced into the carrier gas channel is air. The dopant container contains hexachloroethane dopant and is maintained at 30℃-45℃, preferably 35℃-45℃, for example, 30℃, 33℃, 35℃, 37℃, 39℃, 40℃, 42℃, 43℃, and 45℃.

[0009] In the detection spectrum, the retention time when the peak intensity of the dopant is equal to that of SO2 is determined, and this retention time is taken as the termination retention time.

[0010] Obtain all detection spectra from the start of SO2 elution time to the end of retention time. In the detection spectra corresponding to each retention time, calculate the integral area of ​​the region where the SO2 peak is higher than the dopant peak. Then calculate the sum of the above integral areas of all detection spectra as the index value.

[0011] Based on the aforementioned index value, the SO2 content in the gas sample is calculated.

[0012] In any implementation, the method further includes:

[0013] The dopant internal reference peak intensity P' of the ion mobility spectrometer is obtained, the initial dopant peak intensity P in the detection spectrum is determined, and the correction factor f is calculated by dividing P by P'.

[0014] Divide the index value by the correction factor f to obtain the correction index value;

[0015] The SO2 content in the gas sample is calculated based on the correction index value.

[0016] Therefore, changes in external environmental factors can cause fluctuations in test results. By using correction index values ​​for calculation, the volatility of test results can be reduced, and the accuracy and repeatability of the measurement method can be improved.

[0017] In any implementation, the SO2 content in the gas sample is calculated using the external standard method based on the index value or correction index value.

[0018] In any implementation, the index value or correction index value is substituted into the standard working curve to calculate the SO2 content in the gas sample.

[0019] In any implementation, the standard operating curve is obtained through the following steps:

[0020] A series of SO2 standard gases at different concentrations were detected using an ion mobility spectrometer to obtain detection spectra. The ion mobility spectrometer included a carrier gas channel and a dopant container. The outlet of the dopant container was connected to the interior of the carrier gas channel. The carrier gas introduced into the carrier gas channel was air. The dopant container contained hexachloroethane dopant and was maintained at 30℃-45℃, preferably 35℃-45℃, for example, 30℃, 33℃, 35℃, 37℃, 39℃, 40℃, 42℃, 43℃, and 45℃.

[0021] In the detection spectrum of SO2 standard gas at each concentration, the retention time at which the peak intensity of the dopant is equal to that of SO2 is determined, and this retention time is taken as the termination retention time.

[0022] For each concentration of SO2 standard gas, obtain all detection spectra from the start of SO2 elution time to the end of retention time. In the detection spectra corresponding to each retention time, calculate the integral area of ​​the region where the SO2 peak is higher than the dopant peak. Then calculate the sum of the above integral areas of all detection spectra as the index value of each concentration of SO2 standard gas.

[0023] A standard working curve was established with the index values ​​of SO2 standard gas of a series of concentrations on the ordinate and the concentration on the abscissa.

[0024] In any implementation, the step of obtaining the standard working curve further includes:

[0025] Determine the initial peak intensity P1 of the dopant in the detection spectrum of SO2 standard gas at each concentration, divide P1 by the dopant internal reference peak intensity P' of the ion mobility spectrometer, and calculate the correction factor f1.

[0026] The correction index value of SO2 standard gas at each concentration is obtained by dividing the index value of SO2 standard gas at each concentration by the correction factor f1.

[0027] A standard working curve is established with the calibration index values ​​of SO2 standard gases of a series of concentrations as the ordinate and the concentration as the abscissa.

[0028] In any implementation, the dopant internal reference peak intensity P' of the ion mobility spectrometer is obtained through the following steps:

[0029] SO2 standard gas of the same concentration was detected by an ion mobility spectrometer more than 100 times, preferably more than 500 times, more than 800 times, more than 1,000 times, more than 2,000 times, more than 5,000 times, more than 6,000 times, more than 7,000 times, more than 10,000 times, for example, more than 7,000 times, to obtain a search spectrum.

[0030] The initial peak intensity of the dopant that appears most frequently in all detected spectra is taken as the dopant internal reference peak intensity P'.

[0031] In any embodiment, in the step of obtaining the dopant internal reference peak intensity P', the detection of SO2 standard gas of the same concentration is completed within 10-100 days (preferably 20-60 days, for example 10 days, 20 days, 30 days, 40 days, 60 days, 80 days, 100 days).

[0032] In any embodiment, the gas sample and / or the SO2 standard gas are independently a mixture of SO2 and N2.

[0033] In any embodiment, the ion mobility spectrometer is required to be used for detection after the dopant in the dopant container has diffused into the carrier gas channel and reached a saturation concentration.

[0034] In any implementation, the other detection conditions of the ion mobility spectrometer are the default startup conditions. "Default startup conditions" refers to the default startup settings when the device is delivered to the user.

[0035] In any embodiment, the ion mobility spectrometer is the MI1000 odor detector manufactured by Tongfang Weishi.

[0036] The beneficial effects achieved by this invention are as follows:

[0037] The method of this invention has high accuracy, good repeatability and high precision in determining the SO2 content in gas samples. Attached Figure Description

[0038] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0039] Figure 1 This is the ion migration spectrum of hexachloroethane gas, the dopant in this embodiment of the invention;

[0040] Figure 2 This is a three-dimensional ion migration spectrum of SO2 standard gas with a concentration of 40 ppm in an embodiment of the present invention;

[0041] Figure 3 This is a diagram illustrating the correlation between the initial peak intensity of the dopant in the SO2 standard gas and the calculated integral area in this embodiment of the invention.

[0042] Figure 4 This is the standard operating curve in the embodiments of the present invention;

[0043] Figure 5 The ion migration spectrum of SO2 standard gas at a concentration of 40 ppm was determined for comparative purposes. Detailed Implementation

[0044] The embodiments of the present invention will now be clearly and completely described in conjunction with examples. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] Example 1: Determination of SO2 content in the test gas

[0046] (1) Standard gases of different concentrations:

[0047] SO2 gas and nitrogen gas were mixed using a standard gas mixing instrument (manufacturer: Beijing Nico Rongguang Instrument Co., Ltd., model GDS-D5) to prepare SO2 standard gases with concentrations of 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, and 70ppm.

[0048] (2) Detection:

[0049] The dopant hexachloroethane gas was introduced into an ion mobility spectrometer (Tongfang Weishi MI1000 odor detector) for detection. Except for the absence of a dopant container, the other detection conditions were the same as described below. The resulting ion mobility spectrum is shown below. Figure 1 As shown, the vertical axis represents retention time, and the horizontal axis represents migration time.

[0050] from Figure 1 As can be seen, the dopant peak is located to the left of the RIP peak, which allows for better separation from the SO2 peak.

[0051] The gas to be tested and standard gases of different concentrations were detected by an ion mobility spectrometer (Tongfang Weishi MI1000 odor detector);

[0052] Detection conditions for the ion mobility spectrometer: the carrier gas introduced into the carrier gas channel is air; the outlet of the dopant container is connected to the inside of the carrier gas channel, the dopant container is filled with hexachloroethane solid particles and the dopant container is kept at a constant temperature of 40°C, and it is put into use one day after installation to ensure that the dopant concentration in the carrier gas channel reaches saturation; the other detection conditions are the instrument's default conditions when it is turned on.

[0053] The three-dimensional ion migration spectrum of SO2 standard gas at a concentration of 40 ppm is shown below. Figure 2 As shown.

[0054] from Figure 2The three-dimensional spectrum shows that the dopant peak completely replaces the original RIP, and the dopant peak and SO2 peak maintain sufficient distance, which is beneficial for accurately calculating the integral area of ​​the two peaks. Furthermore, the peak intensity of the dopant peak is negatively correlated with the peak intensity of the SO2 peak, that is, as the retention time increases, the peak intensity of the dopant peak gradually increases, while the peak intensity of the SO2 peak gradually decreases.

[0055] (3) Data processing and calculation:

[0056] exist Figure 2 In the study, the retention time corresponding to the point where the peak intensities of the dopant peak and the SO2 peak are equal is recorded as the termination retention time. Ion migration spectra (vertical axis represents peak intensity, and horizontal axis represents migration time) are collected at each moment from the start of SO2 peak elution to the termination retention time. The integrated area of ​​the region in each ion migration spectrum where the peak intensity of the SO2 peak is higher than that of the dopant peak is calculated, and then the integrated areas obtained from all ion migration spectra are summed.

[0057] The same concentration of SO2 standard gas was measured multiple times according to the method in (2), and the initial peak intensity of the dopant was taken. A total of 7000 measurements were performed, and the initial peak intensity of the dopant with the highest frequency was taken as the internal reference peak intensity.

[0058] The correction factor f is obtained by dividing the initial dopant peak intensity of SO2 standard gas measured by ion mobility spectrometry by the internal reference peak intensity.

[0059] During quantitative testing, the inventors of this invention discovered that the initial peak intensity of the dopant in the SO2 standard gas is positively correlated with the sum of the integral areas calculated according to the aforementioned method (see...). Figure 3 ), Figure 3 In the diagram, the dashed line represents the initial peak intensity of the dopant, and the solid line represents the sum of the integral areas. Therefore, the sum of the integral areas obtained from the ion migration spectrum of SO2 standard gas is divided by the correction factor to obtain the correction index value.

[0060] A standard working curve is established using the correction index value calculated with SO2 standard gas as the ordinate and SO2 concentration as the abscissa, where Y = 0.00867 × X. 3 +0.53865×X 2 +19.3448×X+88.6109, such as Figure 4 As shown.

[0061] Based on the three-dimensional ion migration spectrum of the gas to be tested, the initial peak intensity of the dopant in the gas to be tested is measured by an ion mobility spectrometer and divided by the internal reference peak intensity to obtain the correction factor. Referring to the above method, the integral area sum is obtained from the ion migration spectrum of the gas to be tested. Then, the integral area sum is divided by the correction factor to obtain the correction index value of the gas to be tested. Substitute it into the standard working curve to calculate the SO2 content of the gas to be tested.

[0062] Example 2 Accuracy Verification

[0063] The mixture of SO2 and nitrogen with known SO2 concentration was tested according to the method of Example 1 [prepared according to the method of item (1) of Example 1]. Each sample was tested 5 times, and the results are shown in Table 1.

[0064] Table 1 Test Results

[0065]

[0066] As shown in Table 1, the deviation of SO2 concentration tested by the method of the present invention is less than or equal to 2.2%, indicating that the method of the present invention has high precision and accuracy, and the repeatability of the test is good.

[0067] Comparative Example

[0068] In the detection conditions of ion mobility spectrometry, no dopant container is set up, and the rest remain unchanged.

[0069] The ion mobility spectrometer was used to detect 40 ppm SO2 standard gas, and the ion mobility spectra are as follows: Figure 5 As shown.

[0070] The results showed that the RIP and SO2 peaks were quite close. After the SO2 standard gas was injected, the SO2 peak could be seen. However, as the concentration decreased, the SO2 peak gradually shifted towards the RIP, causing the RIP and SO2 peak intensities to affect each other. It was impossible to accurately obtain the SO2 peak intensity or peak area. At the same time, as the SO2 concentration decreased, it was impossible to accurately determine the injection end time based on the spectral data, which directly affected the accuracy of the peak area calculation.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for determining the SO2 content in a gas sample, comprising the following steps: The gas sample was detected using an ion mobility spectrometer to obtain the detection spectrum; among which... The ion mobility spectrometer includes a carrier gas channel and a dopant container. The outlet of the dopant container is connected to the interior of the carrier gas channel. The carrier gas introduced into the carrier gas channel is air. The dopant container contains hexachloroethane dopant and is maintained at 30 ℃ - 45 ℃. In the detection spectrum, the retention time when the peak intensity of the dopant is equal to that of SO2 is determined, and this retention time is taken as the termination retention time. Obtain all detection spectra from the start of SO2 elution time to the end of retention time. In the detection spectra corresponding to each retention time, calculate the integral area of ​​the region where the SO2 peak is higher than the dopant peak. Then calculate the sum of the above integral areas of all detection spectra as the index value. Based on the aforementioned index value, the SO2 content in the gas sample is calculated.

2. The method according to claim 1, further comprising: The dopant internal reference peak intensity P' of the ion mobility spectrometer is obtained, the initial dopant peak intensity P in the detection spectrum is determined, and the correction factor f is calculated by dividing P by P'. Divide the index value by the correction factor f to obtain the correction index value; The SO2 content in the gas sample is calculated based on the correction index value.

3. The method according to claim 1, wherein, Based on the aforementioned index value, the SO2 content in the gas sample is calculated using the external standard method.

4. The method according to claim 2, wherein, The SO2 content in the gas sample is calculated using the external standard method based on the correction index value.

5. The method according to claim 3, wherein, The SO2 content in the gas sample is obtained by substituting the index value into the standard working curve.

6. The method according to claim 4, wherein, The SO2 content in the gas sample is obtained by substituting the correction index value into the standard working curve.

7. The method according to claim 5, wherein, The standard working curve is obtained through the following steps: A series of SO2 standard gases at different concentrations were detected using the aforementioned ion mobility spectrometer to obtain detection spectra; In the detection spectrum of SO2 standard gas at each concentration, the retention time at which the peak intensity of the dopant is equal to that of SO2 is determined, and this retention time is taken as the termination retention time. For each concentration of SO2 standard gas, obtain all detection spectra from the start of SO2 elution time to the end of retention time. In the detection spectra corresponding to each retention time, calculate the integral area of ​​the region where the SO2 peak is higher than the dopant peak. Then calculate the sum of the above integral areas of all detection spectra as the index value of each concentration of SO2 standard gas. A standard working curve was established with the index values ​​of SO2 standard gas of a series of concentrations on the ordinate and the concentration on the abscissa.

8. The method according to claim 6, wherein, The standard operating curve is obtained through the following steps: A series of SO2 standard gases at different concentrations were detected using the aforementioned ion mobility spectrometer to obtain detection spectra; In the detection spectrum of SO2 standard gas at each concentration, the retention time at which the peak intensity of the dopant is equal to that of SO2 is determined, and this retention time is taken as the termination retention time. For each concentration of SO2 standard gas, obtain all detection spectra from the start of SO2 elution time to the end of retention time. In the detection spectra corresponding to each retention time, calculate the integral area of ​​the region where the SO2 peak is higher than the dopant peak. Then calculate the sum of the above integral areas of all detection spectra as the index value of each concentration of SO2 standard gas. Determine the initial peak intensity P1 of the dopant in the detection spectrum of SO2 standard gas at each concentration, divide P1 by the dopant internal reference peak intensity P' of the ion mobility spectrometer, and calculate the correction factor f1. The correction index value of SO2 standard gas at each concentration is obtained by dividing the index value of SO2 standard gas at each concentration by the correction factor f1. A standard working curve is established with the calibration index values ​​of SO2 standard gases of a series of concentrations as the ordinate and the concentration as the abscissa.

9. The method according to claim 2, wherein, The dopant internal reference peak intensity P' of the ion mobility spectrometer is obtained through the following steps: SO2 standard gas of the same concentration was detected by ion mobility spectrometry more than 100 times to obtain the search spectrum; The initial peak intensity of the dopant that appears most frequently in all detected spectra is taken as the dopant internal reference peak intensity P'.

10. The method according to any one of claims 1 to 9, wherein, The gas sample was a mixture of SO2 and N2.

11. The method according to claim 7 or 8, wherein, The SO2 standard gas is a mixture of SO2 and N2.

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