Organic matter detection method based on gas phase ion mobility spectrometry

Abstract

The invention discloses an organic matter detection method based on gas-phase ion mobility spectrometry, and relates to the technical field of gas-phase ion mobility spectrometry. Through detection time segmentation and detection program setting, sample detection time is divided into positive ion mode peak appearance time, negative ion mode peak appearance time and no-peak time, instrument modes and migration tube voltage are reasonably set in different time periods, meanwhile, when the positive ion mode and the negative ion mode are switched, the migration tube voltage is turned off firstly, and the migration tube voltage is turned off; and after the voltage returns to zero, the mode is switched and the voltage is started again, so that electric field interference caused by direct switching is avoided, the stabilization time is shortened to a minute level, and the detection efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas phase ion mobility spectrometry, and specifically to an organic matter detection method based on gas phase ion mobility spectrometry. Background Technique

[0002] Gas phase ion mobility spectrometry technology is a technology widely used in the detection of volatile organic compounds. A gas phase ion mobility spectrometer is suitable for detecting substances with a proton affinity greater than that of water, such as aldehydes, ketones, acids, esters, amines, etc. in the positive ion mode; and is suitable for detecting substances with strong electronegativity, such as halogenated hydrocarbons and thiols, etc. in the negative ion mode.

[0003] However, the existing organic matter detection methods based on gas phase ion mobility spectrometry still have the following deficiencies in the actual application process:

[0004] The switching between the positive and negative ion modes requires a long stabilization time. Especially, switching from the negative ion mode to the positive ion mode requires at least 2 hours of stabilization time. This results in that when detecting multiple target substances in the environmental or petrochemical fields, it takes a long time or multiple instruments are needed to complete the detection, with low efficiency;

[0005] In addition, due to problems such as signal interference and inaccurate peak positioning, the reliability of the detection results is poor, and the detection time cannot be optimized according to the real-time signal analysis results.

[0006] Therefore, an organic matter detection method based on gas phase ion mobility spectrometry is introduced. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems pointed out in the background technique, and to propose an organic matter detection method based on gas phase ion mobility spectrometry.

[0008] The purpose of the present invention can be achieved through the following technical solutions: An organic matter detection method based on gas phase ion mobility spectrometry, including:

[0009] Detection time segmentation: The sample detection time is pre-divided into the peak emergence time in the positive ion mode, the peak emergence time in the negative ion mode, and the time without peaks;

[0010] Detection program setting: During the peak emergence time period in the positive ion mode, the instrument is set to the positive ion mode and the migration tube voltage is turned on. During the peak emergence time period in the negative ion mode, it is switched to the negative ion mode and the migration tube voltage is turned on. During the time without peaks, the migration tube voltage is turned off;

[0011] Shutdown time optimization: preset the shutdown time of each group of migration tube voltage, perform X times of positive and negative ion mode switching at each shutdown time, and evaluate the performance parameters of the instrument during the switching process to determine the final voltage shutdown time in the current sample detection process; where Y>5; performance parameters include stabilization time, energy consumption ratio and material detection data.

[0012] As a preferred implementation of the present invention, the stabilization time and energy consumption ratio of the instrument are evaluated during the switching process, specifically:

[0013] For each shutdown duration, record the instrument stabilization time, that is, the time from voltage recovery to signal stabilization. After recording, calculate the average of the X groups of stabilization time for each shutdown duration to obtain the required stabilization average time corresponding to each shutdown duration.

[0014] Without turning off the voltage, measure the energy consumption of the instrument for the set time as the benchmark value; at each shutdown time, run the instrument for the set time and record the total energy consumption as the shutdown performance energy consumption, and calculate the energy saving ratio corresponding to each shutdown time according to the formula: energy saving ratio = (baseline value - shutdown performance energy consumption) / base value × 100%.

[0015] As a preferred embodiment of the present invention, the material detection data of the instrument is evaluated during the switching process, specifically:

[0016] For each closing time, the peak height and peak area of ​​the target substance were recorded, and the average and standard deviation of each group of peak heights under each closing time were calculated to obtain the peak height mean and peak height deviation. The peak height RSD was obtained by calculating the ratio with the peak height deviation as the numerator and the peak height mean as the denominator. The peak surface RSD was calculated in the same way.

[0017] The peak height RSD and peak surface RSD corresponding to each closing time are multiplied by the corresponding preset weight coefficients, and then the sum is obtained to obtain the repeatability evaluation index corresponding to each closing time.

[0018] As a preferred embodiment of the present invention, the final voltage off time in the current sample detection process is determined as follows:

[0019] The shutdown durations with repeatability evaluation index lower than the preset threshold index are retained as standby shutdown durations, and the required stable average time and energy saving ratio corresponding to each standby shutdown duration are extracted, which are recorded as sda and sdc;

[0020] A set of required stable expected mean time and expected energy saving ratios are preset, denoted as sde and sdr; according to the formula Perform a weighted calculation on the required stable average time sda and the energy-saving ratio sdc corresponding to each standby shutdown duration, so as to determine the comprehensive evaluation index α of each group of standby shutdown durations; where u1 and u2 are the influence weight factors of the required stable average time and the energy-saving ratio respectively;

[0021] Select the standby shutdown duration with the highest comprehensive evaluation index α as the shutdown voltage duration during the subsequent sample detection process in the detection program setting.

[0022] As a preferred implementation manner of the present invention, it further includes:

[0023] Detection time optimization: Establish a connection with the gas-phase ion mobility spectrometer, obtain the electrical signals output by the instrument during the current detection time period and analyze them; Determine the adjustment ratio of the duration of the current detection time period based on the analysis results.

[0024] As a preferred implementation manner of the present invention, obtaining the electrical signals output by the instrument during the current detection time period and analyzing them specifically includes:

[0025] Obtain the starting position and ending position of the peak of the electrical signal, calculate the peak width and peak height, calculate the difference between the signal value at the peak vertex and the baseline value to obtain the peak height; Identify the positions on both sides of the peak vertex where the signal values are equal to half of the peak height, and calculate the distance between these two positions to obtain the peak width; Denote the peak height and peak width as fe1 and fe2;

[0026] Set the standard peak appearance characteristic parameters of the target substance in the positive ion mode and the negative ion mode. The standard peak appearance characteristic parameters include the standard peak height and the standard peak width, and are denoted as ft1 and ft2;

[0027] According to the formula Calculate to obtain the peak height deviation rate w1 and the peak width deviation rate w2, multiply the peak height deviation rate w1 and the peak width deviation rate w2 by the corresponding set weight coefficients respectively, and then sum to obtain the deviation index;

[0028] Set the index threshold corresponding to the deviation index. If the obtained deviation index is less than or equal to the index threshold, it is determined that the current detection time period does not need to be adjusted; otherwise, compare fe1 and fe2 with ft1 and ft2 respectively, and trigger the corresponding adjustment signal based on the comparison result; The adjustment signals include a time extension signal J1 and a time shortening signal J2; It is expressed as

[0029] As a preferred implementation manner of the present invention, determining the adjustment ratio of the duration of the current detection time period specifically includes:

[0030] After determining the comparison result of the current detection time period, form a data pair. The data pair is the difference between fe1 and ft1, and the difference between fe2 and ft2;

[0031] Pre - construct an adjustment database, which includes the value range of each group of data pairs corresponding to the time - extended signal J1 and the time - shortened signal J2 respectively. Each group of data pair value ranges corresponds to a time adjustment ratio. Based on the triggered adjustment signal, match the data pair with each group of data pair value ranges to determine the time adjustment ratio of the current detection time period;

[0032] If the adjustment signal is J1, extend the time adjustment ratio on the duration of the current detection time period. If the adjustment signal is J2, shorten the time adjustment ratio on the duration of the current detection time period.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Through the detection time segmentation and detection program settings, the present invention divides the sample detection time into the peak - emerging time in the positive - ion mode, the peak - emerging time in the negative - ion mode, and the time without peaks. Reasonably set the instrument mode and transfer tube voltage in different time periods. At the same time, when switching between the positive and negative ion modes, first turn off the transfer tube voltage, wait until the voltage returns to zero, then switch the mode and turn on the voltage again to avoid the electric - field interference caused by direct switching, and shorten the stabilization time to the minute level, greatly improving the detection efficiency;

[0035] 2. In the detection time optimization section, the present invention filters the collected original electrical signals to remove noise interference, and accurately obtains the starting position, ending position, peak width, and peak height of the electrical signal by using the first - derivative or second - derivative method. By setting the standard peak - emerging characteristic parameters of the target substance in the positive - ion mode and the negative - ion mode, compare the differences between the actually detected peak height and peak width and the standard values, and judge whether to adjust the detection time according to the deviation index and threshold. When the peak width becomes wider or the peak height becomes lower, extend the detection time to ensure that the signal of the target substance can be completely collected, accurately detect the target substance, avoid detection errors, and improve the accuracy of the detection results;

[0036] 3. In the optimization of the shutdown duration, the present invention presets the shutdown duration of each group for turning off the transfer tube voltage, performs multiple positive - and negative - ion mode switches at each shutdown duration, and evaluates the energy - consumption ratio of the instrument. By calculating the energy - saving ratio at different shutdown durations, combined with the required stable average time and the repeatability evaluation index of the substance detection data, comprehensively determine the final voltage shutdown duration, improving the intelligent level of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] For the convenience of those skilled in the art to understand, the present invention is further described below with reference to the drawings.

[0038] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0040] Please refer to Figure 1 As shown, an organic matter detection method based on gas-phase ion mobility spectrometry includes:

[0041] Detection time segmentation: The sample detection time is pre-divided into the peak emergence time in the positive ion mode, the peak emergence time in the negative ion mode, and the time without peaks.

[0042] Detection program setting: During the peak emergence time period in the positive ion mode, the instrument is set to the positive ion mode and the drift tube voltage is turned on. During the peak emergence time period in the negative ion mode, it is switched to the negative ion mode and the drift tube voltage is turned on. During the time period without peaks, the drift tube voltage is turned off as a buffer stage for mode switching.

[0043] It should be noted that when switching between the positive and negative ion modes, first turn off the drift tube voltage. After the voltage returns to zero, switch the mode, and then turn on the voltage again. This method can avoid the electric field interference caused by direct switching and shorten the stabilization time to the minute level.

[0044] Taking tetrahydrothiophene (THT, detected in the positive ion mode) and tert-butyl mercaptan (TBM, detected in the negative ion mode) in natural gas as an example:

[0045] Detection program segmentation:

[0046] The first stage (0 - 5 minutes): Time without peaks, turn off the drift tube voltage;

[0047] The second stage (5 - 15 minutes): Peak emergence time of TBM, switch to the negative ion mode and turn on the voltage;

[0048] The third stage (15 - 20 minutes): Time without peaks, turn off the voltage;

[0049] The fourth stage (20 - 30 minutes): Peak emergence time of THT, switch to the positive ion mode and turn on the voltage.

[0050] Voltage parameter setting:

[0051] Negative ion mode voltage: -1.2 kV, drift tube electric field strength is 300 V / cm;

[0052] Positive ion mode voltage: +1.5 kV, electric field strength is 350 V / cm;

[0053] When the voltage is turned off, the drift tube electric field strength is 0;

[0054] The above content completes the detection of two sulfides in a single 30-minute test, with a repeatability error of <2% and a sensitivity increase of 40% compared with traditional methods;

[0055] Shutdown time optimization: preset the duration of shutting down the migration tube voltage for each group, perform X times of positive and negative ion mode switching at each shut-down time, and evaluate the performance parameters of the instrument during the switching process to determine the final voltage shut-down time in the current sample detection process; where Y>5; the specific value is preset by the technician; the performance parameters include stabilization time, energy consumption ratio, and material detection data;

[0056] Specifically:

[0057] S1: For each shutdown time, record the instrument stabilization time, that is, the time from voltage recovery to signal stabilization. After recording, calculate the average of the X groups of stabilization time for each shutdown time to obtain the required stabilization average time corresponding to each shutdown time;

[0058] S2: For each closing time, the peak height and peak area of ​​the target substance were recorded, and the average and standard deviation of each group of peak heights under each closing time were calculated to obtain the peak height mean and peak height deviation. The peak height RSD was obtained by calculating the ratio with the peak height deviation as the numerator and the peak height mean as the denominator. The peak surface RSD was calculated in the same way.

[0059] That is, the average value and standard deviation of the peak area of ​​each group under each closing time are calculated to obtain the peak area mean and peak area deviation, and the peak area RSD is obtained by calculating the ratio with the peak area deviation as the numerator and the peak area mean as the denominator;

[0060] The peak height RSD and peak surface RSD corresponding to each closing time are multiplied by the corresponding preset weight coefficients, and then the sum is obtained to obtain the repeatability evaluation index corresponding to each closing time;

[0061] S3: Without turning off the voltage, measure the energy consumption of the instrument for the set time as the benchmark value; the set time is 1 hour; at each shutdown time, run the instrument for the set time and record the total energy consumption as the shutdown performance energy consumption, according to the formula energy saving ratio = (baseline value - shutdown performance energy consumption) / base value × 100%. Calculate the energy saving ratio corresponding to each shutdown time:

[0062] S4: retain the shutdown durations whose repeatability evaluation index is lower than the preset threshold index as the standby shutdown durations, and extract the required stable average time and energy saving ratio corresponding to each standby shutdown duration, which are recorded as sda and sdc;

[0063] A set of required stable expected mean time and expected energy saving ratios are preset, denoted as sde and sdr; according to the formula Perform a weighted calculation on the required stable average time sda and the energy-saving ratio sdc corresponding to each standby shutdown duration to determine the comprehensive evaluation index α for each group of standby shutdown durations. Among them, u1 and u2 are the influence weight factors of the required stable average time and the energy-saving ratio respectively, and u1 > u2;

[0064] Select the standby shutdown duration with the highest comprehensive evaluation index α as the shutdown voltage duration during the subsequent sample detection process in the detection program settings;

[0065] It should be noted that when determining the final shutdown voltage duration, multiple factors such as the required stable average time, the repeatability evaluation index, and the energy-saving ratio are comprehensively considered. By presetting the required stable average time and the expected energy-saving ratio, and setting different influence weight factors for the required stable average time and the energy-saving ratio, a weighted calculation is performed on each standby shutdown duration to obtain the comprehensive evaluation index. This comprehensive evaluation method can comprehensively measure the comprehensive impact of each shutdown duration on the instrument performance, avoiding the limitations of single-index evaluation. Finally, the shutdown duration with the highest comprehensive evaluation index is selected, achieving the best balance among detection efficiency, stability, and energy consumption, and enabling the detection method to have better comprehensive performance in practical applications;

[0066] Suppose the following shutdown durations are preset: 1 second, 5 seconds, 10 seconds, 30 seconds, 1 minute, 2 minutes, and 5 times of positive and negative ion mode switching are performed at each shutdown duration;

[0067] Shutdown for 1 second: The stable times are 5 seconds, 6 seconds, 4 seconds, 5 seconds, and 5 seconds respectively;

[0068] Shutdown for 5 seconds: The stable times are 8 seconds, 9 seconds, 7 seconds, 8 seconds, and 8 seconds respectively;

[0069] Shutdown for 10 seconds: The stable times are 10 seconds, 11 seconds, 9 seconds, 10 seconds, and 10 seconds respectively;

[0070] Shutdown for 30 seconds: The stable times are 12 seconds, 13 seconds, 11 seconds, 12 seconds, and 12 seconds respectively;

[0071] Shutdown for 1 minute: The stable times are 15 seconds, 16 seconds, 14 seconds, 15 seconds, and 15 seconds respectively;

[0072] Shutdown for 2 minutes: The stable times are 20 seconds, 21 seconds, 19 seconds, 20 seconds, and 20 seconds respectively;

[0073] Calculate the stable average time:

[0074] Shutdown for 1 second: The stable average time is 5 seconds;

[0075] Shutdown for 10 seconds: The stable average time is 10 seconds;

[0076] The stable average times for other shutdown durations are calculated similarly;

[0077] When closed for 10 seconds, the peak height data from 5 detections are 5300, 5350, 5320, 5340, and 5330;

[0078] The average peak height = 5330, the standard deviation of the peak height ≈ 17.32, and the RSD of the peak height ≈ 0.33%;

[0079] When closed for 10 seconds, the peak area data from 5 detections are 16000, 16100, 15950, 16050, and 16000;

[0080] The average peak area = 16020, the standard deviation of the peak area ≈ 50.99, and the RSD of the peak area ≈ 0.32%;

[0081] Preset weight coefficients: the weight of the RSD of the peak height = 0.6, and the weight of the RSD of the peak area = 0.4;

[0082] The repeatability evaluation index = 0.6 × 0.33% + 0.4 × 0.32% = 0.198% + 0.128% = 0.326%;

[0083] When the voltage is not turned off, the energy consumption of the instrument running for 1 hour is 500 Wh. When closed for 10 seconds, the total energy consumption of the instrument running for 1 hour is 400 Wh, and the energy-saving ratio is 20%;

[0084] Preset threshold index: the threshold of the repeatability evaluation index = 0.5%, and retain the closing duration with the repeatability evaluation index < 0.5%.

[0085] For example, when closed for 10 seconds, the repeatability evaluation index = 0.326% < 0.5%, and it is retained as the standby closing duration;

[0086] Extract the required stable average time and energy-saving ratio: when closed for 10 seconds: the required stable average time (sda) = 10 seconds, and the energy-saving ratio (sdc) = 20%;

[0087] Preset expected values: the required stable expected average time (sde) = 8 seconds, and the expected energy-saving ratio (sdr) = 25%;

[0088] The weight of the required stable average time (u1) = 0.7, and the weight of the energy-saving ratio (u2) = 0.3;

[0089] Calculate the comprehensive evaluation index to be 0.765;

[0090] When closed for 10 seconds: 0.765, when closed for 1 minute: 0.720, when closed for 30 seconds: 0.680. Select the closing duration with the highest comprehensive evaluation index, that is, when closed for 10 seconds.

[0091] Detection time optimization: Establish a connection with the gas-phase ion mobility spectrometer, obtain the electrical signals output by the instrument during the current detection time period and analyze them; the electrical signals reflect the changes in ion intensity during the migration of the target substance; determine the adjustment ratio of the current detection time period based on the analysis results;

[0092] Reasonably set the sampling frequency of the signal according to the peak emergence characteristics of the target substance and the response speed of the instrument;

[0093] Specifically:

[0094] Filter the collected original electrical signals to remove noise interference; use the first derivative or second derivative method to obtain the starting and ending positions of the peaks of the electrical signals, calculate the peak width and peak height, calculate the difference between the signal value at the peak vertex and the baseline value to obtain the peak height; identify the positions on both sides of the peak vertex where the signal values are equal to half of the peak height, calculate the distance between these two positions to obtain the peak width; record the peak height and peak width as fe1 and fe2;

[0095] Take the first derivative of the preprocessed signal, and the points where the derivative is zero are the possible extreme points. By traversing the derivative array, find the positions where the derivative sign changes, and the signal points corresponding to these positions are the extreme points, which can be used as the peak vertices or valley points;

[0096] Take the second derivative of the signal, and the points where the second derivative is zero may be inflection points. Combining the first derivative information can more accurately determine the starting and ending positions of the peak;

[0097] Based on the multiple detection results of the current known samples, set the standard peak emergence characteristic parameters of the target substance in the positive ion mode and negative ion mode. The standard peak emergence characteristic parameters include the standard peak height and standard peak width, and are recorded as ft1 and ft2;

[0098] It should be noted that if the peak width becomes wider than the standard peak emergence characteristic parameters, it indicates that the separation effect of the target substance becomes worse. Appropriately extend the current detection time period to ensure that the target substance can be accurately detected;

[0099] If the peak height becomes lower than the standard peak emergence characteristic parameters: it means that the concentration of the target substance decreases or the detection sensitivity decreases. Similarly, extend the current detection time period to increase the accumulation of detection signals;

[0100] According to the formula Calculate the peak height deviation rate w1 and the peak width deviation rate w2, multiply the peak height deviation rate w1 and the peak width deviation rate w2 by the corresponding set weight coefficients respectively, and then sum to obtain the deviation index; the weights are set according to the characteristics of the target substance;

[0101] Set the index threshold corresponding to the deviation index. If the obtained deviation index is less than or equal to the index threshold, it is determined that no adjustment is required for the current detection time period; otherwise, compare fe1 and fe2 with ft1 and ft2 respectively, and trigger the corresponding adjustment signal based on the comparison result. The adjustment signals include a time extension signal J1 and a time shortening signal J2; it is expressed as

[0102] After determining the comparison result of the current detection time period, form a data pair, where the data pair is the difference between fe1 and ft1, and the difference between fe2 and ft2;

[0103] Pre - construct an adjustment database, which includes the value ranges of each group of data pairs corresponding to the time extension signal J1 and the time shortening signal J2 respectively. Each group of data pair value ranges corresponds to a time adjustment ratio. Based on the triggered adjustment signal, match the data pair with the value ranges of each group of data pairs to determine the time adjustment ratio of the current detection time period;

[0104] The value range of the data pair is represented by n1 to n2, b1 to b2. The matching means matching the difference between fe1 and ft1 with n1 to n2, and the difference between fe2 and ft2 with b1 to b2; n1, n2, b1, b2 are set to specific values by technicians according to historical data;

[0105] If the adjustment signal is J1, extend the time adjustment ratio on the duration of the current detection time period. If the adjustment signal is J2, shorten the time adjustment ratio on the duration of the current detection time period;

[0106] It should be noted that by filtering to remove the noise interference of the original electrical signal and using the first - and second - order derivatives to accurately obtain the start and end positions of the peak, as well as the peak width and peak height, the peak appearance of the target substance can be analyzed more accurately. For example, when detecting sulfides in natural gas, accurately determine the peak characteristics of substances such as mercaptan and thiophene, avoid detection errors caused by signal interference and inaccurate peak positioning, and improve the reliability of the detection results.

[0107] Adjust the detection time according to the comparison result of the peak width and peak height with the standard peak appearance characteristic parameters. When the peak width becomes wider or the peak height becomes lower, extend the detection time to ensure that the signal of the target substance can be completely collected and the target substance can be accurately detected. For example, when detecting volatile organic compounds in ambient air, if the peak width of a certain substance becomes wider, extending the detection time can obtain more complete peak information and accurately judge the content of the substance;

[0108] Taking the detection of tetrahydrothiophene (THT) and tert-butyl mercaptan (TBM) in natural gas as an example, assume that after multiple detections, it is determined that the standard peak height ft1 of THT in the positive ion mode is 500, and the standard peak width ft2 is 10 (the unit is determined according to the actual detection situation). In an actual detection, the peak height fe1 of THT is obtained as 400, and the peak width fe2 is 12

[0109] Calculate the peak height deviation rate w1 = 20%, and the peak width deviation rate w2 = 20%. Assume that according to the characteristics of THT, the weight coefficient of the peak height deviation rate is 0.6, and the weight coefficient of the peak width deviation rate is 0.4. Then the deviation index is 0.6×20% + 0.4×20% = 20%.

[0110] If the set index threshold is 15%, since 20% > 15%, it is determined that the detection time needs to be adjusted. At this time, fe1 - ft1 = 400 - 500 = -100, fe2 - ft2 = 12 - 10 = 2, forming the data pair (-100, 2).

[0111] In the adjustment database, assume that the value range of a certain data pair corresponding to the time extension signal J1 is n1 = -150 to n2 = -50, b1 = 1 to b2 = 3. The data pair (-100, 2) matches this value range, and the corresponding time adjustment ratio is 10%. Since the adjustment signal is J1, the duration of the current detection time period is extended by 10% to more accurately detect the THT content.

[0112] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for detecting organic matter based on gas phase ion mobility spectrometry, characterized in that: include: Detection time segmentation: pre-divide the sample detection time into positive ion mode peak time, negative ion mode peak time and no-peak time; Detection program setting: In the positive ion mode peak time period, set the instrument to positive ion mode and turn on the migration tube voltage; in the negative ion mode peak time period, switch to negative ion mode and turn on the migration tube voltage; in the non-peak time period, turn off the migration tube voltage; Shutdown time optimization: preset the shutdown time of each group of migration tube voltage, perform X times of positive and negative ion mode switching at each shutdown time, and evaluate the performance parameters of the instrument during the switching process to determine the final voltage shutdown time in the current sample detection process; where Y>5; performance parameters include stabilization time, energy consumption ratio and material detection data.

2. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 1, characterized in that: During the switching process, the instrument's stabilization time and energy consumption ratio are evaluated, specifically: For each shutdown duration, record the instrument stabilization time, that is, the time from voltage recovery to signal stabilization. After recording, calculate the average of the X groups of stabilization time for each shutdown duration to obtain the required stabilization average time corresponding to each shutdown duration. Without turning off the voltage, measure the energy consumption of the instrument for the set time as the benchmark value; at each shutdown time, run the instrument for the set time and record the total energy consumption as the shutdown performance energy consumption, and calculate the energy saving ratio corresponding to each shutdown time according to the formula: energy saving ratio = (baseline value - shutdown performance energy consumption) / base value × 100%.

3. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 2, characterized in that: During the switching process, the material detection data of the instrument is evaluated, specifically: For each closing time, the peak height and peak area of ​​the target substance were recorded, and the average and standard deviation of each group of peak heights under each closing time were calculated to obtain the peak height mean and peak height deviation. The peak height RSD was obtained by calculating the ratio with the peak height deviation as the numerator and the peak height mean as the denominator. The peak surface RSD was calculated in the same way. The peak height RSD and peak surface RSD corresponding to each closing time are multiplied by the corresponding preset weight coefficients, and then the sum is obtained to obtain the repeatability evaluation index corresponding to each closing time.

4. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 3, characterized in that: Determine the final voltage off time during the current sample detection process, specifically: The shutdown durations with repeatability evaluation indexes lower than the preset threshold index are retained as standby shutdown durations, and the required stable average time and energy saving ratio corresponding to each standby shutdown duration are extracted, which are recorded as sda and sdc; A set of required stable expected mean time and expected energy saving ratios are preset, denoted as sde and sdr; according to the formula The required stable average time sda ​​and energy saving ratio sdc corresponding to each standby shutdown time are weightedly calculated to determine the comprehensive evaluation index α of each group of standby shutdown time; where u1 and u2 are the influencing weight factors of the required stable average time and energy saving ratio respectively; The standby shutdown time with the highest comprehensive evaluation index α is selected as the shutdown voltage time in the subsequent sample testing process in the detection program setting.

5. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 4, characterized in that: Also includes: Detection time optimization: establish a connection with the gas phase ion mobility spectrometer, obtain the electrical signal output by the instrument during the current detection time period and analyze it; The adjustment ratio of the duration of the current detection time period is determined based on the analysis results.

6. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 5, characterized in that: Obtain the electrical signal output by the instrument during the current detection period and analyze it, specifically: Obtain the peak start and end positions of the electrical signal, calculate the peak width and peak height, and calculate the difference between the signal value at the peak vertex and the baseline value to obtain the peak height; identify the positions on both sides of the peak vertex where the signal value is equal to half of the peak height, and calculate the distance between the two positions to obtain the peak width; record the peak height and peak width as fe1 and fe2; Set the standard peak characteristic parameters of the target substance in positive ion mode and negative ion mode. The standard peak characteristic parameters include standard peak height and standard peak width, which are recorded as ft1 and ft2; According to the formula The peak height deviation rate w1 and the peak width deviation rate w2 are calculated, and the peak height deviation rate w1 and the peak width deviation rate w2 are multiplied by the corresponding set weight coefficients respectively, and then the sum is summed to obtain the deviation index; The indicator threshold corresponding to the deviation indicator is set. If the obtained deviation indicator is less than or equal to the indicator threshold, it is determined that the current detection time period does not need to be adjusted; otherwise, fe1 and fe2 are compared with ft1 and ft2 respectively, and the corresponding adjustment signal is triggered based on the comparison result; the adjustment signal includes a time extension signal J1 and a time shortening signal J2; it is expressed as 7. The method for detecting organic matter based on gas phase ion mobility spectrometry according to claim 6, characterized in that: Determine the adjustment ratio of the current detection time period, specifically: After determining the comparison result of the current detection time period, a data pair is formed, and the data pair is the difference between fe1 and ft1, and the difference between fe2 and ft2; Pre-build an adjustment database, which includes the value ranges of each group of data pairs corresponding to the time extension signal J1 and the time shortening signal J2, each group of data pair value ranges corresponds to a time adjustment ratio, and match the data pairs with the value ranges of each group of data pairs based on the triggered adjustment signal, so as to determine the time adjustment ratio of the current detection time period; If the adjustment signal is J1, the time adjustment ratio is extended based on the duration of the current detection time period. If the adjustment signal is J2, the time adjustment ratio is shortened based on the duration of the current detection time period.

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