Method for detecting bhc and extraction head

Abstract

The application discloses a detection method and an extraction head for BHC (Benzene Hexachloride). The detection method comprises the following steps: preparing a Poly-6-IAA+PANI+IL+CNTs composite extraction head; extracting BHC in a headspace mode by using the composite extraction head; constructing a gas chromatography-mass spectrometry (GC-MS), and detecting BHC by using the extraction head. Thus, the Poly-6-IAA+PANI+IL+CNTs composite extraction head has better extraction efficiency and mechanical stability for BHC. The method is used for detecting BHC in actual samples, and the recovery rate is between 88.77% and 100.08%, and the method has good practicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a detection method of BHC and an extraction head. BACKGROUND

[0002] With the wide promotion of pesticides, the application times and preparation ratios are improved, resulting in pesticide residues in plants. Pesticide residues refer to the total of pesticide original bodies, toxic metabolites, degradation products and impurities in microorganisms in vegetables, water and atmosphere after the use of pesticides for a period of time without decomposition. Organochlorine pesticides are a common type of pesticide residues.

[0003] Organochlorine pesticides are effective organic compounds for preventing and treating plant pests, mainly including benzene and cyclopentadiene. The acute toxicity to humans is mainly the stimulation of the central nervous system, and the chronic poisoning is manifested as loss of appetite, weight loss, and sometimes cerebellar disorder and hematopoietic organ disorder. BHC is an organochlorine pesticide with benzene as raw material, which is the earliest used and most widely applied insecticide.

[0004] BHC can invade the human body through the digestive tract, respiratory tract and skin, and excessive intake will cause poisoning. It is very harmful to the human body, affects the normal function of organs, and causes unbalanced nutrition of the human body. BHC not only has great toxicity, but also is difficult to be degraded in the environment, so the detection of BHC residue is very important. In the prior art, a capillary column gas chromatography-electron capture detector method is used to detect the residue of BHC in food, which has the advantages of high sensitivity, small amount of reagent, high selectivity, good reproducibility, high recovery rate and the like. However, the pretreatment of the sample is relatively complicated, and extraction, dehydration, concentration and evolution are required. Some people use ultrasonic extraction-concentrated sulfuric acid purification-gas chromatography detection method to detect and analyze BHC in soil, but the operation of this method is relatively complex and the reproducibility is not good enough. SUMMARY

[0005] The present application proposes a detection method of BHC and an extraction head to solve the above problems.

[0006] According to one aspect of the present application, a detection method of BHC is provided, comprising the following steps:

[0007] Preparation of Poly-6-IAA+PANI+IL+CNTs composite extraction head; headspace extraction of BHC by the composite extraction head; construction of gas chromatography-mass spectrometry (GC-MS), and detection of BHC by the extraction head. Its beneficial effect is that the Poly-6-IAA+PANI+IL+CNTs composite extraction head has better extraction efficiency and mechanical stability for BHC. The method of the application is used for detection of BHC in actual samples, and the recovery rate is between 88.77% and 100.08%, which has good practicability.

[0008] In some embodiments, the preparation of the composite extraction head comprises the following steps:

[0009] Preparation of a polymerization solution containing 6-IAA, PANI, tetrabutylammonium perchlorate, ILCNTs, and acetonitrile solution; the three-electrode system is put into the polymerization solution, and CV scanning is performed to prepare the composite extraction head. Its beneficial effect is that the thus-prepared composite extraction head has good electrical conductivity and mechanical stability, and has better sensitivity for detection of BHC.

[0010] In some embodiments, the concentration ratio of 6-IAA to PANI is 5:12. Its beneficial effect is that the coating of the extraction head under this ratio is uniformly distributed, has good stability, and thus has better electrical conductivity and sensitivity for detection of target substances.

[0011] In some embodiments, the method further comprises the following steps:

[0012] The extraction head is fixed in the self-made injector, and after drying, the Poly-6-IAA+PANI+IL+CNTs injection device is prepared. Its beneficial effect is that the subsequent extraction operation is more convenient.

[0013] In some embodiments, the method further comprises the following steps: aging the prepared injection device in a gas chromatograph. Its beneficial effect is that impurities on the extraction head can be purified, and the detection accuracy and sensitivity are improved.

[0014] In some embodiments, the aging conditions are:

[0015] The self-made injector is placed at the GC injection port, when the temperature rises to 90°C, the handle is pushed to push out the extraction head for aging, after 30 min, the injection port temperature is raised to 230°C, and the aging continues for 1.5 h, and after the aging is completed, it is placed for standby. Its beneficial effect is that impurities on the extraction head can be purified, and the detection accuracy and sensitivity are improved.

[0016] In some embodiments, the headspace extraction of BHC by the composite extraction head comprises the following steps:

[0017] The saturated brine and the mixed standard solution containing organic chlorine are added into an extraction container to form a first mixed solution; the first mixed solution is stirred and constant temperature water bathed;

[0018] The sampling device is inserted into the extraction bottle and the extraction head is exposed to the solution headspace, and the headspace extraction is carried out under stirring. The beneficial effect is that the subsequent detection operation is more convenient.

[0019] In some embodiments, the temperature of the constant temperature water bath is 50 DEG C; the stirring is magnetic stirring, the stirring speed is 300-500 r / min, and the time is 30 min. The beneficial effect is that the coating of the extraction head at this temperature is uniformly distributed, has good stability, and thus has better conductivity and sensitivity to target substance detection.

[0020] In some embodiments, the extraction time is 30 min; and the extraction temperature is 40-80 DEG C. The beneficial effect is that the coating of the extraction head at this temperature and time is uniformly distributed, has good stability, and thus has better conductivity and sensitivity to target substance detection.

[0021] In some embodiments, the cyclic voltammetry range of the CV scan is 0-1.8 V; the scan rate is 0.05 mV / S, and the scan number is 100. The beneficial effect is that the coating of the extraction head prepared in this way is uniformly distributed, has good stability, and thus has better conductivity and sensitivity to target substance detection.

[0022] In some embodiments, the concentration of the saturated brine is 0.05 g / mL-0.35 g / mL. The beneficial effect is that the brine at this concentration has a good response effect on the target position.

[0023] According to another aspect of the application, an extraction head for detecting BHC is provided, and the extraction head is a P-6-IAA-PANI-CNTs-IL extraction head. The beneficial effect is that the coating of the extraction head is uniformly distributed, has good stability, and thus has better conductivity and sensitivity to target substance detection. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The voltammetry behavior of the 6-IAA extraction head of the application;

[0025] Figure 2 The voltammetry behavior of the PANI extraction head of the application;

[0026] Figure 3 The voltammetry behavior of the Monomer extraction head of the application;

[0027] Figure 4Voltammetry of Monome+MWCNTs extraction head of the present application;

[0028] Figure 5 Voltammetry of Monome+IL extraction head of the present application;

[0029] Figure 6 Voltammetry of Poly-6-IAA+PANI+IL+CNTs extraction head of the present application;

[0030] Figure 7 Schematic of the preparation of Poly-6-IAA+PANI+IL+CNTs extraction head of the present application;

[0031] Figure 8 1000x magnification micrograph of aniline polymerization in acetonitrile of the present application;

[0032] Figure 9 20000x magnification micrograph of aniline polymerization in acetonitrile of the present application;

[0033] Figure 10 1000x magnification micrograph of aniline polymerization in nitric acid of the present application;

[0034] Figure 11 20000x magnification micrograph of aniline polymerization in nitric acid of the present application;

[0035] Figure 12 1000x magnification of 6-IAA to PANI concentration ratio of 5:12 of the present application;

[0036] Figure 13 10000x magnification of 6-IAA to PANI concentration ratio of 5:12 of the present application;

[0037] Figure 14 1000x magnification of 6-IAA to PANI concentration ratio of 6:11 of the present application;

[0038] Figure 15 10000x magnification of 6-IAA to PANI concentration ratio of 6:11 of the present application;

[0039] Figure 16 1000x magnification of 6-IAA to PANI concentration ratio of 5:12 of the present application;

[0040] Figure 17 10000x magnification of 6-IAA to PANI concentration ratio of 7:10 of the present application;

[0041] Figure 18Figure 8: 1000X magnification of 6-IAA to PANI concentration ratio of 8:9 of the present application;

[0042] Figure 19 Figure 9: 10000X magnification of 6-IAA to PANI concentration ratio of 8:9 of the present application;

[0043] Figure 20 Figure 10: 1000X magnification of 6-IAA to PANI polymerization of the present application;

[0044] Figure 21 Figure 11: 10000X magnification of 6-IAA to PANI polymerization of the present application;

[0045] Figure 22 Figure 12: 1000X magnification of Monomer-MWCNTs of the present application;

[0046] Figure 23 Figure 13: 10000X magnification of Monomer-MWCNTs of the present application;

[0047] Figure 24 Figure 14: 1000X magnification of Monomer-IL-MWCNTs of the present application;

[0048] Figure 25 Figure 15: 10000X magnification of Monomer-IL-MWCNTs of the present application;

[0049] Figure 26 Figure 16: Different extraction head response to HCH peak area of the present application;

[0050] Figure 27 Figure 17: Change in extraction head response to target substance peak area as NaCl concentration increased from 0.05 g / mL to 0.35 g / mL of the present application;

[0051] Figure 28 Figure 18: Change in target substance response peak area as a function of different concentration ratios of indole-6-carboxylic acid to polyaniline of the present application;

[0052] Figure 29 Figure 19: Change in target substance response peak area as a function of different extraction times;

[0053] Figure 30 Figure 20: Change in target substance response peak area as a function of different extraction temperatures;

[0054] Figure 31 Figure 21: Change in target substance response peak area as a function of different stirring rates;

[0055] Figure 32 Figure 22: Response peak area of different concentrations of organochlorine mix solution;

[0056] Figure 33 Chromatogram for the actual sample of tomato;

[0057] Figure 34 Chromatogram for the actual sample of cucumber;

[0058] Figure 35 Tomato spiked chromatogram, 3.4 μg / mL;

[0059] Figure 36 Tomato spiked chromatogram, 4.6 μg / mL;

[0060] Figure 37 Tomato spiked chromatogram, 5.4 μg / mL;

[0061] Figure 38 Cucumber spiked chromatogram, 3.4 μg / mL;

[0062] Figure 39 Cucumber spiked chromatogram, 4.6 μg / mL;

[0063] Figure 40 Cucumber spiked chromatogram, 5.4 μg / mL;

[0064] Figure 41 Lettuce spiked chromatogram, 3.4 μg / mL;

[0065] Figure 42 Lettuce spiked chromatogram, 4.6 μg / mL;

[0066] Figure 43 Lettuce spiked chromatogram, 5.4 μg / mL; DETAILED DESCRIPTION

[0067] The application will be further described in detail below with reference to the accompanying drawings.

[0068] Instruments and Reagents

[0069] Main instruments and models: gas chromatograph-mass spectrometer (Shimadzu GCMS-QP2010), gas chromatograph (Shimadzu GC-2010), electrochemical analyzer (CHI660D), infrared spectrometer (iS50 FT-IR), ultrasonic cleaner (KQ5200E), constant temperature magnetic stirrer (S10-3 type), sample injector (self-made).

[0070] Main reagents and specifications: methanol (AR, Fengchuan Chemical Reagent Technology Co., Ltd.); multi-walled carbon nanotubes (MWCNTs); nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) purchased from Nanjing Xianfeng Nanometer Material Technology Co., Ltd. (Nanjing, China); carboxylated multi-walled carbon nanotubes (C-MWCNTs); anhydrous ethanol (AR); diethyl imidazole; 1-ethyl-3-methyl imidazole hexafluorophosphate (99%, purchased from Jiuding Chemical); 1-hexadecyl-3-methyl imidazole tetrafluoroborate; tetrabutylammonium perchlorate (99%, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.); indole-6-carboxylic acid (6-IAA) (98%, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.); aniline (NAI) (99%); organochlorine mixed standard (China Standard Material Network); acetonitrile (AR, Tianjin Kemi Chemical Reagent Co., Ltd.), sodium chloride (AR, Nanhui Pengzhen Barracks Chemical Plant); Purity water (professional distillation method); polyamide resin and epoxy resin.

[0071] Electrochemical Workstation Operating Conditions

[0072] Parameter settings: cyclic voltammetry range between 0-1.8V; scan rate: 0.05mV / s; scan number: 80 circles, under this condition, electro-sedimentation is carried out.

[0073] Example 1: Preparation of SEPM

[0074] First, an acetonitrile solution containing 0.05mol / L of 6-IAA, 0.12mol / L of PANI, 0.05mol / L of tetrabutylammonium perchlorate, 0.05mol / L of IL, and 0.05mg / mL of CNTs is prepared; wherein CNTs is selected from MWCNTs. Among them, IL is selected from 1-hexadecyl-3-methyl imidazole tetrafluoroborate ionic liquid.

[0075] A three-electrode system with platinum wire as the counter electrode, saturated calomel electrode as the reference electrode, and stainless steel wire as the working electrode is assembled. Then, it is immersed in the prepared solution to carry out CV scanning to prepare the extraction head. The cyclic voltammetry range is between 0-1.8V; the scan rate is 0.05mV / s; and the scan number is 100 circles. As shown in Figure 7 , it is the preparation principle diagram of Poly-6-IAA+PANI+IL+CNTs extraction head.

[0076] Then, epoxy resin and polyamide resin are prepared in a ratio of 1:1, and used to fix the extraction head in the self-made sample introduction device. After drying, the sample introduction device of Poly-6-IAA+PANI+IL+CNTs is prepared.

[0077] Finally, the prepared sample introduction device was placed in the gas chromatograph for aging for 2 h: the self-made sample introduction device was placed at the GC sample inlet, when the temperature was increased to 90°C, the handle was pushed to push the extraction head out for aging, 30 min later the sample inlet temperature was increased to 230°C, and the aging was continued for 1.5 h, after the aging was completed, the sample introduction device was placed for standby.

[0078] In addition, the preparation conditions of the three types of extraction heads of polymerized Monomer, polymerized Monomer+IL, and polymerized Monomer+CNTs were consistent with the above preparation method except that the electrolyte composition was changed accordingly, and the aging conditions were also consistent.

[0079] The voltammetric behavior of SEPM was characterized:

[0080] In this embodiment, the solid-phase microextraction head was prepared by cyclic voltammetry. The stainless steel wire was used as the working electrode, the platinum wire was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. The electrodes were inserted into a 5 mL solution of 0.05 mol / L indole-6-carboxylic acid and 0.12 mol / L aniline, a 0.05 mol / L IL solution electrolyte, and 0.1 mg / mL CNTs. The electrochemical working station of one pool of three electrodes was cycled in the range of 0-1.8 V at a scanning speed of 0.05 mV / S for 100 cycles under the parameter conditions of electrodeposition. From Figure 1 - Figure 6 As can be seen from the above table, with the increase of the number of polymerization circles, the current gradually increases, which indicates that the polymerized coating has good conductivity. Figure 1 In the CV curve of 6-IAA as the monomer without other dopants, the oxidation potential is about 1.4 V, and the peak current is maximum 0.0004. Figure 2 is the polymerization of polyaniline monomer. As can be seen from the figure, without other doping, the oxidation potential of the CV curve is about 1.6 V, and the peak current is maximum -0.0001, without a more obvious oxidation peak. Figure 3 is the polymerization of two monomers together, and a more obvious oxidation peak appears at an oxidation potential of about 1.4, and there is no much change with the increase of the number of circles. For example, Figure 4 , Figure 5 In the CV graph of separately doping IL or CNTs, there is a more obvious oxidation peak, but the response current of doping CNTs is obviously larger than that of doping IL, so CNTs is better than IL. As shown in Figure 6 , at a potential of 1.0 V, there is an obvious oxidation peak, and with the increase of the number of polymerization circles and the growth of the polymerization time, the peak current gradually increases, becomes more uniform and dense, and highlights the advantages of doping, which significantly indicates that the polymerized coating has good conductivity after doping IL and CNTs.

[0081] Characterization of polymerization of aniline in organic solution:

[0082] Figure 8 Figure 9 The polymerization of aniline (ANI) in acetonitrile solution is relatively tight, and the polymerization effect is good. However, when aniline is added to nitric acid, Figure 10 Figure 11 as shown, the polymerization is unstable, and cracks appear on the surface.

[0083] Example 2:

[0084] The concentration ratio of 6-IAA to PANI was adjusted to 6:11, 7:10, and 8:9, respectively, and other parameters were the same as in Example 1 (the ratio of the two in Example 1 was 5:12).

[0085] The coating prepared according to the above proportions was characterized by Figures 12 to 19 From the larger magnification Figure 13 and Figure 15 , it can be seen that the coatings with a concentration ratio of 5:12 and 6:11 are relatively tight, indicating that the conductivity of the coating is better; and from the smaller magnification Figure 12 and Figure 14 , it can be seen that the coating with a ratio of 5:12 is relatively evenly distributed, indicating that the stability of this coating is relatively good. From Figures 16 to 19 , it can be seen that when the concentration ratio is 7:10 and 8:9, the coating surface is sparse and relatively unstable, and when the concentration ratio is 8:9, the substance is almost not adsorbed on the stainless steel wire. Therefore, it can be concluded that when the concentration ratio of indole-6-carboxylic acid and polyaniline is 5:12, the obtained coating is relatively stable and has good conductivity.

[0086] As shown in Figure 20 Figure 21 , the microcharacterization of the coating in which the two monomers are polymerized together can be seen that 6-IAA and PANI can be well attached to the stainless steel wire carrier. To further characterize its microstructure, from the high magnification SEM image Figure 21 , magnification 10000 times, it can be seen that the surface structure of the coating is still not tight enough, and there are gaps.

[0087] Then MWCNTs are added to Monomer, and after electrochemical polymerization, as shown in Figure 22 , the polymerized Monomer-MWCNTs can be well attached to the stainless steel wire carrier, and the distribution is relatively uniform; and from the high magnification SEM Figure 23 , it can be seen that the surface of the coating is relatively tight.

[0088] ​​​The microstructure of the obtained extraction head prepared from Monomer (indole-6-carboxylic acid-aniline), 1-hexadecyl-3-methyl imidazolium tetrafluoroborate ionic liquid (IL), and multi-walled carbon nanotubes (MWCNTs) was characterized under SEM. As can be seen from the SEM images, the obtained Monomer, IL, and MWCNTs can be well attached to the stainless steel wire carrier. Figure 24 As can be seen from the high-magnification SEM images (10000x) of the obtained coating, the porous structure is clear. The structure of the obtained coating becomes more compact, because IL and MWCNTs participate in the polymerization reaction, effectively changing the morphology of the coating. At the same time, the phenomenon of IL and MWCNTs being loaded into the voids of the monomer indicates that IL and MWCNTs are effectively doped into the polymer coating. Figure 25 Figure 24 Figure 25

[0089] Example 3: Comparison of the peak area response of different extraction heads to BHC

[0090] This example verifies the response effect of the peak area of different extraction heads prepared in Example 1 to the same target analyte BHC. As described in the previous examples, four kinds of extraction heads of polymerized Monomer, polymerized Monomer-IL, polymerized Monomer-CNTs, and polymerized Monomer-IL-CNTs were prepared, and the stable response to BHC was polymerized Monomer, polymerized Monomer-CNTs, and polymerized Monomer-IL-CNTs.

[0091] As can be seen from the bar chart, Figure 26 the peak area response of polymerized Monomer to the substance is the smallest, and the peak area response of polymerized Monomer+IL+CNTs is larger. This further indicates that the addition of IL and MWCNTs effectively improves the use efficiency of the extraction head, and has more research value.

[0092] Example 4: Preparation of the solution

[0093] 4.1 Preparation of the standard solution:

[0094] The purchased organochlorine mixed standard solution was dissolved in methanol, and the volume was adjusted to 10 mL to prepare a mixed standard mother liquor with a concentration of 0.2 mg / mL. Then 10 mL of the mother liquor was dissolved in methanol, and the volume was adjusted to 50 mL to prepare a standard solution of 40 μg / mL.

[0095] 4.2 Preparation of the working solution:

[0096] ​​​The standard solution was stored in a refrigerator (4°C). During the experiment, 7.00 mL of saturated brine was accurately pipetted into a 20.00 mL extraction flask, and then the working solution was obtained by adding the mixed solution with different concentrations.

[0097] Headspace extraction:

[0098] In a 20 mL extraction flask, 7 mL of saturated NaCl and 500 μL of organochlorine mixed standard solution (40 μg / mL) were added in sequence, and then a magnetic stirrer was added. The flask was sealed with a fresh rubber plug and an aluminum cap after being sealed with a fresh rubber plug and an aluminum cap. The temperature of the constant temperature magnetic stirrer was adjusted to 50°C, and the extraction flask was placed in a water bath. Then, the self-made sampler was inserted into the extraction flask, the handle was pushed, and the extraction head was exposed to the solution headspace. The headspace extraction was carried out under the magnetic stirring at 500 r / min. After 30 min, the extraction head was retracted into the protective sleeve, and the extraction head was inserted into the gas chromatography gasification chamber sample inlet in the shortest time. After 5 min of full analysis, the sampler with the extraction head was pulled out, and the GC-MS was started for separation and detection.

[0099] The GC-MS operating conditions are as follows:

[0100] The GC conditions are as follows: the separation column is DB-1701, the column oven temperature is 60°C, the injection port temperature is 250°C, the injection mode is selected as splitless injection, the pressure is 73.0 kPa, the total flow rate is 44.0 mL / min, the column flow rate is 1.21 mL / min, the linear velocity is 40.1 cm / sec, and the purge flow rate is 3.0 mL / min.

[0101] The column oven temperature program is set as follows: 60°C for 1 min, increased to 140°C at a rate of 15°C / min, maintained for 1 min, increased to 180°C at a rate of 25°C / min, and maintained for 5 min; the total program time is 12.93 min.

[0102] The MS conditions are as follows: the ion source temperature is 230°C, and the interface temperature is 200°C.

[0103] Table 1 - Characteristic ion table of BHC

[0104]

[0105] 4.3 Response characteristics of target substances

[0106] (1) When the salt concentration is different: for example, Figure 27The figure shows the change in the peak area of ​​the extraction head in response to the target substance as the NaCl concentration increases from 0.05 g / mL to 0.35 g / mL. With the continuous increase of NaCl concentration, the extraction efficiency also continuously increases. In a saturated NaCl solution, the coating exhibits the best peak area in response to the target substance; therefore, this application selects a saturated NaCl solution as the extraction medium.

[0107] (2) When the concentration ratios of 6-IAA and PANI are different: such as Figure 28 As shown, the target substance exhibits a larger response peak area when the concentration ratio of 6-IAA to PANI is 5:12. The five different concentration ratios show that the concentration of 6-IAA is continuously increased while the concentration of PANI is decreased. As the PANI concentration decreases, the performance of the extraction head declines, further illustrating that the PANI concentration should not be too low; an appropriate PANI concentration can improve the extraction efficiency of the extraction head.

[0108] (3) When extraction times are different: from bottom to top Figure 29 As can be seen from the curve relationship, the peak area increases with the increase of extraction time; the peak area of ​​the target analyte is the largest at 30 min. When the extraction time is further increased, the response decreases. Since the adsorption of the extraction head has reached equilibrium at 30 min, after 30 min, the adsorbed analyte will be desorbed again, which will not be effective. Therefore, the selected extraction time of 30 min is the best.

[0109] (4) Changes in peak area of ​​target analyte when extraction temperature varies from 40 to 80℃: As the temperature increases, the peak area of ​​the extracted target analyte increases, but then begins to decrease after reaching a certain value, such as... Figure 30 As shown, the extraction efficiency is highest at 50℃. At this temperature, the extraction efficiency of the coating increases with rising temperature, but the extraction effect decreases with further increases in temperature. Therefore, 50℃ is considered the optimal temperature for headspace extraction experiments.

[0110] (5) When the stirring speeds are different: such as Figure 31 As shown, the results indicate that the peak area of ​​the target analyte gradually increases from 300 to 500 r / min, then begins to decrease, and finally the decreasing trend becomes stable. The higher the rate, the more difficult it is to control, which can lead to larger systematic and random errors in the experiment. Therefore, according to this application, 500 r / min is selected as the most suitable stirring rate.

[0111] The extraction head mentioned above is the Poly-Monomer-IL-MWCNTs extraction head prepared in Example 1.

[0112] Example 5:

[0113] The extraction head prepared in Example 1 was used to analyze different concentrations of organochlorine mixed standard solution, respectively, and it was found that the response peak area increased with the increase of concentration, showing good linear correlation, indicating that this analysis method had wide linear range and sensitivity. At the same time, 1 extraction head was used to perform 3 parallel experiments on the same concentration of organochlorine mixed standard, and the relative standard deviation (RSD) was 1.5%, respectively. The RSD values of 3 parallel prepared extraction heads for analyzing the same concentration of organochlorine mixed standard were 3.12%, respectively, indicating that the experimental precision was high and the extraction head had good reproducibility. Figure 32

[0114] The above-mentioned extraction head is the Poly-Monomer-IL-MWCNTs extraction head prepared in Example 1.

[0115] Table 2 - Analysis parameters of Poly-Monomer-IL-MWCNTs extraction head for hexachlorocyclohexane (BHC)

[0116]

[0117] Example 6: Analysis and detection of actual samples:

[0118] The actual samples selected were randomly purchased lettuce, tomatoes, and cucumbers on the market. The specific operation steps are as follows: 25 g of crushed lettuce, tomato, and cucumber samples were weighed, respectively, and 50 mL of methanol solution was added for dissolution and extraction, and they were fully homogenized on a high-speed homogenizer for 2 min, then the excess residue was filtered with filter paper, and the filtered liquid was added to a 0.06% NaCl solution and shaken on a vortex instrument for 2 min, then it was taken out and left to stand at room temperature for 20 min until the solution was layered, and 10 mL of the methanol layer in the layered liquid phase was taken to a beaker and evaporated in a constant temperature water bath at 40°C until the solution was evaporated to 1 mL, then 1 mL of the sample liquid was added to 6 mL of saturated salt solution in an extraction bottle, which was sealed, headspace extracted, and detected. A small amount of hexachlorocyclohexane was detected in the selected samples of tomatoes and cucumbers, and no hexachlorocyclohexane was detected in the lettuce, and the chromatograms are shown in Figure 33 and Figure 34 In addition, in order to evaluate the above detection method, different concentrations of mixed standard samples were added to the samples, and the concentration gradient was 3.4 μg / mL, 4.6 μg / mL, and 5.8 μg / mL for detection, and it was found that the response peak area of the extraction head to the target analyte hexachlorocyclohexane increased continuously with the increase of concentration, and the recovery rate was between 88.77% and 100.08%, indicating that this method can be used for the detection of actual samples. The spiked recovery chromatograms are shown in Figure 35 、 36 、37.

[0119] ​Compared with the prior art, the application has the following beneficial effects:

[0120] The application uses 6-IAA and PANI as polymerization monomers, sequentially adds IL and CNTs into the copolymerization solution, and uses cyclic voltammetry to perform electro-polymerization under the conditions of a potential of 0-1.8V, a scanning rate of 0.05mV / s, and 100 scanning cycles to prepare the extraction head. The optimal conditions are as follows: 7ml of saturated brine is added under a monomer ratio of 5:12, and headspace extraction is performed at 500r / min and 50℃ for 30min.

[0121] The target substance used for detection is a mixed label solution of 1mg / mL, which is diluted to prepare a standard solution with a concentration of 40μg / mL, and then is diluted to standard working solutions with different concentration gradients for detection of a standard curve. The linear equation of the detected standard sample is y=-35660+748C, R 2 =0.98846, the linear range is 3.4μg / mL-5.8μg / mL, and the detection limit is 0.28μg / mL. Finally, the target substance in the sample is detected, and the recovery rate of the standard addition is between 88.77% and 100.08%.

[0122] In the experiment of preparing the extraction head, the purpose of adding IL and CNTs is to improve the adsorption capacity and conductivity of the extraction head, so that the prepared SPME head has high sensitivity and stability, and can be used for analysis and detection of BHC substances in agricultural products.

[0123] The above only describes some embodiments of the application. For ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application.

Claims

1. A method for detecting BHC, characterized by, The method comprises the following steps: Preparation of Poly-6-IAA+PANI+IL+CNTs composite extraction head; The composite extraction head is used for headspace extraction of BHC; Gas chromatography-mass spectrometry (GC-MS) is constructed, and the extraction head is used for detection of BHC; Preparation of the composite extraction head comprises the following steps: A mixed solution containing 6-IAA, PANI, tetrabutylammonium perchlorate, IL, CNTs and acetonitrile solution is configured; The electrode system is put into the mixed solution, and CV scanning is performed to prepare the composite extraction head; The concentration ratio of 6-IAA to PANI is 5:12; CNTs are selected from MWCNTs; IL is selected from 1-hexadecyl-3-methyl imidazole tetrafluoroborate ionic liquid; 6-IAA is indole-6-carboxylic acid; The composite extraction head for headspace extraction of BHC comprises the following steps: Saturated brine and an organic chlorine-containing mixed standard solution are added to an extraction container to form a first mixed solution; The first mixed solution is stirred and kept in a constant temperature water bath; The sampling device is inserted into the extraction bottle, and the extraction head is exposed to the top space of the solution for headspace extraction under stirring; The temperature of the constant temperature water bath is 50°C; The stirring is magnetic stirring, the stirring speed is 300-500 r / min, and the stirring time is 30 min; The extraction time is 30 min; The extraction temperature is 40-80°C; The concentration of saturated brine is 0.05 g / mL-0.35 g / mL. The method further comprises the following steps:

2. The method of detecting BHC according to claim 1, wherein, The extraction head is fixed in the self-made sampling device, and after drying, a Poly-6-IAA+PANI+IL+CNTs sampling device is prepared. The method further comprises the following steps:

3. The method of detecting BHC according to claim 2, wherein, The prepared sampling device is aged in a gas chromatograph. The aging conditions are as follows:

4. The method of detecting BHC according to claim 3, wherein, The self-made sampling device is placed at the GC sampling port, when the temperature rises to 90°C, the handle is pushed to push out the extraction head for aging, after 30 min, the sampling port temperature is raised to 230°C, and the aging is continued for 1.5 h, and after the aging is finished, it is placed for standby. The cyclic voltammetry range of the CV scanning is 0-1.8 V; the scanning rate is 0.05 mV / S, and the scanning number is 100 times.

5. The BHC detection method according to claim 1, characterized in that, ​

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