阅读说明：本技术 乳、乳制品及谷物粉中农药残留检测前处理方法 (Pretreatment method for detecting pesticide residue in milk, dairy products and grain powder ) 是由 高玉杰 张悦 张立佳 李翠枝 刘丽君 于 2020-04-14 设计创作，主要内容包括：本发明公开了一种检测乳、乳制品及谷物粉中多种农药残留的样品前处理方法,该方法包括盐包净化和固相萃取柱净化,其中所述盐包为硫酸镁+氯化钠盐包。本发明的样品前处理方法结合了盐包净化和固相萃取柱净化的双重优点,可实现农药残留与复杂基质中干扰物质的分离,具有快速、准确、高效等优点。(The invention discloses a sample pretreatment method for detecting various pesticide residues in milk, dairy products and cereal powder. The sample pretreatment method disclosed by the invention combines the dual advantages of salt bag purification and solid-phase extraction column purification, can realize the separation of pesticide residues and interfering substances in a complex matrix, and has the advantages of rapidness, accuracy, high efficiency and the like.)

1. A sample pretreatment method for pesticide residue detection is characterized by comprising salt bag purification and solid phase extraction column purification.

2. The method for sample pretreatment according to claim 1, wherein the sample is milk (e.g., raw milk, raw goat milk, raw camel milk), dairy product, or cereal flour.

3. The sample pretreatment method according to claim 1, wherein the salt pack used in the salt pack purification is a magnesium sulfate + sodium chloride salt pack.

4. The sample pretreatment method according to claim 3, wherein the mass of the magnesium sulfate is 3.8 to 5.0 times the mass of the sodium chloride.

5. The method for pretreating a sample according to claim 1, wherein the elution is performed using a mixture of acetone and acetonitrile in the solid-phase extraction column purification;

Preferably, the volume of acetone in the mixed solution is 0.67 to 1.5 times the volume of acetonitrile.

6. The sample pretreatment method according to claim 1, wherein the packing of the solid phase extraction column is lipophilic divinylbenzene and hydrophilic N-vinylpyrrolidone, and the specification is 60 mg.

7. The method for pretreating a sample according to claim 1, wherein after the step of purifying the solid phase extraction column, the method further comprises the steps of performing redissolution by using a mixed solution of ethyl acetate and n-hexane;

preferably, in the mixed solution, the volume of ethyl acetate is 0.15 to 0.2 times the volume of n-hexane.

8. The sample pretreatment method according to claim 1, wherein the amount of the sample is 2.00 to 5.00 g.

9. The sample pretreatment method according to claim 1, wherein the pesticide is an organophosphorus or heterocyclic pesticide; preferably, the pesticide is bromopropylate, trithione, chlorpyrifos, coumaphos, fostering phosphorus, systemic phosphorus, diazinon, dichlorvos, dimethoate, disulfoton, endosulfan, thiophosphoryl, ethion, dicofom, pyralid, fenitrothion, fenthion sulfone, fenthion, bromophenyl, malathion, aphithion, fon, pyrathion, parathion, methyl parathion, phorate sulfone, phorate, synergistic ether, prothioconazole, pyrazothion, fenitrothion, chlorfenvinphos, fenamate, fenamiphos, triadimefon or toxic phosphorus.

10. A method for detecting pesticide residues in a sample, which is characterized by comprising the sample pretreatment method according to any one of claims 1 to 9, and then detecting the pretreated sample to be detected by using GC-MS/MS.

Technical Field

The invention belongs to the technical field of food detection, and particularly relates to a sample pretreatment method for detection of organophosphorus and heterocyclic pesticides in milk, dairy products and grain powder.

Background

With the increase of the consumption of Chinese dairy products and infant food, people put higher requirements on the food safety. Food safety issues arising from the widespread use of pesticides have received widespread attention, as the residues have become one of the important sources of contamination of milk and dairy products, as they can accumulate and pass stage by stage through the food chain into the organism. After the pesticide residue in human body is accumulated to exceed a certain concentration, the pesticide residue has micro-dose and chronic fine toxicity harm to human health. In particular to an organophosphorus pesticide which is an insecticide widely used in various countries in the world, belongs to nerve poison and parenchymal organ poison, and causes abnormal development of the brain and intelligence of infants, endocrine diseases and even carcinogenesis. In order to strictly control the food safety risk of pesticide residues, the maximum pesticide residue limit in food safety national standard food (GB 2763-. However, in the implementation process, the application range of the partial detection method still has limitations, and therefore, the detection method of pesticide residues in food needs to be updated and developed continuously.

At present, the conventional pretreatment technology for detecting pesticide residue comprises the following steps: QuEChERS, Solid Phase Extraction (SPE), matrix dispersed solid phase extraction (MSPD), and Gel Permeation Chromatography (GPC). But the advantages and disadvantages of the conventional technology are obvious, such as the QuEChERS technology is simple and fast and cannot process complex matrix samples; SPE technology is efficient but the process is cumbersome; the MSPD technology has less pollution, short time and high cost; GPC techniques can handle complex matrices but are time consuming to operate. Aiming at dairy products and infant food (such as formula milk powder, rice flour and the like), the matrix oil content is high, and macromolecular substances such as protein and the like are more, so that the quick and efficient separation and purification effect cannot be achieved by using a pretreatment technology. Therefore, in view of the prior pretreatment technologies, it is urgently needed to develop a compound pretreatment technology suitable for detecting pesticide residues in dairy products and infant food.

Disclosure of Invention

The invention aims to improve the prior pretreatment technology to at least a certain extent, and provides a sample pretreatment method for detecting pesticide residues in milk, dairy products and grain powder.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

1. a sample pretreatment method for pesticide residue detection is characterized by comprising salt bag purification and solid phase extraction column purification.

2. The method for pretreating a sample according to claim 1, wherein the sample is milk (e.g., raw milk, raw goat milk, raw camel milk), dairy product, or cereal flour.

3. The sample pretreatment method according to claim 1, wherein the salt pack used for the salt pack purification is a magnesium sulfate + sodium chloride salt pack.

4. The sample pretreatment method according to claim 3, wherein the mass of the magnesium sulfate is 3.8 to 5.0 times the mass of the sodium chloride.

5. The method for pretreating a sample according to claim 1, wherein the elution is performed using a mixed solution of acetone and acetonitrile in the solid-phase extraction column purification;

preferably, the volume of acetone in the mixed solution is 0.67 to 1.5 times the volume of acetonitrile.

6. The sample pretreatment method according to claim 1, wherein the filler of the solid phase extraction column is lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone, and the specification is 60 mg.

7. The sample pretreatment method according to 1, wherein after the step of purifying the solid phase extraction column, redissolving by using a mixed solution of ethyl acetate and n-hexane;

Preferably, in the mixed solution, the volume of ethyl acetate is 0.15 to 0.2 times the volume of n-hexane.

8. The method for pretreating a sample according to claim 1, wherein the amount of the sample is 2.00 to 5.00 g.

9. The method for pretreating a sample according to claim 1, wherein the pesticide is an organophosphorus or heterocyclic pesticide; preferably, the pesticide is bromopropylate, trithione, chlorpyrifos, coumaphos, fostering phosphorus, systemic phosphorus, diazinon, dichlorvos, dimethoate, disulfoton, endosulfan, thiophosphoryl, ethion, dicofom, pyralid, fenitrothion, fenthion sulfone, fenthion, bromophenyl, malathion, aphithion, fon, pyrathion, parathion, methyl parathion, phorate sulfone, phorate, synergistic ether, prothioconazole, pyrazothion, fenitrothion, chlorfenvinphos, fenamate, fenamiphos, triadimefon or toxic phosphorus.

10. The method for detecting the pesticide residue in the sample is characterized by comprising the sample pretreatment method of any one of 1-9, and then detecting the pretreated sample to be detected by adopting GC-MS/MS.

In a specific embodiment of the present invention, the sample pretreatment method for pesticide residue detection according to the present invention can be specifically operated as follows:

1) Sample extraction: extracting a sample to be detected by acetonitrile vortex oscillation, and specifically comprising the following steps:

weighing a proper amount (2.00-5.00g) of sample to be detected in a 30mL centrifuge tube with a plug, adding 10mL acetonitrile, performing vortex oscillation and extraction for 10min, and obtaining an extracting solution;

2) purifying a salt bag: adding magnesium sulfate and sodium chloride salt bags into the extracting solution obtained in the step 1), sequentially performing vortex oscillation and centrifugation, and collecting supernatant;

wherein, the vortex shaking time is 5min, and the centrifugation is carried out for 10min at the temperature of 4 ℃ at 15000 r/min;

wherein, in the salt bag, the mass of the magnesium sulfate is 3.8 to 5 times of that of the sodium chloride;

3) purifying by a solid phase extraction column: absorbing 5mL of the supernatant obtained in the step 2), transferring the supernatant to a solid phase extraction column, eluting the solid phase extraction column by using a mixed solution of acetone and acetonitrile, and collecting all eluates;

wherein the solid phase extraction column is a solid phase extraction column (Waters, WAT094226) filled with lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone, has specification of 60mg, and is activated by 3mL of acetonitrile before use;

wherein the volume of acetone in the mixed solution is 0.67 to 1.5 times the volume of acetonitrile.

4) Concentrating and redissolving the eluent obtained in the step 3) for determination of GC-MS/MS, wherein the specific steps are as follows:

Blowing the eluent obtained in the step 3) to be nearly dry by nitrogen at 40 ℃, adding an external epoxy heptachlor B internal standard (10 mu g/mL), then adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture through a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume of ethyl acetate in the mixed solution is 0.15 to 0.2 times that of n-hexane.

The invention adopts salt bag and SPE column composite purification pretreatment technology, and has the following advantages:

the inventor finds that adding a magnesium sulfate and sodium chloride salt package in a certain proportion into the solution after acetonitrile extraction is beneficial to removing macromolecular substances in a complex matrix, and achieves the effect of purifying the matrix. Wherein the mass ratio of the salt package is related to the matrix effect, such as: for dimethoate, the matrix enhancement effect can be caused by the higher mass ratio of sodium chloride, and the detection result of pesticide residue is influenced.

In addition, the purification is carried out by using a solid phase extraction column, impurities are retained on the column by utilizing the purification effect of lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone packing, and the target compound directly flows out. And eluting through a mixed solution of acetone and acetonitrile, so that the target substance remained on the column is eluted and impurities are remained on the column, wherein the detection result is influenced by too large or too small volume ratio of the acetone to the acetonitrile. And concentrating the further purified sample, and performing redissolution by using a mixed solution of ethyl acetate and n-hexane so as to directly detect the sample on a machine.

In the traditional QuEChERS pretreatment technology, the salt package components are complex but the complex matrix can not be treated, while the SPE technology utilizes the adsorption principle to treat the matrix, four steps of activation, sample loading, leaching and elution are needed, the time consumption is long, a large amount of reagents are needed, and the environmental pollution is large. Compared with the traditional pretreatment technology, the method combines the advantages of QuEChERS and SPE technologies, the salt package can achieve the effect of purifying the matrix only by magnesium sulfate and sodium chloride, and the method is quick, efficient and low in cost; the SPE column can achieve the effect of purifying complex matrix only by activating, loading and eluting, and can shorten pretreatment time and reduce reagent dosage. In conclusion, the sample pretreatment method is simple and convenient in operation process, ensures high recovery rate, and greatly improves the detection efficiency of pesticide residues in milk, dairy products and grain powder.

Drawings

Figure 1 shows a total ion flow plot of 37 pesticide residues in a sample.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.

The methods used in the following examples are conventional methods unless otherwise specified, and the reagents used are commercially available reagents unless otherwise specified.

Definition of

In the present context, the term "milk" mainly includes animal-based raw milk, such as raw cow milk or raw sheep milk or raw camel milk.

In this context, the term "dairy product" refers to a finished product after milk processing, including but not limited to pasteurized milk, ultra high temperature flash sterilized milk, milk powder, fermented milk, cheese, milk beverages, and the like.

As used herein, the term "cereal flour" refers to flour produced by grinding five-cereal crops and food products produced by processing the same, including, but not limited to, rice flour, bean flour, coarse cereal flour, infant formula rice flour, infant formula soymilk flour, and the like.

In a particular embodiment of the invention, the salt package used is a magnesium sulfate + sodium chloride salt package, wherein the mass of magnesium sulfate is 3.8-5.0 times the mass of sodium chloride. Specifically, the mass of the magnesium sulfate may be 3.8 to 4.5 times or 3.8 to 4.2 times that of sodium chloride. More specifically, the magnesium sulfate may be 3.8 times, 4.0 times, 4.1 times, 4.2 times, 4.3 times, 4.4 times, or 4.5 times the mass of sodium chloride.

In a specific embodiment of the invention, the solid phase extraction column is eluted using a mixture of acetone and acetonitrile, wherein the volume of acetone in the mixture is 0.67-1.5 times the volume of acetonitrile. Specifically, the volume of acetone may be 0.7 to 1.3 times, 0.8 to 1.2 times, or 0.9 to 1.1 times the volume of acetonitrile. More specifically, the volume of acetone may be 0.8 times, 0.9 times, 1.0 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, or 1.5 times the volume of acetonitrile.

In a specific embodiment of the present invention, a mixture of ethyl acetate and n-hexane is used as the redissolving solution, wherein the volume of ethyl acetate in the mixed solution is 0.15 to 0.2 times the volume of n-hexane. Specifically, the volume of ethyl acetate may be 0.15 to 0.18 times, 0.16 to 0.18 times, or 0.17 to 0.18 times the volume of n-hexane.

Example 1 detection of organophosphorus and heterocyclic 37 pesticide residues in milk

In this embodiment, a certain commercially available brand of pure milk is selected for pesticide residue detection. The specific method comprises the following steps:

1) sample extraction: weighing 5.00g of a milk sample, placing the milk sample in a 30mL centrifuge tube with a plug, adding 37 pesticides for mixing, performing vortex oscillation for 1min, adding 10mL of acetonitrile, and performing vortex oscillation for 10min to obtain an extracting solution;

2) purifying a salt bag: adding 2g of salt bag with the mass ratio of magnesium sulfate to sodium chloride being 4:1 into the extracting solution obtained in the step 1), carrying out vortex oscillation for 5min, centrifuging at the temperature of 4 ℃ at 15000r/min for 10min, and collecting supernatant;

3) purifying by a solid phase extraction column: accurately measuring 5mL of the supernatant obtained in the step 2), transferring the supernatant to an HLB solid-phase extraction column activated by 3mL of acetonitrile (lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone filler are filled in the HLB solid-phase extraction column, the specification is 60mg), controlling the flow rate to be 1 mL/min-3 mL/min, eluting the solid-phase extraction column by using 5mL of mixed solution of acetone and acetonitrile, and collecting all eluent;

Wherein in the mixed solution, the volume ratio of acetone to acetonitrile is 1: 1;

4) blowing the eluent obtained in the step 3) to be nearly dry at 40 ℃ by using nitrogen, adding 25 mu L of external epoxy heptachlor B internal standard (10 mu g/mL), then adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture through a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume ratio of ethyl acetate to n-hexane in the mixed solution is 1.5:8.5, that is, the volume of ethyl acetate is 0.176 times of the volume of n-hexane.

According to the example, the measurement result shows that 37 pesticide standards of organic phosphorus and heterocyclic are added into the milk sample to be tested, so that the concentration of the 37 pesticides in the sample to be tested is as follows: 0.01 mg/kg. The recovery rates and RSD values of 37 pesticides in the sample as determined by gas chromatography tandem mass spectrometry are shown in table 1.

Table 1 average recovery and relative standard deviation of milk substrate n-6

EXAMPLE 2 detection of organophosphorus and heterocyclic 37 pesticide residues in milk powder

In this example, a certain brand of infant formula milk powder sold in the market is selected for pesticide residue detection. The specific method comprises the following steps:

1) sample extraction: weighing 2.00g of milk powder sample, adding 3mL of water, carrying out vortex oscillation for 1min, adding 37 pesticides for mixing, carrying out vortex oscillation for 1min, adding 10mL of acetonitrile into a 30mL centrifuge tube with a plug, and carrying out vortex oscillation extraction for 10min to obtain an extracting solution;

2) Purifying a salt bag: adding 2g of salt bag (namely 1.6g of magnesium sulfate and 0.4g of sodium chloride) with the mass ratio of the magnesium sulfate to the sodium chloride of 4:1 into the extracting solution obtained in the step 1), carrying out vortex oscillation for 5min, centrifuging at the temperature of 4 ℃ at 15000r/min for 10min, and collecting supernatant;

3) purifying by a solid phase extraction column: accurately measuring 5mL of the supernatant obtained in the step 2), transferring the supernatant to an HLB solid-phase extraction column activated by 3mL of acetonitrile (lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone filler are filled in the HLB solid-phase extraction column, the specification is 60mg), controlling the flow rate to be 1 mL/min-3 mL/min, eluting the solid-phase extraction column by using 5mL of mixed solution of acetone and acetonitrile, and collecting all eluent;

wherein in the mixed solution, the volume ratio of acetone to acetonitrile is 1: 1;

4) blowing the eluent obtained in the step 3) to be nearly dry at 40 ℃ by using nitrogen, adding 25 mu L of external epoxy heptachlor B internal standard (10 mu g/mL), then adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture through a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume ratio of ethyl acetate to n-hexane in the mixed solution is 1.5:8.5, that is, the volume of ethyl acetate is 0.176 times of the volume of n-hexane.

According to the example, the measurement result shows that 37 pesticide standards of organic phosphorus and heterocyclic are added into the milk powder sample to be tested, so that the concentration of the 37 pesticides in the sample to be tested is as follows: 0.075 mg/kg. The recovery rates and RSD values of 37 pesticides in the sample as determined by gas chromatography tandem mass spectrometry are shown in table 2.

Table 2 mean recovery and relative standard deviation of milk powder base n-6

Example 3 detection of organophosphorus and heterocyclic 37 pesticide residues in soymilk

In this example, a certain brand of commercially available soybean milk (black sesame and black soybean flavor) was selected for detection of pesticide residue. The specific method comprises the following steps:

1) sample extraction: weighing 5.00g of a soybean milk sample in a 30mL centrifuge tube with a plug, adding 37 pesticides for mixing, performing vortex oscillation for 1min, adding 10mL of acetonitrile, and performing vortex oscillation for 10min to obtain an extracting solution;

2) purifying a salt bag: adding 2g of salt bag (namely 1.6g of magnesium sulfate and 0.4g of sodium chloride) with the mass ratio of the magnesium sulfate to the sodium chloride of 4:1 into the extracting solution obtained in the step 1), carrying out vortex oscillation for 5min, centrifuging at the temperature of 4 ℃ at 15000r/min for 10min, and collecting supernatant;

3) purifying by a solid phase extraction column: accurately measuring 5mL of the supernatant obtained in the step 2), transferring the supernatant to an HLB solid-phase extraction column activated by 3mL of acetonitrile (lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone filler are filled in the HLB solid-phase extraction column, the specification is 60mg), controlling the flow rate to be 1 mL/min-3 mL/min, eluting the solid-phase extraction column by using 5mL of mixed solution of acetone and acetonitrile, and collecting all eluent;

wherein in the mixed solution, the volume ratio of acetone to acetonitrile is 1: 1;

4) Blowing the eluent obtained in the step 3) to be nearly dry at 40 ℃ by using nitrogen, adding 25 mu L of external epoxy heptachlor B internal standard (10 mu g/mL), then adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture through a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume ratio of ethyl acetate to n-hexane in the mixed solution is 1.5:8.5, that is, the volume of ethyl acetate is 0.176 times of the volume of n-hexane.

According to the example, the measurement result shows that 37 pesticide standards of organic phosphorus and heterocyclic are added into the soybean milk sample to be tested, so that the concentration of the 37 pesticides in the sample to be tested is as follows: 0.01 mg/kg. The recovery rates and RSD values of 37 pesticides in the sample as determined by gas chromatography tandem mass spectrometry are shown in table 3.

TABLE 3 mean soy milk base recovery and relative standard deviation n ═ 6

Example 4 detection of organophosphorus and heterocyclic 37 pesticide residues in yogurt

In this example, some commercially available yogurt is selected for detection of pesticide residue. The specific method comprises the following steps:

1) sample extraction: weighing 2.00g of yogurt sample, adding 3mL of water, carrying out vortex oscillation for 1min, adding 37 pesticides for mixing, carrying out vortex oscillation for 1min, adding 10mL of acetonitrile into a 30mL centrifuge tube with a plug, and carrying out vortex oscillation extraction for 10min to obtain an extracting solution;

2) Purifying a salt bag: adding 2g of salt bag (namely 1.6g of magnesium sulfate and 0.4g of sodium chloride) with the mass ratio of the magnesium sulfate to the sodium chloride of 4:1 into the extracting solution obtained in the step 1), carrying out vortex oscillation for 5min, centrifuging at the temperature of 4 ℃ at 15000r/min for 10min, and collecting supernatant;

3) purifying by a solid phase extraction column: accurately measuring 5mL of the supernatant obtained in the step 2), transferring the supernatant to an HLB solid-phase extraction column activated by 3mL of acetonitrile (lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone filler are filled in the HLB solid-phase extraction column, the specification is 60mg), controlling the flow rate to be 1 mL/min-3 mL/min, eluting the solid-phase extraction column by using 5mL of mixed solution of acetone and acetonitrile, and collecting all eluent;

wherein in the mixed solution, the volume ratio of acetone to acetonitrile is 1: 1;

4) blowing the eluent obtained in the step 3) to be nearly dry at 40 ℃ by using nitrogen, adding 25 mu L of external epoxy heptachlor B internal standard (10 mu g/mL), then adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture through a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume ratio of ethyl acetate to n-hexane in the mixed solution is 1.5:8.5, that is, the volume of ethyl acetate is 0.176 times of the volume of n-hexane.

According to the example, the measurement result shows that 37 pesticide standards of organic phosphorus and heterocyclic are added into the yogurt sample to be tested, so that the concentration of the 37 pesticides in the sample to be tested is as follows: 0.075 mg/kg. The recovery rates and RSD values of 37 pesticides in the sample as determined by gas chromatography tandem mass spectrometry are shown in table 4.

Table 4 mean recovery and relative standard deviation n ═ 6 for the yogurt base

Example 5 detection of organophosphorus and heterocyclic 37 pesticide residues in Rice flour

In this example, a certain brand of rice flour is selected for detection of pesticide residue. The specific method comprises the following steps:

1) sample extraction: weighing 2.00g of a rice flour sample, placing the rice flour sample in a 30mL centrifuge tube with a plug, adding 37 pesticides for mixing, performing vortex oscillation for 1min, adding 10mL of acetonitrile, and performing vortex oscillation for 10min to obtain an extracting solution;

2) purifying a salt bag: adding 2g of salt bag (namely 1.6g of magnesium sulfate and 0.4g of sodium chloride) with the mass ratio of the magnesium sulfate to the sodium chloride of 4:1 into the extracting solution obtained in the step 1), carrying out vortex oscillation for 5min, centrifuging at the temperature of 4 ℃ at 15000r/min for 10min, and collecting supernatant;

3) purifying by a solid phase extraction column: accurately measuring 5mL of the supernatant obtained in the step 2), transferring the supernatant to an HLB solid-phase extraction column activated by 3mL of acetonitrile (lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone filler are filled in the HLB solid-phase extraction column, the specification is 60mg), controlling the flow rate to be 1 mL/min-3 mL/min, eluting the solid-phase extraction column by using 5mL of mixed solution of acetone and acetonitrile, and collecting all eluent;

wherein in the mixed solution, the volume ratio of acetone to acetonitrile is 1: 1;

4) Blowing the eluent obtained in the step 3) to be nearly dry at 40 ℃ by using nitrogen, adding 25 mu L of external epoxy heptachlor B internal standard (10 mu g/mL), adding 1.0mL of mixed solution of ethyl acetate and n-hexane for redissolution, and filtering the mixture by a 0.22 mu m filter membrane for GC-MS/MS determination;

wherein the volume ratio of ethyl acetate to n-hexane in the mixed solution is 1.5:8.5, that is, the volume of ethyl acetate is 0.176 times of the volume of n-hexane.

According to the example, the measurement result shows that 37 pesticide standards of organic phosphorus and heterocyclic are added into a rice flour sample to be detected, so that the concentration of the 37 pesticides in the sample to be detected is as follows: 0.075 mg/kg. The recovery rates and RSD values of 37 pesticides in the sample as determined by gas chromatography tandem mass spectrometry are shown in table 5.

Table 5 mean recovery and relative standard deviation of rice flour substrate n ═ 6

Example 6

The process used in this example is similar to example 1, except that in the salt package the mass of magnesium sulfate is 1.9g and the mass of sodium chloride is 0.5g (i.e. the mass of magnesium sulfate is 3.8 times the mass of sodium chloride). The recovery rates of the 37 pesticides in the samples are detected, the results are similar to those in Table 1, and the requirements of national standard GB/T27417-.

Example 7

The process used in this example is similar to example 1, except that in the salt package, the mass of magnesium sulfate is 2.0g and the mass of sodium chloride is 0.4g (i.e., the mass of magnesium sulfate is 5.0 times the mass of sodium chloride). The recovery rates of the 37 pesticides in the samples are detected, the results are similar to those in the table 1, and the national standard requirements are met (wherein, according to GB/T27417-.

Example 8

The procedure used in this example was similar to that of example 2, except that in step 3) the solid phase extraction column was eluted using a mixture of acetone and acetonitrile in a volume ratio of 2:3 (i.e. the volume of acetone was 0.67 times the volume of acetonitrile). The results of the detection of the recovery rates of the 37 pesticides in the sample are similar to those in Table 2, and all meet the national standard requirements (wherein, according to GB/T27417 and 2017 "guidelines for the confirmation and verification of qualified chemical analysis methods", when the content of the detected component is less than 0.1mg/kg, the recovery rate ranges from 60% to 120% and all meet the requirements).

Example 9

The procedure used in this example was similar to that of example 2, except that in step 3) the solid phase extraction column was eluted using a mixture of acetone and acetonitrile in a volume ratio of 3:2 (i.e. the volume of acetone was 1.5 times the volume of acetonitrile). The results of the detection of the recovery rates of the 37 pesticides in the sample are similar to those in Table 2, and all meet the national standard requirements (wherein, according to GB/T27417 and 2017 "guidelines for the confirmation and verification of qualified chemical analysis methods", when the content of the detected component is less than 0.1mg/kg, the recovery rate ranges from 60% to 120% and all meet the requirements).

Example 10

The method used in this example is similar to example 3, except that in step 4) a mixture of ethyl acetate and n-hexane is used for the reconstitution, wherein the volume ratio of ethyl acetate to n-hexane is 1.5:10.0, i.e. the volume of ethyl acetate is 0.15 times the volume of n-hexane. The recovery rates of 37 pesticides in the detected samples are similar to those in the table 3, and the results all meet the national standard requirements (wherein, according to GB/T27417-2017 'guidelines for confirmation and verification of qualification chemical analysis methods', when the content of the detected component is less than 0.1mg/kg, the recovery rate ranges from 60% to 120% and all meet the requirements).

Example 11

The method used in this example is similar to example 3, except that in step 4) a mixture of ethyl acetate and n-hexane is used for the reconstitution, wherein the volume ratio of ethyl acetate to n-hexane is 1.0:5.0, i.e. the volume of ethyl acetate is 0.2 times the volume of n-hexane. The recovery rates of 37 pesticides in the detected samples are similar to those in the table 3, and the results all meet the national standard requirements (wherein, according to GB/T27417-2017 'guidelines for confirmation and verification of qualification chemical analysis methods', when the content of the detected component is less than 0.1mg/kg, the recovery rate ranges from 60% to 120% and all meet the requirements).

Comparative example 1

In this comparative example, 37 kinds of pesticides in milk powder (middle aged and senior milk powder) were tested according to the method of example 2, except that the salt package used in step 2) was different. Specifically, the salt packages used in this comparative example were sodium chloride salt packages (i.e., no magnesium sulfate contained in the salt package), magnesium sulfate and sodium chloride salt packages in different proportions (2:1, 3:1, 4:1, respectively, in terms of mass ratio of magnesium sulfate to sodium chloride), or magnesium sulfate salt packages (i.e., no sodium chloride contained in the salt package), respectively, and the experimental results were as follows.

Table 6 salt packet comparison data

The results are shown in Table 6, wherein under the conditions of sodium chloride salt package, magnesium sulfate, sodium chloride (2:1) and magnesium sulfate, sodium chloride (3:1), the recovery rates of dimethoate, fenthion sulfone, parathion and the like are relatively high, wherein the recovery rates are out of the national standard specified range (60-120%), for example, the recovery rate of fenthion sulfone reaches 122.75%; in addition, the substrate effect of the parathion and the dimethoate is obviously enhanced under the condition of magnesium sulfate and sodium chloride (3:1) (the recovery rates are 115.63 percent and 116.15 percent respectively); under the condition of adding a magnesium sulfate bag, the recovery rates of chlorpyrifos, systemic phosphorus, dichlorvos and the like are relatively low. Comprehensive analysis shows that the overall recovery rate is optimal under the condition of salt package of magnesium sulfate and sodium chloride (4: 1).

Comparative example 2

In this comparative example, 37 kinds of pesticides in soybean milk (original flavor) were detected by the method of example 3, except that the specifications of the solid phase extraction column in step 3) were different. In this comparative example, the packing of the lipophilic divinylbenzene and hydrophilic N-vinylpyrrolidone solid phase extraction columns used were 60mg, 200mg and 500mg, respectively.

TABLE 7 comparison data of packing specifications of solid-phase extraction column

The results are shown in Table 7, and the recovery rate of 60mg of solid phase extraction column packing is obviously better than 200mg and 500mg for dichlorvos, endosulfan, fenthion sulfone, bromophenyl phosphorus and pyrazothion. And (4) conclusion: the optimum condition is that the solid phase extraction column packing of lipophilic divinylbenzene and hydrophilic N-vinyl pyrrolidone is 60 mg.

Comparative example 3

In this comparative example, 37 kinds of pesticides in soybean milk (original flavor) were tested by the method of example 3, except that acetone (i.e., containing no acetonitrile) and acetonitrile (i.e., containing no acetone) were used to elute the solid-phase extraction column in step 3), respectively, and the results were as follows.

Table 8 eluent comparison data

As shown in Table 8, dichlorvos, dicrotophos, metoclopramide, phorate and fenamiphos were more effectively eluted with a mixture of acetone and acetonitrile at a volume ratio of 1:1 than with acetone (i.e., containing no acetonitrile) or acetonitrile (i.e., containing no acetone). And (4) conclusion: the mixed solution with the volume ratio of acetone to acetonitrile in the eluent being 1:1 has the best effect.

Comparative example 4

The purpose of this comparative example was to screen for the best reconstituted solution.

In this comparative example, 37 kinds of pesticides were tested in milk powder (middle aged and senior milk powder) according to the method of example 2, and in order to ensure that the recovery rate was not affected by the fluctuation of the extraction and purification processes, 37 kinds of pesticides were added in step 4). This comparative example differs from example 2 in the reconstitution solution used in step 4). In this comparative example, the redissolving solutions used in step 4) were mixed solutions of ethyl acetate and n-hexane (the volume ratio of ethyl acetate to n-hexane was 1.5:8.5 and 3:7, respectively, i.e., the volume of ethyl acetate was 0.176 times and 0.429 times the volume of n-hexane, respectively), or n-hexane (i.e., no ethyl acetate), respectively, in different ratios, and the experimental results were as follows.

TABLE 9 redissolution comparative data

As shown in table 9, the recovery ratio of coumaphos, systemic phosphorus, dichlorvos, dimethoate, endosulfan, fenthion sulfone, parathion, pyrazofos, and chlorfenvinphos revealed that the mixture of ethyl acetate and n-hexane (v: v ═ 1.5:8.5) was superior to the mixture of ethyl acetate and n-hexane (v: v ═ 3:7) and n-hexane (i.e., no ethyl acetate) as a reconstituted solution. And (4) conclusion: a mixed solution of ethyl acetate and n-hexane (v: v ═ 1.5:8.5, i.e., the volume of ethyl acetate was 0.176 times the volume of n-hexane) was most effective as a reconstituted solution.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.