Method for accurately and rapidly detecting pesticide residues in fruits
阅读说明：本技术 水果中农药残留的精确快速检测方法 (Method for accurately and rapidly detecting pesticide residues in fruits ) 是由 宋国新 于 2020-09-24 设计创作，主要内容包括：本发明公开了一种水果中农药残留的精确检测方法,由下述步骤组成：(1)将水果用匀浆机匀浆,加入水和乙腈进行分散；(2)投入磁性纳米材料进行连续震荡萃取；(3)利用磁铁将萃取吸附农药的磁性纳米材料从水果溶液中进行分离；(4)采用少量有机试剂将磁性纳米材料所吸附的农药进行超声洗脱,洗脱液加入无水硫酸钠进行脱水；(5)加入内标化合物溶液；(6)利用气相色谱质谱联用仪对待测液进行分析检测。本发明所述水果中农药残留的精确检测方法,具有操作时间短,有机试剂消耗少,分析成本低,分析结果精确以及易于推广普及的优点。(The invention discloses a method for accurately detecting pesticide residues in fruits, which comprises the following steps: (1) homogenizing fruits with a homogenizer, adding water and acetonitrile for dispersion; (2) adding magnetic nano materials for continuous oscillation extraction; (3) separating the magnetic nano material for extracting and adsorbing the pesticide from the fruit solution by using a magnet; (4) ultrasonically eluting the pesticide adsorbed by the magnetic nano material by adopting a small amount of organic reagent, and adding anhydrous sodium sulfate into eluent for dehydration; (5) adding an internal standard compound solution; (6) and analyzing and detecting the liquid to be detected by using a gas chromatography-mass spectrometer. The method for accurately detecting the pesticide residue in the fruits has the advantages of short operation time, less consumption of organic reagents, low analysis cost, accurate analysis result and easy popularization.)
1. The method for accurately detecting the pesticide residue in the fruits is characterized by comprising the following steps of:
(1) homogenizing fruits with a homogenizer, adding water and acetonitrile for dispersion;
(2) adding magnetic nano materials for vibration extraction;
(3) separating the magnetic nano material for extracting and adsorbing the pesticide from the fruit solution by using a magnet;
(4) carrying out ultrasonic elution on the magnetic nano material adsorbed with the pesticide by adopting a small amount of organic reagent, and then adding anhydrous sodium sulfate for dehydration;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution to obtain a solution to be detected;
(6) and analyzing and detecting the liquid to be detected by using a gas chromatography-mass spectrometer.
2. The method for accurately detecting pesticide residues in fruits according to claim 1, which comprises the following steps:
(1) homogenizing 20-50 g of fruits by using a homogenizer to obtain a slurry; taking 5-20 g of slurry into a 50-100 mL centrifuge tube with a plug, then adding 20-40 mL of deionized water and 3-5 mL of acetonitrile, and shaking for 2-4 minutes;
(2) adding 50-200 mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing to vibrate for 5-10 minutes;
(3) placing a magnet on the side wall of the centrifuge tube, adsorbing the magnetic nano material on the side wall of the centrifuge tube close to the magnet, washing the magnetic nano material with deionized water for 2-3 times, and removing the washing liquid;
(4) ultrasonically eluting the magnetic nano material for 5-10 minutes by adopting 2-5 mL of organic solvent, eluting the pesticide adsorbed by the magnetic nano material into the organic solvent to obtain eluent, adding 100-300 mg of anhydrous sodium sulfate into the eluent for dehydration, and concentrating, wherein the organic solvent is acetonitrile and methanol in a volume ratio of (3-4): 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
3. The method for accurately detecting pesticide residues in fruits according to claim 2, wherein the amount of deionized water used for washing the magnetic nano material in each step (3) is 1-3 mL.
4. The method for accurately detecting pesticide residues in fruits according to claim 2, wherein the magnetic nanomaterial in step (2) is Fe3O4@SiO2The @ PDA @ StVp magnetic nano material is characterized in that PDA is polydopamine, and StVp is a copolymer with the surface coated with pyrrolidone and styrene.
5. The method for accurately detecting pesticide residues in fruits according to claim 4, wherein the Fe3O4@SiO2The specific synthesis process of the @ PDA @ StVp magnetic nano material is as follows:
s1 weighing dopamine hydrochloride and Tris buffer solution with the molar concentration of 10mM, and mixing the solution in a solid-to-liquid ratio of 1: (0.8-1.2) mg/mL;
s2 weighing Fe3O4@SiO2Magnetic nanospheres, according to Fe3O4@SiO2And the dopamine hydrochloride Tris buffer solution in a mass ratio of 1: (4-5) adding;
s3 weighing n-vinyl pyrrolidone according to Fe3O4@SiO2And n-vinyl pyrrolidone in a mass ratio of 1: (3-5) adding;
s4 weighing styrene according to Fe3O4@SiO2And styrene in a mass ratio of 1: (1-2) adding;
s5, mechanically stirring the solution at room temperature at 100-400 rpm for 1-2 hours; then reacting for 8-12 hours at the temperature of 60-120 ℃;
s6, after the reaction is finished, centrifuging the reaction solution for 10-15 minutes at 2000-3000 r/min, and collecting the bottom solid;
s7, washing the bottom solid with absolute ethyl alcohol of which the weight is 50-70 times that of the bottom solid and deionized water of which the weight is 100-200 times that of the bottom solid respectively;
s8, drying the solid for 6-10 hours at 50-70 ℃ and under the vacuum degree of 0.07-0.09 MPa to obtain the Fe3O4@SiO2@ PDA @ StVp magnetic nano material.
Technical Field
The invention relates to the technical field of detection, in particular to a method for accurately and quickly detecting pesticide residues in fruits.
Background
With the rapid growth of the economy of China and the improvement of the living standard of people, the production and consumption of fruits are rapidly increased year by year. In order to meet the product yield and prolong the quality guarantee period, the fruit growers use pesticides and other preservatives in the production process to achieve the maximization of economic benefit. With the limited use of organic chlorine pesticides such as dichlorodiphenyl trichloroethane, hexachloro cyclohexane and the like and highly toxic methamidophos in China, the common pesticides used by fruit growers at present mainly comprise other organophosphorus with relatively weak toxicity and pyrethroid pesticides with medium and low toxicity. The output of the organophosphorus pesticide in China accounts for one third of the total quantity all over the world, and the output of the organophosphorus pesticide accounts for more than half of the total quantity of the pesticide in China. The two types of pesticides have good stability and relatively long residual period, if the nonstandard phenomenon exists in the using and picking processes, the residual quantity of the pesticides in fruits is easy to exceed the standard, pesticide poisoning events caused by the pesticide poisoning events and disputes caused in regional agricultural product trades occur, the harm of pesticide residues to human bodies is controlled, one of the most effective methods is to enhance the detection strength of the pesticides in the fruits, meet the requirements of 'maximum residual limit of pesticides in national standard food for food safety GB 2763 and 2019', and fully guarantee the edible safety of consumers. In order to detect and analyze various pesticide residues in fruits, currently, widely applied national standard methods include GB/T5009.218-2008 for determining pesticide residues in fruits and vegetables, GB 23200.8-2016 for determining residues of 500 pesticides and related chemicals in fruits and vegetables, and NY/T1380-2007 for determining multiple residues of 51 pesticides in vegetables and fruits, and the like, and the standards provide a very reliable detection method for the pesticide residues in the fruits. However, in the practical implementation process, on one hand, the pretreatment method provided by the national standard needs to use a large amount of organic reagents with high purity, and the reagents inevitably cause health hazards to experimenters; on the other hand, various solid phase adsorption columns with high price are required to be used, and the reagents and the columns have to be properly treated after being used; in particular, the whole pretreatment process has the defects of multiple steps, long time, time and labor waste, relatively low recovery rate, high cost and the like. Although the patented technology is optimized on sample pretreatment, high-end instruments such as an ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometer which are expensive, and have high maintenance and use costs are required in the detection process, and the technology is difficult to rapidly popularize in a short time. Therefore, a rapid, economic, efficient, green and environment-friendly pretreatment method combined with an easily-popularized detection technology must be developed to perform rapid and accurate qualitative and quantitative analysis on various pesticide residues in fruits.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for accurately measuring various pesticide residues in fruits by using a simple one-dimensional gas chromatography-mass spectrometer. The method can solve the technical problem of providing a simpler, efficient, accurate and green method for measuring various residual pesticides in fruits.
The technical problem to be solved by the invention is realized by the following technical scheme:
the invention relates to a method for accurately detecting pesticide residues in fruits, which comprises the following steps:
(1) homogenizing fruits with a homogenizer, adding water and acetonitrile for dispersion;
(2) adding magnetic nano materials for continuous oscillation extraction;
(3) separating the magnetic nano material for extracting and adsorbing the pesticide from the fruit solution by using a magnet;
(4) ultrasonically eluting the pesticide adsorbed by the magnetic nano material by adopting a small amount of organic reagent to obtain an eluent, adding anhydrous sodium sulfate, dehydrating and concentrating;
(5) adding an internal standard compound solution to obtain a solution to be detected;
(6) and analyzing and detecting the liquid to be detected by using a gas chromatography-mass spectrometer.
Specifically, the accurate method for simultaneously detecting the pesticides in the fruits comprises the following steps:
(1) homogenizing 20-50 g of fruits by using a homogenizer to obtain a slurry; taking 10-20 g of slurry into a 50-100 mL centrifuge tube with a plug, then adding 10-40 mL of deionized water and 3-5 mL of acetonitrile, and shaking for 2-4 minutes;
(2) adding 50-200 mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing to vibrate for 5-10 minutes;
(3) placing a magnet on the side wall of a centrifuge tube, fully adsorbing the pesticide in the fruit solution by the magnetic nano material, adsorbing the magnetic nano material on the side wall close to the magnet, discarding the mixed liquid of acetonitrile and water of the fruit, cleaning the magnetic nano material for 2-3 times by deionized water, and discarding the cleaning liquid;
(4) and ultrasonically eluting the magnetic nano material in the centrifuge tube with the plug for 5-10 minutes by adopting 2-5 mL of organic solvent, eluting the pesticide adsorbed by the magnetic nano particles into the organic solvent to obtain eluent, adding 100-300 mg of anhydrous sodium sulfate, dehydrating and concentrating. Wherein the organic solvent is acetonitrile and methanol in a volume ratio of (3-4): 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
Preferably, the usage amount of the deionized water for cleaning the magnetic nano material in the step (3) is 1-3 mL.
Preferably, the magnetic nano material in the step (2) is Fe3O4@SiO2The @ PDA @ StVp magnetic nano material is characterized in that PDA is polydopamine, and StVp is a copolymer with the surface coated with pyrrolidone and styrene.
Said Fe3O4@SiO2The specific synthesis process of the @ PDA @ StVp magnetic nano material is as follows:
s1 weighing dopamine hydrochloride and Tris buffer solution with the molar concentration of 10mM, and mixing the solution in a solid-to-liquid ratio of 1: (0.8-1.2) mg/mL;
s2 weighing Fe3O4@SiO2Magnetic nanospheres, according to Fe3O4@SiO2And the dopamine hydrochloride Tris buffer solution in a mass ratio of 1: (4-5) adding;
s3 weighing n-vinyl pyrrolidone according to Fe3O4@SiO2And n-vinyl pyrrolidone in a mass ratio of 1: (3-5) adding;
s4 weighing styrene according to Fe3O4@SiO2And styrene in a mass ratio of 1:(1-2) adding;
s5, mechanically stirring the solution at room temperature at 100-400 rpm for 1-2 hours; then reacting for 8-12 hours at the temperature of 60-120 ℃;
s6, after the reaction is finished, centrifuging the reaction solution for 10-15 minutes at 2000-3000 r/min, and collecting the bottom solid;
s7, washing the bottom solid with absolute ethyl alcohol of which the weight is 50-70 times that of the bottom solid and deionized water of which the weight is 100-200 times that of the bottom solid respectively;
s8, drying the solid for 6-10 hours at 50-70 ℃ and under the vacuum degree of 0.07-0.09 MPa to obtain the Fe3O4@SiO2@ PDA @ StVp magnetic nano material.
By adding Fe3O4@SiO2The magnetic nano-microspheres are modified by PDA and StVp at the same time, the magnetic microspheres modified with hydrophilic groups PDA can be fully dispersed in water, and the PDA groups have excellent adsorption capacity for polar pesticide compounds, and after the StVp is modified, the hydrophobic groups (benzene rings) of the material can effectively enrich the weak-polar pesticide compounds in fruit solutions and the pesticide compounds containing the benzene rings through pi-pi acting force and hydrophobic-hydrophobic acting force. Particularly, PDA and StVp are modified simultaneously, the amido of dopamine and the carbonyl of n-vinyl pyrrolidone can react to produce a frame structure similar to network channels, the frame structure has an ordered open pore channel and a core-shell structure, the specific surface area of the material is obviously improved, and correspondingly, the characteristics can obviously improve the effects of selectivity, strong adsorption, efficient enrichment, rapid separation and cyclic utilization of the material on pesticide residues. Experimental results show that the composite structure modification can obviously improve the dispersion performance, the magnetic performance and the adsorption performance of the magnetic material to pesticides with different properties, and obviously improve the adsorption capacity of the material to various pesticides with different properties.
Compared with the prior art, the invention has the advantages that: the pesticide residue in the fruit is pretreated by the magnetic solid phase extraction method, so that the treatment time and the treatment cost can be greatly reduced, and Fe is pretreated3O4@SiO2The magnetic nano-microspheres are modified by PDA and StVp at the same time, so that ordered open pore channels are provided, the adsorption performance of the material is obviously improved, and the adsorption efficiency of the material to pesticides with different properties is enhanced; the conventional gas chromatography-mass spectrometer is adopted for measurement, so that the method is easy to popularize and popularize, and the measurement is quicker and more accurate in qualitative determination. Generally, the method is quick, economic, efficient and accurate, and the adverse effects of the traditional test method on personnel and environment are greatly reduced.
The specific information of the reagents used is as follows:
33 pesticide standards purchased from Sigma-aldrich Sigma aldrich trade ltd, both at 100 μ g/mL solvent for toluene and acetone;
an internal standard solution, 2,4', 5-tribromobiphenyl, CAS number 59080-36-3, purchased from SEPULCO USA, with an initial concentration of 1000. mu.g/mL and acetonitrile as solvent;
the pesticide matrix mixed standard working solution is prepared by respectively adding a certain amount of mixed standard solution and internal standard 2,4', 5-tribromobiphenyl solution into 1.0mL of sample blank matrix extracting solution, and uniformly mixing to prepare the matrix mixed standard working solution. The matrix mixing standard working solution should be ready for use.
Acetonitrile, CAS No.: 75-05-8, analytically pure, purchased from Shanghai national pharmaceutical chemicals, Inc.;
methanol, CAS No.: 67-56-1, analytically pure, available from Shanghai national Chemicals, Inc.;
absolute ethanol, CAS No.: 64-17-5, analytically pure, purchased from Shanghai national Chemicals, Inc.;
ammonia, CAS No.: 7647-01-0, analytically pure, from Shanghai national Chemicals, Inc.;
hydrochloric acid solution, CAS No.: 7664-41-7, analytically pure, from Shanghai national Chemicals GmbH;
ethylene glycol, CAS No.: 107-21-1, analytically pure, purchased from Shanghai national Chemicals, Inc.;
sodium acetate CH3COONa·3H2O, CAS number: 127-09-3, analytically pure, available from Shanghai national Chemicals, Inc；
Anhydrous sodium sulfate Na2SO4CAS number: 7757-82-6: analytically pure, purchased from Shanghai national chemical reagent, Inc., burned at 650 deg.C for 4h before use, stored in a drier, and cooled for use;
Fe3O4@SiO2magnetic sphere, CAS No.: 1317-61-9, available from Nanjing Xiancheng nanomaterial science and technology Limited;
dopamine hydrochloride, CAS number: 62-31-7, available from Afaha chemical Co., Ltd;
tris buffer with a molar concentration of 10mM, namely Tris (Tris hydroxymethyl aminomethane) buffer with a molar concentration of 10mM, purchased from Nantong moist chemical Co., Ltd;
n-vinyl pyrrolidone, CAS No.: 88-12-0, Shanghai national Chemicals, Inc.;
styrene, CAS No.: 100-42-5, Shanghai national Chemicals, Inc.
The instruments, equipment and conditions used in the detection process were as follows:
a refiner, provided by Shanghai Bilang instruments manufacturing Limited, model number BILON;
a vortex oscillator provided by Wuxi Voxin instruments Inc. with model number XH-B;
the electronic balance is provided by Shenzhen light balance instrument Limited and has the model of XS105 DU;
an automatic concentrator, model 6 DryVap, supplied by Leiberttaceae instruments, Beijing.
Agilent 6893/5975 gas chromatograph/mass spectrometer equipped with an electron bombardment source (EI).
A chromatographic column: HP-5MS quartz capillary column, 30m 0.25mm,0.25 μm
Chromatographic conditions are as follows: column temperature: the initial temperature is 60 ℃, and the temperature is kept for 1 min; heating to 150 deg.C at 30 deg.C/min, and maintaining for 1 min; then the temperature is increased to 300 ℃ at the speed of 10 ℃/min and kept for 10 min.
The temperature of a sample inlet is 250 ℃;
carrier gas: he (> 99.999%), flow rate: 1 mL/min;
and (3) sample introduction mode: no shunt sampling; sample introduction amount: 1 mu L of the solution;
mass spectrum conditions: ionization mode EI, ionization energy 70eV, and ion source temperature 250 ℃; quadrupole temperature: 150 ℃; the scanning mode is as follows: ion scanning is selected, and specific scanning information is shown in table 1:
TABLE 1 name of pesticide detected and retention time and qualitative and quantitative ion information
The method for accurately detecting the pesticide residue in the fruits has the advantages of short operation time, low consumption of organic reagents, low analysis cost, high recovery rate, low detection limit, accurate quantitative analysis result, easiness in popularization and the like.
Detailed Description
The present invention is further illustrated by the following examples, but the present invention is not limited to the following examples.
The magnetic nano material Fe3O4@SiO2Nanjing Xiancheng nanometer material science and technology Co.
Example 1
A method for accurately detecting pesticide residues in fruits comprises the following steps:
(1) homogenizing 20g of apples with a homogenizer at 9500 rpm for 1 minute to obtain a slurry; taking 5g of slurry in a 50mL centrifuge tube with a plug, then adding 20mL of deionized water and 2mL of acetonitrile, and shaking at 1800 rpm for 2 minutes;
(2) adding 50mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing shaking at 1800 rpm for 4 minutes;
(3) placing a magnet on the side wall of a centrifuge tube, fully adsorbing the pesticide in the fruit by the magnetic nano material, adsorbing the magnetic nano material with magnetism on the side wall close to the magnet, discarding the mixed solution of the fruit, acetonitrile and water, cleaning the magnetic nano material for 3 times by 2mL of deionized water each time, and discarding the cleaning solution;
(4) ultrasonically eluting the magnetic nano material in the centrifuge tube with the plug by adopting 4mL of organic solvent under the conditions of ultrasonic power of 300W and ultrasonic frequency of 25kHz for 8 minutes, eluting the pesticide adsorbed by the magnetic nano particles into the organic solvent, adding 200mg of anhydrous sodium sulfate for dehydration, and then concentrating the eluent to 1mL on an automatic concentrator; wherein the organic solvent is acetonitrile/methanol in a volume ratio of 3: 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution which is equivalent to 0.20mg/kg of a sample to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
The magnetic nano material is Fe3O4@SiO2。
Preparing a standard working solution: taking a proper amount of each pesticide standard, and preparing a standard working solution with 7 concentration points in a concentration range of 0.03-1.00 mg/kg in 5g of samples by using acetonitrile extract of a blank matrix, wherein an internal standard 2,4', 5-tribromobiphenyl solution which is the same as the samples is added at each concentration point.
In the detection process, an automatic sampler is adopted for sample injection, the sample injection volume is 1 mu L, qualitative and quantitative determination is carried out by adopting an internal standard working curve method, and results of 37 pesticide residues in fruits are obtained by calculation. Performing gas chromatography/mass spectrometer measurement on the standard working solution with each concentration gradient, and performing regression analysis on the corresponding concentration of the standard working solution according to the chromatographic peak area ratio of the quantitative ions and the internal standard characteristic ions of each pesticide in the standard working solution to obtain a standard working curve; and (4) measuring the liquid to be measured in the step (4) under the same conditions, measuring the quantitative ion chromatographic peak area of the 37 pesticides in the liquid to be measured and the peak area ratio of the internal standard characteristic ion, substituting the peak area ratio into the standard curve to obtain the content of the 37 pesticides in the liquid to be measured, and calculating according to the mass of the sample represented by the liquid to be measured to obtain the residual quantity of the 37 pesticides in the sample.
The detection indexes are shown in table 2.
Table 2 names of pesticides tested, limits of testing, linear range, linear correlation coefficient, normalized recovery and relative standard deviation.
Example 2
A method for accurately detecting pesticide residues in fruits comprises the following steps:
(1) homogenizing 20g of apples with a homogenizer at 9500 rpm for 1 minute to obtain a slurry; taking 5g of slurry in a 50mL centrifuge tube with a plug, then adding 20mL of deionized water and 2mL of acetonitrile, and shaking at 1800 rpm for 2 minutes;
(2) adding 50mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing shaking at 1800 rpm for 4 minutes;
(3) placing a magnet on the side wall of a centrifuge tube, fully adsorbing the pesticide in the fruit by the magnetic nano material, adsorbing the magnetic nano material with magnetism on the side wall close to the magnet, discarding the mixed solution of the fruit, acetonitrile and water, cleaning the magnetic nano material for 3 times by 2mL of deionized water each time, and discarding the cleaning solution;
(4) ultrasonically eluting the magnetic nano material in the centrifuge tube with the plug by adopting 4mL of organic solvent under the conditions of ultrasonic power of 300W and ultrasonic frequency of 25kHz for 8 minutes, eluting the pesticide adsorbed by the magnetic nano particles into the organic solvent, adding 200mg of anhydrous sodium sulfate for dehydration, and then concentrating the eluent to 1mL on an automatic concentrator; wherein the organic solvent is acetonitrile/methanol in a volume ratio of 3: 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution which is equivalent to 0.20mg/kg of a sample to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
The magnetic nano material is Fe3O4@SiO2@ PDA, the specific synthetic process is as follows:
s1 weighing dopamine hydrochloride and Tris buffer solution with the molar concentration of 10mM, and mixing the solution in a solid-to-liquid ratio of 1: mixing at 0.8 mg/mL;
s2 weighing Fe3O4@SiO2Magnetic nanospheres, according to Fe3O4@SiO2And the dopamine hydrochloride Tris buffer solution in a mass ratio of 1: 8, adding;
s3, stirring the solution at 30 ℃ at 300 revolutions per minute for 1 hour; then reacting for 8 hours at the temperature of 80 ℃;
after the reaction of S4, centrifuging the reaction solution at 2000 rpm for 15 minutes, and collecting the bottom solid;
s5, washing the bottom solid with absolute ethyl alcohol of which the weight is 50 times that of the bottom solid and deionized water of which the weight is 100 times that of the bottom solid respectively;
s6 drying the solid at 50 deg.C and 0.09MPa for 6 hr to obtain Fe3O4@SiO2@ PDA magnetic nanomaterial.
Preparing a standard working solution: taking a proper amount of each pesticide standard, and preparing a standard working solution with 7 concentration points in a concentration range of 0.03-1.00 mg/kg in 5g of samples by using acetonitrile extract of a blank matrix, wherein an internal standard 2,4', 5-tribromobiphenyl solution which is the same as the samples is added at each concentration point.
In the detection process, an automatic sampler is adopted for sample injection, the sample injection volume is 1 mu L, qualitative and quantitative determination is carried out by adopting an internal standard working curve method, and results of 37 pesticide residues in fruits are obtained by calculation. Performing gas chromatography/mass spectrometer measurement on the standard working solution with each concentration gradient, and performing regression analysis on the corresponding concentration of the standard working solution according to the chromatographic peak area ratio of the quantitative ions and the internal standard characteristic ions of each pesticide in the standard working solution to obtain a standard working curve; and (4) measuring the liquid to be measured in the step (4) under the same conditions, measuring the quantitative ion chromatographic peak area of the 37 pesticides in the liquid to be measured and the peak area ratio of the internal standard characteristic ion, substituting the peak area ratio into the standard curve to obtain the content of the 37 pesticides in the liquid to be measured, and calculating according to the mass of the sample represented by the liquid to be measured to obtain the residual quantity of the 37 pesticides in the sample.
The detection indexes are shown in table 3.
Table 3 name of pesticide tested, limit of detection, linear range, linear correlation coefficient, recovery from spiking, and relative standard deviation.
Example 3
A method for accurately detecting pesticide residues in fruits comprises the following steps:
(1) homogenizing 20g of apples with a homogenizer at 9500 rpm for 1 minute to obtain a slurry; taking 5g of slurry in a 50mL centrifuge tube with a plug, then adding 20mL of deionized water and 2mL of acetonitrile, and shaking at 1800 rpm for 2 minutes;
(2) adding 50mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing shaking at 1800 rpm for 4 minutes;
(3) placing a magnet on the side wall of a centrifuge tube, fully adsorbing the pesticide in the fruit by the magnetic nano material, adsorbing the magnetic nano material with magnetism on the side wall close to the magnet, discarding the mixed solution of the fruit, acetonitrile and water, cleaning the magnetic nano material for 3 times by 2mL of deionized water each time, and discarding the cleaning solution;
(4) ultrasonically eluting the magnetic nano material in the centrifuge tube with the plug by adopting 4mL of organic solvent under the conditions of ultrasonic power of 300W and ultrasonic frequency of 25kHz for 8 minutes, eluting the pesticide adsorbed by the magnetic nano particles into the organic solvent, adding 200mg of anhydrous sodium sulfate for dehydration, and then concentrating the eluent to 1mL on an automatic concentrator; wherein the organic solvent is acetonitrile/methanol in a volume ratio of 3: 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution which is equivalent to 0.20mg/kg of a sample to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
The magnetic nano material is Fe3O4@SiO2@ StVp, the specific synthetic process is as follows:
s1 weighing n-vinyl pyrrolidone according to Fe3O4@SiO2And n-vinyl pyrrolidone in a mass ratio of 1: 6 is added;
s2, weighing styrene according to Fe3O4@SiO2And styrene and a mass ratio of 1: 2 is added;
s3, stirring the solution at 30 ℃ for 1 hour at 300 revolutions per minute; then reacting for 8 hours at the temperature of 80 ℃;
after the reaction of S4, centrifuging the reaction solution at 2000 rpm for 15 minutes, and collecting the bottom solid;
s5, washing the bottom solid with absolute ethyl alcohol of which the weight is 50 times that of the bottom solid and deionized water of which the weight is 100 times that of the bottom solid respectively;
s6 drying the solid at 50 deg.C under 0.09MPa for 6 hr to obtain Fe3O4@SiO2@ StVp magnetic nanomaterial.
Preparing a standard working solution: taking a proper amount of each pesticide standard, and preparing a standard working solution with 7 concentration points in a concentration range of 0.03-1.00 mg/kg in 5g of samples by using acetonitrile extract of a blank matrix, wherein an internal standard 2,4', 5-tribromobiphenyl solution which is the same as the samples is added at each concentration point.
In the detection process, an automatic sampler is adopted for sample injection, the sample injection volume is 1 mu L, qualitative and quantitative determination is carried out by adopting an internal standard working curve method, and results of 37 pesticide residues in fruits are obtained by calculation. Performing gas chromatography/mass spectrometer measurement on the standard working solution with each concentration gradient, and performing regression analysis on the corresponding concentration of the standard working solution according to the chromatographic peak area ratio of the quantitative ions and the internal standard characteristic ions of each pesticide in the standard working solution to obtain a standard working curve; and (4) measuring the liquid to be measured in the step (4) under the same conditions, measuring the quantitative ion chromatographic peak area of the 37 pesticides in the liquid to be measured and the peak area ratio of the internal standard characteristic ion, substituting the peak area ratio into the standard curve to obtain the content of the 37 pesticides in the liquid to be measured, and calculating according to the mass of the sample represented by the liquid to be measured to obtain the residual quantity of the 37 pesticides in the sample.
The detection indexes are shown in table 4.
Table 4 name of pesticide tested, limit of detection, linear range, linear correlation coefficient, recovery from spiking, and relative standard deviation.
Example 4 a method for accurately detecting pesticide residues in fruits, consisting of the following steps:
(1) homogenizing 20g of apples with a homogenizer at 9500 rpm for 1 minute to obtain a slurry; taking 5g of slurry in a 50mL centrifuge tube with a plug, then adding 20mL of deionized water and 2mL of acetonitrile, and shaking at 1800 rpm for 2 minutes;
(2) adding 50mg of magnetic nano material into the centrifuge tube with the plug in the step (1), and continuing shaking at 1800 rpm for 4 minutes;
(3) placing a magnet on the side wall of a centrifuge tube, fully adsorbing the pesticide in the fruit by the magnetic nano material, adsorbing the magnetic nano material with magnetism on the side wall close to the magnet, discarding the mixed solution of the fruit, acetonitrile and water, cleaning the magnetic nano material for 3 times by 2mL of deionized water each time, and discarding the cleaning solution;
(4) ultrasonically eluting the magnetic nano material in the centrifuge tube with the plug by adopting 4mL of organic solvent under the conditions of ultrasonic power of 300W and ultrasonic frequency of 25kHz for 8 minutes, eluting the pesticide adsorbed by the magnetic nano particles into the organic solvent, adding 200mg of anhydrous sodium sulfate for dehydration, and then concentrating the eluent to 1mL on an automatic concentrator; wherein the organic solvent is acetonitrile/methanol in a volume ratio of 3: 1;
(5) adding an internal standard 2,4', 5-tribromobiphenyl solution which is equivalent to 0.20mg/kg of a sample to obtain a solution to be detected;
(6) and (3) loading the fruit to be tested, analyzing the liquid to be tested by using a gas chromatography-mass spectrometer, and performing qualitative and quantitative calculation by using an internal standard working curve method to obtain an accurate determination result of the pesticide residue in the fruit.
The magnetic nano material is Fe3O4@SiO2The specific synthetic process of the @ PDA @ StVp comprises the following steps:
s1 weighing dopamine hydrochloride and Tris buffer solution with the molar concentration of 10mM, and mixing the solution in a solid-to-liquid ratio of 1: mixing at 0.8 mg/mL;
s2 weighing Fe3O4@SiO2Magnetic nanospheres, according to Fe3O4@SiO2And the dopamine hydrochloride Tris buffer solution in a mass ratio of 1: 4 proportion of Fe3O4@SiO2In the above solution;
s3 weighing n-vinyl pyrrolidone according to Fe3O4@SiO2And n-vinyl pyrrolidone in a mass ratio of 1: 3 is added;
s4 weighing styrene according to Fe3O4@SiO2And styrene in a mass ratio of 1: 1 is added;
s5, stirring the solution at 30 ℃ at 300 revolutions per minute for 1 hour; then reacting for 8 hours at the temperature of 80 ℃;
after the reaction of S6, centrifuging the reaction solution at 2000 rpm for 15 minutes, and collecting the bottom solid;
s7, washing the bottom solid with absolute ethyl alcohol of which the weight is 50 times that of the bottom solid and deionized water of which the weight is 100 times that of the bottom solid respectively;
s8 drying the solid at 50 deg.C and 0.09MPa for 6 hr to obtain Fe3O4@SiO2@ PDA @ StVp magnetic nano material.
Preparing a standard working solution: taking a proper amount of each pesticide standard, and preparing a standard working solution with 7 concentration points in a concentration range of 0.03-1.00 mg/kg in 5g of samples by using acetonitrile extract of a blank matrix, wherein an internal standard 2,4', 5-tribromobiphenyl solution which is the same as the samples is added at each concentration point.
In the detection process, an automatic sampler is adopted for sample injection, the sample injection volume is 1 mu L, qualitative and quantitative determination is carried out by adopting an internal standard working curve method, and results of 37 pesticide residues in fruits are obtained by calculation. Performing gas chromatography/mass spectrometer measurement on the standard working solution with each concentration gradient, and performing regression analysis on the corresponding concentration of the standard working solution according to the chromatographic peak area ratio of the quantitative ions and the internal standard characteristic ions of each pesticide in the standard working solution to obtain a standard working curve; and (4) measuring the liquid to be measured in the step (4) under the same conditions, measuring the quantitative ion chromatographic peak area of the 37 pesticides in the liquid to be measured and the peak area ratio of the internal standard characteristic ion, substituting the peak area ratio into the standard curve to obtain the content of the 37 pesticides in the liquid to be measured, and calculating according to the mass of the sample represented by the liquid to be measured to obtain the residual quantity of the 37 pesticides in the sample.
The detection indexes are shown in table 5.
Table 5 name of pesticide tested, limit of detection, linear range, linear correlation coefficient, recovery from spiking, and relative standard deviation.
Comparison of 4 application examples, example 1 with Fe directly3O4@SiO2Magnetic nanospheres, which are not modified; example 2 the material used was a single modified Fe3O4@SiO2@ PDA magnetic nano-microsphere; example 3 the material used was a single modified Fe3O4@SiO2@ StVp magnetic nanospheres; example 4 the material used was complex modified Fe3O4@SiO2The conditions are completely the same except for @ PDA @ StVp magnetic nano-microsphere. Comparing the normalized recovery rates of the 4 examples, it can be seen that the overall recovery rate index is the lowest in example 1, and relatively, the recovery rate of the pyrethroid pesticide in example 2 is significantly lower than that in example 3, the recovery rate of the organophosphorus pesticide in example 3 is significantly lower than that in example 2, and the recovery rates of the organophosphorus pesticide and the pyrethroid pesticide in example 4 are much higher than those in examples 2 and 3, which illustrates that the complex modified Fe used in the present invention is3O4@SiO2The material of @ PDA @ StVp can obviously improve Fe3O4@SiO2@ PDA and Fe3O4@SiO2The two single modification materials of @ StVp have insufficient adsorption performance on pesticides with different properties.
By adding Fe3O4@SiO2The magnetic nano-microspheres are modified by PDA and StVp at the same time, the magnetic microspheres modified with hydrophilic groups PDA can be fully dispersed in water, and the PDA groups have excellent adsorption capacity for polar pesticide compounds, and after the StVp is modified, the hydrophobic groups (benzene rings) of the material can effectively enrich the weak-polar pesticide compounds in fruit solutions and the pesticide compounds containing the benzene rings through pi-pi acting force and hydrophobic-hydrophobic acting force. In particular, PDA and StVp modification, dopamine amine group and n-ethyl are carried out simultaneouslyThe carbonyl group of the alkenyl pyrrolidone can react to produce a frame structure similar to network channels, the frame structure has an ordered open pore channel and a core-shell structure, the specific surface area of the material is obviously improved, and correspondingly, the characteristics can obviously improve the effects of selectivity, strong adsorption, efficient enrichment, rapid separation and cyclic utilization of the material on pesticide residues. The experimental results also show that the composite structure modification can obviously improve the dispersion performance, the magnetic performance and the adsorption performance of the magnetic material to pesticides with different properties, and obviously improve the adsorption capacity of the material to various pesticides with different properties.
The present invention is not limited to the above-described preferred embodiments, and any structural changes or process modifications made in the light of the present invention shall be construed as being within the scope of the present invention, and all technical solutions similar or equivalent to the present invention shall be construed as being included in the present invention.