CN109212079B - Gas chromatography-mass spectrometry combined method for determining four trace p-halophenoxyacetic acid plant growth regulators in tomatoes - Google Patents

Gas chromatography-mass spectrometry combined method for determining four trace p-halophenoxyacetic acid plant growth regulators in tomatoes Download PDF

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CN109212079B
CN109212079B CN201811163763.2A CN201811163763A CN109212079B CN 109212079 B CN109212079 B CN 109212079B CN 201811163763 A CN201811163763 A CN 201811163763A CN 109212079 B CN109212079 B CN 109212079B
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丁立平
蔡春平
张睿
姜晖
郑铃
郑香平
黄菁菁
郑麟毅
陈志涛
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Integrated Technical Service Center Fuqing Enty-Exit Inspection & Quarantine Bureau
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Abstract

The invention relates to a method for analyzing and detecting trace harmful substances, in particular to a gas chromatography-mass spectrometry combined method for measuring four trace p-halophenoxyacetic acids in tomatoes. The method comprises the steps of extracting a target object by using a 10% methanol aqueous solution, adjusting the pH value of an extracting solution, enriching a target compound in the extracting solution by using a novel adsorbent p-toluenesulfonate-magnesium-aluminum type hydrotalcite, dissolving the adsorbent by using an acid to realize complete elution of the target object, efficiently extracting the compound by using a small amount of an organic solvent, and rapidly analyzing and determining by using a gas chromatography-mass spectrometry combination method after derivation. The novel adsorbent adopted by the method realizes the rapid and efficient adsorption of the target object by adopting a dispersed solid-phase extraction mode, and can save a large amount of adsorption time compared with a solid-phase extraction mode; the complete desorption of the target can be realized by using the acid to dissolve the adsorbent; only a small amount of organic solvent is suitable for extraction, and compared with the existing method which needs a large amount of organic solvent, the method has the advantages of safety, environmental protection and economic advantage.

Description

Gas chromatography-mass spectrometry combined method for determining four trace p-halophenoxyacetic acid plant growth regulators in tomatoes
Technical Field
The invention relates to a method for analyzing and detecting harmful trace substances, in particular to a gas chromatography-mass spectrometry combined method for determining trace p-fluorophenoxyacetic acid, p-chlorophenoxyacetic acid, p-bromophenoxy acetic acid and p-iodophenoxyacetic acid in tomatoes.
Background
The p-fluorophenoxyacetic acid, the p-chlorophenoxyacetic acid, the p-bromophenoxy acetic acid and the p-iodophenoxyacetic acid are four plant growth regulators with similar chemical structures, broad spectrum and auxin activity, are mainly used for preventing flower and fruit drop, inhibiting bean rooting, promoting fruit setting, inducing seedless fruit and promoting ripening and growth. Wherein the parachlorophenoxy acetic acid is the most commonly used one of the four substances in agricultural production, and is commonly used for fruit retention of tomatoes. The compound belongs to a medium-low toxicity substance, but has certain reproductive toxicity to mammals according to research.
Only a single detection method for p-chlorophenoxyacetic acid in 'determination of the residual amount of p-chlorophenoxyacetic acid in export food SN/T3725-2013' is provided at present. In the standard, the p-chlorophenoxyacetic acid residue in the food matrix is extracted by an ethyl acetate organic solvent, purified by an anion exchange solid phase extraction column, measured by a liquid chromatography-mass spectrometry/mass spectrometry method, and quantified by an external standard method. However, there is no literature or standard for simultaneous detection of these four compounds mentioned in the present invention, and the relevant practical detection methods are lacking.
Layered Double Hydroxide (LDHs) is a typical Layered material with a supramolecular intercalation structure, and the space adjustability among Layered plates and the replaceability of intercalation anions are two remarkable characteristics of the material. Based on the method, people can modify the LDHs material according to the difficulty of replaceability of intercalation anions of the LDHs material and the adjustability of the distance between the layers, and then select different types of intercalation anions according to the requirements of practical application to modify the material to obtain a functional material with novel application.
Currently, the LDHs material is used for the related research and reports of the trace substance residue detection in food. However, there are actually reports in the literature that show that such substances can be used as adsorbents for certain specific compounds, thus providing the potential for their use in the detection of harmful residues. In the field of LDHs materials used as adsorbents, different intercalation anions can be selected to synthesize different types of modified LDHs materials according to various factors such as molecular size, structure, polarity, functional groups and the like of adsorbed targets. The modified LDHs materials have different interlayer spacing, so that the modified LDHs materials have the adsorption selection effect of limiting the molecules of a specific target substance to enter the interlayer; meanwhile, the modified material intercalation anions have different replacement difficulty degrees, so that the modified material intercalation anions show different adsorption selectivity on different targets. Therefore, in practical application, the adsorption effect of different LDHs materials on a specific target needs to be selected, verified and optimized through adsorption experiments.
The inventor carries out an adsorption experiment on the four substances in water by applying the p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent in the previous research, and the result shows that the p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent has a good adsorption effect on a target object. On the basis, the inventor further optimizes the performance and application method of the developed adsorbent for enriching the target compound, and establishes a gas chromatography-mass spectrometry combined method for detecting trace p-halophenoxyacetic acid in tomatoes by taking p-toluenesulfonate-magnesium aluminum type hydrotalcite as the adsorbent.
Disclosure of Invention
In order to overcome the defects that the existing method for simultaneously detecting trace p-halophenoxyacetic acid in tomatoes is lack, a large amount of organic solvent is used as an extraction solvent, the types of selectable anion exchange solid phase extraction columns are limited, and the types of detection substances are single, the invention aims to solve the technical problem of providing a gas chromatography-mass spectrometry combined method which is based on novel adsorbent dispersed solid phase extraction and is suitable for detecting four trace p-halophenoxyacetic acids in tomatoes.
The invention achieves the above object by the following technical means.
A gas chromatography-mass spectrometry combined method for measuring four trace p-halophenoxyacetic acid plant growth regulators in tomatoes comprises the following steps:
step 1 extraction and adsorption of the compound: cutting a tomato sample into pieces, stirring and crushing, weighing a proper amount of sample in a plastic centrifuge tube with a plug, adding a certain amount of extraction solution, homogenizing and extracting at high speed, centrifuging, pouring the supernatant into another plastic centrifuge tube with a plug, re-extracting once, combining the supernatants, adding a proper amount of sodium hydroxide solution into the centrifuge tube, and adjusting the pH value of the supernatant to a proper range; adding 0.50g of p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent, sealing, and oscillating for a certain time to make the adsorbent adsorb the target compound in the supernatant;
step 2 desorption of compound: centrifuging the centrifuge tube with the plug to separate the solid adsorbent from the water solution and discard the supernatant, adding a certain amount of hydrochloric acid solution to dissolve the solid adsorbent, and finishing desorption of the adsorbed compound;
step 3, extraction and derivatization of compounds: adding a certain amount of anhydrous sodium sulfate and an organic solvent into the centrifugal tube for extraction, performing vortex and centrifugation, taking supernatant liquid to a derivatization bottle, adding a derivatization reagent into the supernatant liquid, sealing, uniformly mixing, and putting the mixture in a constant-temperature water bath to finish the derivatization process;
analytical testing of the compound of step 4: adding a stop solution into a derivatization bottle to remove redundant derivatization agents, adding a proper amount of solid sodium bicarbonate and anhydrous sodium sulfate, carrying out vortex, absorbing an upper layer organic solution, filtering, and then carrying out analysis and test by using a gas chromatography-mass spectrometry method according to the following conditions:
a) a chromatographic column: DB-1701 capillary column, 30m × 0.25mm, 0.25 μm film thickness; column flow rate: 1.20 mL/min.
b) Sample inlet temperature: 260 ℃; and (3) sample introduction mode: no shunt sampling; sample introduction amount: 1 μ L.
c) Temperature rising procedure: 40 deg.C (1 min hold), 10 deg.C/min to 130 deg.C (5 min hold), 15 deg.C/min to 260 deg.C (3 min hold).
d) EI bombardment source: 70 ev; temperature of a chromatography-mass spectrometry connection port: 280 ℃; temperature of the quadrupole rods: 230 ℃; ion source temperature: at 150 ℃.
e) Carrier gas: high-purity helium (the purity is more than or equal to 99.999%).
f) Mass spectrum data acquisition mode: selected ion scan mode (SIM), solvent delay time: for 10 min.
g) The quantitative and qualitative ion of the compounds are given in the following table:
serial number Name of Compound Quantitative ion Qualitative ion
1 P-fluorophenoxyacetic acid derivatives 125.1 184.1,111.1
2 P-chlorophenoxyacetic acid derivatives 141.0 200.0,111.1
3 Para-bromophenoxyacetic acid derivatives 243.9 184.9,156.9
4 P-iodophenoxyacetic acid derivatives 291.9 232.9,202.9
Wherein,
the tomato sample in the step 1 is weighed by 5.00g, the extraction solution is 10% methanol-water solution, the dosage of the extraction solution is 30mL, the high-speed homogenizing speed is 15000rpm, the time is 1min, the concentration of the sodium hydroxide solution is 0.05mol/L, the adjusted pH value range is 4.0-9.0, and the oscillating adsorption time is 15 min.
The hydrochloric acid solution in the step 2 is prepared from concentrated hydrochloric acid and water according to the volume ratio of 1:1, and the dosage is 2.50 mL.
In the step 3, 2.0g of anhydrous sodium sulfate, 5.00mL of ethyl acetate as an organic extraction solvent, 0.2mL of methanol as a derivatization reagent and 0.1mL of 2moL/L trimethylsilylated diazomethane n-hexane solution are added, the water bath temperature is 30 ℃, and the derivatization time is 30 min.
The stop solution in the step 4 is the hydrochloric acid solution in the claim 3, the addition amount is 0.05mL, the addition amount of solid sodium bicarbonate is 0.1g, the addition amount of anhydrous sodium sulfate is 0.5g, the filter membrane is an organic phase filter membrane, and the pore diameter is 0.22 μm.
In the above steps, the vortex is 1min to 2min, and the centrifugation is carried out for 3min at the rotating speed of 4500 rpm.
In the previous adsorption test, the inventor tests the adsorption pH of four target compounds in water by using p-toluenesulfonate-magnesium aluminum type hydrotalcite as an adsorbent. Under the condition that the same extraction solvent, pretreatment conditions and test conditions are fixed, the factor of the initial pH value of the absorbed water sample is considered and optimized singly, the range is from pH value to 4.0 to 14.0, and the result shows that the target can obtain good absorption effect in the range of pH value to 4.0 to 9.0.
Meanwhile, in the process of research and development of the method, the inventor researches and optimizes the use amount of the adsorbent, the selection and the proportion of the extraction solvent, the selection and the optimization of a target derivatization method, the selection and the optimization of chromatographic separation conditions, the selection and the optimization of mass spectrum conditions, the selectivity and the anti-interference performance of quantitative and qualitative ions and other factors according to the characteristics of the adsorption target object, and provides a relatively better detection method on the basis. Meanwhile, in consideration of quantitative accuracy of the target object, the method quantifies the target object by adopting the matrix correction curve on the premise that the isotope of the target object cannot be obtained so as to quantify the target object by an isotope internal standard method, so that systematic errors are eliminated as much as possible, and the quantitative accuracy is improved.
The invention has the advantages that:
(1) the novel adsorbent adopted by the invention can rapidly adsorb trace amount of p-halophenoxyacetic acid in water by adopting a dispersed solid-phase extraction mode on the p-toluenesulfonate-magnesium-aluminum type hydrotalcite, and can save a large amount of adsorption time compared with a solid-phase extraction mode;
(2) according to the invention, by utilizing the characteristic that the p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent can be dissolved in acid, the adsorbent after adsorbing the target object is dissolved by using a hydrochloric acid solution, so that the target object can be completely desorbed from the adsorbent;
(3) the method is only suitable for taking a small amount of organic solvent as the extraction solvent of the target object, and has obvious advantages of safety, environmental protection and economic advantage compared with the prior method which needs to use a large amount of organic solvent.
Drawings
FIG. 1 is a chromatogram of a standard solution of p-halophenoxyacetic acid of 500.0. mu.g/L, wherein 1 is p-fluorophenoxyacetic acid, 2 is p-chlorophenoxyacetic acid, 3 is p-bromophenoxy acetic acid, and 4 is p-iodophenoxyacetic acid.
Detailed Description
For further disclosure, but not limitation, the present invention is described in further detail below with reference to examples.
(1) The reagent medicines involved in the embodiments of the present invention are as follows:
p-fluorophenoxyacetic acid, p-chlorophenoxyacetic acid, p-bromophenoxy acetic acid and p-iodophenoxyacetic acid, with purity of 98.0% or higher, Dr. Ehrensorfer Co., Ltd., Germany;
methanol, ethyl acetate, anhydrous sodium sulfate, sodium bicarbonate, analytically pure, group of Chinese medicines;
hydrochloric acid, super pure, group of national medicine; the water is first-grade water meeting the GB/T6682 specification.
Trimethylsilyldiazomethane solution, 2.0M in hexane, Alfa Aesar.
(2) The instruments involved in the examples of the present invention are as follows:
KH-75A type electric heating constant temperature air-blast drying oven, Kangheng instruments ltd, Guangzhou;
model 7890B-5977A gas chromatography-mass spectrometer with electron bombardment source (EI), Agilent technologies, Inc., USA.
(3) Analyzing and testing conditions by a gas chromatography-mass spectrometer:
a) a chromatographic column: DB-1701 capillary column, 30m × 0.25mm, 0.25 μm film thickness; column flow rate: 1.20 mL/min.
b) Sample inlet temperature: 260 ℃; and (3) sample introduction mode: no shunt sampling; sample introduction amount: 1 μ L.
c) Temperature rising procedure: 40 deg.C (1 min hold), 10 deg.C/min to 130 deg.C (5 min hold), 15 deg.C/min to 260 deg.C (3 min hold).
d) EI bombardment source: 70 ev; temperature of a chromatography-mass spectrometry connection port: 280 ℃; temperature of the quadrupole rods: 230 ℃; ion source temperature: at 150 ℃.
e) Carrier gas: high-purity helium (the purity is more than or equal to 99.999%).
f) Mass spectrum data acquisition mode: selected ion scan mode (SIM), solvent delay time: for 10 min.
g) The quantitative and qualitative ion of the compounds are given in the following table:
Figure GDA0001849914600000041
Figure GDA0001849914600000051
(4) preparation of matrix calibration curve and determination of detection limit and quantitative limit
Accurately weighing the p-halophenoxyacetic acid, dissolving the p-halophenoxyacetic acid by using methanol to a constant volume, and preparing a standard stock solution with the concentration of 1000mg/L, and storing the stock solution at the temperature of-4 ℃. When in use, the standard stock solution is gradually diluted by deionized water to prepare standard use solution with the concentration gradient of 10.0 mug/L, 20.0 mug/L, 40.0 mug/L, 100.0 mug/L and 200.0 mug/L.
Taking five 50mL plastic centrifuge tubes with plugs, respectively weighing 5.00g blank tomato samples, respectively taking 5.00mL of the standard use solution, respectively, preparing a matrix calibration standard curve with a series of concentrations, then adding 30mL of 10% methanol-water solution as an extraction solution, homogenizing at a high speed of 15000rpm for 1min, and centrifuging at a speed of 4500rpm for 3 min; pouring the supernatant into another 100mL plastic centrifuge tube with a plug, and adjusting the pH value to about 7 by using 0.05mol/L sodium hydroxide solution; adding 0.50g of p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent into a centrifugal tube, sealing, and shaking for 15min to make the adsorbent adsorb the target compound in the supernatant;
centrifuging a 50mL centrifuge tube with a plug at 4500rpm for 3min to separate the solid adsorbent from the aqueous solution and discard the supernatant, adding 2.50mL of 1-time diluted hydrochloric acid solution into the centrifuge tube, and desorbing the adsorbed target after the solid adsorbent is dissolved;
adding 2.0g of anhydrous sodium sulfate into the centrifuge tube, adding 5.0mL of ethyl acetate, whirling for 1min, centrifuging at the rotating speed of 4500rpm for 3min, taking the supernatant into a derivatization bottle, adding 0.2mL of methanol and 0.1mL of trimethylsilylated diazomethane n-hexane solution with the concentration of 2moL/L, sealing, uniformly mixing, standing in a water bath at 30 ℃ for derivatization for 30min, and finishing the derivatization process;
adding 0.05mL of the hydrochloric acid solution into the derivatization bottle to remove the redundant trimethylsilylated diazomethane, then adding 0.1g of solid sodium bicarbonate and 0.5g of anhydrous sodium sulfate, vortexing to remove the residual hydrochloric acid and water, sucking the upper organic solution, passing the upper organic solution through an organic phase filter membrane with the pore diameter of 0.22 mu m, and then analyzing and testing by gas chromatography-mass spectrometry.
And (3) taking the concentration of the p-halophenoxyacetic acid in the sample solution as an X axis, and taking the peak area of a chromatographic peak of the p-halophenoxyacetic acid derivative on a gas chromatography-mass spectrometer as a Y axis to draw a matrix standard curve and use the matrix standard curve for quantification by an external standard method.
The triple value of the signal-to-noise ratio S/N is taken as the detection limit of the method (LOD, LOD is 3S/N), the ten times of the signal-to-noise ratio S/N is taken as the quantification limit of the method (LOQ, LOQ is 10S/N), and the detection limit and the quantification limit of each compound in water are calculated by combining the volume of the added matrix.
The relevant parameters of the matrix standard curve, LOD and LOQ are shown in Table 1.
TABLE 1 information on the substrate standard curve, detection limit and quantitation limit of p-halophenoxyacetic acid
Figure GDA0001849914600000061
(5) Synthesis of p-methyl benzene sulfonate-magnesium-aluminum type hydrotalcite adsorbent
In order to enable those skilled in the art to repeatedly carry out the relevant experiments of the present invention, a method for synthesizing p-toluenesulfonate-magnesium aluminum type hydrotalcite adsorbent, which is a key substance used in the present invention, is now provided as follows:
the reagent and the drug related to the synthesis of the adsorbent are as follows:
sodium p-toluenesulfonate, analytically pure, pharmaceutical group;
Mg6Al2(OH)16CO3·4H2o, analytical grade, Aldrich, usa.
② the apparatus related to the synthesis of the adsorbent is as follows:
an EXCEL type microwave digestion instrument, Shanghai Yao Instrument science and technology development Co., Ltd., digestion tank volume of 100 mL; microwave muffle furnace (sintering furnace), CEM corporation, usa; model VD53 vacuum drying cabinet, German Bindd technologies; HJ-5 multifunctional constant temperature stirrer, Kantai Ronghua Instrument manufacturing Co., Ltd; FS-12 type separatory funnel oscillator, New optical technology, Japan; 3K-15 type centrifuge, sigma technologies, germany; BF518945C-1 model box resistance furnace (muffle furnace), Saimer Feishell science, USA.
The concrete steps of synthesizing the adsorbent are as follows:
(a) roasting: mg of purchased Mg-Al type hydrotalcite6Al2(OH)16CO3·4H2Placing O in a muffle furnace, heating at a heating rate of 5 ℃/min to 500 ℃, and roasting for 6h to obtain a roasted product Mg6Al2O8(OH)2
(b) Weighing: 13.509g of intercalation agent sodium p-toluenesulfonate and 7.236g of roasting product Mg are weighed in a microwave digestion tank6Al2O8(OH)2
(c) Microwave crystallization hydrothermal synthesis: boiling deionized water and keeping for 30min, adding 100mL into the microwave digestion tank filled with the intercalation agent and the roasting product, sealing, placing the microwave digestion tank into a microwave digestion instrument, and performing microwave heating at 150 ℃ for 30min to complete synthesis;
(d) washing and drying: pouring out all solids and liquid in the microwave tank, heating and stirring with deionized water boiled for more than 30min to remove carbon dioxide, shaking, washing, centrifuging, vacuum drying at 90 deg.C for 12h, grinding, and storing.
Example 1
In this example 1, tomatoes were used as a sample matrix to perform a spiking recovery experiment to verify the feasibility of the method of the present invention, and the processing was performed according to the following steps:
1. extraction and adsorption of the compounds:
taking a 50mL plastic centrifuge tube with a plug, respectively weighing 5.00g of blank tomato samples, respectively taking 5.00mL of standard use solutions of 10.0. mu.g/L, 20.0. mu.g/L and 200.0. mu.g/L, respectively, preparing to obtain three-level six-parallel standard sample, then adding 30mL of 10% methanol-water solution as an extraction solution, homogenizing at the high speed of 15000rpm for 1min, and centrifuging at the speed of 4500rpm for 3 min; pouring the supernatant into another 100mL plastic centrifuge tube with a plug, and adjusting the pH value to about 4.0 by using 0.05mol/L sodium hydroxide solution; adding 0.50g of p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent into a centrifugal tube, sealing, and shaking for 15min to make the adsorbent adsorb the target compound in the supernatant;
2. desorption of the compound:
centrifuging a 50mL centrifuge tube with a plug at 4500rpm for 3min to separate the solid adsorbent from the aqueous solution and discard the supernatant, adding 2.50mL of 1-time diluted hydrochloric acid solution into the centrifuge tube, and desorbing the adsorbed target after the solid adsorbent is dissolved;
3. extraction and derivatization of compounds:
adding 2.0g of anhydrous sodium sulfate into the centrifuge tube, adding 5.0mL of ethyl acetate, whirling for 1min, centrifuging at the rotating speed of 4500rpm for 3min, taking the supernatant into a derivatization bottle, adding 0.2mL of methanol and 0.1mL of trimethylsilylated diazomethane n-hexane solution with the concentration of 2moL/L, sealing, uniformly mixing, standing in a water bath at 30 ℃ for derivatization for 30min, and finishing the derivatization process;
4. analysis and test:
adding 0.05mL of the hydrochloric acid solution into the derivatization bottle to remove the redundant trimethylsilylated diazomethane, then adding 0.1g of solid sodium bicarbonate and 0.5g of anhydrous sodium sulfate, vortexing to remove the residual hydrochloric acid and water, sucking the upper organic solution, passing the upper organic solution through an organic phase filter membrane with the pore diameter of 0.22 mu m, and then analyzing and testing by gas chromatography-mass spectrometry.
The parameters relevant to the spiking recovery experiment of example 1 are shown in Table 2.
Table 2 tomato sample add-on concentration and recovery experimental data (n ═ 6)
Figure GDA0001849914600000071
Figure GDA0001849914600000081
Example 2
In this example 2, cherry tomato (tomato) was used as a sample matrix for a spiking recovery experiment to verify the feasibility of the method of the present invention, and the method was performed according to the following steps:
1. extraction and adsorption of the compounds:
taking a 50mL plastic centrifuge tube with a plug, respectively weighing 5.00g of blank tomato samples, respectively taking 5.00mL of standard use solutions of 10.0. mu.g/L, 20.0. mu.g/L and 200.0. mu.g/L, respectively, preparing to obtain three-level six-parallel standard sample, then adding 30mL of 10% methanol-water solution as an extraction solution, homogenizing at the high speed of 15000rpm for 1min, and centrifuging at the speed of 4500rpm for 3 min; pouring the supernatant into another 50mL plastic centrifuge tube with a plug, and adjusting the pH value to about 9.0 by using 0.05mol/L sodium hydroxide solution; adding 0.50g of p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent into a centrifugal tube, sealing, and shaking for 15min to make the adsorbent adsorb the target compound in the supernatant;
2. desorption of the compound:
centrifuging a 50mL centrifuge tube with a plug at 4500rpm for 3min to separate the solid adsorbent from the aqueous solution and discard the supernatant, adding 2.50mL of 1-time diluted hydrochloric acid solution into the centrifuge tube, and desorbing the adsorbed target after the solid adsorbent is dissolved;
3. extraction and derivatization of compounds:
adding 2.0g of anhydrous sodium sulfate into the centrifuge tube, adding 5.0mL of ethyl acetate, whirling for 1min, centrifuging at the rotating speed of 4500rpm for 3min, taking the supernatant into a derivatization bottle, adding 0.2mL of methanol and 0.1mL of trimethylsilylated diazomethane n-hexane solution with the concentration of 2moL/L, sealing, uniformly mixing, standing in a water bath at 30 ℃ for derivatization for 30min, and finishing the derivatization process;
4. analysis and test:
adding 0.05mL of the hydrochloric acid solution into the derivatization bottle to remove the redundant trimethylsilylated diazomethane, then adding 0.1g of solid sodium bicarbonate and 0.5g of anhydrous sodium sulfate, vortexing to remove the residual hydrochloric acid and water, sucking the upper organic solution, passing the upper organic solution through an organic phase filter membrane with the pore diameter of 0.22 mu m, and then analyzing and testing by gas chromatography-mass spectrometry.
The parameters relevant to the spiking recovery experiment of example 2 are shown in Table 3.
Table 3 experimental data on add-on concentration and recovery rate of cherry tomato sample (n ═ 6)
Figure GDA0001849914600000082
Figure GDA0001849914600000091
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the spirit of the invention, which falls within the scope of the invention, and therefore the scope of the patent of the invention shall be governed by the appended claims.

Claims (6)

1. A gas chromatography-mass spectrometry combined method for measuring four trace p-halophenoxyacetic acid plant growth regulators in tomatoes is characterized by comprising the following steps:
(1) extraction and adsorption of the compounds: cutting a tomato sample into pieces, stirring and crushing, weighing a proper amount of sample in a plastic centrifuge tube with a plug, adding a certain amount of extraction solution, homogenizing and extracting at high speed, centrifuging, pouring the supernatant into another plastic centrifuge tube with a plug, re-extracting once, combining the supernatants, adding a proper amount of sodium hydroxide solution into the centrifuge tube, and adjusting the pH value of the supernatant to a proper range; adding 0.50g of p-toluenesulfonate-magnesium-aluminum type hydrotalcite adsorbent, sealing, and oscillating for a certain time to make the adsorbent adsorb p-fluorophenoxyacetic acid, p-chlorophenoxyacetic acid, p-bromophenoxy acetic acid and p-iodophenoxyacetic acid in the supernatant;
(2) desorption of the compound: centrifuging the centrifuge tube with the plug to separate the solid adsorbent from the water solution and discard the supernatant, adding a certain amount of hydrochloric acid solution to dissolve the solid adsorbent, and finishing desorption of the adsorbed compound;
(3) extraction and derivatization of compounds: adding a certain amount of anhydrous sodium sulfate and an organic solvent into the centrifugal tube for extraction, performing vortex and centrifugation, taking supernatant liquid to a derivatization bottle, adding a derivatization reagent into the supernatant liquid, sealing, uniformly mixing, and putting the mixture in a constant-temperature water bath to finish the derivatization process;
(4) analytical testing of compounds: adding a stop solution into a derivatization bottle to remove redundant derivatization agents, adding a proper amount of solid sodium bicarbonate and anhydrous sodium sulfate, carrying out vortex, absorbing an upper layer organic solution, filtering, and then carrying out analysis and test by using a gas chromatography-mass spectrometry method according to the following conditions:
a) a chromatographic column: DB-1701 capillary column, 30m × 0.25mm, 0.25 μm film thickness; column flow rate: 1.20 mL/min;
b) sample inlet temperature: 260 ℃; and (3) sample introduction mode: no shunt sampling; sample introduction amount: 1 mu L of the solution;
c) temperature rising procedure: maintaining at 40 deg.C for 1min, heating to 130 deg.C at a rate of 10 deg.C/min, maintaining for 5min, heating to 260 deg.C at a rate of 15 deg.C/min, and maintaining for 3 min;
d) EI bombardment source: 70 ev; temperature of a chromatography-mass spectrometry connection port: 280 ℃; temperature of the quadrupole rods: 230 ℃; ion source temperature: 150 ℃;
e) carrier gas: high-purity helium with the purity more than or equal to 99.999 percent;
f) mass spectrum data acquisition mode: selection of ion scan mode, solvent delay time: 10 min;
g) the quantitative and qualitative ion of the compounds are given in the following table:
serial number Name of Compound Quantitative ion Qualitative ion 1 P-fluorophenoxyacetic acid derivatives 125.1 184.1,111.1 2 P-chlorophenoxyacetic acid derivatives 141.0 200.0,111.1 3 Para-bromophenoxyacetic acid derivatives 243.9 184.9,156.9 4 P-iodophenoxyacetic acid derivatives 291.9 232.9,202.9
2. The gas chromatography-mass spectrometry combination method for determining four trace p-halophenoxyacetic acid plant growth regulators in tomatoes as claimed in claim 1, wherein the tomato sample in step (1) is weighed to 5.00g, the extraction solution is 10% methanol-water solution, the amount of the extraction solution is 30mL, the high-speed homogenizing rate is 15000rpm, the time is 1min, the concentration of the sodium hydroxide solution is 0.05mol/L, the adjusted pH value range is 4.0-9.0, and the time of shaking adsorption is 15 min.
3. The gas chromatography-mass spectrometry combination for determining four trace p-halophenoxyacetic acid plant growth regulators in tomatoes as claimed in claim 1, wherein the hydrochloric acid solution in step (2) is prepared from concentrated hydrochloric acid and water at a volume ratio of 1:1, and the amount is 2.50 mL.
4. The gas chromatography-mass spectrometry combination for determining four trace p-halophenoxyacetic acid plant growth regulators in tomato as claimed in claim 1, wherein the amount of anhydrous sodium sulfate added in step (3) is 2.0g, the amount of organic extraction solvent is 5.00mL of ethyl acetate, the amount of derivatization reagent is 0.2mL of methanol and 0.1mL of 2moL/L trimethylsilylated diazomethane n-hexane solution, the temperature of water bath is 30 ℃, and the derivatization time is 30 min.
5. The gas chromatography-mass spectrometry combination method for measuring four trace p-halophenoxyacetic acid plant growth regulators in tomatoes as claimed in claim 1, wherein the stop solution in step (4) is hydrochloric acid solution, the addition amount is 0.05mL, the addition amount of solid sodium bicarbonate is 0.1g, the addition amount of anhydrous sodium sulfate is 0.5g, the filter membrane for filtration is an organic phase filter membrane, and the pore diameter is 0.22 μm.
6. The method for measuring the four trace amounts of the p-halophenoxyacetic acid plant growth regulator in the tomato as claimed in claim 1, wherein the vortexing is performed at a speed of 4500rpm for 3min and 1min to 2 min.
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