Method for determining pesticide residues in vegetables and fruits
Technical Field
The invention relates to a method for determining pesticide residues in vegetables and fruits, belonging to the technical field of analytical chemistry
Background
The pesticide is used as an important agricultural production material, plays a vital role in protecting crops from being damaged by diseases, pests and weeds, improving the agricultural production efficiency, guaranteeing the crop yield and the like, but simultaneously, because the pesticide is unreasonably used, the pesticide residue exceeds the standard, and the harm is also caused to the public health and the food safety. With the continuous progress of the pesticide industry, the types and the amount of pesticides used at present are also continuously increased. The safety problem of agricultural products is always the focus of social attention, and is directly related to public health and ecological environment safety. At present, a pesticide residue analysis method is one of important means for evaluating the quality safety level of agricultural products. Among them, the gas (liquid) chromatography-tandem mass spectrometry technology is popular with researchers of pesticide residue because of its advantages of high sensitivity, strong selectivity, reliable qualitative means, short analysis time and the like, and is widely used for detecting trace substances under the background of complex matrix.
Vegetables and fruits are one of the most important edible agricultural products in the world, and along with the improvement of the social and economic level of China, the proportion of the vegetables and fruits in the public diet is continuously improved. Meanwhile, most vegetables and fruits have the characteristics of short interval between market and harvesting, common plant diseases and insect pests and high economic value of crops, so that the types and the using amount of pesticides applied in production are relatively more, and the problem of overproof pesticide residues in the vegetables and fruits is obvious.
The existing method for detecting the pesticide in the vegetables and the fruits usually adopts a gas chromatography-mass spectrometry method and a liquid chromatography-tandem mass spectrometry method, and generally comprises the steps of extracting pesticide residues in fruit trees, purifying an extracting solution and the like. In the prior art, the extracting solution is generally required to be purified by a solid-phase extraction column, and due to the characteristics of the solid-phase extraction column, the operation steps are complex, the key control points of the method are more, so that the purification cost is more time, and the overall detection efficiency is reduced.
Disclosure of Invention
The invention adopts the method of combining the solid-phase extraction pretreatment with the liquid chromatography, establishes the determination method of the pesticides in various agricultural products, and overcomes the defect of qualitative and quantitative detection of pesticide residues in various agricultural products by the existing method.
The invention provides a method for determining pesticide residue in agricultural products, which comprises a sample pretreatment step; the sample pretreatment step comprises an extraction step and a purification step
The extraction steps are as follows: dissolving the vegetable and fruit products by using an organic solvent, homogenizing, centrifuging, and separating to obtain a sample to be purified;
the purification steps are as follows: moving a sample to be purified into a purification pipe filled with filler, carrying out vortex mixing for 1-2 min, and carrying out centrifugal separation treatment to obtain upper and lower layered liquid; adding anhydrous magnesium sulfate, PSA and C18 filler, wherein the volume ratio of the anhydrous magnesium sulfate to the PSA to the C18 is 4: 1-3: 3-1;
the detection step is liquid chromatography detection; the liquid chromatography conditions are as follows:
a chromatographic column: a silica gel column;
mobile phase: mobile phase A: water, mobile phase B: acetonitrile;
isocratic elution: 30-50% of A.
Based on the technical scheme, preferably, the organic solvent is any one of methanol, n-hexane and acetonitrile.
Based on the above technical solution, preferably, the specification of the chromatographic column is preferably: 2mm x 80-100 mm.
Based on the above technical scheme, preferably, the particle size of the stationary phase is 5-8 μm.
Based on the technical scheme, the flow rate of the mobile phase is preferably 0.2-0.25 mL/min.
Based on the technical scheme, the preferable column temperature of the chromatographic column is 35-45 ℃.
Based on the technical scheme, preferably, the injection volume is preferably 10-15 mu L.
Has the advantages that:
the method comprises a sample pretreatment step; the sample pretreatment step comprises an extraction step and a purification step; the extraction steps are as follows: dissolving the vegetable and fruit products, homogenizing, centrifuging, and separating to obtain a sample to be purified; the purification steps are as follows: the purification is carried out by adopting the purification tube filled with the filler, the operation steps are simple, and the satisfactory separation effect and the satisfactory detection sensitivity are obtained. The method overcomes the defect of qualitative and quantitative detection of pesticide residue in various agricultural products by the existing method.
Detailed Description
Example 1
A method for determining residual pesticide levels in agricultural products, said method comprising the steps of:
a sample pretreatment step:
the extraction step comprises: adding 10g of pineapple sample into a mixed solution of 30mL of water and 30mL of dichloromethane, homogenizing at 20000r/min for 2min, centrifuging at 5000r/min for 5min, and separating supernatant to obtain a sample to be purified;
a purification step: adding 400mg of anhydrous magnesium sulfate, 100mg of PSA and 300mg of C18 filler into a purification tube to obtain the purification tube filled with the filler; measuring 7mL of a sample to be purified into a purification tube filled with a filler, carrying out vortex mixing for 2min, and carrying out centrifugal separation treatment to obtain upper and lower layered liquid; drying the supernatant in the upper and lower layered liquid, and dissolving with a mobile phase;
a liquid chromatography detection step:
chromatographic conditions are as follows:
a chromatographic column: silica gel column (2 mm. times.100 mm, 5 μm);
mobile phase: mobile phase A: water, mobile phase B: acetonitrile;
isocratic elution: 50% of A;
the flow rate of the mobile phase is 0.22 mL/min;
the temperature of the chromatographic column is 40 ℃;
the injection volume was 10. mu.L.
The limit of quantitation of the pineapple sample is 0.008 mg/kg.
Example 2
A method for determining residual pesticide levels in agricultural products, said method comprising the steps of:
a sample pretreatment step:
the extraction step comprises: adding 1g of Longjing tea sample into 20mL of water, homogenizing for 2min at 20000r/min, centrifuging for 5min at 5000r/min, separating supernatant, adding equal volume of dichloromethane, extracting, and discarding dichloromethane layer to obtain a sample to be purified;
a purification step: adding 400mg of anhydrous magnesium sulfate, 100mg of PSA and 300mg of C18 filler into a purification tube to obtain the purification tube filled with the filler; measuring 7mL of a sample to be purified into a purification tube filled with a filler, carrying out vortex mixing for 2min, and carrying out centrifugal separation treatment to obtain upper and lower layered liquid; drying the supernatant in the upper and lower layered liquid, and dissolving with a mobile phase;
a liquid chromatography detection step:
chromatographic conditions are as follows:
a chromatographic column: silica gel column (2 mm. times.100 mm, 5 μm);
mobile phase: mobile phase A: water, mobile phase B: acetonitrile;
isocratic elution: 30% of A;
the flow rate of the mobile phase is 0.22 mL/min;
the temperature of the chromatographic column is 40 ℃;
the injection volume was 10. mu.L.
The limit of quantification of the Longjing tea sample is 0.015 mg/kg.
Example 3
A method for determining residual pesticide levels in agricultural products, said method comprising the steps of:
a sample pretreatment step:
the extraction step comprises: adding 2g of corn sample into 20mL of 25 v/v% acetone aqueous solution, homogenizing at 20000r/min for 2min, centrifuging at 5000r/min for 5min, separating supernatant, adding equal volume of dichloromethane, extracting, and removing dichloromethane layer to obtain a sample to be purified;
a purification step: adding 400mg of anhydrous magnesium sulfate, 100mg of PSA and 300mg of C18 filler into a purification tube to obtain the purification tube filled with the filler; measuring 7mL of a sample to be purified into a purification tube filled with a filler, carrying out vortex mixing for 2min, and carrying out centrifugal separation treatment to obtain upper and lower layered liquid; drying the supernatant in the upper and lower layered liquid, and dissolving with a mobile phase;
a liquid chromatography detection step:
chromatographic conditions are as follows:
a chromatographic column: silica gel column (2 mm. times.100 mm, 5 μm);
mobile phase: mobile phase A: water, mobile phase B: acetonitrile;
isocratic elution: 50% of A;
the flow rate of the mobile phase is 0.22 mL/min;
the temperature of the chromatographic column is 40 ℃;
the injection volume was 10. mu.L.
The limit of quantitation for the corn sample was 0.008 mg/kg.
It should be noted that, in this document, the term "comprises/comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.