SN/T 2233-2020Determination of Fenpropathrin Residues in Exported Plant-derived Foods (English PDF)

7.1 Vegetables and fruits

Take a representative sample of 500g, take the edible part and fully break it with a tissue mixer, mix it evenly, put it into a clean container, and seal it.

Indicate the mark.

7.2 Wheat and tea

Take a representative sample of 500g, smash all the samples with a grinder, and mix them; divide them into two samples and put them into clean containers.

Inside, sealed, marked with a mark.

7.3 Storage of samples

Vegetables and fruits are stored at -18°C; wheat and tea samples are stored below 4°C. During the sample preparation operation, the sample should be prevented from Contaminated or changed in residue content.

8.1 Extraction and purification

8.1.1 Vegetables and fruits

Weigh 10 g of a homogeneous sample (accurate to 0.01g) and place it in a 50 mL centrifuge tube (add 5.0 mL for dry vegetables Water), add 10 mL acetonitrile (5.1), vortex for 2 min, add 4.0 g anhydrous magnesium sulfate (5.5), 1.0 g sodium chloride (5.6), 1.0 g sodium citrate (5.7) and 0.5 g disodium hydrogen citrate (5.8), shake vigorously for 10 min. Then centrifuge the tube at 4000 r/min Heart for 5 minutes, transfer 8mL supernatant to a 15mL centrifuge tube, add.200 mg PSA (5.11),.200 mg C18 (5.9), 1000 mg anhydrous magnesium sulfate (5.5), vortex for 2 min, centrifuge at 4000 r/min for 5 min, take 5 mL of the supernatant and blow it to near dryness.

Vortex the residue with acetonitrile and dilute to 0.5 mL. It is filtered through a 0.22µm organic microporous filter membrane for determination by gas chromatography-mass spectrometry/mass spectrometer.

8.1.2 Cereals

Grain samples, crush and mix evenly, accurately weigh 2g (accurate to 0.01g), place it in a 50 mL centrifuge tube, and add 10.0 mL After soaking in deionized water for 30 minutes, add 10 mL of acetonitrile solution (5.13) containing 1% acetic acid, vortex for 2 minutes, and add 4.0 g Anhydrous magnesium sulfate (5.5), 1.0 g sodium chloride (5.6), 1.0 g sodium citrate (5.7) and 0.5 g disodium hydrogen citrate (5.8), shake vigorously Swing for 10 minutes. Then the centrifuge tube was centrifuged at 4000 r/min for 5 min, and the 8 mL supernatant was transferred to a 15 mL centrifuge tube, and then added Into 400 mg PSA (5.11), 400 mg GCB (5.10), 1200 mg anhydrous magnesium sulfate (5.5), vortex and mix for 2 min, 4000 r/min Centrifuge for 5 min. Take 5 mL of the supernatant and blow it to near dryness. Vortex the residue with acetonitrile and dilute to 1.0 mL. Through 0.22 µm organic micropores Membrane filtration for determination by gas chromatography-mass spectrometry/mass spectrometer.

8.1.3 Tea

Tea sample, crush and mix evenly, accurately weigh 2 g (accurate to 0.01g), place it in a 50 mL centrifuge tube, and add 10.0 mL After soaking in deionized water for 30 minutes, add 10 mL of acetonitrile solution (5.13) containing 1% acetic acid, vortex for 2 minutes, and add 4.0 g Anhydrous magnesium sulfate (5.5), anhydrous sodium acetate 1.0 g (5.12), shake vigorously for 10 min. Then the centrifuge tube was centrifuged at 4000 r/min for 5 min, Transfer 8 mL of the supernatant to a 15 mL centrifuge tube, add 400 mg PSA (5.11), 400 mg GCB (5.10), 300 mg in turn C18 (5.9), 1200 mg anhydrous magnesium sulfate (5.5), vortex for 2 min, centrifuge at 4000 r/min for 5 min, and take 5 mL of the supernatant Blow nitrogen to near dryness, vortex the residue with acetonitrile and dilute to 1.0 mL. Filtered by 0.22 µm organic microporous filter membrane for gas chromatography-mass spectrometry/Determination by mass spectrometer.

8.1.4 GC-MS/MS confirmation reference conditions

The GC-MS/MS instrument reference conditions are as follows.

a) Chromatographic column. DB-5MS capillary column, 30 m × 0.25 mm (inner diameter) × 0.25 µm (film thickness) or equivalent;

b) Column temperature. the initial temperature is 60 °C, keep it for 1 min, raise the temperature to 280 °C at 30 °C/min, keep it for 2 min, and then increase it at 120 °C/min Raise the temperature to 300 °C and keep it for 5 min;

c) Injection port. programmed temperature injection, the initial temperature is 70 °C, hold for 0.1 min, and the temperature is increased to 280 °C at 360 °C/min;

d) Gas chromatography-mass spectrometry/mass spectrometry interface temperature. 290 °C;

e) Carrier gas. helium, with a purity greater than or equal to 99.999%; constant flow mode; flow rate. 1.0 mL/min;

f) Injection volume. 5.0 µL;

g) Sampling method. splitless sampling;

h) Ionization source. electron bombardment ion source (EI source);

i) Ionization energy. 70 eV;

j) Solvent delay time. 6.0 min;

k) Scan mode. Multi-reactive ion monitoring mode (MRM), see Table A.1 in Appendix A for details of ion pair conditions.

8.1.5 Qualitative determination

Under the same experimental conditions, the retention time of the substance to be tested in the sample differs from the corresponding retention time in the standard working solution.

Within ±2.5%; after subtracting the background, the mass spectra of the tested sample and the standard are similar, and all the selected monitoring ions are when the abundance ratio is consistent, and the allowable deviation does not exceed the range specified in Table 1, it can be determined that the drug is present in the sample Residue.

8.1.6 Quantitative determination

In order to reduce the influence of the matrix on the quantification of the results, this method uses a negative sample solution to prepare a matrix-matched standard working solution.

Method quantification, according to the measured fenpropathrin residue content in the sample solution, select a standard working solution with a similar peak area. Standard working fluid and the response value of the analyte in the sample solution should be within the linear range of the instrument, and the standard working solution and sample solution should be measured according to the same volume.

Insert sample measurement. Refer to Figure B.1 in Appendix B for the multi-reaction monitoring chromatogram of fenpropathrin; refer to Appendix C for the total ion chromatogram of fenpropathrin in Figure C.1.

8.2 Blank test

Except that no sample is added, all follow the above steps.

10.1 Lower limit of determination

Use this method to treat tomatoes, carrots, sweet peppers, red cabbage, spinach, leeks, celery, Chinese cabbage, eggplant, apples, citrus, Fenpropathrin residues in 16 kinds of matrices including grapes, mushrooms, wheat, soybeans and tea were determined. Gas chromatography-tandem mass spectrometry was used to remove wheat, the lower limit of determination of various substrates other than soybean tea is 0.005 mg/kg, the lower limit of determination of wheat and soybean is 0.01 mg/kg, and the lower limit of determination of tea is 0.005 mg/kg.

It is 0.05mg/kg.

10.2 Recovery rate

Use this method to treat tomatoes, carrots, sweet peppers, red cabbage, spinach, leeks, celery, Chinese cabbage, eggplant, apples, citrus, 16 kinds of substrates including grapes, mushrooms, wheat, soybeans and tea were added to the recovery rate test. The addition level and recovery of fenpropathrin...