Pesticide multi-residue determination method (2)

(2) Liquid chromatography-tandem mass spectrometry

1.

Table 13-2 Mobile phase gradient

2.

3.

4.

(3) Matters needing attention

(1) Prepare the reference solution according to the types of monitored pesticides specified under each species and refer to the relevant pesticide limit regulations

(3) The sample recovery rate should be between 70% and 120%

(4) When performing sample determination, if the retention time of the detected chromatographic peak is consistent with that of the reference substance, and the selected monitoring ion pair appears in the mass spectrum after background subtraction, and the selected monitoring ion pair peak area ratio It is consistent with the peak area ratio of the monitored ion to the reference substance (relative ratio>50%, allow ±20% deviation; relative ratio>20%～50%, allow ±25% deviation; relative ratio>10%～20%, allow ± 30% deviation; relative proportion ≤10%, allow ±50% deviation), then it can be judged that the pesticide is present in the sample

(5) For pesticides determined by gas chromatography-tandem mass spectrometry, q-fenthion is recommended as the internal standard; for pesticides determined by liquid chromatography-tandem mass spectrometry, deuterated atrazine is recommended as the internal standard

(6) The monitoring ion pair measurement conditions provided by the method are recommended conditions, and each laboratory can make appropriate adjustments according to the specific conditions of the configured instrument; in the case of measurement interference with the sample matrix, other monitoring ion pairs can be selected

(7) For specific pesticides or test products, the proportion of purification materials in the dispersion solid-phase extraction purification tube can be adjusted appropriately, but methodological investigations must be made to ensure the accuracy of the results

(8) When performing gas chromatography-tandem mass spectrometry, in order to further optimize the performance of the method, the final volume of the test solution can be replaced by toluene via acetonitrile (1ml of toluene can be added after blowing with nitrogen until it is nearly dry)