Abstract:
The QuEChERS was used for extraction and purification, and gas chromatography-tandem mass spectrometry was proposed to determine residues of 70 pesticides and their metabolites in
Gastrodiae Rhizoma. 3.00 g of powder sample, which sieved through 20 mesh (850 μm) sieve, was taken and placed in a 50 mL-polypropylene stoppered centrifuge tube. 15 mL of 1% (volume fraction) acetic acid solution was added, and the mixture was vortexed well, and soaked for 30 min. 15 mL of acetonitrile was added, and the mixture was shaken for 5 min. 6 g of anhydrous magnesium sulfate and 1.5 g of sodium acetate were added, and the mixture was shaken immediately, shaken for 3 min, cooled in an ice bath for 10 min, and centrifuged at a rotational speed of 4 000 r·min
−1 for 5 min. 9 mL of the supernatant was taken and placed in a QuEChERS dispersion solid-phase extraction tube (including 900 mg of anhydrous magnesium sulphate, 300 mg of
N-propylethylenediamine, 300 mg of octadecylsilane bonded silica gel, 300 mg of silica gel, 90 mg of graphitized carbon black). The mixture was vortexed and shaken for 5 min, and centrifuged at a rotational speed of 4 000 r·min
−1 for 5 min. 5 mL of the supernatant was taken, concentrated to 0.4 mL by nitrogen at 40 ℃, and diluted to 1.0 mL with acetonitrile, which was passed through a 0.22 μm nylon filter membrane. The filtrate was determined according to the operating conditions of the instrument. 70 pesticides and their metabolites were separated using the HP-5MS chromatographic column under programmed heating conditions, ionized by electron impact ion source, and detected using the multiple reaction monitoring mode, with matrix matching method for quantification. As shown by the results, linear relationships between values of the mass concentration and the peak area of 70 pesticides and their metabolites were kept in the range of 5-150 μg·L
−1, with lower limits of determination of 0.01 mg·kg
−1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 87.9%-111%, with the intra-day RSDs (
n=5) of the determined values less than 10% and the inter-day RSDs (
n=10) of the determined values less than 20%. This method was used for the analysis of 18 batches of
Gastrodiae Rhizoma samples, and 70 pesticides and their metabolites were not detected.