Abstract: A method of gas chromatography-tandem mass spectrometry was established for simultaneous detection of 41 organochlorine and pyrethroid pesticide residues in Lijiang-grown maca. Pesticide residues were extracted from the crushed samples with acetonitrile-sodium chloride saturated aqueous solution (5:4, V/V) with the aid of ultrasonic stirring. Then the extracts were purified with a graphitized carbon/amino composite column and eluted with a mixed solvent of acetonitrile and toluene (3:1, V/V). The purified extracts were separated with a medium-polar stationary phase (50% phenyl-methylpolysiloxane) capillary column. Finally, the analytes were detected by triple quadrupole mass spectrometry in the full scan mode, and quantified in the multiple reaction monitoring mode by an external standard method. The results showed that good linearity was observed for all analytes in the concentration range of 0.02–10 μg/mL or 0.04–20 μg/mL with a correlation coefficient (R2) over 0.99. The limits of detection (LODs) ranged from 0.01 to 2.38 μg/kg, and the average recovery rates of spiked samples varied from 90.2% to 108.8% with relative standard deviation between 2.1% and 10.9%. In summary, the proposed method proved to be simple, rapid, accurate, sensitive, economical and suitable for the screening and quantitative detection of organochlorine and pyrethroid pesticide residues in large batches of maca samples.

Key words: solid phase extraction; gas chromatography-tandem mass spectrometry; organochlorine pesticides; pyrethroid pesticides; Lijiang-grown maca