Determinationofisopyrazamanditsmetabolitesresiduesinwatermelonandcucumberbygaschromatography-tandemmassspectrometry

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method for the determination of isopyrazam and its metabolites residues in watermelon and cucumber was developed using dispersive solid-phase extraction as the sample preparation method. The samples were extracted with acetonitrile, purified with primary secondary amine and C₁₈ purificant, determined using GC-MS/MS, analyzed under multiple reaction monitoring (MRM) mode, and quantified by internal standard method. Factors influencing the extraction efficiency, such as the type of extraction solvent, clean-up sorbent and instrumental condition, were optimized. The results indicated that the calibration curves were linear in the range of 1-500 μg/L and the correlation coefficient of 0.994 3-0.999 9 for isopyrazam and its metabolites. In terms of watermelon samples, the recoveries at spiked levels of 0.01, 0.1 and 1 mg/kg were 70%-105%, with the relative standard deviations (RSD, n = 5) of 3.4%-13%. With regard of cucumber samples, and the recoveries at the same spiked levels were 82%-104%, with the relative standard deviations (RSD, n = 5) of 1.3-9.3%. The limits of quantity (S/N = 10) for the isopyrazam and its metabolites were 0.3-0.6 μg/kg and the limits of detection (S/N = 3) were 0.1-0.2 ng. This developed method is easy, quick and efficiency.