Multiresidue Analysis of Pesticides in Straw Roughage by Liquid Chromatography-Tandem Mass Spectrometry

A multiresidue analytical method using a modification of the "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) sample preparation approach combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis was established and validated for the rapid determination of 69 pesticides at different levels (1-100 ng/g) in wheat and rice straws. In the quantitative analysis, the recoveries ranged from 70 to 120%, and consistent RSDs <= 20% were achieved for most of the target analytes (53 pesticides in wheat straw and 58 in rice straw). Almost all of the analytes achieved good linearity with R-2 > 0.98, and the limit of validation levels (LVLs) for diverse pesticides ranged from 1 to 10 ng/g. Different extraction and cleanup conditions were evaluated in both types of straw, leading to different options. The use of 0.1% formic acid or not in extraction with acetonitrile yielded similar final outcomes, but led to the use of a different sorbent in dispersive solid-phase extraction. Both options are efficient and useful for the multiresidue analysis of targeted pesticides in wheat and rice straw samples.