Determination of 34 pesticide residues in rice, proso millet and wheat with QuEChERS-on line gel permeation chromatography-gas chromatography-mass spectrometry

A method for the simultaneous determination of 34 pesticides in rice,proso millet and wheat by QuEChERS coupled with on line gel permeation chromatography-gas chromatographymass spectrometry(GPC-GC-MS)was developed.The effects of the sample weight,extraction solvent,sorbent for purification were investigated.The matrix effect and the usefulness of analyte protectant were also studied.The identification and quantification were performed by GPC-GC-MS in selected ion monitoring(SIM)mode and external standard method.The calibration curves of the34 pesticides showed good linearity in the range of 0.012 5-0.2 mg/L with the correlation coefficients(r2)between 0.968 and 0.999.The average recoveries were 94.5%-117.1%,83.1%-121.7%and 93.1%-120.2% with the relative standard deviations(RSDs,n=6)no more than14.5%,15.1%and15.2%in rice,proso millet and wheat samples,respectively.The LODs of this method were 0.028 1-5.31,0.028 2-4.82 and 0.027 3-5.13μg/kg(S/N=3)for rice,proso millet and wheat samples,respectively.The low cost and less consumption of reagents of this method are in accordance with the concept of green chemistry.The convenient operation and versatility of this method are suitable for the fast screening and detection of the 34 pesticide residues in rice,proso millet and wheat.