ABSTRACT
For the first time, a multi-residue method for simultaneous determination of 41LC-amenable pesticides in rice, belonging to different chemical classes has been developed in Iran by LC-MS/MS. The pesticides were analyzed simultaneously in a single run using positive electrospray ionization with multiple reaction monitoring [MRM] after extraction with slightly modified QuEChERS method. The calibration curves for each analyte were linear in the concentration range 0.02-1.0 microg/g with a correlation coefficient range between 0.993 and 0.999. The LOQ and LOD were0.025 microg/g and 0.008 microg/g respectively, for all 41 pesticides and the mean recoveries obtained for three fortification levels [0.025, 0.08 and 0.250 microg/g ] were71-119% with satisfactory precision [RSD<20%]. The developed method was used to investigate the occurrence of pesticides in 30domestic and 30 imported rice samples collected from Tehran market. Five compounds were detected in 11 domestic and 9 imported positive samples in concentration range from 0.032 microg/g to 0.081 microg/g and 0.028 microg/g to 0.074microg/g, respectively. With the exception of prohibited pesticides, phosphmidon and TCMTB, three permitted pesticides, cinosulfuron, triadimenol and tricyclazole, found in positive rice samples were below MRLs established by Institute of Standards and Industrial Research of Iran [ISIRI]