A multi-residue method for the analysis of organophosphorus residues in cooked and polished rice using accelerated solvent extraction and dispersive-solid phase extraction (D-SPE) technique and uncertainty measurement

Quick, simple and efficient multi-residue analytical methods were developed and validated for the determination of organophosphorous insecticides from polished and cooked rice. Polished rice was extracted using a simple, automated technique namely accelerated solvent extraction (ASE) using dichloromethane as the extraction solvent. Cooked rice was extracted with acetone and cleaned up using dispersive-solid phase extraction (D-SPE) technique. The single step extraction method adopted for polished rice using accelerated solvent extractor provided satisfactory recovery for eight organophosphorus pesticides (OPPs) which ranged from 85.5-116.7%; 90.0-110.3% and 93.5-118.8% at 1, 5 and 10 limit of quantification (LOQ) levels, respectively. The recovery of cooked rice was in the range of 74-124%; from 75-100% and from 73-87% for 1, 5 and 10 level of fortification, respectively. The total uncertainty was evaluated, taking four main independent sources viz., weighing, purity of the standard, GC calibration curve and repeatability under consideration. The expanded uncertainty was found to be in the range of 5-20%.