In this work, 33 organochlorine pesticides (OCPs) and 9 pyrethroid pesticides (PYPs) in Morinda officinalis were effectively and selectively extracted and cleaned up by accelerated solvent extraction assisted matrix solid phase dispersion (ASE/MSPD) method, followed by gas chromatography-electron capture detection (GC-ECD). Carbophenothion was selected as the internal standard and added into the final extracts to improve the precision and accuracy of the method. Parameters for ASE/MSPD procedure including ratio of acetone to n-hexane, temperature and amount of Florisil were optimized to improve the performance of the method through orthogonal experimental design. Under the optimized conditions, the average recoveries (six replicates) for all pesticides (spiked at 0.05, 0.5 and 1.0 mg kg(-1)) ranged from 69.3% to 112% with RSD less than 14.14%. A wide linear range of 10-1000 ng mL(-1) was observed with r values of 0.9963-0.9999. Meanwhile, the method gave high selectivity and sensitivity (LODs<3 μg kg(-1) and LOQs<8.0 μg kg (-1)), good repeatability (RSD of 9.64%, on average) and precision (RSD of 5.48%, averagely) and excellent stability (RSD <9.47%). The feasibility of the proposed method was demonstrated by applying it for preconcentration and determination of OCPs and PYPs in 40 batches of real samples. Four kinds of pesticides (beta-endosulfan, tecnazene, hexachlorobenzene and alpha-BHC) were detected in three batches of samples, which were successfully confirmed by GC-MS. The results indicated that ASE/MSPD is a reliable and half-automated extraction and purification technique, with many advantages over traditional techniques. The combination of ASE/MSPD and GC-ECD could be especially useful for trace analysis of pesticide residues in complex matrices.
Keywords: Accelerated solvent extraction; GC–ECD; Matrix solid phase dispersion; Morinda officinalis; Orthogonal experimental design.
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