An Improved Method for the Determination of Chlorpyrifos in Palm Oil Matrices Using Gas Chromatography

The objective of this study was to improve the method for determining chlorpyrifos, an organophosphorus insecticide, in various palm oil matrices. Chlorpyrifos was separated from the oil matrices using acetonitrile extraction and then subjected to the solid phase extraction (SPE) clean-up process. A silica-based SPE was used for the clean-up process. Quantification of the extracted chlorpyrifos was carried out using a gas chromatograph (GC) equipped with an electron capture detector (ECD). The GC detector response was tested using standard solutions containing 0.005 to 0.12 mg ml-1 of chlorpyrifos. The retention time for chlorpyrifos was 4.8 min with the minimum detection limit at 0.005 mg ml-1. The average recoveries of chlorpyrifos from crude palm oil (CPO) spiked with 0.02, 0.04, 0.06, 0.08 and 0.1 mg ml-1 chlorpyrifos were 94 ± 2.3%, 93 ± 1.4%, 99 ± 1.6%, 97 ± 2.9% and 95 ± 0.7%, respectively. In the case of crude palm kernel oil (CPKO) and refined, bleached, deodorised palm olein (RBDPOo), the recovery of chlorpyrifos from the spiked oil samples containing 0.02 to 0.1 mg ml-1 of chlorpyrifos ranged from 100% to 101% and from 93% to 99%, with the coefficient of variation ranging from 1.3% to 3.0% and from 0.7% to 2.9%, respectively. The method developed was used to determine the chlorpyrifos content in samples of CPO, CPKO and RBDPOo from mills and a refinery in Selangor, Malaysia. No chlorpyrifos residue was detected in any of the CPO, CPKO and RBDPOo