Cloud point extraction coupled with ultrasonic-assisted back-extraction for the determination of organophosphorus pesticides in concentrated fruit juice by gas chromatography with flame photometric detection

A new method for the determination of nine organophosphorus pesticides (OPPs): Dichlorvos, methamidophos, acephate, diazinon, dimethoate, chlorpyrifos, parathion-methyl, malathion and parathion-ethyl in concentrated fruit juice was developed using the cloud point extraction coupled with ultrasonic-assisted back-extraction prior to gas chromatography with flame photometric detection (GC-FPD) analysis. The parameters and variables that affect the extraction were investigated. Under optimum conditions: a solution containing 6% (W/V) polyethylene glycol 6000 (PEG 6000) and 20% (W/V) Na2SO4 for the extraction of the OPPs. The coacervation phase obtained was back extracted with ethyl acetate. The upper ethyl acetate solution was centrifugated simply for further cleanup for the sake of automatic injection. A preconcentration factor of 50 was obtained for these nine pesticides. Using this method, the limits of detection (LOD) and limits of quantification (LOQ) were in the range of 0.5-3.0 and 1.5-9.0 mu g kg(-1) in concentrated fruit juice, respectively; the relative standard deviations (RSD) were < 9%. (C) 2011 Elsevier Ltd. All rights reserved.