Determination of Organophosphorus Pesticide Residues in the Liver by Gas Chromatography with Flame Photometric Detection

A method for simultaneous determination of residues of six organophosphorus pesticides in animal liver samples has been developed and validated. The method is based on the extraction of organophosphorus pesticides with a mixture of acetone-petroleum ether, clean up on a gel permeation chromatography, further clean up on a small silica gel column, and finally determination by gas chromatography with flame photometric detection. The recovery, investigated by analysing blank liver samples spiked with chlorpyrifos-methyl, chlorpyrifos, diazinon, parathion, and pirimiphos-methyl at levels of 5, 25, 50, and 75 μg/kg, and with chlorfenvinphos at levels of 5, 10, and 15 μg/kg, ranged from 75.6% to 107.5%. Performance characteristics, such as repeatability and within-laboratory reproducibility, expressed as coefficient of variation, were less than 20%, and uncertainty <21%. Linearity ranged between 5 and 1,000 ng/mL. The limits of quantification were 5 μg/kg for all compounds and allowed determination of residues below the MRLs set by the European Union. The satisfactory z-score results of international proficiency tests confirmed good accuracy, reproducibility, and reliability of the developed method.