Application of Supercritical Fluid Extraction for the Analysis of Organophosphorus Pesticide Residues in Grain and Dried Foodstuffs

A supercritical fluid extraction (SFE) method using carbon dioxide (CO₂ ) and cleanup by solid-phase extraction (SPE) with graphitized carbon black is presented. Gas chromatography using flame photometric detection (GC/FPD) and gas chromatography-mass spectrometric detection (GC-MSD) allow the quantitative determination of organophosphorus (OP) pesticide residues in grains such as wheat, maize, and rice as well as other dried foodstuffs such as cornflakes and kidney beans. The method is robust and sensitive, allowing residues to be determined down to 0.05 mg/kg or lower using GC-MSD. Extraction, cleanup, and determination are automated, allowing higher sample throughput compared to methods using solvent extraction and gel permeation chromatography. Solvent consumption is minimal using the SFE method, and hazardous waste is reduced. The SFE and cleanup methods used are likely to be suitable for the determination of OP pesticide residues in other dried foodstuffs without the need to alter the SFE or SPE conditions.