Supercritical fluid extraction of pesticides from meat: a systematic approach for optimisation.

A method for quantification of pesticide residues in meat and fatty matrices was developed using supercritical fluid extraction (SFE). The SFE method allows selective extraction of residues and subsequent gas chromatography analysis without further clean-up. Quantification was done by GC using nitrogen-phosphorus detection and electron capture detection. Initial method development was made using organophosphorus pesticides (OPPs). The dependence of fat and OPP residue recovery on supercritical fluid density, temperature, flow rate and extraction time was investigated through a reduced factorial design. Since temperature and density were found to have pronounced effect on the recovery of OPPs these extraction parameters were studied using a new arbitrary measure for co-extractivity. An optimisation score was established as relative pesticide recovery subtracted by relative fat recovery. Using this algorithm a response plane was modelled varying the primary factors temperature and density. The applicability of this approach and the algorithm was verified. The polarity range covered by the SFE method was demonstrated using OPPs: chlorpyrifos, chlorpyrifos-methyl, malathion, pirimifos-methyl and prothiofos. Additionally the final method was evaluated using four pesticides that are not OPPs: carbofuran, phorate, procymidone and vinclozolin. All pesticides showed good recovery (78-95%), and limits of detection (0.01-0.03 mg kg-1) and limits of determination (0.01-0.05 mg kg-1) meet the requirements set by the European Council (Directive 96/33/EEC). Compared to traditional methods based on organic solvent extraction, the SFE method is fast, less labour intensive, uses smaller amounts of potentially harmful solvents and has the potential to be fully automated.