Optimized method for the determination of organophosphorus pesticides in meat and fatty matrices.

A method was developed and optimized for determination of residues of organophosphorous pesticides (OPs) in meat and fatty matrices. The method was developed for the national Danish monitoring programme, whereby priority was given to simplify the clean-up, avoid use of toxic and harmful organic solvents and allow quantification at ppb level using GC with nitrogen-phosphorus detection (NPD). Homogenized meat was extracted using ethyl acetate, the co-extracted water being removed using anhydrous Na2SO4. The clean-up was done through fat precipitation by cooling the extract flowed by solid-phase extraction on C18 mini-columns. Pesticide residues were determined by GC-NPD using a DB1701 capillary column. The limit of detection was 1 to 20 ppb and limit of determination was 2 to 33 ppb and the method is feasible for control of fat-soluble OPs according to the maximum residue limits set by the European Communities. The method developed covers a broad polarity range from polar OPs, such as acephate and methamidophos, through medium polar OPs to non-polar pesticides, such as prothiofos.