Gas chromatography with pulsed flame photometric detection multiresidue method for organophosphate pesticide and metabolite residues at the parts-per-billion level in representative commodities of fruit and vegetable crop groups

A gas chromatographic method with a pulsed flame photometric detector (P-FP D) is presented for the analysis of 28 parent organophosphate (OP) pesticid es and their OP metabolites, A total of 57 organophosphates were analyzed i n 10 representative fruit and vegetable crop groups, The method is based on a judicious selection of known procedures from FDA sources such as the Pes ticide Analytical Manual and Laboratory Information Bulletins, combined in a manner to recover the OPs and their metabolite(s) at the part-per-billion (ppb) level, The method uses an acetone extraction with either miniaturize d Hydromatrix column partitioning or alternately a miniaturized methylene d ichloride liquid-liquid partitioning, followed by solid-phase extraction (S PE) cleanup with graphitized carbon black (GCB) and PSA cartridges, Determi nation of residues is by programmed temperature capillary column gas chroma tography fitted with a P-FPD set in the phosphorus mode, The method is desi gned so that a set of samples can be prepared in I working day for overnigh t instrumental analysis, The recovery data indicates that a daily column-cu tting procedure used in combination with the SPE extract cleanup effectivel y reduces matrix enhancement at the ppb level for many organophosphates, Th e OPs most susceptible to elevated recoveries around or greater than 150%, based on peak area calculations, were trichlorfon, phosmet, and the metabol ites of dimethoate, fenamiphos, fenthion, and phorate.