SOLID-PHASE EXTRACTION FOR MULTI-RESIDUE ANALYSIS OF SOME TRIAZOLE AND PYRIMIDINE PESTICIDES IN WATER

A multi-residue analytical method based on solid-phase extraction (C18) has been developed for the analysis of 12 compounds in groundwater. These compounds are triazoles, e.g. diclobutrazol, flutriafol, hexaconazole, paclobutrazol and its ketone analogue and pyrimidines, e.g. bupirimate, pirimicarb, pirimiphos-methyl, ethirimol, and other pesticides: fluazifop-P-butyl, fluazifop and fomesafen. In summary, one litre of water modified with 1% methanol was extracted using a C18 solid-phase extraction column, containing 1 g of adsorbent. The retained compounds were eluted from the column with successive elutions of acetonitrile and methanol. No further clean-up was necessary. Residues were determined either by capillary gas-liquid chromatography (GLC) using a nitrogen-phosphorus selective detector, or high performance liquid chromatography (HPLC) using a UV detector. Recovery data on these compounds were obtained by fortifying water at 0.05-100 mu-g/l levels. Depending on the compound, mean recoveries were within the range of 80-107% with a coefficient of variation of 9-15%. The limit of determination, defined as four times the baseline noise, varied between 0.003-0.1-mu-g/l also depending on the compound and detection sensitivity of the instrument. These recovery data have also been compared to values generated by conventional liquid-liquid partition. Various techniques were used to confirm the identity of these compounds. Gas Chromatography - Mass Spectrometry (GC-MS) using selective ion monitoring (SIM) was used to confirm the compounds which were amenable to gas-liquid chromatography. These were all the triazoles and bupirimate, pirimicarb, pirimiphos-methyl and fluazifop-P-butyl. HPLC methods were developed using different mobile phase and adsorbent combinations for the confirmation of ethirimol, fluazifop and fomesafen residues in water.