Solid-phase extraction for multi-residue analysis of some triazole and pyrimidine pesticides in water

Summary 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 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 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.