Determination of binary and ternary mixtures of pesticides in wetland waters by gas chromatography using partial least-squares analysis

Partial least-squares (PLS) analysis was applied for the first time to tern ary and binary mixtures of pesticides producing overlapping peaks in gas ch romatograms, Several preprocessing algorithms for pretreatment of data were tested for optimization of the PLS models, and the most advantageous were used in each case. Three different mixtures of pesticides were resolved wit h satisfactory results: parathion-methyl, chlorpyrifos-methyl, and vinclozo lin; parathion-ethyl, chlorpyrifos, and triadimefon; and endosulfan sulfate and carbophenothion, The proposed models were applied to the determination of 3 mixtures of pesticides at levels of 0.02-1.00 ng/mL in wetland water samples after a preconcentration step with C-18 cartridges, with recoveries ranging from 82.7 to 117.4%. The reported method is sufficiently sensitive to measure pesticide residues at the maximum allowable concentrations give n in the European Union Drinking Water Directive.