Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 mu L sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures - liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mt methyl tert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5 mu g L-1. Recoveries of the overall procedure were >80 % and the precision was better than 15 %. Detection limits were <30 ng L-1 from 200-mu L injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated solid-phase extraction with C-18 cartridges has been applied to water samples (50 mL) spilled at 0.01, 0.1 and 1 mu g L-1 The overall procedure was satisfactory (recoveries >80 % and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ngL(-1). Finally, several surface water samples were analysed, and triazine herbicides were detected at concentrations of approx. 0.1-0.2 mu g L-1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 mu L.