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SummaryThis paper describes a study of the potential of largevolume on-column injection for the determination of triazine herbicides in clean water samples (groundwater). The sensitivity of chromatographic determination has been increased by two orders of magnitude by injection of up to 200 gL of pesticide solutions and nitrogen-phosphorus detection. Analytical characteristics expressed as precision, linear range and limit of detection have been determined, the results indicating adequate analytical performance and the ruggedness of the injection technique. As an application, gas chromatography with large-volume on-column injection and nitrogen-phosphorus detection was combined with offline liquid-liquid micro-extraction with hexane (1 mL water/1 mL hexane). The procedure was applied to spiked groundwater samples at two concentration levels (1 and 10 ~tg L -1) with good recoveries (between 81 and 103 %, except for deethylatrazine) and repeatability (better than 15 % at the 1 ~tg L -1 level). Limits of detection of the triazine herbicides studied ranged from 0.08 to 0.16 p~g L -1.

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 ~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 mL methyl tert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5 #gL -1. Recoveries of the overall procedure were >80% and the precision was better than 15 %. Detection limits were <30 ng L 1 from 200-#L injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated solidphase extraction with Cls cartridges has been applied to water samples (50 mL) spiked at 0.01, 0.1 and 1 #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 ng L 1. Finally, several surface water samples were analysed, and triazine herbicides were detected at concentrations of approx. 0.1 0.2 #g L 1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2/~L.

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