Optimizing recoveries of two chlorotriazine herbicide metabolites and 11 pesticides from aqueous samples using solid-phase extraction and gas chromatography-mass spectrometry.

A method was developed for solid-phase extraction of two chlorotriazine herbicide metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), from aqueous samples. Two C18 phases in cartridge format were compared and recoveries were found to be highly sensitive to sorbent amount, sample volume and presence of parent compounds. Recoveries were significantly improved using a partially non-endcapped C18 phase compared to the normal C18 phase, particularly for DIA, apparently due to polar interactions. Combinations of sample volume and sorbent amount were tested using deionized water to determine an optimal combination of 200 ml and 1.0 g, respectively. Recoveries from a variety of river, stream, runoff and ground waters averaged 105-116% and 109-117% at concentrations of 0.5-1.0 ng/ml for DIA and DEA, respectively, with minimum detection limits of 0.05 ng/ml. Other pesticides tested also have acceptable recoveries using this method.