DETERMINATION OF ORGANONITROGEN PESTICIDES IN LARGE VOLUMES OF SURFACE-WATER BY LIQUID-LIQUID AND SOLID-PHASE EXTRACTION USING GAS-CHROMATOGRAPHY WITH NITROGEN-PHOSPHORUS DETECTION AND LIQUID-CHROMATOGRAPHY WITH ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

During a recent study to determine the fluxes and fates of contaminant s in the St. Lawrence River, the majority of organonitrogen pesticides analysed in samples of surface water were found in the dissolved phas e. This paper compares two extraction techniques and two analytical te chniques for 10 chemicals (metolachlor, seven triazines and two degrad ation products of atrazine-cyanazine-propazine and simazine) in the di ssolved phase in large volumes of surface water, using a fibre glass f ilter with 0.7 mu m porosity. Samples of filtered surface water (1-20 1) were extracted by means of a liquid-liquid technique using the Goul den large-sample extractor, and by means of a solid-phase extraction t echnique, using cartridges filled with 500 mg of a large particle-size graphitized carbon black as adsorbent: Clarbopack B (500-666 mu m) Th e pesticides were analysed by gas chromatography on two DB-5 and DB-21 0 capillary columns with nitrogen-phosphorus detection (GC-NPD) and by liquid chromatography coupled with mass spectrometry equipped with an atmospheric pressure chemical ionization interface (LC-APCI-MS). The recoveries were high (67-100%) for the majority of the target pesticid es in a volume of 17.85 1 of Milli-Q water, compared to recoveries in the same volume of filtered surface water (51-102%). The detection lim its ranged from 0.4 to 4 ng/l and from 0.6 to 3 ng/l for GC-NPD and LC -ACPI-MS techniques, respectively. (C) 1998 Elsevier Science B.V. All rights reserved.