ULTRATRACE DETERMINATION OF ORGANOPHOSPHORUS AND ORGANONITROGEN PESTICIDES IN SURFACE-WATER

A method was developed to analyse 16 organophosphorus and organonitrog en pesticides in surface waters. Sample volumes of 35.7 L were filtere d through glass fiber filters (0.7 mu m) to separate suspended particu late matter and filtered water (dissolved phase). Suspended particulat e matter was extracted with a Soxhlet extractor while filtered water w as extracted using the Goulden large-sample extractor (GLSE), both usi ng dichloromethane (DCM). The pesticides were analysed by gas chromato graphy on DB-5 and DB-210 capillary columns with a nitrogen-phosphorus detector (GC-NPD). With the exception of metribuzin, all pesticides w ere recovered from distilled water at relatively high levels (71-95%) compared to filtered surface water (3-106%). These compounds were reco vered from spiked blank filters (39-118%). Detection limits were betwe en 0.0003 and 0.003 mu g.L-1 for filtered water, and between 0.01 and 0.2 mu g for suspended particulate matter.