AUTOMATED SAMPLE PREPARATION FOR MONITORING GROUNDWATER POLLUTION BY CARBAMATE INSECTICIDES AND THEIR TRANSFORMATION PRODUCTS

We investigated automated on-line solid-phase extraction (SPE) followe d by liquid chromatographic (LC) techniques for monitoring carbamates and triazines and their transformation products. Analytical determinat ions were performed by LC with UV or postcolumn fluorescence detection (U.S. Environmental Protection Agency Method 531.1 for carbamate inse cticides) after preconcentration with on-line SPE using C-18 Empore ex traction disks, On-line SPE/LC/thermospray mass spectrometry with time -scheduled selected-ion monitoring was used as confirmatory method, Th e method was used to determine pesticide traces in well waters of a ty pical aquifer in the Almeria area (Andalucia, south of Spain) from Mar ch 1993 to February 1994, The major pollutants, found in highest amoun ts, were carbofuran, methiocarb, and methomyl, at levels of 0.32, 0.3, and 0.8 mu g/L, respectively, According to results of seasonal variat ion studies, pollution by carbamate insecticides is sporadic and excee ds the limit of 0.5 mu g/L for total pesticides allowed by the Europea n Economic Community Drinking Water Directive only twice a year, 3-Hyd roxycarbofuran and methiocarb sulfone also were detected, showing the importance of including the main toxic break down products of carbamat e insecticides in future monitoring programs.