Enhanced Preconcentration of Pesticides from Water Using the Goulden Large-Sample Extractor

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Abstract
Recoveries of nine model pesticides measured in water samples ranging from 4 to 120 liters using the Goulden large-sample extractor and were similar to recoveries predicted by a continuous liquid-liquid extraction model. Recoveries from the largest volumes were affected by emulsion formation at high sample flow rates. Limits of detection using the Goulden extractor under optimized conditions were lower than those obtained from 1 liter serial batch extractions by factors inversely proportional to sample volumes for pesticides with logarithm of solvent/water partition coefficients greater than 2. Average limits of detection for the pesticides were 9ng/l for 10 liter samples and 1 ng/l for 120 liter samples. Extraction of large water samples with methylene chloride using the Goulden large-sample extractor is an alternative technique to extraction of water by using solid-phase sorbents.