Analysis for Organic Pesticides in Aquatic Environments

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Abstract
The detection of organic pesticides in aquatic environments represents an unique analytical problem. It is unique in the context that specificity is required under extremely sensitive conditions as opposed to gross analysis for trace organics in water. First, there is the problem of pesticide identity. Second, direct measurement is not feasible because of sensitivity and specificity requirements. Extraction, concentration, and cleanup techniques must be employed prior to qualitative analysis and quantification. Third, natural waters may contain such organic interferences as aromatic and aliphatic compounds from industrial waste waters, and naturally occurring colored compounds. These impurities are often present in concentrations greater than the pesticide. Two objectives are offered herein: (1) a brief critique of extraction, cleanup, identification, and quantification techniques is given in order to highlight limitations fallacies, and pitfalls, and (2) a model system for the recovery, separation, and confirmation of organophosphate pesticides, oxons, and their hydrolysis products. This model system provides the basic needs of pesticide methodology; namely, simplicity and minimum sample handling. The problems of recovery from water by liquid-liquid extraction, separation by gas-liquid chromatography, and subsequent confirmation by micro-ultraviolet absorption spectrophotometry are discussed.