Effective liquid-liquid extraction method for analysis of pyrethroid and phenylpyrazole pesticides in emulsion-prone surface water samples.

The distribution of pyrethroid and phenylpyrazole pesticides in the water environment has raised public concerns because of their potential risks to ecosystem and human health. However, co-extraction of emulsifier type compounds (by liquid-liquid extraction, LLE) present in environmental samples can present a challenge for quantifying typically low concentrations of pesticides. Several methods were evaluated for breaking emulsions in problematic environmental surface water samples extracted by LLE using methylene chloride. Target pesticides included 11 typical pyrethroid and phenylpyrazole pesticides commonly used in agricultural and landscape insect pest control. The most effective method was selected for validation in fortification studies with GC-ECD analysis. The average recoveries of spiked pyrethroid and phenylpyrazole pesticides were 88.2-123.4% for water samples with moderate emulsions and 93.0-117.4% for water samples with severe emulsions. Recoveries of the pesticides ranged 81.0-126.4% (water samples with moderate emulsions) and 95.9-110.6% (water samples with severe emulsions) for lowest fortification level (5-20 ngL(-1)), 88.2-123.4% (water samples with moderate emulsions) and 93.0-117.4% (water samples with severe emulsions) for middle fortification level (10-40 ngL(-1)), and 90.2-119.9% (water samples with moderate emulsions) and 91.2-105.9% (water samples with severe emulsions) for highest fortification level (50-200 ngL(-1)). Relative standard deviations of pesticide recoveries were usually < 10%. Results indicate that this method is a robust and reproducible option for LLE of pyrethroid and phenylpyrazole pesticides from emulsion-prone surface water samples.