(620) Complicating factors in the analysis of lambda-cyhalothrin in environmental samples.
Kuivila, K1, Pedersen, T1, Nicholas, P1, 1 US Geological Survey, Sacramento, CA, USA
ABSTRACT- The increasing use of the pyrethroid insecticide, lambda-cyhalothrin, on rice fields in California is a concern because of its toxicity to aquatic organisms at low concentrations. One problem with current methods for analysis of lambda-cyhalothrin in environmental water samples is poor or variable recovery during sample processing and analysis. Laboratory studies were conducted to estimate the potential for loss of the compound during sampling, extraction, and instrumental analysis of water samples. During sampling, lambda-cyhalothrin sorbed readily to Teflon and glass container walls like other pyrethroid insecticides. The results of spiking studies showed that as much as half of the compound can be lost from a water sample in several hours due to sorption. During extraction, the recovery of added lambda-cyhalothrin is controlled strongly by the sample matrix. In river water with relatively low specific conductance and concentrations of dissolved organic carbon (DOC), liquid-liquid extraction recoveries of spiked lambda-cyhalothrin were greater than 95%. However, in rice field irrigation-return water with higher specific conductance and concentrations of DOC, extraction efficiency decreased to 55-75%. A similar matrix effect on extraction efficiency was observed during extraction of filtered and spiked water samples onto solid-phase extraction cartridges. During analysis by gas-chromatography/mass-spectrometry with ion-trap detection, the analytical response factor varied among samples. The response factor of lambda-cyhalothrin standards in ethyl acetate was consistent throughout a sample run; however, the response factor of standard additions of lambda-cyhalothrin to extracts of rice field irrigation-return water was variable, generally decreasing throughout the run. Future studies will focus on improving the efficiency of extraction and the quantification of lambda-cyhalothrin in environmental samples.
Key words: lambda-cyhalothrin, pyrethroid, analysis