Laboratory study of the response of select insecticides to toxicity identification evaluation procedures

A laboratory study was used to evaluate the response of select insecticides to toxicity identification evaluation procedures.Fourteen insecticides, one degradation product, and one synergist were spiked into organic-grade water and carried through toxicity identification evaluation procedures.Concentrations of each compound were analyzed by gas chromatography/mass spectrometry.During Phase I, the water sample was pumped through a C-8 solid-phase extraction cartridge and then eluted with methanol.Dimethoate was not removed by the extraction, but remained in the rinsate.In contrast, permethrin was removed by the extraction, but was not recovered by the methanol elution, and 80 percent of the permethrin remained on the cartridge, teflon tubing, and glassware.Chlorpyrifos also was not recovered completely with the methanol elution (only 62 percent was recovered).The other insecticides were extracted by C-8 solid-phase extraction cartridge and recovered by elution with methanol (80 percent or greater).During Phase II, a new spiked water sample was extracted by C-8 solid-phase extraction cartridge and then eluted with varying concentrations of methanol and water into different fractions.Each methanol:water fraction was analyzed for the added compounds.Most of the insecticides eluted in two fractions, with concentrations of 10 percent or greater.The largest number of insecticides eluted in the 75 percent methanol: water fraction.