Quantification of selected pesticide metabolites in human urine using isotope dilution high-performance liquid chromatography/tandem mass spectrometry

The annual domestic use of pesticides is continually increasing, virtually ensuring that everyone is exposed to some level of pesticides on a regular basis through diet or environment. The potential developmental and physical adverse effects these chronic pesticide exposures have on children are of increasing concern. To adequately evaluate the potential adverse effects re sulting from these exposures, accurate methods to measure the amount of the pesticide absorbed by the body must be developed. We have developed a sens itive method to measure the urinary metabolites of atrazine, diazinon, mala thion, 2,4-dichlorophenoxyacetic acid (2,4-D), and certain synthetic pyreth roids in human urine. in our method, stable isotopically labeled analogues of the metabolites were spiked into the urine, which was subsequently extra cted at both a neutral and acidic pH using organic solvents. The extracts w ere analyzed by highperformance liquid chromatography coupled with tandem m ass spectrometry (HPLC-MS/MS) using atmospheric pressure chemical ionizatio n. Our method has limits of detection ranging from 20 to 500 ng/l (parts pe r trillion) and relative standard deviations of less than 11%. This method has been used to measure the internal doses of these pesticides in both adu lts and children (n = 130) with no documented exposure to the pesticides. W e detected atrazine and synthetic pyrethroid metabolites in less than 12% o f the samples analyzed. The metabolites of 2,4-D, malathion, and diazinon w ere detected in 22%, 32%, and 57% of the samples, respectively.