Isotope dilution high-performance liquid chromatography/tandem mass spectrometry method for quantifying urinary metabolites of atrazine, malathion, and 2,4-dichlorophenoxyacetic acid

We have developed an isotope dilution high-performance liquid chromatograph y/tandem mass spectrometry (HPLC/MS/MS) method for quantifying the urinary metabolites of the pesticides atrazine, malathion, and 2,4-dichlorophenoxya cetic acid (2,4-D). Urine samples are extracted with an organic solvent, an d the organic fraction is concentrated. The concentrate is then analyzed us ing HPLC/MS/MS. The limits of detection for the metabolites are less than 0 .5 mu g/L (parts per billion) in 10 mL of urine, with a high degree of accu racy and precision.