Liquid—Solid Extraction and Fast Atom Bombardment High-Resolution Mass Spectrometry for the Determination of Hydroxyatrazine in Water at Low—ppt Levels

Parts-per-trillion levels of hydroxyatrazine (HA) have been quantitatively extracted and eluted from water by liquidsolid extraction with a graphitized carbon-black cartridge. Recoveries of HA (>80%) for this procedure are superior to those obtained when a C-18 cartridge or liquid-liquid extraction with dichloromethane are used. Quantification of HA at picogram levels was accomplished by using isotope dilution and fast atom bombardment high resolution mass spectrometry. No significant interfering spectral background occurs at the masses of interest, those of the [M + H]⁺ ions of both the analyte and the internal standard, when the liquid matrix is 3:1 dithiothreitol/ dithioerythritol. Aqueous samples were fortified with ¹³C₃-labeled hydroxyatrazine ([¹³C₃]HA), and sample extracts were analyzed by recording the mass profiles of the target ions. Identification of HA is based on the exact mass of the [M + H]⁺ ion, and confirmation is by tandem mass spectrometry (FAB-MS/MS) analysis. The method precision in relative standard deviation is 10%, and the accuracy in relative error is <10% for seven standard water samples containing HA at 100 parts per trillion. The method has been used successfully for the first time for the determination of HA and for the simultaneous determination of HA and atrazine, its parent compound, in groundwater.