HERBICIDE TRACE ANALYSIS BY HIGH-RESOLUTION FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY - QUANTIFICATION OF LOW PARTS-PER-TRILLION LEVELS OF ATRAZINE IN WATER

A method for determining trace levels of atrazine in groundwater and tap water by using fast atom bombardment mass spectrometry is reported. Low-picogram detection limits were achieved by considering explicitly the chemistry leading to the production of background ions from the liquid matrix (3:1 dithiothreitol/dithioerythritol) and by using the minimum volume of matrix required to achieve ionization. Protonated atrazine was produced abundantly in the gas phase with relatively low abundance background ions at the atrazine ion mass region. The method, which uses a high-resolution magnetic sector mass spectrometer, is sensitive, fast, and simple. The response curve for atrazine is linear from 1 to 1000 pg. Appropriate procedures for isolating atrazine from water were developed. The analytical results compared well with those obtained by using the capillary gas chromatography/high-resolution mass spectrometry method developed in this laboratory. The accuracy and precision of the method were assessed by analyzing six standard water samples containing 1 part-per-trillion atrazine. Both the precision and accuracy of the method were better than 10% (relative standard deviation) for standard water samples. After the sample was fortified with the [C-13(3)]atrazine internal standard, the native atrazine in local tap water samples could be determined directly or after a single-step extraction with dichloromethane. The method has also been successfully used for analysis of atrazine at 6-94 parts-per-trillion levels in several well-water samples.