MICROBORE LIQUID-CHROMATOGRAPHIC MASS-SPECTROMETRIC DETERMINATION OF ATRAZINE AND ITS MAJOR HYDROXYLATED DEGRADATE IN WATER AT PARTS-PER-TRILLION LEVELS USING ELECTROSPRAY

A liquid chromatography-electrospray ionization mass spectrometry (LC- ESI-MS) method was developed to determine atrazine (ATR) and hydroxyat razine (HA) in water at parts-per-trillion (ppt) levels. In addition t o protonated molecular ions, sodiated molecular and dimer ions were ob served in full-scan electrospray mass spectra of the analytes, providi ng additional information for the identification of ATR and HA. The qu antification is based on the use of isotopically labeled internal stan dards that were added to water samples prior to the sample extraction using a carbon black cartridge. The relative response factor for each of the native compounds relative to its corresponding internal standar d was measured and used to minimize the analytical error. The precisio n and accuracy data were obtained from the analysis of standard water samples containing 50 ppt ATR and 100 ppt HA. Relative standard deviat ion and relative error are less than 15% (n=6) for both ATR and HA det erminations. The method has been successfully used to analyze agricult ural run-off samples for ATR and HA levels. Analytical results compare d well with those obtained by using GC-high-resolution and fast atom b ombardment high-resolution MS methods developed in this laboratory. Pr eliminary results for analysis of a standard containing a mixture of A TR, HA, deethylatrazine and deisopropylatrazine suggest that the LC-ES I-MS method can be applied to simultaneous trace-level determination o f the major products of atrazine degradation in the environment.