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 hydroxyatrazine (HA) in water at parts-per-trillion (ppt) levels. In addition to protonated molecular ions, sodiated molecular and dimer ions were observed in full-scan electrospray mass spectra of the analytes, providing additional information for the identification of ATR and HA. The quantification is based on the use of isotopically labeled internal standards 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 standard was measured and used to minimize the analytical error. The precision and accuracy data were obtained from the analysis of standard water samples containing 50 ppt ATR and 100 ppt HA. Relative standard deviation and relative error are less than 15% (n=6) for both ATR and HA determinations. The method has been successfully used to analyze agricultural run-off samples for ATR and HA levels. Analytical results compared well with those obtained by using GC-high-resolution and fast atom bombardment high-resolution MS methods developed in this laboratory. Preliminary results for analysis of a standard containing a mixture of ATR, HA, deethylatrazine and deisopropylatrazine suggest that the LC-ESI-MS method can be applied to simultaneous trace-level determination of the major products of atrazine degradation in the environment.