Development of US EPA Method 536: A Direct Injection Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) Method for the Analysis of the Chloro-s- Triazines and Their Degradates

摘要

Atrazine and related choro-s-triazines are a class of broadleaf herbicides that prevent the growth of target weeds by interfering with the normal function of photosynthesis. Widespread agricultural application of these herbicides has resulted in an increased presence of these compounds along with their degradation products in both surface and ground waters. The chloro-s-triazines have been evaluated using gas chromatography/mass spectrometry (GC/MS), but the polar degradates present problems associated with low volatility and thermal instability. Thus, liquid chromatography/mass spectrometry (LC/MS) represents a more attractive analytical alternative. Several published reports employ solid phase extraction (SPE) in conjunction with LC/MS in order to attain trace level sensitivities; however, SPE can result in variable recoveries due to differences in polarity among the chloro-s-triazines and their degradates. SPE also suffers the disadvantage of concentrating unwanted matrix components from a sample in addition to the compounds of interest. As a result, matrix enhancement/suppression effects can become problematic in subsequent LC/MS analyses. This poster describes the work conducted at EPA's Office of Ground Water and Drinking Water (OGWDW) laboratory to develop a direct injection, LC-tandem mass spectrometry (MS/MS) method for the analysis of the chloro-s-triazines (atrazine, simazine, cyanazine, and propazine) and their dealkylated degradates (desethylatrazine, desisopropylatrazine, and diaminochlorotriazine). Potential matrix effects were minimized by selection of appropriate internal standards, and by the use of tandem MS for detection. Analyte stability was ensured during storage through careful selection of proper dechlorinating and antimicrobial reagents and through buffering sample pH. Method 536 has sufficient sensitivity to accurately detect all target analytes at or below 0.1 ug/L and is sufficiently robust to support either survey work or compliance monitoring as determined in the future by the OGWDW.