Factors affecting atrazine concentration and quantitative determination in chlorinated water

Although the herbicide atrazine has been reported to not react measurably with free chlorine during drinking water treatment, this work demonstrates that at contact times consistent with drinking water distribution system residence times, a transformation of atrazine can be observed. Some transformation products detected through the use of high performance liquid chromatography–electrospray mass spectrometry are consistent with the formation of N-chloro atrazine. The effects of applied chlorine, pH, and reaction time on the transformation reaction were studied to help understand the practical implications of the transformation on the accurate determination of atrazine in drinking waters. The errors in the determination of atrazine are a function of the type of dechlorinating agent applied during sample preparation and the analytical instrumentation utilized. When a reductive dechlorinating agent, such as sodium sulfite or ascorbic acid is used, the quantification of the atrazine can be inaccurate, ranging from 2-fold at pH 7.5 to 30-fold at pH 6.0. The results suggest HPLC/UV and ammonium chloride quenching may be best for accurate quantification. Hence, the results also appear to have implications for both compliance monitoring and health effects studies that utilize gas chromatography analysis with sodium sulfite or ascorbic acid as the quenching agent.