Evaluation of atrazine positive and false positive immunoassay detections in ground water

False positive responses on an atrazine (6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine) immunoassay kit were investigated to explain possible causes for these occurrences. Ground water samples were evaluated with the immunoassay kit and positive responses (> 0.20 microgram L-1) were confirmed using gas chromatography/mass spectrometry (GC/MS). Non-confirming samples (false positives) were analyzed for seven additional compounds on GC. Resulting GC/MS and GC analyses showed that 70% of the false positives could be attributed to two compounds. Prometon (6-methoxy-N,N'-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine) was responsible for the majority (64%) of the false positive responses The atrazine metabolite, deethylatrazine (2-chloro-4-amino-6-isopropylamino-1,3,5-triazine), was responsible for the other 6% of the false positives measured. Unattributed false positives (30%) were probably due to an overestimation of pesticide concentrations in the kit's lower detection range.