Abstract

Ion-chromatographic (IC) methods were investigated to determine chlorate and chlorite in drinking water with a lower detection limit (LDL) of 0.01 mg/L. The IC method with the Dionex AS-3 column separated insufficiently 0.050 mg/L Cl0-3 (0.100 mg/L Cl0-2) from 0.33 mg/L NO-3 (0.100 mg/L Cl-) to achieve the LDL, even after modification. The Dionex Ionpac AS-9 column separated 0.050 mg/L Cl0-3 (0.100 mg/L Cl0-2) and 50.0 mg/L NO-3 (150 mg/L Cl-) sufficiently to determine a LDL of 0.007 mg/L Cl0-3 and 0.004 mg/L Cl0-2. Chlorine (0.50 mg/L) and anions normally present in drinking water did not interfere. Chlorite in drinking water must be determined as soon as possible after sampling. A method different from IC has to be developed for the confirmation of the identity and the concentrations of chlorate and chlorite measured. Concentrations of 0.0070 - 0.041 mg/L Cl0-3 and 0.0021 - 0.064 mg/L Cl0-2 were measured in 17 samples of drinking water, and 1.10 g/L Cl0-3 was found in the sodiumhypochlorite solution used for the chlorine interference study.