Ion chromatographic determination of trace iodate, chlorite, chlorate, bromide, bromate and nitrite in drinking water using suppressed conductivity detection and visible detection

An ion chromatography method for the simultaneous determination of trace iodate, chlorite, chlorate, bromide, bromate and nitrite in drinking water has been developed using an anion-exchange column and the suppressed conductivity detector, followed by post-column addition of reagent to enhance visible absorbance detection of ions. A high capacity anion exchange Ion Pac9-HC column (250 mm × 4 mm I.D.) was used. Eight millimole per liter sodium carbonate was used as eluent, an auto-suppression external water mode was selected, 0.5 g/l o-dianisidine·2HCl (ODA) + 4.5 g/l KBr + 25% methanel + 5.6% nitric acid was used as post-column reagent. The post-column reaction (PCR) temperature was at 60 °C, and the visible absorbance detected wavelength at 450 nm. The sample's pH and coexist anions had no influence on determination. The method enjoyed a wide linear range and a good linear correlation coefficient (r > 0.999). The method detection limits were between 0.023 and 2.0 μg/l. The average recoveries ranged from 87.5 to 110.0%, and the relative standard deviations (RSD) were in the range of 1.1–4.6%. The analytical results by the method of post-column addition of reagent to enhance visible absorbance detection of anions was compared with that of the suppressed conductivity detection, and the former was proved to be better in sensitivity and selectivity. The results showed that this method was accurate, sensitive and might be good for application and suitable for trace analysis at the level of μg/l.