Carbonate interferences by ion chromatographic determination of anions in mineral waters.

The high content of hydrogen carbonate anions and dissolved CO2 in some mineral waters interfere with the determination of anions in such samples by ion chromatography. It was found that the irreproducibility of retention times of all anions present in the samples was caused by on-column neutralisation of CO(3)2- to HCO3- by CO2. Microbubbles of CO2 released downstream by the suppressor inhibited exchange of Na+ with H3O+ resulting in lower conductivity and consequently in the decrease of chloride peak.