SIMULTANEOUS ION-EXCLUSION CHROMATOGRAPHY CATION-EXCHANGE CHROMATOGRAPHY WITH CONDUCTIMETRIC DETECTION OF ANIONS AND CATIONS IN ACID-RAIN WATERS

A simple, selective and sensitive method was investigated for simultaneously determining anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Mg2+, Ca2+) in acid rain and related environmental waters in central Japan. The method involves simultaneous ion-exclusion-cation-exchange chromatography with conductimetric detection on a polyacrylate weakly acidic cation-exchange resin column with a weak-acid eluent. With the weak-acid eluent (tartaric acid) both anions and cations were separated simultaneously, based on ion-exclusion and cation-exchange mechanism. Owing to the presence of H+ ions in the tartaric acid eluent, the detector response was positive for the anions and negative for the cations. Using a 5 mM tartaric acid-7.5% methanol-water eluent, good simultaneous separation and detection were achieved in about 30 min. The results indicated an ionic balance of about 100% between the anions (including HCO3-) and the cations (including H+).