Determination of inorganic acids by ion chromatography with n-tetradecylphosphocholine (zwitterionic surfactant) as the stationary phase and pure water as the mobile phase

A new ion chromatographic (IV) system, in which n-tetradecylphosphocholine (TDPC, a phosphobetaine type of zwitterionic surfactant) was used as the st ationary phase, pure water as the mobile phase, and conductivity as the met hod of detection, has been developed for the determination of inorganic aci ds. Five model acids' HCl, HNO3, HClO4, H2SO4, and H3PO4, were separated to baseline and eluted in the order H3PO4 > HCl > HNO3 > H2SO4 > HClO4. When peak areas were plotted against the concentrations of the acids in samples, linear calibration curves were obtained. Ultimate determination limits wer e approximately 1 mmol L-1, but the discrimination of the method between so lutions of different concentration was better than 10 mu mol L-1 for those model analytes. Salts of divalent cations could also be separated, but they were eluted faster than the acids. No separation was observed for the salt s of monovalent cations. This newly proposed approach is applicable to the simultaneous determination of the inorganic acids (produced by reactions of NOx, SOx, and HCl with water) in aerosols.