Ion-exclusion/cation-exchange chromatography with an eluent containing the bile salt-type zwitterionic surfactant CHAPS was performed in order to evaluate variations in anion (SO(4)(2-), NO(3)(-), and SCN(-)) and cation (Na(+), K(+), NH(4)(+), Mg(2+), and Ca(2+)) concentrations in human saliva. CHAPS prevents the adsorption of proteins to the stationary phase, i.e., weakly acidic cation-exchange resin, since it aggregates proteins without denaturing them. Addition of 1mM CHAPS to the eluent comprising 6mM tartaric acid and 7 mM 18-crown-6 yielded reproducible separations of anions and cations in protein-containing saliva. The resolutions of anions and cations were not significantly affected by the addition of CHAPS to the eluent. The concentrations of Na(+) and K(+) varied before and after meals; or that of SCN(-), upon smoking. The relative standard deviations of peak areas ranged from 0.3 to 5.1% in 1 day (n=20) and from 1.4 to 5.8% over 6 days (n=6).