SIMULTANEOUS DETERMINATION OF COMMON MONO-CATIONS AND DIVALENT-CATIONS BY ION CHROMATOGRAPHY WITH AN UNMODIFIED SILICA-GEL COLUMN

In order to characterize the cation-exchange properties of a silica ge l column in the acidic region, the retention behavior of common mono- and divalent cations (Na+, NH4+, K+, Mg2+ and Ca2+) was investigated. When using 5 mM nitric acid (pH 2.3) as an eluent, these cations were retained on a silica gel column (150x4.6 mm I.D.) packed with Develosi l 30-5 unmodified silica gel that has a very large surface area (ca. 7 70 m(2)/g), showing that such a stationary phase could be used as a ca tion-exchanger for ion chromatography with acidic eluents. When using 1.5 mM nitric acid and 0.5 mM 2,6-pyridinedicarboxylic acid as an elue nt, a good separation of these cations was obtained in 12 min using co nductimetric detection. This separation was applied successfully to th e simultaneous determination of the five cations in various environmen tal water samples.