Simultaneous determination of common mono- and divalent cations in natural water samples by conductimetric detection ion chromatography with an unmodified silica gel column and oxalic acid/18-crown-6 as eluent Original Research Article

An unmodified silica gel (Super Micro Beads Silica Gel B-5: SMBSG B-5) was used for the ion chromatographic (IC) separation of common mono- and divalent cations (Na+, NH+4, K+, Mg2+ and Ca2+) in various natural water samples with strongly acidic eluents. When using 1 mM oxalic acid as the eluent, the SMBSG B-5 silica gel acted as a cation-exchange stationary phase and incomplete separation of these cations was achieved. Therefore, the effect of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) added to 1 mM oxalic acid as the eluent was investigated for the achievement of complete separation of these cations. As a result, when using 1 mM oxalic acid/3 mM 18-crown-6 as the eluent and a 15 cm SMBSG B-5 column, highly sensitive and excellent separation for these cations was achieved in 15 min. The proposed IC method was successfully applied to the determination of these cations in various natural water samples.