Ion chromatographic separation of common mono- and divalent cations on silica gel modified with zirconium using tartaric acid-15-crown-5 as eluent Original Research Article

The Zorbax BP-SIL silica gel acted as a cation exchanger under strongly acidic conditions and was successfully applied to ion chromatography with conductimetric detection (IC-CD) for the simultaneous separation of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+, and Ca2+). Therefore, the main cause of the cation-exchange characteristics of the Zorbax BP-SIL silica gel was investigated for the preparation of a newly advanced silica-based cation-exchange stationary phase for IC-CD using strongly acidic eluents. As a result, it was found that the main cause could be attributed to zirconium present as an impurity in the silica matrix. The preparation of silica gel modified with zirconium (Zr-silica) was carried out by the reaction of the silanol group on the surface of silica gel with zirconium butoxide (Zr(OCH2CH2CH2CH3)4) and the Zr-silica prepared was applied to IC-CD for these mono- and divalent cations. Highly sensitive indirect-conductimetric detection and excellently simultaneous separation for these mono- and divalent cations were achieved in 12 min on the Zr-silica column (150 mm×4.6 mm i.d.) using a 5 mM tartaric acid containing 10 mM 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) as eluent.