Ion chromatographic behavior of alkali and alkaline earth metal cations on silica gel columns with cation exchange characteristics

Ion chromatographic behavior of alkali metal cations and ammonium ion on various unmodified silica gel columns by elution with 2 mM nitric acid (pH 2.7) was investigated. As a result it was found that one silica gel (Develosil 30-5) column acted as a cation exchange column under acidic eluent conditions and an excellent separation of these cations was achieved. Therefore, in order to produce silica gel, which acts as a cation exchanger for ion chromatography under strongly acidic conditions, the main cause of the cation exchange characteristics of the Develosil 30-5 silica gel was investigated. As a result it was found that the main cause could be attributed to aluminium present as an impurity in the silica gel. This finding suggests that the modification of silica gel with aluminium is very useful for the production of new advanced silica-based cation exchangers for ion chromatography.