High-speed ion chromatographic separation of cations at elevated temperature

The application of temperatures up to 90 °C for high-speed cation separations by ion chromatography is investigated. A Dionex CS12A column (150×3 mm I.D.) and suppressed conductivity detection are used for the separation of Li+, Na+, NH4+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+. Elevated temperatures reduce the viscosity of the eluent, which allows the use of flow-rates up to 1.3 ml/min, which are significantly higher than that typically used (0.5 ml/min). Further, separation efficiencies improved with temperature, even at high flow-rates. However, elevated temperatures decrease the retention of all cations, with the decrease being most pronounced for the strongly retained cations. This limits the optimal column temperature to 60 °C. Nevertheless at 60 °C, the separation of nine cations is accomplished in under 5 min, compared to 12 min under conventional conditions, i.e., 60% reduction in analysis time.