High-speed ion chromatographic separation of cations at elevated temperature

The application of temperatures up to 90 degrees C for high-speed cation separations by ion chromatography is investigated. A Dionex CS12A column (150 x 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 degrees C. Nevertheless at 60 degrees 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.