[en] Adjustment of the formic acid concentration results in the separation of sodium from cesium during the elution of CS-100. As the formic acid concentration decreases from 2M to 0.1M, sodium elutes progressively earlier with respect to cesium. At 0.1M formic acid the two peaks are about 95% resolved. The total volume of elutriant required to elute all the cesium doubles in going from 2M to 0.1M formic acid. This could result in a 19% increase in total cycle time, assuming present TDS specified flows are maintained. Continuous monitoring of either conductivity or pH can be used to detect completion of the sodium elution