Cation chromatography with sequential suppression enables the determination of cations in their hydrogen carbonate form. The eluent – usually nitric acid – is converted into carbonic acid. Following its decomposition into carbon dioxide and water, the former is continuously removed by the CO2 suppressor. The reduction of baseline noise thus achieved permits the lowering of the detection limits and improves reproducibility, even at very low cation concentrations. This Note shows the reproducibilities determined for cation concentrations of 10 µg/L.