Calcium, Na, K and Mg Concentrations in Seawater by Inductively Coupled Plasma-Atomic Emission Spectrometry: Applications to IAPSO Seawater Reference Material, Hydrothermal Fluids and Synthetic Seawater Solutions

We report a measurement procedure to determine simultaneously the major cation concentrations (Na, Ca, K and Mg) of seawater-derived solutions by inductively coupled plasma-atomic emission spectrometry. The best results were obtained when the IAPSO (‘standard’) seawater reference material was diluted by thirty times with Milli-Q® water. We obtained an average reference value rK (the ratio of the mass fraction of potassium to that of chlorine, i.e., (g kg−1)/(g kg−1)) for IAPSO seawater of 0.0205 ± 0.0006 (2.9% RSD), not significantly different from 0.0206 ± 0.0005 (2.4% RSD) for seawater composition reported in the literature. The measured Na, Ca and Mg concentrations correspond to rNa, rCa and rMg values of 0.5406 ± 0.0026 (0.5% RSD), 0.02192 ± 0.00048 (2.2% RSD) and 0.06830 ± 0.00047 (0.7% RSD), respectively, in line with previous values measured by wet-chemistry and atomic absorption spectrophotometry or wet-chemical titration. Our measurement procedure was used successfully on synthetic seawater solutions and high-temperature hydrothermal fluids.