In the present work the degradation of chloroplatinates emitted into the aquatic environment has been investigated in model studies. CE coupled to inductively coupled plasma sector field MS (ICP-SFMS) was employed as an analytical method of measurement. The CE-ICP-MS interface utilized the functional make-up flow design with a microconcentric nebulizer. [Pt(Cl(4))](2-) and [Pt(Cl(6))](2-) were separated within 5 min. During a measurement period of 6 h an excellent reproducibility of migration times (RSD 2.3%) could be achieved. The high sensitivity of ICP-SFMS resulted in an LOD of 80 ng/L platinum for the two compounds. External calibration using rhenium as internal standard was linear over three orders of magnitude. However, with external calibration a long-term drift of signal intensity was observed. In order to reduce the uncertainty of the obtained results, quantification of [PtCl(6)](2-) was performed for the first time by species-specific on-line isotope dilution MS using (194)[PtCl(6)](2-) as spike. The two different quantification strategies were compared in terms of their total combined uncertainty of measurement according to the EURACHEM guideline. The method was employed for monitoring the time-dependent degradation of [Pt(Cl(4))](2-) and [Pt(Cl(6))](2-) in water containing 0 and 2.8 mmol/L Cl(-) and river water. [Pt(Cl(6))](2-) was stable whereas [Pt(Cl(4))](2-) showed rapid degradation following pseudo first-order kinetics.