Ion exchange chromatography coupled to inductively coupled plasma mass spectrometry for the study of Pt electro-dissolution

• Pt species are generated by the electro-dissolution of a Pt electrode in 0.5 M H2SO4.
• These species are neutral or cationic and cannot be separated by anion chromatography.
• Conversion of the species to chloro-complexes using 0.1 M KCl enabled their separation.
• Chloro-aqua complexes were observed in addition to predominant PtCl42− and PtCl62−.
• At least 80% of Pt was present as Pt(II) in samples generated by cyclic voltammetry.

There is an ongoing debate regarding the mechanism of Pt electrochemical dissolution. However, only off-line methods have so far been used, where separation of Pt species is performed separately from their detection. In this study, ion exchange chromatography coupled to inductively coupled plasma mass spectrometry was used for the first time to separate and detect Pt species generated by the electro-dissolution of a Pt electrode in 0.5 M aqueous H2SO4 solution. Because these species are either neutral or cationic, they were converted to chloro-complexes using 0.1 M KCl to enable their separation by anion exchange chromatography. Chloro-aqua complexes were observed in addition to the two predominant species, namely PtCl42− and PtCl62−. A good linear relationship was observed between the sum of peak areas for all complexes of a given Pt oxidation state and the Pt concentration, with a detection limit of 0.1 μg L−1 being reached for Pt(II) and Pt(IV). Application of this speciation analysis method to real samples generated by potential cycling using cyclic voltammetry (CV) revealed that, in general, at least 80% of Pt was present as Pt(II), irrespectively of the cyclic potential range or of temperature (up to 60 °C). Still, quantitative spike recovery was achieved after adding known amounts of Pt(II) or Pt(IV) to a sample prepared by CV, which demonstrated that no significant species inter-conversion took place.

The formation of chloro-complexes allows separation of the different Pt species in the electrolyte by anion exchange chromatography and reveals that Pt(II) is the predominant form.Figure optionsDownload as PowerPoint slide