A practical wet-chemical framework applicable to high-silica glasses for determining the redox state of cations

Redox equilibria play a central role in glass science, governing the processing efficiency of glass-forming melts, the macroscopic properties of the resulting glasses, and the functionalities of the derived glass-ceramics. Despite their importance, the quantification of redox states remains challenging: robust methodologies are established for a limited number of elements and typically require experimentally demanding procedures. In the present work, two recently developed wet-chemical methods – Quantification of Oxidizing Species (QOS) and Quantification of Reductive Species (QRS) – are extended to silica-rich glass matrices (> 65 mol.%), which are particularly difficult to dissolve and therefore require adapted analytical protocols. The modified quantification procedure, involving hydrofluoric acid and performed under an ambient air atmosphere, preserves the practicality, rapid execution, and precision of the original approaches while relying only on a limited set of readily available reagents, laboratory glassware, and measurement apparatus. Redox states determined for transition-metal-doped SiO 2 -rich glasses (V, Cr, Mn, Fe, Co, Ni, and Cu) are in good agreement with literature data and established predictive models. A detailed step-by-step guide with representative case studies is provided to further facilitate broader adoption of the methods. Taken together, the original and HF-adapted wet-chemical procedures constitute a versatile and operator-friendly toolbox for redox state quantification, across many and diverse redox species-matrix combinations.