Fluorine loss determination in bioactive glasses by laser-induced breakdown spectroscopy (LIBS)

Fluoride-containing bioactive glasses and glass-ceramics in the SiO2-P2O5-CaO-CaF2 system are of great interest for dental applications, where the precipitation of fluorapatite supports tooth remineralization. Fluorine quantification in those glasses is key to estimate thermal properties and crystallization tendency. This work presents a study on fluorine determination by laser induced breakdown spectroscopy (LIBS) in four melt-derived glass powders with varying P2O5 concentrations. LIBS enables fluorine quantification with a reduced analysis time, minimal to no sample preparation, and high spatial resolution. The fluorine calibration curve was obtained from CaF2 and SiO2 mixtures as reference samples, and the fluorine loss upon glass melting has been determined as a function of P2O5 content. The P2O5-free glass shows the lowest fluorine loss (13%), with HF volatilization likely being responsible for the loss. By contrast, the glass with the highest P2O5 content (11.33 wt%) exhibits the largest fluorine loss (55%), owing to additional mechanisms involving the volatilization of phosphorus species like POF3.