Fluorine mapping via LA-ICP-MS/MS: a proof of concept for biological and geological specimens

Fluorine (F) plays an important role in biology and geology but is hard to analyse and quantify using element-specific techniques. This is related to its high first ionisation potential and analytical methods depending on high energy sources for excitation and/or ionisation of F. In particular ICP-MS was initially found incapable of detecting F; however, recent methodological advances, i.e., the application of Ba as a plasma modifier and the application of tandem mass spectrometry, enabled its analysis by targeting BaF⁺. In this study, we suggest this approach in conjunction with laser ablation to perform the mapping of F in both biological and geological samples. In a proof of concept, tooth samples as biological samples and a Rhynie chert as a geological sample were analysed. For method development and to evaluate the performance of the developed method, gelatine-based F-standards were prepared and characterised using combustion ion chromatography. Standards were further interrogated to estimate LODs and LOQs. Depending on the required spatial resolution, figures of merit in the upper ng g⁻¹ range and lower μg g⁻¹ range were achievable. This is the first example of F mapping using LA-ICP-MS instrumentation and the developed methods close an important analytical gap by enabling the spatially resolved F analysis at relevant biological and geological concentrations.