Relative Sensitivity Factors of 16O2H relative to 18O in deuterium-implanted spinel-structured oxides

Spinel-structured oxides (hereafter referred to as ‘spinels’) are a group of nominally anhydrous minerals characterized by a wide range of solid solutions. To allow the analysis of hydrogen in spinels by secondary ion mass spectrometry, Relative Sensitivity Factors (RSFs), which are typically matrix-dependent, need to be determined. Anticipating analysis of the OH- dimer rather than the H+ monomer, we present here RSF values of 16O2H relative to 18O for five natural spinels, including franklinite, Fe-bearing spinel, Mg-chromite, magnetite, and jacobsite. The Al2O3 content in the matrix of these crystals ranged from 0.09 wt% to 67.54 wt%. Our data indicate increasing RSF values with increasing Al2O3 content, from 2.76 x 10^20 to 2.72 x 10^21 atoms per cm3, with an RSD for two repeat analyses of about 4.3%. The increase of RSF with Al2O3 follows a second order polynomial form: RSF = 2.27x10^17 Al2O3^2 + 2.05 x10^19 Al2O3 + 3.02 x10^20. Further analyses at other instruments under different analytical conditions will be required to understand how robust the accuracy of these data can be considered. Expanded analyses of the here presented spinels, including depth-profiling, are reported in Zellmer et al. (2025).