Novel application of the X-ray fluorescence method for the determination of FeO content for reference materials characterization

Novel X-ray fluorescence technique is applied for determination of ferrous iron (FeO) content for reference material characterization in addition (or as alternative) to volumetric method. Approach is based on the dependence of FeK beta(5) line relative intensity on the iron valence state. A set of 99 reference materials was studied to choose optimal calibration set containing rocks of different composition: ultrabasic, basic, intermediate, and acid igneous rocks, silicate sedimentary and metamorphic rocks. The ratio of FeK beta(5) and FeK beta(1,3) lines intensities was chosen as analytical parameter. A set of 40 GeoPT samples was analyzed, and it was shown that the uncertainty of proposed X-ray fluorescence technique is comparable to one of certified volumetric (potassium dichromate titration) technique for the samples with Fe2O3tot content more than 1 wt%. The presence of Sr and Co in usual for rocks content (up to similar to 0.23 wt% and similar to 200 mu g/g respectively) does not affect to the measurement uncertainty. Analytical potential, limitations and features of proposed technique are discussed.