X-Ray Spectrometric Analysis of Trace Elements in Rocks. Correction for Instrumental Interferences+

- Investigating trace element determination in rocks and taking into account possible instrumental inter-ferences, it is shown that the general relationship between I (net peak intensity) and (. (fluorescent elemeiit concentration) is (I- I,)M = Ac + B where M is the matrix effect correction factor and A is a constant proportional to the eff iciency of excitation; B and Io correspond to the intensities due to, respec tively, the scattering (especially, by the sample) of any instrumental interferhg radiation. and a possible stray emi.sision by the instrument itself. Using this equation under optimized conditions allows interferences as high as 200 ppm (if expressed in equivalent concentration) to be compensated without any significant decrease regarding the general accuracy of determinations.-In geochemistry, we often need accurate measurement of trace elements on a large number of samples, for example in order to study magmatic processes such as crystallization or partial melting. Though accuracy and large series are rarely compatible, it appears that they can yet be reconciled when using X-ray fluorescence spectrometry. Then the first point to be considered is the necessary correction for matri