Kinetic spectrophotometric determination of iron oxidation states in geological materials

Summary A kinetic spectrophotometric approach is applied to the determination of iron oxidation states in geological materials. Silicate rock samples were sealed in a Teflon vial under argon atmosphere and were decomposed with a mixture of hydrofluoric acid and sulphuric acid by the microwave digestion technique. The absorbance of iron(III)-Tiron complex was followed at 560 nm and the absorbance/time relation was analyzed by non-linear least squares fitting. The FeO and Fe₂O₃ determinations in silicate rocks by the proposed kinetic method agree with those done by the static o-phenanthroline method. The analytical results for standard igneous rock samples are compared with published data.