KINETIC SPECTROPHOTOMETRIC DETERMINATION OF IRON OXIDATION-STATES IN GEOLOGICAL-MATERIALS

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 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.