High precision measurement of iron isotopes by plasma source mass spectrometry

Multiple-collector inductively coupled plasma mass spectrometry has been used for the precise measurement of natural variations in the isotopic composition of Fe. The contributions of Ar-O and Ar-N molecular species to the mass spectrum in the Fe mass region are minimised and the repeatability of the Fe-57/Fe-54 ratio of a sample Fe solution relative to the IRMM-14 Fe isotope standard is better than 100 ppm at 95% confidence. Variations in sample Fe-57/Fe-54 ratio are expressed as epsilon(57)Fe units, which are deviations in parts per 10(4) from the same ratio in the IRMM-14 Fe isotope reference standard. Measurements of epsilon(57)Fe are presented for samples of meteoritic iron and terrestrial Fe-oxides and carbonates. (C) 2000 Elsevier Science B.V.