High precision measurement of iron isotopes by plasma source mass spectrometry

Multiple-collector inductively coupled plasma mass spectrometry has been us ed for the precise measurement of natural variations in the isotopic compos ition of Fe. The contributions of Ar-O and Ar-N molecular species to the ma ss spectrum in the Fe mass region are minimised and the repeatability of th e Fe-57/Fe-54 ratio of a sample Fe solution relative to the IRMM-14 Fe isot ope 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 deviatio ns in parts per 10(4) from the same ratio in the IRMM-14 Fe isotope referen ce standard. Measurements of epsilon(57)Fe are presented for samples of met eoritic iron and terrestrial Fe-oxides and carbonates. (C) 2000 Elsevier Sc ience B.V.