Rapid determination of 26 elements in iron meteorites using matrix removal and membrane desolvating quadrupole ICP-MS

Abstract

We describe a rapid and simple method for determination of major and trace elements ranging in concentration from the percent to the parts per billion level in bulk iron meteorites using a quadrupole inductively coupled plasma mass spectrometer (ICP-MS) operated in solution mode. Contamination of samples during the cutting process is avoided by using a laser to cut samples to an appropriate size. Polyatomic interferences derived from the sample matrix, solvents, and Ar gas are reduced using a membrane desolvation sample introduction system. Interferences derived from the iron-rich sample matrix, in particular interferences of iron oxides with isotopes of Ge, are further reduced by removal of Fe from the sample solution using ion exchange prior to measurement. This method allows the precise and accurate measurement of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Ru, Rh, Pd, Cd, In, Sn, Sb, Te, W, Re, Os, Ir, Pt and Au in iron meteorites. After Fe removal, Ge can be accurately measured in IVA and IVB type iron meteorites having Fe/Ge ratios as high as 10⁷, with negligible interference from FeO. Samples subjected to the ion-exchange procedure can be measured at a 10 times lower dilution factor, and as a result, it may also be possible to measure the concentrations of those elements which are preferentially partitioned into the silicate mantle of asteroids, and are therefore present in iron meteorites at sub-ppm concentrations.