Determination of zirconium, niobium, hafnium and tantalum at ng g(-1) levels in geological materials by direct nebulisation of sample HF solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and T a (denoted as HFSE) in geological samples by inductively coupled plasma-mas s spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE copr ecipitated with insoluble Mg and Ca fluoride residues formed during the ini tial HF attack. This HF solution was directly nebulized into an ICP mass sp ectrometer. An external calibration curve method and an isotope dilution me thod (ID) were applied for the determination of Nb and Ta, and of Zr and Hf , respectively. Recovery yields of HFSE were, 96% for peridotite, basalt an d andesite compositions, apart from Zr and Hf for peridotite (, 85%). No ma trix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 a nd 0.1 ng g(-1) for Zr, Nb, Hf and Ta, respectively. This technique require d only 0.1 mi of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mi neral separates. We also present newly determined data for the Zr, Nb, Hf a nd Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR -1, BHVO-1 and AGV-I, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3 , and the Smithsonian reference Allende powder.