A new method was developed for the high precision measurement of Rb, Sr, Ba, and Pb concentrations in silicate rocks. This method is based on the combined use of isotope dilution and ICP quadrupole mass spectrometry, with matrix element removal. The concomitant separation of the analytes is achieved by extraction chromatography (Ba, Sr, Pb) and inorganic cation exchange chromatography (Rb), on two small tandem columns filled with 0.1 ml of ''Sr resin'' and 1 ml of zirconium (or titanium) phosphate, respectively. Compared to previous separation schemes based on cation-and anion-exchange, this method allows the rapid, concomitant isolation of four trace elements of great interest in geochemistry, with a greatly reduced volume of reagents. The capabilities of the method in terms of precision (equal to or better than 1% RSD) and accuracy are demonstrated by duplicate analyses of four international reference materials (BIR-1, BHVO-1, AGV-1 and RGM-1, from the US Geological Survey) representative of various silicate rock bulk compositions and spanning a large range (0.2-1000 mg g 21 ) of analyte concentrations.
Experimental InstrumentationA quadrupole ICP-MS instrument (PlasmaQuad 21, VG Elemental, Winsford, UK) was used in the semi-quantitative
A simple method is described for the determination of lanthanides in depleted rocks based on acid dissolution, cation‐exchange chromatography and ICP‐MS analysis using a low flow, microconcentric nebuliser. The potential of the method is evaluated by analysis in triplicate of eleven low‐concentration level geochemical reference materials (UB‐N, NIM‐D, BIR‐1, DNC‐1, JB‐2, JGb‐1, JGb‐2, NIM‐N, NIM‐P, FK‐N and MA‐N). The repeatability of the three dissolutions is between 0.2% and 0.6% relative standard deviation (RSD) for basaltic samples BIR‐1 and JB‐2, with the exception of La in BIR‐1 (2.6% RSD), presumably because of blank or memory effects. The results are more scattered for coarsegrained rocks. A good agreement between the results and working values is observed for most mafic samples and the serpentinite UB‐N. Significant deviations observed between the data obtained in this work and working values for some reference materials might reflect heterogeneities of the REE distributions in coarse‐grained (especially granitic) rocks at the 10 0 mg sub‐sampling scale.
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