Precise Quantitative Determination of Niobium at Low Level Concentrations in Geological Samples by WD‐XRF

Abstract

We show in this paper that wavelength dispersive X‐ray fluorescence spectrometry (WD‐XRF) can provide high quality determinations (in terms of accuracy and precision) of Nb in rocks at low level concentrations comparable with data from much more sensitive analytical techniques. Two different sample preparation methods were investigated and combined with a long count time XRF strategy. We first developed a standard additions procedure for rock powders in conjunction with a careful evaluation of the position of analytical lines (peak and background). The precision (2s) varied from within 0.03 μg g−1 to 0.2 μg g−1 in the 0‐5 μg g−1 concentration range, and the detection limit was 0.2 μg g−1. We then separated Nb from the geological matrix using the chemical procedure described by Rehkämper (1994); after separation, Nb was collected on an anion‐exchange membrane which was directly excited by X‐rays. This method yielded a precision (2s) of 0.2 μg g−1 at the μg g−1 level if 100 mg of sample was used, the detection limit being dependent on the mass of sample studied. Detailed descriptions of analytical procedures are given, particularly of innovative aspects of Nb collection on membranes. XRF results obtained by the two sample preparation methods were compared with instrumental neutron activation (INAA) Ta analysis. We found that the ion‐exchange method tended to provide Nb concentrations which were about 10‐15% lower than concentrations found by the standard additions method. We report data for fifteen international reference materials (NIM‐N, AL‐I, AN‐G, BE‐N, MRG‐1, JA‐1, JB‐2, JB‐3, JA‐2, JF‐1, JGB‐1, BIR‐1, DNC‐1, W‐1, W‐2), for which our XRF results are in good agreement with literature data.

Niobium-Doped Hydroxyapatite Bioceramics: Synthesis, Characterization and In Vitro Cytocompatibility

“…This technique can provide high quality determinations of Nb at low level concentrations ( i.e. , μg g −1 ) comparable with data from more sensitive analytical techniques like ICP-MS (inductively coupled plasma-mass spectrometry) [ 45 ]. Calibration curve was prepared using pure NbCl 5 (Aldrich, St. Louis, MO, USA) as standard and boric acid as diluent.…”

Precise Determination of Rubidium in Geological Reference Materials by ID‐TIMS and WD‐XRF: A Discussion for the Basalt BIR‐1

“…To obtain Rb concentrations, we used the standard additions procedure for rock powders, combined with a long count time XRF strategy. The procedure has already been fully described elsewhere for the precise determination on Nb in rock samples at low level concentration (Etoubleau et al 1999). Briefly, the details of the procedure were as follows.…”

Origin of volcanism on the flanks of the Pacific‐Antarctic ridge between 41°30′S and 52°S

“…All samples (either glasses or rock chips) were washed in an ultrasonic bath of 2M HCl, followed by double distilled water before further crushing in an agate mortar for trace element analysis. Trace element analyses were performed by ICP‐MS at Brest using Finnigan Element2 and following the method described by Barrat et al [1996] and Etoubleau et al [1999]. On the basis of standard measurements and sample duplicates trace element concentrations reproducibility is generally better than 5% [ Barrat et al , 2007].…”