Low-blank digestion of geological samples for platinum-group element analysis using a modified Carius Tube design

Abstract

We have developed a modified Carius Tube design that permits the low-blank digestion of geological samples prior to platinum-group element analysis. The new Carius Tubes incorporate a liner of high-purity quartz glass that retains the sample and acids during the digestion procedure. This dramatically reduces the comparatively high Pt blank associated with dissolutions in conventional Carius Tubes. Using the new Carius Tube design we are able to achieve total procedural blanks for the determination of the PGE in geological samples that are at the 1-15 pg/g level for Ru, Pd, Ir and Pt. This constitutes a reduction of blank values by a factor of ~10-100 compared to standard NiS fire assay sample preparation techniques.

Evaluation of a technique for determining Re and PGEs in geological samples by ICP-MS coupled with a modified Carius tube digestion

“…This is because the abundance of 99 Ru is relatively low (12.7%), making it difficult to obtain good precision in Ru analysis with our instrument even if Ru recovery is 100%. Rehkämper et al (1998) used only 12 ml of aqua regia to dissolve 10 g of silicate sample after a HF desilicification to remove silica. Using HF to remove silica can increase the sample mass and reduce the amount of aqua regia used, but the desilicification can possibly increase the procedural blanks, and makes the procedure more complicated, especially for transferring the residue to a Carius tube.…”

“…The determination of PGEs in geological materials is difficult because of their low abundance and heterogeneous distributions and the complexity of sample preparation. Methods for dissolving geological samples and thereby for concentrating PGEs include nickel sulfide (NiS) fire assay coupled with Te coprecipitation (Jackson et al, 1990;Zhou et al, 2001;Gros et al, 2002;Juvonen et al, 2002;Sun and Sun, 2005), acid attack combined with Na 2 O 2 fusion (Morgan and Walker, 1989;Yi and Masuda, 1996;Dai et al, 2001;Qi et al, 2003Qi et al, , 2004, aqua regia dissolution in a sealed Carius tube, and high pressure asher (HPA-S) (Shirey and Walker, 1995;Cohen and Waters, 1996;Rehkämper et al, 1998;Pearson and Woodland, 2000;Brauns, 2001;Meisel et al, 2001Meisel et al, , 2003aMeisel et al, , 2003bPretorius et al, 2003;Meisel and Moser, 2004). The advantages and disadvan-bration between spikes and samples.…”

“…The autoclave is of low cost and easy to maintain. Because methods for PGE pre-concentration and measurement were reported by many papers (Shirey and Walker, 1995;Birck et al, 1997;Rehkämper et al, 1998;Pearson and Woodland, 2000;Meisel et al, 2001;Jensen et al, 2003;Pretorius et al, 2003), we focus on the efficiency of this modified technique for digesting geological samples at different temperature.…”

Sample Digestion Methods for the Determination of Traces of Precious Metals by Spectrometric Techniques

“…98 Highly efficient acid (HNO3, HCl) digestion procedures for various types of rocks including silicates and sulfides (0.1 -5 g samples) have been developed using a Carius tube design. [99][100][101][102] In the Carius design, an acid treatment is accomplished in a sealed thick-walled Pyrex tube at high temperature (240˚C) and elevated pressure for ∼12 h. 99 High efficiency in leaching analytes and low procedural blanks have been achieved. A modified Carius design incorporating a liner of high-purity quartz glass inside the outer borosilicate shell allowed a reduction of the blank values by a factor of 10 -100, as compared with the standard NiS-FA sample-preparation technique.…”

“…A modified Carius design incorporating a liner of high-purity quartz glass inside the outer borosilicate shell allowed a reduction of the blank values by a factor of 10 -100, as compared with the standard NiS-FA sample-preparation technique. 101 A preliminary desilification procedure with HF is usually added to the sample-preparation step for examining materials with silicate matrices.…”