High‐precision Determination of Gold Mass Fractions in Geological Reference Materials by Internal Standardisation

摘要

pDetermination of gold abundances in natural rock is critical for applications, but very challenging. Here, we report a method for determining gold with a very low mass fraction ( 0.01 ng gsup−1/sup) in rocks. The method involves Carius tube digestion with reverse iaqua regia/i, chromatographic separation to remove most of the sample matrix and measurement by high‐sensitivity fcICP/fc‐fcMS/fc. The mono‐isotopic element gold was quantified by external calibration using an internal standardisation of gold to platinum that was precisely determined by isotope dilution. The method is robust and the obtained results are indistinguishable ( 5–10%, 2is/i) from those independently obtained by a standard addition technique on the same solution. The results from reference materials fcTDB/fc‐1 and fcGP/fct‐2 are consistent with the certified values and those determined by fcHF/fc‐iaqua regia/i digestion, confirming the validity of the method. fcTDB/fc‐1 (in = /i20), fcGP/fct‐2 (in = /i6), fcBHVO/fc‐2 (in = /i9) and other mafic fcRM/fcs are homogenous for gold (10–20%, 2is/i) at the 2 g test portion level; however, sample heterogeneity affects some fcRM/fcs. Gold and platinum‐group elements also display different extents of sample heterogeneity for different fcRM/fcs. Given the homogeneity observed for fcTDB/fc‐1, fcGP/fct‐2 and fcBHOV/fc‐2, they are recommended as well‐suited fcRM/fcs for inter‐laboratory comparison studies of gold./ptitleKey Points/titleplistlistItemA high‐precision, low‐blank method is established to determine gold mass fractions in rock reference materials./listItemlistItemInternal standardization is simple and robust for the determination of gold and achieves results indistinguishable ( 5–10%, 2is/i) from those by standard addition./listItemlistItemTDB‐1, GPt‐2 and BHVO‐2 are homogenous in gold mass fractions and suitable for inter‐laboratory comparison./listItem/listblockFixedmediaResourceGroupmediaResource/mediaResource/mediaResourceGroup/blockFixed/p