Homogeneity of the Geochemical Reference Material BRP‐1 (Paraná Basin Basalt) and Assessment of Minimum Mass

Abstract

Reference materials (RM) are required for quantitative analyses and their successful use is associated with the degree of homogeneity, and the traceability and confidence limits of the values established by characterisation. During the production of a RM, the chemical characterisation can only commence after it has been demonstrated that the material has the required level of homogeneity. Here we describe the preparation of BRP‐1, a proposed geochemical reference material, and the results of the tests to evaluate its degree of homogeneity between and within bottles. BRP‐1 is the first of two geochemical RM being produced by Brazilian institutions in collaboration with the United States Geological Survey (USGS) and the International Association of Geoanalysts (IAG). Two test portions of twenty bottles of BRP‐1 were analysed by wavelength dispersive‐XRF spectrometry and major, minor and eighteen trace elements were determined. The results show that for most of the investigated elements, the units of BRP‐1 were homogeneous at conditions approximately three times more rigorous than those strived for by the test of “sufficient homogeneity”. Furthermore, the within bottle homogeneity of BRP‐1 was evaluated using small beam (1 mm2) synchrotron radiation XRF spectrometry and, for comparison, the USGS reference materials BCR‐2 and GSP‐2 were also evaluated. From our data, it has been possible to assign representative minimum masses for some major constituents (1 mg) and for some trace elements (1‐13 mg), except Zr in GSP‐2, for which test portions of 74 mg are recommended.

Flux‐Free Fusion of Silicate Rock Preceding Acid Digestion for ICP‐MS Bulk Analysis

“…The results we achieved with our method also indicate complete digestion of zircon and high recoveries of trace elements, as confirmed by the digestion of JG‐3 (Figure 2). Thus, these differences may reflect sample heterogeneity caused by different element concentrations for different bottles of RM (Cotta et al. 2007).…”

An Automated Iridium-Strip Heater for LA-ICP-MS Bulk Analysis of Geological Samples

“…Published analytical data and sample information of these samples can be found in the GeoReM database. BRP-1 is a new basaltic reference material (Cotta et al 2007), for which few analytical data are yet available. In addition, we have also analy sed ocean island basalts from Lanai (Hawaii), which were collected by A.W.…”

“…To demonstrate the reliability of the LA-ICP-MS whole-rock fusion technique for the trace element analysis of silicate samples with SiO 2 contents ranging from 47% m/m to 59% m/m, we analysed several international reference materials (Table 4) including the poorly analysed reference material BM and the new homogenous (Cotta et al 2007) basaltic reference material BRP-1 (Table 5), for which reference values will soon be available. With the exception of some siderophile/chalcophile elements (e.g., Cu, Mo, W, Ni), the precision (1 RSD) was about 2-3%.…”

“…To establish a well-characterised Brazilian basaltic reference material, Cotta et al (2007) prepared BRP-1, which was collected from the Cretaceous Paraná Province. The analysis of test portions showed that this material has a homogeneous composition for most elements.…”

“…The analysis of test portions showed that this material has a homogeneous composition for most elements. Representative minimum test sizes were 1 mg for major and 1-15 mg for trace elements (Cotta et al 2007). …”