NIST SRM 610, 611 and SRM 612, 613 Multi-Element Glasses: Constraints from Element Abundance Ratios Measured by Microprobe Techniques

The SRM 600 series of glasses, SRM 611 to SRM 619, which nominally contain 500 (SRM 610, 611), 50 (SRM 612, 613), 1 (SRM 614, 615) and 0.02 (SRM 616, 617) μg g⁻¹ of sixty one elements are now being extensively used as microprobe standards. Recent compilations of the trace element concentrations, which include many new multi-element bulk analyses, do not all give the same value within the stated uncertainty; this observation appears to raise questions about the degree of homogeneity on a microscale reported from probe measurements. The ion microprobe cannot give absolute concentrations, but can accurately measure the abundance ratios between glasses of similar major element chemistry. Recent and new probe measurements show that, although the absolute concentrations are significantly lower than the nominal values, the average dilution factors are 12 : 1 : 0.02 : 0.0004 and close to weighed amounts. The consistency between the ratios of random samples of glasses (SRM 610/SRM 612 and SRM 611/SRM 613) strongly supports a high degree of homogeneity on all scales. The measured abundance ratios between two glasses can, therefore, act as a useful check on bulk measurement accuracy. A clear correlation in the SRM 610, 611/SRM 612, 613 ratios measured by ion probe and SRM 612 trace concentrations measured by bulk techniques demonstrates that SRM 610, 611 has a much more uniform trace content than SRM 612, 613.     

New ID-TIMS, ICP-MS and SIMS Data on the Trace Element Composition and Homogeneity of NIST Certified Reference Material SRM 610-611

We present new concentration data for twenty four lithophile trace elements in NIST certified reference material glasses SRM 610-SRM 611 in support of their use in microanalytical techniques. The data were obtained by solution ICP-MS and isotope dilution TIMS analysis of two different sample wafers. An overall assessment of these new results, also taking into account ion probe studies that have been published in the literature, shows that these wafers can be considered to be homogeneous. Therefore, individually analysed wafers are believed to be representative of the entire batch of the SRM 610-611 glasses. Possible exceptions are the alkali metals (and a few volatile or non-lithophile trace elements). The analysed concentrations range between 370 μg g⁻¹ (Cs) and 500 μg g⁻¹ (Sr) and agree well with published values. On the basis of our new data and data recently published in the literature we propose "preferred average" values for the elements studied. These values are, within a few percent, identical to those proposed by other workers.