Abstract
A procedure is presented whereby the fossil fuel community may design andmix SRMs in different proportions and thereby produce in their laboratorystandards for sulfur in distillate fuel oil, residual fuel oil, and coal ofalmost any desired concentration with uncertainties that are calculable andtraceable to NIST SRM certified values. The expanded uncertainty, U, of abinary blend is always less than the U of the component with the largest uncertainty,and in some cases it is less than either of the SRM components. Because thesulfur content of all fossil fuel SRMs was certified at NIST with high accuracyand precision by isotope dilution thermal ionization mass spectrometry, inalmost all cases the total expanded uncertainties of the standards producedfrom binary mixtures are an order of magnitude smaller than the reproducibilityof current methods used in commercial laboratories. The use of this methodgives the SRM user a continuum of concentrations available for calibrantsand quality control test samples. Unlike calibrants prepared from high puritycomponents, this method enables the SRM user to create a customized seriesof calibrants in the fossil fuel matrix of interest. This should reduce oreliminate biases that result from differences in matrix composition amongstandards and unknowns.
Published Version
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