Combining accuracy and precision of traceable standards to estimate uncertainties in trace element content measurements

The accuracy and precision systematic of traceable certified reference material (CRM) standards can be combined to estimate the uncertainties that are achieved in analytical measurements. Standards (CRMs or other well characterized materials) in matrices similar to the unknown sample can be used for evaluation of the accuracy. The standards should be prepared following same preparation steps as the unknown samples and analyzed in the same analytical sequence as the samples using similar instrumental methods. The accuracy and precision of these quality control (QC) standards are combined to calculate uncertainty estimates for trace element contents. The uncertainties calculated from the QC standards are compared with those estimated following the guide to expression of uncertainty in measurements (GUM). For trace element content measurements using ICP-AES and ICP-MS instruments, the uncertainty estimates obtained by combining the accuracy and precision of the QC standards are found to be more conservative than those calculated by a model following GUM methodology. LA-UR-17-31180.