Uncertainty and traceability in alloy analysis by borate fusion and XRF

Owing to the increasing demand for compliance with quality system standards, analytical laboratories may need to demonstrate the traceability of their results to the International System of Units (SI) or to the values of a certified reference material. To do that, they need to demonstrate the components of uncertainty in their analytical work. At NIST, the goal is to demonstrate traceability to SI units to ensure that results are accepted on a worldwide basis. For XRF spectrometry with borate fusion, traceability to SI is achieved through calibration with spectrometric solution standards or high‐purity compounds. The method is capable of achieving relative expanded uncertainty estimates (95% confidence level) of 1% or lower. In this paper, the capability is demonstrated for low alloy‐steel and an Al? Ti? Nb? W aerospace alloy. XRF results are compared with certified values and with results from atomic emission methods through a simple bias test. NIST uses the borate fusion/XRF method as part of the value assignment process for Standard Reference Materials^®. Copyright © 2004 John Wiley & Sons, Ltd.