Rationale

3.2.8.1 Discussion—A check standard is preferably a material that is either a certified reference material with traceability to a nationally recognized body or a material that has an accepted reference value established through an interlaboratory testing program that is open to and has diversified representation from different organizations. Interlaboratory testing performed by laboratories within a single parent organization may share sources of bias and/or variability that negatively impact the accuracy of the ARV or the standard error of the ARV. Therefore, materials tested in such programs should not be used as check standards. For some measurement systems, a pure, single component material having known value or a simple gravimetric or volumetric mixture of pure components having calculable value may serve as a check standard. Users should be aware that for measurement systems that show matrix dependencies, accuracy determined from pure compounds or simple mixtures may not be representative of that achieved on actual samples