Traceability of Chemical Measurements
The terms "traceability" and "traceable to national standards maintained by National Bureau of Standards (NBS) and even "traceable to NBS" are receiving increasing usage. While chemical measurements are usually more complex than physical measurements, the concept of traceability is essentially similar. Chemical properties are measured with reference to those of known chemical standards. The analyst who prepares standards for her/his own use has the responsibility for their accuracy and for all traceability considerations involved. Obviously, only chemical constituents of requisite and documented purity should be used. When used by others to prepare standards, additional uncertainties may be introduced that must be evaluated by the preparer. The physical standards such as volumetric apparatus and masses, commonly used in preparing chemical standards, are available from vendors. The producer of reference materials has the responsibility for the appropriateness of the Standard Reference Material used for either standardization or quality assurance of the certification process.