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Determining the attributes of any analytical method or comparing methods is best carried out using an actual sample of known composition. When this is lacking, a standard reference material, that is, an appropriate material of reliably known composition which is generally available, may be substituted.
An ASTM Committee E-37 task force recognized the need for a set of thermal purity standard reference materials, chose the phenacetin-aminobenzoic acid system, and, in a collaborative study, showed the viability of a set of standards over the 100 to 98.5 mol % purity range. As an outgrowth of this, quantities of materials sufficient for distribution by the National Bureau of Standards (NBS) and covering a wider impurity range, were prepared. The mixtures were then assayed by independent analysts employing different methods and at various times. Concordant results proved the composition and showed each mixture to be stable and homogeneous.
The NBS is now in the process of evaluating the set of mixtures for designation as Standard Reference Materials.
thermal purity analysis, purity reference materials
Assistant director, Quality Control Department, Hoffmann-La Roche Inc., Nutley, NJ