The identity of a material that is intended to replace an established reference substance of the same molecular constitution may be verified by means of tests that are capable of demonstrating that the characteristic properties of the two specimens are identical. For this purpose, a comparison of their infrared absorption spectra often suffices. Similarly, where a newly proposed reference substance consists of a compound whose structure has been satisfactorily elucidated, its identity may be confirmed by matching the infrared spectra of the material and of an authentic compound. Other highly specific techniques, such as nuclear magnetic resonance spectroscopy, mass spectrometry, or X-ray diffraction crystallography, may also be used for such comparisons.
However, where no authentic specimen of the proposed reference substance is available for comparison and definitive data about its properties are lacking, it may be necessary to verify the identity of the material by applying several analytical techniques currently used to characterize new compounds. Such analytical methods may include elemental analyses, crystallographic studies, mass spectrometry, nuclear magnetic resonance spectroscopy, functional group analyses, infrared spectrophotometry, and ultraviolet spectrophotometry, as well as such other supplementary tests as are necessary and sufficient to establish that the proposed reference material is the required substance.