(1997; 248 pages) [French]
3. Chemical and physical methods used in evaluating reference substances
The methods used to establish a proposed material fall into two broad groups: those intended primarily to identify the material and those to establish the purity. With most methods, the percentage purity of a reference substance cannot be expressed as an absolute value it the impurities have not been identified. In such instances, the quoted purity is an estimate based upon the data obtained by use of the various analytical methods employed to establish the purity of the reference substance.