Impurities evaluation

Ahuja, S, Impurities Evaluation of Pharmaceuticals, Marcel Dekker, New York, 1988. 

An overview of impurity evaluations of drug substances and products by HPLC is given in this chapter, from regulatory and laboratory viewpoints. 

Impurity testing is pivotal in pharmaceutical development to establish drug safety and quality. In this chapter, an overview of impurity evaluations of drug substances and products by HPLC is presented from both the laboratory and regulatory standpoints. Concepts from the development of impurity profiles to the final establishment of public specifications are described. Useful strategies in the identification and quantification of impurities and degradants are summarized with practical examples to illustrate impurity method development. 

HPLC applications assays, impurity evaluation, dissolution testing, cleaning validation, high-throughput screening, and chiral separations (Chapters 13-18). 

Nowadays, the pharmacopoeias make use of chromatographic methods and try to replace less sensitive TLC methods with HPLC tests. However, CE methods are rarely used even though they can at times he more useful than HPLC for determining the impurity evaluation of a drug (Chapter 11). CE is currently used, especially in the case of peptides and proteins, in the EP and the USP. These methods and perspectives for new applications are given in the same Chapter. 

IV. ROLE OF DRUG MASTER FILES (DMF)—TYPE II AND IMPURITIES EVALUATION... 

Determination of the catalytic activity of the hydroxyl ion is difficult, because the mutarotation becomes too rapid for accurate measurement when the concentration of hydroxyl ions rises above 10 /unolar. With a minute concentration of hydrogen ions, accurate measurements require rigorous exclusion of carbon dioxide and other impurities. Evaluation of the rate constant is also complicated by ionization of the sugar, a subject that was not considered by the early workers. 

Ahuja S (1998) Impurity Evaluation of Pharmaceuticals. New York Dekker. 

It would be difficult to survey all possible and existing applications of DSC, which is one the most commonly, used calorimetric methods. Among these, we can mention the determination of impurities, evaluation of phase transformations of the first and second orders, detennination of heat capacities and heat conductivities, reaction kinetics, study of metastable states and glasses, determination of water clusters, thermal energy storage, etc.. 

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