Applications and Potentiality of Electroanalytical Methods for Inorganic Trace Analysis in the Pharmaceutical Industry

Abstract

As the vast majority of the active principles of pharmaceuticals are organic compounds, inorganic analysis* has usually played a minor role in all the analyses performed in the pharmaceutical industry. But during the last few years its importance has steadily grown. The classical task of inorganic analysis was the simple analysis of residues, usually performed by relatively unselective methods. Examples are determination of sulphate ash, or “heavy metal” analysis by the method of sulphide precipitation. Methods such as complexometric titration played a certain role, e.g., in the case of assay determination of inorganic active principles, such as calcium formulations. The rise of the importance of inorganic analysis has various reasons. First of all come certainly safety considerations. These led to the pharmaceutical industry to use analyses which are more specific, selective, and sensitive than the methods prescribed by authorities. Nowadays other factors than safety considerations play an important role, as traces of metals may have an effect on the mechanism of the action of certain compounds (e.g. proteins which are prone to metal — protein interaction), or metals which strongly influence the production process (e.g. catalysis). The case of protein based innovative pharmaceuticals is also a good example to illustrate the change in inorganic analysis. Being up to now a macro trace analysis the amount of sample available for analysis was never an aspect to be considered. The restricted amount of synthesized proteins (milligrams only) necessitate micro scale trace determination.