Eliminating pharmaceutical impurities: Recent advances in detection techniques

The elimination of organic impurities to produce highly pure drug substances is an important goal of process chemistry. For the detection of general impurities, hyphenated techniques (eg, liquid chromatography-mass spectrometry [LC-MS]) play a critical role in rapid structural identification (qualitative detection) and in understanding the mechanisms of formation of the impurities, enabling informed decisions to control and eliminate the impurities resulting from the chemical process where possible. Concern regarding genotoxic impurities (GTIs), which must typically be controlled at low parts-per-million limits, continues to increase, and significant advances have been achieved in recent years for the selective and sensitive quantitation (quantitative detection) of such impurities. Conventional detection techniques, such as ultraviolet (UV) detection, are often inadequate for the detection of potentially minute quantities of GTIs; therefore, various advanced MS-based detection strategies, either stand-alone or in conjunction with chemical approaches, are playing an increasing role in this field. The primary aim of this review is to highlight recent advances in qualitative and quantitative detection of impurities at trace levels, with a particular focus on GTIs.