Nitrosamines are genotoxic impurities present all around us; in the air, water, food, cosmetics and, last but not least, medicines. Since 2018, with the emergence of massive recalls of medicines contaminated with nitrosamine impurities, nitrosamines have become regulatory authorities’ major focus. Despite intensive research in this field, no suitable analytical method has yet been developed for efficiently and simultaneously determination of multiple low-molecular-weight nitrosamines in different products. The aim of this master's thesis was therefore to develop a sensitive, selective, accurate and robust method for the simultaneous determination of thirteen low-molecular-weight nitrosamines in different medicinal products from different therapeutic groups. The method is based on sample pre-treatment by solid phase extraction, where several extraction cartridges were considered and the Strata X-C cartridge was found as the most suitable. The extraction process was then optimised, focusing on the selection of the optimal tablet mass and sample loading volume on the cartridge, and on the adjustment of the sample drying parameters in order to concentrate the analytes. Sample pre-treatment was followed by analysis by liquid chromatography coupled to high-performance mass spectrometry. The method has been successfully validated according to the USP chapter on nitrosamine impurities, confirming its excellent linearity, accuracy and precision. The achieved limit of quantitation represents the determination of nitrosamines in a concentration that is less than 45% of the acceptable daily intake limit for all nitrosamines, confirming its sensitivity. The developed analytical method was applied to determine the nitrosamine content in sixteen pharmaceuticals containing one to three active pharmaceutical ingredients with different physicochemical properties. N-nitrosodimethylamine (NDMA) was detected in samples of two medicines containing ranitidine as the active pharmaceutical ingredient that were 43.2- and 58.8-fold higher than the acceptable daily intake of this nitrosamine. This was expected as these were expired samples and it is known that NDMA is formed in the degradation processes of ranitidine, which can be further induced by the presence of nitrite in the drug, resulting in an increase of NDMA content over time. The robustness of the method was further confirmed on several samples of medicines containing different active pharmaceutical ingredients. This demonstrated the suitability of the method for routine quality control of pharmaceuticals, thereby reducing the risk to human health.
|
