In 2018, both the US and European Regulatory Authorities initiated a recall of contaminated batches of sartan medicines due to the presence of carcinogenic nitrosamine impurities. Two compounds containing a nitroso group have received particular attention: NDMA and NDEA. Nitrosamines pose a risk of cancer in humans, so one of the key steps in prevention has been the development of a sufficiently sensitive and selective analytical method. For most methods found in literature, no more than two nitrosamines are simultaneously detected, or the methods are suitable just for the analysis of a particular sartan substance in medicines. Therefore, the main objective of our thesis was to develop a sufficiently sensitive method for simultaneous quantification of five nitrosamines (NDMA, NMBA, NDEA, NEIPA and NDIPA) in selected sartan medicines. As the method for the detection of nitrosamines by LC-MS/MS has been previously developed we focused on optimizing the sample preparation procedure to reduce the matrix effect. We have examined the influence of the extraction solvent, injection volume and the ion source (ESI and APCI) on the matrix effect. The lowest matrix effect (90–110 %) and highest recovery (90–110 %) with good reproducibility (RSD ˂ 5 %) were obtained by extracting the nitrosamines with 20 % methanol in water and using APCI ion source. Along with reduced matrix effect also improved sensitivity and reproducibility of the method was achieved. The method was validated and proved to be selective, linear, accurate and reproducible. The limit of quantification for the selected nitrosamines is in the concentration range between 0.08 µg/L and 0.61 µg/L. The method was then applied to real samples and tested for the presence of nitrosamine impurities in selected sartan-containing medicines present on the Slovenian market. The analysis of the six selected pharmaceuticals did not detect nitrosamines, which was expected as Authorities demand from the drug manufacturers the use of appropriate control strategies to prevent or minimize the nitrosamine presence. The results showed that our method enables the detection of all tested nitrosamines in selected medicines at the regulatory level. In addition, the method is capable to quantify the selected nitrosamines in medicines, only NDEA and NEIPA are slightly below the limit of quantification in certain cases. Compared to other methods in the literature, the proposed method enables simultaneous quantification of five nitrosamines in medicines containing mono active ingredient from the sartan group. An advantage is also the method sensitivity, which could be further improved by the adjusted sample preparation and LC-MS/MS analysis.
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