A comprehensive LC-UHPLC-MS/MS method for the monitoring of N-nitrosamines in lipophilic drugs: A case study with rifampicin

In the last five years, the presence of N-nitrosamines in commonly used medicines has become a significant concern for patients, physicians, and the pharmaceutical industry, due to their carcinogenic properties, even at low concentrations. Analytical methods that enable the unequivocal monitoring of these compounds, with low detection limits and covering a range of drugs, are indispensable. The present work proposes a bidimensional liquid chromatography-tandem mass spectrometry method capable of quantifying eleven N-nitrosamines in lipophilic active pharmaceutical ingredients (APIs). The API is retained in the first chromatographic dimension, while the fraction containing the N-nitrosamines is transferred to the second chromatographic dimension and, after separation, to the mass spectrometer. The logP values for the APIs and N-nitrosamines enabled prediction of the APIs that could be separated from the target analytes. The method was validated and successfully applied for the quantification of 1-methyl-4-nitroso piperazine (MNP) and N-nitrosodimethylamine (NDMA) in rifampicin, a drug used to treat tuberculosis. Although NDMA was not detected in two pharmaceutical analyzed, MNP was found at concentrations of 0.44 ± 0.05 and 2.1 ± 0.3 µg g−1. Given the ability to apply the method to various APIs, together with its reliance solely on logP values for determining suitability, the proposed technique could be extended to the determination of N-nitrosamines in other drugs besides rifampicin.