Risk-Based Determination of Analytical Sensitivity (LOQ) for Nitrosamine Impurities Using Acceptable Intake Limits

Abstract

N-nitrosamine impurities found in the global pharmaceutical supply chain have forced an urgent transformation in the development of risk-based analytical monitoring and advanced quality control standards. The pivotal 2018 finding of the compound N-nitrosodimethylamine in the "sartan" drug class prompted the transition of regulatory authorities, including the United States Food and Drug Administration (USFDA) and the European Medicines Agency (EMA), from voluntary screening to a directive of ultra-trace quantification. These impurities fall under the "Cohort of Concern" group and are potent mutagenic carcinogens that are metabolized into reactive electrophilic alkyldiazonium ions, covalently modifying DNA to promote tumorigenesis. This review summarizes the present scientific knowledge regarding nitrosamine formation chemistry, the identification of root causes and the corresponding mathematical relationships between toxicological acceptable intake (AI) limits and analytical performance metrics. This review demonstrates that the limit of quantification (LOQ) must be mathematically derived from health-based AI limits, ideally achieving ≤10% of the AI concentration; for high-dose drugs such as metformin (maximum daily dose, MDD, 2000 mg) this necessitates LOQs as low as 4.8 ppb for N-nitrosodimethylamine (NDMA), driving the need for advanced mass spectrometry (MS)-based platforms. The importance of LOQ is assessed, emphasising that analytical sensitivity should increase as MDD increases to maintain health-based safety margins. The technical challenges associated with matrix interference and isobaric co-elution are also addressed. Advanced mass spectrometry techniques, namely liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–tandem mass spectrometry (GC–MS/MS), remain leading approaches for parts-per-billion (ppb)-level detection, with method selection guided by analyte volatility, polarity, matrix characteristics, and available instrumentation. An overarching framework is also proposed to harmonise analytical capabilities with toxicological requirements, thereby supporting the pharmaceutical industry in meeting evolving regulatory expectations and protecting patient safety.