Importance of Advanced Analytical Tools - Nitrosamines in Pharmaceutical Drug Substances and Drug Products
Bhaskar Vallamkonda, ARD-Manager, Odin Pharmaceuticals LLC
Nitrosamine impurities pose carcinogenic risks, prompting global regulatory concern. This review highlights recent advances in LC-MS/MS methods for detecting trace levels of nitrosamines, emphasizing sensitivity, precision, linearity and accuracy. It underscores the importance of regulatory compliance, as guided by FDA, EMA, ICH, and WHO, in ensuring safe pharmaceutical products through advanced analytical techniques.
Introduction
Genotoxicity refers to damage to cellular genetic material, mainly DNA and RNA, which can lead to mutations, cancer, or impaired cellular function. Genotoxic substances, or genotoxins, often originate from industrial processes, including drug manufacturing, and pose serious health risks even at trace levels. Among these, N-nitrosamines (N-NAs) are a significant concern due to their potent genotoxic and carcinogenic properties. These compounds, formed by nitrosation reactions involving amines and nitrosating agents under acidic conditions, can alkylate DNA, initiating mutations and potentially leading to cancer.
N-NAs can form during active pharmaceutical ingredient (API) synthesis, drug products (DPs), or storage due to environmental factors like humidity and temperature. Structurally diverse, nitrosamines vary in carcinogenic potential, with some being highly potent while others show lower or negligible activity. Medications like sartans and ranitidine have drawn attention for their susceptibility to N-NA formation.
Due to their health risks, regulatory agencies demand stringent monitoring and control of nitrosamine impurities in pharmaceuticals. Their presence in water, food, and tobacco highlights widespread exposure. Therefore, sensitive and reliable analytical techniques are essential to detect and quantify N-NAs, ensuring product safety and compliance with global regulatory standards.
Regulatory Concerns and Impurities in Pharmaceuticals
Global regulatory bodies, including the FDA, EMA, and WHO, recognize N-nitrosamines (NAs) as probable human carcinogens and require strict control of these impurities. Following ICH M7 guidance, risk assessments focus on identifying contamination sources during drug manufacturing. The FDA’s three-step approach—risk assessment, testing, and corrective action—guides mitigation efforts. Acceptable intake (AI) limits, based on toxicology data, ensure safety. However, challenges persist in detecting trace NAs, especially for small manufacturers. Advanced methods like LC-MS/MS are essential but resource-intensive. Regulatory agencies stress collaboration among stakeholders to harmonize standards and strengthen supply chain transparency and quality control.
Table-1: Regulatory Agencies defined Limits for General NA’s
| Nitrosamine | AI Limit (ng/day) |
| NDMA | 96 |
| NDEA | 26.5 |
| NMBA | 96 |
| NMPA | 26.5 |
| NIPEA | 26.5 |
| NDIPA | 26.5 |
| N-nitroso-desmethyl-almotriptan | 26.5 |
| Sitagliptin - NTTP | 100 |
| N-nitroso-desmethyl-citalopram | 26.5 |
Analytical Techniques for Nitrosamine Analysis
Detecting N-NAs in pharmaceuticals is essential due to their classification as probable human carcinogens. Accurate detection not only ensures regulatory compliance and product quality but also protects public health and prevents costly recalls. As regulatory standards evolve, sensitive analytical methods are key to identifying both known and emerging NAs and supporting proactive risk management.
Liquid chromatography-mass spectrometry (LC-MS), particularly tandem mass spectrometry (LC-MS/MS), is the most widely used technique for NA analysis due to its high sensitivity, specificity, and suitability for complex drug matrices. It effectively identifies trace levels of NAs in both APIs and DPs, aligning with global regulatory expectations.
Recent studies have expanded the use of LC-MS/MS to biological and pharmaceutical matrices. For instance, Shinde et al. analyzed seven NAs in urine samples using UHPLC-MS/MS with detection limits as low as 0.1 ng/mL. Another study quantified 13 regulated NAs in various commercial drug products, identifying NDMA in two ranitidine-based samples. NDMA was shown to form via degradation of ranitidine, intensified by nitrite presence.
The limit of quantification (LOQ) for most NAs was within 45% of acceptable intake (AI) limits, based on 6% of the maximum daily API dose. However, LOQ values for compounds like NPIP and NPYR varied significantly (0.7%–91%), suggesting inconsistent sensitivity and highlighting the need for further method optimization.
In sartan drugs, the detection of NAs such as NDMA and NMBA is particularly critical due to their potential formation during manufacturing. These impurities arise from interactions between nitrosating agents and amide-containing solvents under acidic, high-temperature conditions. LC-MS/MS techniques have proven effective in detecting these impurities at low levels—down to 3 ng/mL—ensuring regulatory compliance. Novel techniques like Direct Analysis in Real Time Mass Spectrometry (DART-MS) also offer rapid, low-preparation detection methods aligned with green chemistry principles.
These advancements are crucial not only for impurity detection but also for understanding contamination sources, such as packaging materials or process-related extractables. As research progresses, improving sensitivity and refining sample preparation will be vital to maintaining consistent detection across various NA types and drug products.
Overall, robust analytical strategies—especially LC-MS/MS—remain indispensable for ensuring pharmaceutical safety and quality. Continued innovation and harmonization of detection methods are essential to meet regulatory demands, address emerging risks, and protect public health.
A few examples of how critical these studies are, in a single drug of Sitagliptin (STP) a multiple studies were done in public domain to express the severity of NA’s. A summary of few publically available methods are as follows. Due to their carcinogenic and genotoxic hazards STP, a type 2 diabetes medication, is being studied for nitrosamine impurities. The sensitive UHPLC-MS/MS approach established by Bessa-Jambrina et al. detects nitrosamines, including NTTP, in STP salts. Chromatographic separation was done on an Acquity HSS T3 column with 0.1% HCOOH in water and MeOH. A sensitive UFLC-MS/MS approach quantified eight genotoxic NAs in valsartan medicinal substance and tablet formulations. It detected contaminants at 0.1 ppb and measured them precisely, making it suitable for quality monitoring. Hao et al. used LC-MS/MS to identify nitroso-STG-19, a STP tablet degradation nitrosamine. Their method addressed degrading issues and found 37 ng daily consumption limits. Wang et al. validated another LC-MS/MS method with 0.98 ng mL-1 detection; robust sensitivity for regulatory compliance. ESI multiple reaction monitoring with triple quadrupole detection quantified NTTP. The authors also used advanced LC-MS/MS to identify NDMA and NDEA in STP-metformin formulations, highlighting methodological modifications for complex matrices. [46] A PerkinElmer QSight 200 series triple quadrupole MS in positive ion mode was used with an Atlantis T3 column and a gradient mobile phase of 0.1% HCOOH in water and MeOH. Optimization of diluents improved recovery and peak shape, and the method was robust at 45.7 mg mL-1 metformin hydrochloride. Routine NA monitoring in pharmaceutical formulations is efficient with this technology.
Another few examples are as follows; Gopireddy analyzed six NAs in drugs with LOQ <0.003 ppm; Öncü et al. used LC-MS/MS to detect six NA impurities in Sartan drugs, achieving separation in 18 minutes; Pereira dos Santos et al. developed a green HS-SDME method using water and an Arduino-controlled robot for detecting N-NAs in losartan. Integrated with HPLC-UV, it minimizes matrix interference without relying on mass spectrometry for preconcentration and analysis; Mavis et al. quantified eleven NAs in sartans using dMRM, achieving separation in 17 minutes with excellent method validation. Patel et al. quantified NAs in losartan and hydrochlorothiazide fixed-dose tablets using an Agilent Pursuit XRs Ultra diphenyl column with gradient elution (0.1% HCOOH in water and MeOH) at 0.4 mL/min. Tarawneh et al. compared HPLC-DAD and LC-MS/MS for NDMA detection in valsartan. Nagendla et al. developed and validated an LC-APCI-MS/MS method for NAs in sartan drugs. González et al. quantified NDMA in olmesartan using an Agilent Eclipse XDB-C18 column with a binary gradient (water and 0.1% HCOOH in MeOH) at 0.5 mL/min, ionized in positive APCI mode and quantified via MRM.
In a summary the ratio of analytical techniques that were used for the NA’s analysis is as follows;
Concluding Remarks and Future Prospects
Managing nitrosamine impurities remains a significant challenge due to their genotoxic nature and associated health risks. LC-MS/MS has become the gold standard for detecting these impurities, offering high sensitivity and precision at trace levels to meet stringent regulatory demands. However, its high cost, technical complexity, and validation requirements can be burdensome, particularly for smaller manufacturers.
Recent innovations in sample preparation such as solid-phase microextraction and diffusive inclusion complex microextraction have improved analyte recovery and selectivity, strengthening LC-MS/MS's reliability in complex matrices. Emerging techniques like QuEChERS-based extraction and molecularly imprinted polymers further address matrix interferences, enabling detection limits in the nanogram to picogram range. Despite these advancements, challenges such as co-elution of similar compounds and variability in impurity behavior across matrices persist.
Efforts to reduce nitrosamine formation, such as ascorbic acid supplementation, highlight the potential for integrated control strategies. The detection of tobacco-specific nitrosamines (TSNAs) in products like e-cigarettes and critical medications emphasizes the urgency of proactive impurity management.
Future directions include advancing affordable technologies like two-dimensional chromatography and single quadrupole systems, enabling broader access to accurate detection methods. Standardizing protocols across matrices and adopting real-time monitoring will be key to global harmonization. Collaboration between regulatory agencies, manufacturers, and suppliers is essential to strengthen oversight and analytical capabilities. Transparent, unified efforts are vital to protecting public health and ensuring consistent, global standards in nitrosamine detection and control.
Bhaskar Vallamkonda has more than 16 years of experience in analytical research and development. He currently oversees the Analytical R&D department at Odin Pharmaceuticals in New Jersey, where his work focuses on method development and validation for complex pharmaceutical dosage forms. His expertise extends to impurity characterization, including nitrosamines and genotoxic impurities, and he has made significant contributions to FDA regulatory filings in this domain.
