Analysis of Pharmaceuticals’ Impurity - Regulations and Analysis for Carcinogenic Substances -

Importance of Topic

Active pharmaceutical ingredients may contain trace-level DNA-reactive impurities such as nitrosamines and alkyl sulfonates that pose potential carcinogenic risks. Regulatory bodies including ICH, FDA, and EMA have established guidelines (ICH M7, Q3C/Q3D) defining threshold of toxicological concern (1.5 µg/person/day) and compound-specific limits. Sensitive and selective analytical methods are essential to detect these impurities at sub-ppm or ng/mL levels, ensuring patient safety and regulatory compliance.

Study Objectives and Overview

This application note reviews current regulations governing carcinogenic impurities in pharmaceuticals and demonstrates analytical protocols for quantifying nitrosamines in sartan drugs, ranitidine, and metformin, as well as mesylate, besylate, and tosylate esters in various formulations. The aim is to illustrate method development, validation, and real-sample testing using GC-MS, GC-MS/MS, LC-MS/MS, and QTOF platforms to achieve reliable trace-level quantitation.

Methodology and Instrumentation

• Classification of mutagenic impurities under ICH M7 using literature, in silico SAR, and TTC-based intake limits.
• Headspace-GC/MS (Shimadzu HS-20 + GCMS-QP2020 NX) for volatile nitrosamines (NDMA, NDEA) in -sartan drugs.
• Direct injection GC-MS/MS (GCMS-TQ8050 NX) for multi-nitrosamine panels (up to seven compounds including NEIPA, NDIPA, NDBA).
• Triple-quadrupole LC-MS/MS (LCMS-8060) for nitrosamines (NDMA to NMBA) in olmesartan and metformin matrices.
• Quadrupole TOF LC-MS (LCMS-9030) for high-resolution detection of NDMA in ranitidine preparations.
• Derivatization-based headspace GC/MS for alkyl mesylates, benzenesulfonates, and p-toluenesulfonates in salt forms.

Main Results and Discussion

Developed methods achieved LOQs down to 0.05 ppm (GC-MS) and sub-ng/mL (LC-MS/MS). Calibration curves over relevant ranges exhibited excellent linearity (r²>0.999) and recoveries within 80–120%. GC-MS/MS enabled femtogram-level sensitivity with RSDs <5%. QTOF LC-MS provided accurate mass confirmation for NDMA in ranitidine at 0.11 ppm. Derivatization strategies effectively quantified mesylates and sulfonates at low µg/g in commercial drugs.

Benefits and Practical Applications

• Compliance with ICH M7 and global regulatory expectations for carcinogenic impurity control.
• Flexible choice of analytical platform based on volatility and matrix complexity.
• High-throughput potential with minimized matrix interferences and simplified sample prep.
• Direct applicability for routine QC laboratories to support batch release and stability testing.

Future Trends and Potential Applications

Incorporation of high-resolution MS with automated data processing will streamline impurity profiling and strengthen specificity. AI-driven SAR and predictive toxicology tools may enhance risk assessment workflows. Portable MS systems and real-time process monitoring will enable on-site screening during manufacturing. Expanded multi-residue assays and continuous analytical platforms will support dynamic quality control.

Conclusion

Controlling carcinogenic impurities in pharmaceuticals requires rigorous regulatory adherence and advanced analytical techniques. The presented GC and LC-MS methods demonstrate robust and sensitive quantitation of nitrosamines and alkyl sulfonate esters at trace levels. Adoption of these protocols will enhance product safety, quality assurance, and compliance with global guidelines.

References

• ICH M7 Guideline: Assessment and Control of DNA-Reactive (Mutagenic) Impurities.
• FDA: NDMA/NDEA Impurity Assay by GC/MS-Headspace.
• FDA: Direct Injection NDMA/NDEA Impurity Assay by GC/MS.
• FDA: Multi-Compound Nitrosamine Assay by GC-MS/MS.
• EMA Referral Document on Nitrosamines in Medicines.
• Health Sciences Authority Singapore: NDMA in Metformin by HRAM GC-MS.
• European Pharmacopoeia 9.0: Mesylate Ester Analysis Methods.