Determination of genotoxic nitrosamines in Valsartan with gas chromatography and mass spectrometry

Significance of topic

Genotoxic nitrosamines such as NDMA and NDEA are probable human carcinogens that were unexpectedly detected in valsartan drug substances in 2018, prompting global recalls and new regulatory limits far below typical toxicological thresholds. Robust analytical methods are essential to ensure trace levels of these impurities remain below acceptable limits and to safeguard public health.

Study objectives and overview

This study evaluates three gas chromatography mass spectrometry based workflows recommended by Chinese and US regulatory agencies for quantitative detection of NDMA and NDEA in valsartan. The methods include a liquid injection single quadrupole GC-MS method, a headspace single quadrupole GC-MS method, and a direct injection triple quadrupole GC-MS/MS method. Each approach was tested for system suitability, sensitivity, linearity, repeatability and recovery according to pharmacopoeial and FDA guidelines.

Methodology and instrumentation

Sample preparation workflows varied by method. The liquid injection method used methanol extraction and centrifugation followed by splitless GC-MS analysis. The headspace method dissolved the drug in dimethyl sulfoxide, equilibrated at elevated temperature, and transferred headspace vapor for GC-MS detection. The triple quadrupole workflow applied direct injection of dichloromethane extracts with isotope plus mass labelled transitions monitored by SRM in timed mode for enhanced selectivity and sensitivity. Key hardware included a TRACE 1310 GC with splitless inlet, ISQ 7000 single quadrupole and TSQ 9000 triple quadrupole mass spectrometers, and a TriPlus 500 headspace autosampler. Chromeleon CDS managed acquisition and quantitative processing.

Main results and discussion

All methods met or exceeded resolution and signal-to-noise criteria. System suitability tests showed resolution between NDMA or NDEA and internal standards well above 1.5 and S/N ratios above 60 at low ppb levels. Linearity was excellent across 1 to 100 ppb, with correlation coefficients above 0.998 in each workflow. Method limits of detection and quantitation ranged from 0.05 to 0.9 ppb LOD and 0.16 to 3.1 ppb LOQ, surpassing regulatory thresholds. Repeatability of peak area across six injections displayed RSDs below 3 percent. Recovery studies at multiple spike levels in a commercial valsartan capsule yielded values between 84 and 108 percent, demonstrating accuracy in real matrices.

Benefits and practical applications of the method

• Compliance with both Chinese Pharmacopoeia and US FDA recommended procedures
• High sensitivity to detect impurities well below acceptable limits
• Robust repeatability and accuracy across various sample types
• Flexible analytical portfolio allowing liquid, headspace, or MS/MS approaches
• Minimized instrument downtime through vacuum interlock design for rapid maintenance

Future trends and potential applications

Emerging directions include integration of isotopically labelled internal standards for absolute quantitation, expansion to additional nitrosamine analogues, further automation and online sample prep interfaces, and adoption of high resolution mass spectrometry for non-targeted screening. Continuous tightening of regulatory limits will drive demand for ever lower detection thresholds and method innovation.

Conclusion

The evaluated GC-MS and GC-MS/MS methods provide reliable, sensitive and regulatory compliant workflows for detection of genotoxic nitrosamines in valsartan. Thermo Fisher Scientific platforms offer the performance and robustness needed for routine quality control laboratories to enforce strict impurity limits and protect patient safety.

Reference

• Chinese Pharmacopoeia recommended GC-MS method for nitrosamines in valsartan
• US FDA headspace GC-MS method for NDMA in valsartan
• US FDA combined NDMA and NDEA headspace GC-MS method
• US FDA triple quadrupole GC-MS/MS impurity assay for NDMA and NDEA