Improvement Upon a Multi-Residue Method for Nitrosamine Analysis in Losartan Drug Product Using an Enhanced LC/MS/MS System

Importance of the Topic

Nitrosamine impurities are genotoxic and probable carcinogens found at trace levels in pharmaceutical products. Regulatory agencies have set stringent limits (e.g., 96 ng/kg long-term intake), prompting recalls of ARBs such as losartan. Accurate quantification of multiple nitrosamines in finished drug products is critical for patient safety and regulatory compliance.

Goals and Study Overview

This study aimed to enhance an existing multi-residue method for eight nitrosamines in losartan drug product using an improved LC/MS/MS system. Key objectives included lowering quantification limits, validating calibration performance, and demonstrating reliable matrix analysis in an ARB formulation.

Methodology and Instrumentation

Sample Preparation:

• Spiking nitrosamine standards (0.0125–10 ng/mL) into solvent and losartan matrix (0.05–1 ng/mL).
• Dissolving 100 mg losartan potassium in methanol/water, sonication, centrifugation, dilution.

Instrumentation:

• Agilent 1290 Infinity II Bio LC (high-speed pump, multisampler, multicolumn thermostat).
• Agilent 6495D Triple Quadrupole LC/MS with APCI source.
• MassHunter Workstation for data acquisition and MRM quantitation.

Main Results and Discussion

Calibration curves for all eight nitrosamines exhibited linearity (R² > 0.997) across low ng/mL ranges with 1/x weighting. The 6495 LC/TQ system achieved limits of quantification below 0.01 ng/mL for most analytes. In losartan matrix, all compounds were quantified at 0.03 ng/mL with acceptable accuracy (85–110%) and precision (%RSD < 15%). The enhanced APCI interface and optimized MRM transitions improved signal-to-noise ratios substantially.

Benefits and Practical Application

The method delivers high sensitivity and robustness suitable for routine QA/QC of ARBs and other pharmaceuticals. Laboratories can reliably monitor nitrosamine levels well below regulatory thresholds, supporting product safety and compliance.

Future Trends and Opportunities

• Extension of the approach to additional drug classes susceptible to nitrosamine formation.
• Integration with automated sample preparation and data processing workflows.
• Further enhancements in sensitivity via next-generation ion sources.
• Harmonization of regulatory limits and inter-laboratory standardization.

Conclusion

The enhanced LC/MS/MS method on Agilent 6495 demonstrates ultra-trace quantification of eight nitrosamines in losartan with exceptional sensitivity and reliability, underscoring its value for pharmaceutical impurity control.

Reference

• U.S. FDA. FDA Updates on ARB Recalls (Valsartan, Losartan, Irbesartan). March 2023.
• FDA CDER. Control of Nitrosamine Impurities in Human Drugs: Guidance for Industry. Feb 2021.
• EMA. Procedure under Article 5(3) EMEA/H/A-5(3)/1490 on Nitrosamines. 2020.