Determination of Nitrosamine Impurities in Losartan Potassium Drug Substance and Drug Product using the Xevo TQ-S micro and Atlantis Premier BEH C18 AX Column

Significance of the Topic

The presence of nitrosamine impurities in pharmaceuticals poses significant health risks due to their carcinogenic nature. Regulatory bodies such as the FDA have set stringent limits on nitrosamine levels to ensure drug safety. Sensitive and reliable analytical methods are essential for monitoring these impurities in drug substances and products.

Objectives and Study Overview

This study aimed to develop a robust and highly sensitive UPLC-MS/MS method for quantifying three nitrosamines (NDMA, NDEA, NMBA) in losartan potassium drug substance and tablet formulations. The method aligns with FDA guidelines, targeting detection limits below 0.03 ppm and acceptable intake of 26.5 ng/day.

Methodology and Instrumentation

Samples of losartan API and tablets were extracted with methanol:water (5:95) and spiked with isotopically labeled internal standards. Chromatographic separation used an Atlantis Premier BEH C18 AX column at 40 °C, a 0.45 mL/min gradient of ammonium formate/formic acid in water and methanol, and a 10 µL injection volume. Mass spectrometric detection employed APCI+ on a Xevo TQ-S micro triple quadrupole MS.
Instrumentation:

• ACQUITY UPLC I-Class System
• Atlantis Premier BEH C18 AX column (2.1 × 100 mm, 1.7 µm)
• Xevo TQ-S micro Triple Quadrupole MS with APCI source
• MassLynx v4.2 and TargetLynx software

Main Results and Discussion

The C18 AX column provided superior retention for polar NDMA compared to fluorophenyl alternatives, enhancing separation from matrix interferences. Calibration curves were linear (R² > 0.997) over 0.5–100 ng/mL for NDMA/NDEA and 1–100 ng/mL for NMBA, with limits of quantitation at 0.5 ng/mL (0.005 ppm). Instrument precision (%RSD) was < 12% at 1 ng/mL, and QC checks showed accuracy within ± 21% at low levels. Extraction efficiencies for spiked samples exceeded 70% for all analytes, confirming reliable sample preparation.

Benefits and Practical Applications

The validated method offers high sensitivity, selectivity, and repeatability for nitrosamine analysis at regulatory threshold levels. It supports quality control during drug manufacturing, ensuring compliance and safeguarding patient safety.

Future Trends and Potential Applications

Continued evolution of regulatory standards will drive demand for even lower detection limits and wider nitrosamine panels. Integration with automated sample preparation, high-throughput workflows, and novel stationary phases will further improve sensitivity and efficiency. The approach can be extended to other APIs and biologics requiring rigorous impurity monitoring.

Conclusion

A robust UPLC-MS/MS workflow was established for trace-level quantification of NDMA, NDEA, and NMBA in losartan matrices. The method meets FDA guidelines, achieves LOQs of 0.005 ppm, and demonstrates strong performance for routine pharmaceutical analysis.

References

• FDA CDER. Control of nitrosamine impurities in human drugs. Revision 1, February 2021.
• Lee J-H, Lee S-U, Oh J-E. Analysis of nine nitrosamines in water by SPE-HPLC–APCI-MS/MS. Int J Environ Anal Chem. 2018;93(12):1261–1273.