A Sensitive LC-MS/MS Method for the Analysis of Azido Impurity in Losartan Drug

Importance of the Topic

Losartan and related sartan drugs are widely used antihypertensive agents. The detection of trace azido impurities, which may possess mutagenic or carcinogenic properties, has become critical for ensuring drug safety and regulatory compliance. Developing highly sensitive analytical methods to monitor these impurities addresses a significant public health concern and meets stringent guidelines from agencies such as EMA, Health Canada, and MFDS.

Objectives and Study Overview

This study aimed to establish and validate a sensitive LC-MS/MS method for quantifying four azido impurities (AZBT, AZBC, AMBBT, AMBBC) in losartan active pharmaceutical ingredients. Key performance metrics included linearity, limit of detection (LOD), limit of quantification (LOQ), repeatability, and recovery, using a Shimadzu LCMS-8050 triple quadrupole mass spectrometer coupled to the Nexera X3 LC system.

Methodology and Instrumentation

Sample Preparation:

• Weighed 100 mg of losartan and dissolved it in 100 mL of water:acetonitrile (20:80, v/v).
• Vortexed until fully dissolved, centrifuged at 4,000 rpm for 10 minutes, and injected 5 µL of supernatant.

Chromatographic and Mass Spectrometric Conditions:

• LC system: Shimadzu Nexera X3 with Shim-pack GIST C18 column (3.0 mm ID × 100 mm, 3 µm) at 40 °C.
• Mobile phase A: 0.1 % formic acid in water; B: 0.1 % formic acid in 95 % acetonitrile; flow rate 0.4 mL/min.
• Gradient: B 35 % at 0 min to 40 % at 5.5 min, 100 % at 12–14 min, return to 35 % by 18 min.
• Diverter valve: 0–7.6 min to waste, 7.6–13 min to MS for impurity analysis.
• MS: LCMS-8050 triple quadrupole, ESI positive, MRM transitions optimized for each azido impurity.

Major Results and Discussion

The four azido impurities were baseline-separated from losartan under the described conditions. Calibration curves exhibited excellent linearity (r2 > 0.99). LOD values ranged from 0.01 to 0.2 ng/mL and LOQ from 0.03 to 0.5 ng/mL. Recovery studies at low (1 µg/kg), medium (20 µg/kg), and high (40 µg/kg) spiking levels yielded recoveries between 84 % and 116 %, demonstrating method accuracy and precision.

Benefits and Practical Applications

This validated LC-MS/MS protocol enables trace-level monitoring of mutagenic azido impurities, facilitating batch release testing and regulatory compliance. Its high sensitivity and robust performance make it suitable for routine quality control in pharmaceutical manufacturing.

Future Trends and Potential Applications

Potential extensions include adapting the method to other sartan compounds, integrating high-resolution mass spectrometry for broader impurity profiling, and developing high-throughput or automated workflows. Advances in greener solvents and miniaturized separation techniques may further enhance sustainability and efficiency.

Conclusion

A sensitive and reliable LC-MS/MS method was developed on the Shimadzu LCMS-8050 platform for quantifying four azido impurities in losartan. The method meets stringent performance criteria for linearity, sensitivity, and recovery, supporting enhanced drug safety monitoring.

Reference

• Food and Drug Safety in Korea. Test method for AZBT in sartan drugs using LC-MS/MS (2021).
• European Directorate for the Quality of Medicines and HealthCare. AZBT impurity in Valsartan, Irbesartan, Losartan, Candesartan LC-MS/MS Method (2021).
• Genotoxic substances in sartans. OMCL Swissmedic (2021).