LC-MS/MS Method for Detection and Quantitation of Azido Impurities in Irbesartan Drug Substan

Significance of the Topic

Irbesartan is a widely used antihypertensive that may contain trace mutagenic azido impurities formed during tetrazole ring synthesis. Regulatory agencies have issued recalls and quality guidelines to limit these genotoxic by-products. Sensitive, reliable analytical methods are vital to ensure drug safety and compliance.

Objectives and Study Overview

The study aimed to develop and validate a high-sensitivity multiple reaction monitoring (MRM) LC-MS/MS method using Shimadzu LCMS-8050 and Nexera X3 for quantitation of four azido impurities (AZBT, AZBC, AMBBT, AMBBC) in irbesartan API. Key evaluation metrics included linearity, limits of detection and quantitation, and recovery.

Methodology and Instrumentation

Sample pretreatment comprised dissolution of irbesartan in 80% acetonitrile followed by centrifugation. Chromatographic separation employed a Shim-pack GIST C18 column (3.0×100 mm, 3 μm) with a gradient of 0.1% formic acid in water and 95% acetonitrile. A divert valve excluded the Irbesartan peak from MS detection during early elution. MRM transitions were optimized for each impurity. Instrumentation details were:

• Liquid chromatograph: Nexera X3
• Column: Shim-pack GIST C18 (3.0 mm I.D. x 100 mm L., 3 μm)
• Mass spectrometer: LCMS-8050 with ESI in positive mode

Main Results and Discussion

Baseline separation of the four azido impurities and the Irbesartan API was achieved. Calibration curves were linear over 0.5–50 ng/mL with correlation coefficients above 0.999. Limits of detection ranged from 0.01 to 0.2 ng/mL, and quantitation limits from 0.03 to 0.5 ng/mL. Spike-and-recovery tests at 1, 20 and 40 μg/g demonstrated recoveries between 95% and 111%, confirming method accuracy and precision.

Benefits and Practical Applications

The developed LC-MS/MS method offers high sensitivity and specificity for trace analysis of azido impurities in pharmaceutical quality control. Its robust performance supports regulatory compliance and routine API release testing to mitigate genotoxic risks in drug substances.

Future Trends and Potential Applications

Further efforts may focus on expanding this approach to additional impurity profiles, enhancing throughput through automation, and integrating high-resolution MS technologies. Continuous method refinement will align with evolving regulatory limits and facilitate comprehensive impurity monitoring.

Conclusion

A validated LC-MS/MS protocol was established for simultaneous quantitation of four azido impurities in irbesartan API, demonstrating excellent linearity, low detection limits, and reliable recovery. This method provides a critical tool for ensuring pharmaceutical safety and regulatory adherence.

Reference

• MFDS Method, 2021. Korean Ministry of Food and Drug Safety guideline for azido impurity determination.
• Genotoxic Substances in Sartans, 2021. OMCL Swissmedic official method report.