Simultaneous Determination of Eight Nitrosamine Impurities in Metformin Using the Agilent 6470 Triple Quadrupole LC/MS

Importance of the Topic

Nitrosamine impurities are potent genotoxic compounds formed during drug manufacturing. Regulatory agencies globally require highly sensitive and selective analytical methods to detect these compounds at trace levels in pharmaceutical products to protect patient safety and ensure compliance.

Objectives and Study Overview

This study aimed to develop and validate a robust LC–MS/MS method using the Agilent 6470 triple quadrupole system for the simultaneous quantification of eight regulated nitrosamine impurities in metformin drug substance. The method addresses stringent regulatory limits following recent product recalls due to nitrosamine contamination.

Methodology and Instrumentation

• Sample Preparation: 100 mg metformin drug substance dissolved in 5 mL solvent and vortexed until fully dissolved.
• Chromatography: Agilent 1290 Infinity II UHPLC with Poroshell HPH-C18 column (4.6 × 150 mm, 2.7 µm); mobile phases A (0.1% formic acid in water) and B (0.1% formic acid in methanol); 20-minute gradient at 0.5 mL/min; column at 40 °C; 20 µL injection; diverter valve used to direct the metformin peak to waste.
• Mass Spectrometry: Agilent 6470 triple quadrupole with APCI source in positive mode; optimized multiple reaction monitoring (MRM) transitions for each nitrosamine; drying gas at 300 °C and 7 L/min; nebulizer 25 psi; APCI heater 350 °C; capillary voltage 4000 V; MS1/MS2 resolution 0.7/0.7 unit.

Main Results and Discussion

• Sensitivity: Limits of quantitation between 0.1 and 0.2 ng/mL achieved, with signal-to-noise ratios exceeding 30 for all analytes.
• Linearity: Calibration range of 0.1–50 ng/mL provided R² values above 0.99 for each nitrosamine.
• Reproducibility: Intra-day precision demonstrated RSD values below 6% and accuracy within ±15% at all tested levels.
• Recovery: Spike-recovery experiments in metformin at 0.6 ng/mL yielded recoveries from 94.9% to 102.6%.
• Chromatographic Separation: Effective resolution of positional isomers (e.g., NDIPA vs. NDPA) and minimal matrix suppression were achieved.

Benefits and Practical Applications

• Simultaneous quantification of eight genotoxic nitrosamines streamlines compliance testing for metformin and other drug substances.
• High sensitivity and selectivity reduce sample preparation complexity and improve laboratory throughput.
• Method flexibility allows adaptation to additional active pharmaceutical ingredients for broader quality control applications.

Future Trends and Potential Applications

Advances may include the integration of higher resolution mass spectrometry, automation of sample preparation workflows, and real-time monitoring systems to further enhance sensitivity, shorten analysis times, and extend applicability to diverse pharmaceutical matrices.

Conclusion

The validated LC–MS/MS method on the Agilent 6470 triple quadrupole system provides reliable, sensitive, and reproducible detection of eight nitrosamine impurities at trace levels in metformin. It satisfies stringent regulatory requirements and supports robust pharmaceutical quality assurance.

References

1. U.S. FDA. FDA updates and press announcements: ARB recalls (valsartan, losartan).
2. U.S. FDA. Development and Validation of a RapidFire-MS/MS Method for Screening of Nitrosamine Impurities.
3. U.S. FDA. LC-HRMS Method for Determination of Six Nitrosamine Impurities in ARB Drugs.
4. U.S. FDA. LC-HRMS Method for Determination of Eight Nitrosamine Impurities in Metformin Drug Substance and Product.
5. U.S. FDA. Statement alerting patients and health care professionals: nitrosamine impurities in metformin.
6. Srinivas Chidella K. et al. Determination of Nitrosamine Impurities Using the Ultivo Triple Quadrupole LC/MS. Agilent Technologies Application Note 5994-1383EN, 2019.