Quantification of Nitrosamine Impurities in Metformin Using Agilent GC/MS/MS Instrumentation

Importance of the Topic

The control of nitrosamine impurities has become a critical quality concern in pharmaceutical manufacturing after several recalls of drugs such as sartans, ranitidine and metformin due to unacceptable levels of carcinogenic nitrosamines. Regulatory agencies worldwide have set stringent limits and transition periods to reduce these impurities in finished products. The need to detect nitrosamines at trace levels (sub-ppm) poses significant analytical challenges, driving the development of sensitive, specific, and robust methods.

Objectives and Study Overview

This study aimed to develop and validate a comprehensive GC/MS/MS method for the quantification of five nitrosamine impurities (NDMA, NDEA, NEIPA, NDIPA, NDBA) in metformin drug substances and products. The work evaluates three extraction procedures, establishes limits of quantification, assesses method performance, and compares sample preparation approaches for both immediate-release and extended-release formulations.

Methodology and Instrumentation

Sample preparation was assessed using three methods: direct dichloromethane extraction (Method 1), dichloromethane‐water partitioning (Method 2), and acidified aqueous extraction followed by dichloromethane (Method 3). All methods incorporated an NDMA:C13-d6 internal standard. Separation and detection were performed on an Agilent 8890 GC with a DB-WAX capillary column (30 m × 0.25 mm, 0.5 µm) coupled to an Agilent 7010B Triple Quadrupole GC/MS with a High Efficiency Source (HES). MRM transitions for each analyte were optimized using MassHunter Optimizer to achieve high sensitivity and selectivity.

Instrumentation Used

• Agilent 8890 Gas Chromatograph with touch-screen interface and mobile monitoring.
• Agilent 7010B Triple Quadrupole GC/MS equipped with HES for improved ionization.
• J&W DB-WAX GC column (30 m × 0.25 mm, 0.5 µm).
• Helium carrier gas, MMI pulsed splitless injection.

Main Results and Discussion

Excellent chromatographic resolution was achieved for all five nitrosamines within a 13.3 min run time. Calibration curves (2.5–100 ng/mL) showed linearity with R2 > 0.999. Limits of quantification reached < 0.001 ppm for NDMA, NDEA, NEIPA, NDIPA and < 0.0025 ppm for NDBA. Recoveries at LOQ ranged from 80 to 120% with RSDs < 5%. Method 1 offered simplicity for drug substance analysis but was unsuitable for formulations yielding viscous extracts. Method 2 provided universal applicability but lower absolute peak areas. Method 3 combined robust recovery with clean phase separation across both substance and product samples.

Benefits and Practical Applications

This GC/MS/MS protocol delivers the sensitivity and specificity required for regulatory compliance in nitrosamine testing of metformin. The method supports routine QC laboratories by offering fast throughput, reliable quantification at trace levels, and flexibility for diverse sample types. Mobile instrument monitoring and diagnostic alerts reduce downtime and enhance operational efficiency.

Future Trends and Applications

Future advances may include further lowering detection limits through enhanced source designs, automated sample handling and data processing for higher throughput, and expansion to other drug classes. Integration with laboratory information management systems and artificial intelligence–based peak review will streamline workflows. Emerging regulatory guidance on additional nitrosamine species will drive method extension and robustness studies.

Conclusion

The Agilent 8890 GC coupled with the 7010B Triple Quadrupole GC/MS/MS provides a powerful solution for trace quantification of nitrosamine impurities in metformin. The developed MRM-based method achieves sub-ppb detection limits, robust recovery, and reproducible performance, meeting current regulatory requirements and supporting future analytical needs.

References

• European Medicines Agency guidance on nitrosamine impurity controls.
• U.S. Food and Drug Administration updates on NDMA in metformin.
• EDQM OMCL network methods for nitrosamine determination in metformin.
• Andrianova A., Quimby B., Churley M. Automated MRM Method Development for EPA Method 8270, Agilent Technologies Application Note 5994-2086EN.