Quantitation of Nitroso-Propranolol in Propranolol HCl Formulation and its Placebo Using LC-MS/MS

Significance of the Topic

The presence of N-nitrosamine impurities such as nitroso-propranolol in pharmaceutical products poses significant health risks due to their potent carcinogenicity and has led to regulatory recalls of several APIs over recent years. This necessitates highly sensitive and reliable analytical methods to ensure drug safety and compliance with global guidelines.

Objectives and Overview

Development and validation of a sensitive LC–MS/MS method for the quantitation of N-nitroso propranolol (NNP) in Propranolol HCl API and its formulation, including placebo analysis. The study aims to achieve trace-level detection, meet regulatory requirements, and demonstrate applicability to routine quality control.

Methodology

Chromatographic separation was achieved using a Shim-pack Scepter C8 column (150×3.0 mm, 5 μm) on a Nexera X3 UHPLC system with a gradient of 0.1% formic acid in water and methanol. The flow rate was 0.5 mL/min, injection volume 30 μL, and divert valve directed early eluent to waste. Sample preparation involved dilution of weighed API or formulation equivalent to 25 mg propranolol in a 1:1 water–acetonitrile diluent, vortex mixing, and filtration through a 0.22 μm PTFE membrane. Multiple Reaction Monitoring (MRM) transitions were optimized using automated collision energy selection, yielding quantifier and qualifier ions for reliable detection. Calibration was performed over 10–4000 ppb.

Instrumentation Used

• UHPLC: Nexera X3 (Shimadzu)
• Mass Spectrometer: LCMS-8060NX with APCI source, positive ion mode
• Column: Shim-pack Scepter C8 (150×3.0 mm, 5 μm)
• Software: LabSolutions for automated MRM optimization

Results and Discussion

A six-point calibration curve (10–4000 ppb) demonstrated excellent linearity (r² = 0.999). The method achieved an LOD of 2 ppb and LOQ of 10 ppb with repeatability (%RSD) below 7% at the LOQ level. Analysis of formulation samples revealed NNP concentrations of approximately 3600–3970 ppb, while placebo samples exhibited minimal background. Spike-recovery experiments in placebo at 10 ppb yielded an average recovery of 103%, confirming method accuracy and robustness at trace levels.

Benefits and Practical Applications

• Rapid and reliable quantitation of trace-level nitroso-propranolol for API and finished product quality control.
• Ensures compliance with stringent regulatory limits on nitrosamine impurities.
• Automated MRM optimization accelerates method development and improves reproducibility.

Future Trends and Opportunities

Future developments may include coupling with high-resolution mass spectrometry for enhanced selectivity, miniaturized and automated sample preparation workflows, and expansion to other nitrosamine species and complex matrices. Integration with AI-driven data analysis could further improve throughput and decision-making in quality assurance settings.

Conclusion

The LC–MS/MS method developed on the Shimadzu Nexera X3–LCMS-8060NX platform delivers sensitive, accurate, and reproducible quantification of nitroso-propranolol in Propranolol HCl API and formulations, fully addressing regulatory requirements and supporting robust quality control practices.

References

1. United States Food and Drug Administration (USFDA), Control of Nitrosamine Impurities in Human Drugs Guidance for Industry, September 2024, Revision 2.