Quality Control of Hand Sanitizers

Importance of the Topic

Quality control of hand sanitizers is critical to ensure public health, especially during high-demand scenarios like the COVID-19 pandemic. Ethanol content above 60% v/v is required for effective antimicrobial action. Rapid, reagent-free analysis helps manufacturers maintain accurate formulations, reduce waste, and comply with regulatory standards.

Objectives and Study Overview

This study aims to develop a fast, non-destructive method for quantifying ethanol concentration in hand sanitizers using near-infrared (NIR) spectroscopy. A prediction model was built using ethanol/water standards ranging from 58% to 82% v/v to validate the approach against conventional techniques.

Methodology and Instrumentation

• Sample Preparation: Ethanol/water mixtures at various concentrations to cover relevant formulation ranges.
• Spectroscopic Analysis: NIR spectra collected in transmission mode from 400 to 2500 nm using a DS2500 Liquid Analyzer with integrated temperature control at 40 °C.
• Sample Handling: Disposable 8 mm path length vials to streamline workflow and avoid cleaning.
• Software: Vision Air Complete for data acquisition, calibration, and model development.

Applied Instrumentation

• DS2500 Liquid Analyzer (400–2500 nm range, sample heating up to 80 °C)
• DS2500 Holder for 8 mm vials
• Disposable borosilicate glass vials (8 mm diameter)
• Vision Air 2.0 Complete spectroscopy software

Key Results and Discussion

NIR spectra exhibited clear absorbance changes corresponding to ethanol concentration variations. The prediction model showed excellent agreement with reference values, yielding:

• Coefficient of determination (R2): 0.9977
• Standard error of calibration: 0.41% v/v
• Standard error of cross-validation: 0.56% v/v

Correlation diagrams confirmed model robustness. Analysis time per sample was under one minute, significantly faster than gas chromatography (≈10 minutes including preparation and run time).

Benefits and Practical Applications

Rapid, reagent-free analysis reduces turnaround time and operational costs. Minimal sample handling lowers contamination risk. The method can be deployed on production lines for real-time quality assurance, supporting regulatory compliance and waste minimization.

Future Trends and Potential Applications

• Integration with automated sampling systems for high-throughput environments.
• Extension to other active ingredients or complex formulations using chemometric models.
• Deployment of portable NIR analyzers for field testing and on-site audits.
• Advances in machine learning to enhance prediction accuracy and robustness.

Conclusion

Reagent-free NIR spectroscopy using the DS2500 Liquid Analyzer offers a fast, reliable alternative for determining ethanol in hand sanitizers. High correlation with standard methods and rapid analysis make it suitable for routine quality control applications.

References

• Data and figures from Metrohm application note AN-NIR-087.