Quality Control of Hand Sanitizers

Significance of the Topic

The COVID-19 pandemic drove unprecedented demand for hand sanitizers, making accurate alcohol content determination critical for both efficacy and regulatory compliance. Ensuring at least 60 % (v/v) ethanol protects public health and minimizes waste in large-scale production.

Objectives and Study Overview

This study aimed to develop a fast, reagent-free near-infrared (NIR) spectroscopic method for quantifying ethanol in hand sanitizer formulations. By measuring standards across a range of 58 % to 82 % (v/v) ethanol, the work evaluates the feasibility of routine quality control using a DS2500 Liquid Analyzer and predictive calibration models.

Methodology and Instrumentation

Measurements were performed in transmission mode over 400–2500 nm at controlled temperature (40 °C). Standards of water–ethanol mixtures were loaded into 8 mm disposable vials, eliminating cleaning steps. Spectral acquisition and model development used the Vision Air Complete software package.

Instrumentation

• DS2500 Liquid Analyzer (400–2500 nm, temperature control up to 80 °C)
• DS2500 Holder for 8 mm disposable vials
• Disposable glass vials (8 mm path length)
• Vision Air 2.0 Complete spectroscopy software

Main Results and Discussion

A multivariate calibration model based on 13 Vis-NIR spectra yielded excellent agreement with reference values. Key figures of merit:

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

Correlation plots confirmed high predictive accuracy, supporting routine use for rapid ethanol assessment.

Benefits and Practical Applications

The NIR method offers:

• Reagent-free, non-destructive analysis
• Minimal sample preparation
• Results in seconds, enhancing production throughput
• Robust performance in demanding environments

It serves as a reliable alternative to gas chromatography for in-line or at-line quality control in manufacturing.

Future Trends and Applications

Emerging developments may include:

• Integration with automated sample handling and process control (Industry 4.0)
• Real-time monitoring using flow-through cells and robotics
• Enhanced chemometric algorithms and machine learning for broader solvent mixtures
• Miniaturized, handheld NIR devices for decentralized testing

Conclusion

The DS2500 Liquid Analyzer combined with NIR spectroscopy provides a fast, accurate, and reagent-free approach for ethanol quantification in hand sanitizers. This methodology supports efficient quality assurance and can replace more time-consuming chromatographic techniques.