Quality Control of Hand Sanitizers

Importance of the Topic

This application note highlights the critical need for rapid and accurate quality control of hand sanitizers, which must contain 62–95% alcohol and small amounts of water, glycerol, and hydrogen peroxide to be effective and safe. Conventional methods such as gas chromatography and titrations are time-consuming and require reagents. Near-infrared spectroscopy offers a fast, multi-parameter, reagent-free alternative, delivering results within one minute.

Study Objectives and Overview

The goal was to develop robust Vis-NIR models for simultaneous quantification of ethanol, glycerol, water, and hydrogen peroxide in gel and liquid sanitizer formulations. A total of 189 samples with varied compositions were measured to build and validate prediction models.

Methodology and Instrumentation

• Technique: Transmission Vis-NIR spectroscopy (400–2500 nm) at 40 °C
• Samples: 98 gel and 91 liquid formulations with varying ethanol (70–95 % w/w), glycerol (0.5–3 % w/w), water (2–22 % w/w), and H₂O₂ (0–4 % w/w)
• Instrumentation: DS2500 Liquid Analyzer with 8 mm disposable vials
• Software: Vision Air Complete for spectral acquisition and chemometric modeling

Key Results and Discussion

• Ethanol in gel: R² = 0.9832, SECV = 0.37 w/w %
• Glycerol in gel: R² = 0.9632, SECV = 0.11 w/w %
• Water in gel: R² = 0.941, SECV = 0.09 w/w %
• Ethanol in liquid wipes: R² = 0.9964, SECV = 0.36 w/w %
• Water in liquid wipes: R² = 0.9999, SECV = 0.18 w/w %
• Hydrogen peroxide in liquid wipes: R² = 0.9986, SECV = 0.06 w/w %

These figures demonstrate high accuracy and precision comparable to conventional reference methods, while reducing total analysis time to under one minute per sample.

Benefits and Practical Applications

• Reagent-free, reducing chemical waste and handling risks
• Simultaneous multi-component analysis streamlines QC workflows
• Rapid results (<1 min) increase throughput in production and QC laboratories

Instrumentation Used

• DS2500 Liquid Analyzer (400–2500 nm, up to 80 °C)
• 8 mm diameter disposable glass vials and holder
• Vision Air Complete spectroscopy software

Future Trends and Potential Applications

• Integration with automated sample handling and flow-through cells for high-throughput screening
• Extension to other personal care and pharmaceutical formulations
• On-line process monitoring for real-time quality assurance

Conclusion

Vis-NIR spectroscopy using the DS2500 Liquid Analyzer provides a fast, accurate, and sustainable alternative to standard methods for hand sanitizer quality control. Validated models achieve high correlation with laboratory assays, enabling efficient multi-parameter analysis in under one minute.

References

• AN-NIR-095 Application Note, Metrohm AG