Determination of Alcohol Content in Hand Sanitizers by Headspace GC-FID

Importance of the Topic

Hand sanitizers have become essential tools for infection control during the COVID-19 pandemic. Regulatory bodies such as the U.S. CDC recommend formulations containing at least 60 % ethanol or 70 % isopropanol to ensure antimicrobial efficacy.

Objectives and Study Overview

This study aims to develop and validate a headspace GC-FID method for quantifying alcohol content in commercial hand sanitizers. The focus is on using nitrogen as an economical carrier gas alternative to helium while maintaining analytical performance.

Used Instrumentation and Methodology

A Shimadzu HS-20 headspace autosampler was coupled to a Nexis GC-2030 gas chromatograph fitted with an SH-Rxi™-624Sil MS column and FID detector. Key parameters included:

• Headspace oven: 85 °C; sample line: 100 °C; transfer line: 110 °C; equilibration: 20 min; pressurization: 90 kPa N₂
• GC oven: 50 °C (1 min), ramp to 250 °C at 20 °C/min; injector split ratio 50:1; carrier gas: nitrogen at 27.3 cm/s
• Standards prepared in Milli-Q water with acetonitrile (internal standard) and n-butanol (surrogate standard), employing a 2 % NaCl matrix modifier to enhance sensitivity

Main Results and Discussion

• Separation of ethanol, isopropanol, acetonitrile, and n-butanol was achieved with clear baseline resolution under nitrogen.
• Calibration exhibited excellent linearity (R² > 0.9998) over 0.1–5 % (v/v).
• Repeatability at 0.1 % (v/v) level showed RSD < 0.3 % for ethanol and IPA.
• Analysis of three commercial samples (gel and liquid types) yielded ethanol contents of ~69–70 % and IPA contents of ~2.8–2.9 % or ~72 %, with RSD < 1.2 %.
• Surrogate recovery of n-butanol was ~99–101 %, confirming minimal matrix interference and reliable quantification.

Benefits and Practical Applications of the Method

By utilizing nitrogen as the carrier gas, operating costs are significantly reduced without compromising separation or sensitivity. The headspace approach prevents column contamination from non-volatile additives found in sanitizers. This robust method is suitable for routine quality control in pharmaceutical and regulatory laboratories.

Future Trends and Potential Applications

• Integration of automated sample handling and data processing to improve throughput
• Expansion to monitor other volatile impurities or denaturants in sanitizer formulations
• Adoption of alternative detectors (e.g., MS) for structural confirmation
• Standardization of headspace protocols for regulatory compliance across global markets

Conclusion

The headspace GC-FID method described here offers a cost-effective, precise, and reliable approach for alcohol quantification in hand sanitizers. The use of nitrogen carrier gas and internal/surrogate standards ensures high throughput and minimal matrix effects, meeting the demands of modern QA/QC environments.

Reference

• CDC recommendations for hand hygiene in healthcare settings, 2020
• Shimadzu Application News No. G333, Alcohol Determination of Sanitizer Gel by USP<611>
• Lee J. et al., Int. J. Environ. Res. Public Health, 17(9):3326, 2020
• US EPA Method 5021A, Volatile Organic Compounds by Equilibrium Headspace Analysis, 2014
• Ettre LS, Kolb B., Static Headspace–Gas Chromatography, Wiley, 2006