Determination of Ethanol and Isopropanol Content in Hand Sanitizers Using Nitrogen Carrier Gas

Significance of the topic

The COVID-19 pandemic spurred an unprecedented demand for alcohol-based hand sanitizers. Regulatory bodies such as the US FDA, CDC, WHO and USP require sanitizer products to contain between 60 and 95 percent ethanol or isopropanol to ensure germicidal efficacy. An accurate, cost-effective analytical method is essential to verify compliance with these guidelines and safeguard public health.

Objectives and study overview

This study presents a gas chromatography method with flame ionization detection to quantify ethanol and isopropanol in commercial hand sanitizers. The method employs nitrogen as the carrier gas to reduce analysis costs while maintaining regulatory compliance. Two different sanitizer formulations, one based on ethanol and one on isopropanol, were analyzed to demonstrate method performance.

Methodology and instrumentation

• Instrumentation used Shimadzu GC-2030 chromatograph with split splitless injector, FID and AOC-20 Plus autosampler
• Column Rxi-624Sil MS 30 m length 0.32 mm inner diameter 1.8 µm film thickness
• Carrier gas Nitrogen at constant linear velocity of 40 cm per second
• Injector conditions Split mode at 1 to 20 ratio injection volume 1 µL port temperature 250 °C
• Oven program Initial 30 °C hold 4 min ramp at 30 °C per min to 120 °C hold 2 min
• FID settings Detector temperature 250 °C hydrogen flow 32 mL per min air flow 200 mL per min makeup nitrogen 24 mL per min
• Reagents Ethanol 200 proof isopropanol 99.9 percent n-butanol internal standard at 0.5 percent v v
• Data processing LabSolutions LCGC software with internal standard quantification and linear regression without forcing through zero

Main results and discussion

• Calibration performance Four-point calibration for both analytes achieved linearity with r2 greater than 0.999
• Chromatographic separation Baseline resolution of ethanol isopropanol and n-butanol peaks with no interfering signals in blank injections
• Internal standard selection n-butanol chosen over USP specified acetonitrile to avoid coelution and column wear
• Sample analysis Two hand sanitizer products diluted 100 fold in internal standard solution
• Quantified concentrations Ethanol sample measured at 59.11 percent v v with 2.68 percent RSD isopropanol sample at 56.40 percent v v with 1.18 percent RSD
• No carryover observed in blank injections following samples

Benefits and practical applications

• Cost reduction Substitution of nitrogen for helium significantly lowers carrier gas expenses
• Safety and inertness Nitrogen is safer than hydrogen and inert under analysis conditions
• Regulatory compliance Method aligns with USP general chapter on alcohol determination and meets CDC and WHO guidelines
• Applicability Suitable for routine quality control of hand sanitizer manufacturing and verification of active ingredient content

Future trends and potential applications

• Automation and high throughput Integration with autosamplers for increased sample throughput in production environments
• Alternative detection Coupling with mass spectrometry for enhanced specificity and trace impurity profiling
• Expanded matrices Adaptation of the method to assess alcohol content in gels and wipes
• Real time monitoring Development of at line or online GC analysis for process control in sanitizer production facilities

Conclusion

The described GC FID method using nitrogen carrier gas provides accurate precise and cost-efficient quantitation of ethanol and isopropanol in hand sanitizers. Calibration linearity repeatability and absence of interferences demonstrate its robustness for quality control. Adoption of nitrogen enhances safety and reduces operational costs while maintaining compliance with regulatory requirements.

References

• USP General Chapter 611 Alcohol Determination