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

Importance of Topic

During the COVID-19 pandemic, demand for alcohol-based hand sanitizers soared. Regulatory bodies such as FDA, CDC, WHO and USP mandate that sanitizer formulations contain 60–95% ethanol or isopropanol to ensure effective germicidal action. Accurate and cost-efficient quantification of alcohol content is therefore essential for quality control and regulatory compliance.

Objectives and Study Overview

This study aimed to develop and validate a gas chromatography-flame ionization detection (GC-FID) method using nitrogen as the carrier gas to quantify ethanol and isopropanol in hand sanitizer samples. Two commercial products, one formulated with ethanol and the other with isopropanol, were analyzed to demonstrate method performance.

Methodology and Instrumentation

• Reagents and Standards: Ethanol (200 proof), isopropanol (≥99.9%), and n-butanol (≥99%) as internal standard (IS), diluted in deionized water.
• Instrumentation: Shimadzu GC-2030 with split/splitless injector, flame ionization detector (FID) and AOC-20 Plus autosampler.
• Column: Rxi-624Sil MS (30 m × 0.32 mm × 1.8 µm).
• Injection: 1 µL split (1:20 ratio) at 250 °C.
• Carrier Gas: Nitrogen at constant linear velocity of 40 cm/s.
• Oven Program: 30 °C hold for 4 min; ramp 30 °C/min to 120 °C; hold 2 min.
• FID Conditions: 250 °C; H₂ 32 mL/min; air 200 mL/min; makeup N₂ 24 mL/min.
• Data Handling: LabSolutions LCGC software, linear regression calibration without forcing through zero.

Main Results and Discussion

The method achieved baseline separation of ethanol, isopropanol and n-butanol with no interfering peaks or carryover. Calibration curves over a 0.25–1.0% (v/v) range exhibited excellent linearity (r2 > 0.999) for both analytes. Repeatability was high, with relative standard deviations below 3%. Analysis of two hand sanitizer samples yielded:

• Sample 1: Ethanol 59.11% (v/v), RSD 2.68%.
• Sample 2: Isopropanol 56.40% (v/v), RSD 1.18%.

Benefits and Practical Applications

• Nitrogen carrier gas reduces operating costs compared to helium and offers greater inertness than hydrogen.
• Rapid, accurate quantification aligns with USP and CDC guidelines for sanitizer production and quality control.
• Method simplicity and high throughput make it suitable for routine compliance testing in pharmaceutical, cosmetic and industrial laboratories.

Future Trends and Potential Uses

• Extension to multicomponent analysis, including detection of denaturants and impurities via GC-MS coupling.
• Integration with automated sample handling and data processing for higher throughput.
• Development of green chromatography approaches, such as reduced solvent and energy consumption.
• Application in field-deployable or portable GC systems for on-site quality assurance.

Conclusion

The developed GC-FID method with nitrogen carrier gas provides a reliable, precise and cost-effective approach for determining ethanol and isopropanol content in hand sanitizers. It meets regulatory requirements and supports efficient quality assurance workflows.

References

• USP General Chapter 611, Alcohol Determination.