Fast, cost-effective quantification of alcohol content in hand sanitizers by direct injection GC-FID

Significance of the topic

Effective verification of alcohol content in hand sanitizers is critical for controlling microbial contamination and ensuring compliance with pharmacopeial standards. The rapid expansion of hand sanitizer use during public health emergencies such as the COVID-19 pandemic underscores the need for robust, high-throughput analytical methods that deliver accurate results while minimizing cost and instrument downtime.

Aims and overview of the study

This study demonstrates a shortened capillary GC-FID procedure based on USP <611> for direct quantification of ethanol and isopropanol in commercially available hand sanitizers. The method adapts USP <611> Method IIb by accelerating the oven program and incorporating an internal standard to broaden its applicability. The goal is to deliver precise, rapid and cost-effective testing suitable for high-throughput pharmaceutical or QA/QC laboratories.

Methodology and used instrumentation

• Gas chromatograph: Thermo Scientific TRACE 1310 with Instant Connect Split/Splitless injector and Flame Ionization Detector
• Autosampler: AS 1310 liquid autosampler
• Column: TraceGOLD TG-624 SilMS capillary column (30 m × 0.53 mm × 3.0 µm) with HydroGOLD guard column
• Liner: LinerGold Precision quartz wool liner optimized for water dilution
• Carrier gas: helium at constant flow of 4.55 mL/min
• Oven program: initial 50 °C (1 min), ramp 70 °C/min to 250 °C, hold 5.1 min; total run time 9 min
• Injector settings: split ratio 5:1, injector temperature 210 °C
• Detector settings: FID at 280 °C, H2 35 mL/min, air 350 mL/min, N2 40 mL/min
• Software: Thermo Scientific Chromeleon CDS v7.3, compliant with 21 CFR Part 11

Sample and standard solutions (approx. 2% v/v) were prepared by dilution in HPLC-grade water, with acetonitrile as internal standard. Triplicate injections were used for quantitative analysis.

Main results and discussion

• System suitability: ethanol and isopropanol peak asymmetry factors below 1.2, resolution versus internal standard of 7.05 for ethanol and 2.19 for isopropanol
• Repeatability: ethanol/IS and IPA/IS peak area ratio RSDs of 0.47% and 0.16% (n=10) respectively; retention time RSDs <0.1%
• Accuracy: calculated alcohol content within ±2% of the labeled 70% v/v value for all tested samples
• Robustness: over 200 consecutive water-based injections without maintenance, with peak area ratio RSD of 1.93% and retention time RSD ≤0.04%
• Throughput: approximately 144 samples per 24 hours, more than doubling classical USP <611> analysis capacity

Benefits and practical applications

The optimized method reduces analysis time by almost 75% compared to standard USP <611> protocols while maintaining pharmacopoeial compliance. Robust hardware and high inertness minimize downtime and solvent costs. Automated data processing in Chromeleon CDS ensures data integrity, traceability and simplified reporting for QA/QC and regulatory submission environments.

Future trends and potential applications

Integration of this rapid GC-FID approach with laboratory information management systems, expansion to other alcohol-based formulations and adaptation for on-site quality control could further enhance analytical workflows. Advances in miniaturized GC systems and alternative detectors may enable similar rapid analyses in field or mobile laboratories.

Conclusion

The modified TRACE 1310 GC-FID method provides a fast, reliable and cost-effective solution for routine alcohol content testing in hand sanitizers. Its high sample throughput, minimal maintenance requirements and compliance with USP <611> make it a valuable tool for pharmaceutical and quality control laboratories.

Reference

1. World Health Organization. Hand hygiene and alcohol-based hand rubs. WHO website, 2020.
2. United States Pharmacopeia. USP <611> Alcohol Determination. Pharmacopeial Convention, 2020.
3. United States Pharmacopeia. General Notices and Requirements USP <38>. Pharmacopeial Convention, 2015.
4. United States Pharmacopeia. USP <621> Chromatography, Physical Tests. Pharmacopeial Convention, 2017.