A simple and rapid colorimetric detection of methanol, ethanol, and isopropanol and its application toward alcohol-based hand sanitizer quality control

ABSTRACT

A practical colorimetric analysis for alcohol determination was devised using a composite of food colorants, specifically a green solution of brilliant blue FCF and tartrazine at a ratio of 1:5 v/v. This colorimetric method was characterized by its simplicity, user-friendliness, environmental compatibility, cost-effectiveness, and suitability for self-measurement through visual examination. The colorimetric procedure entails admixture 1 mL of the alcohol sample with 50 µL of the green test solution and 250 µL of a 30% NaOH solution at ambient temperature. The ensuing color changes were visually assessed within 5 min. Through color sensing, methanol, ethanol, and isopropanol were identified by the manifestation of lemon yellow, orange, and biphasic solutions, respectively. Ethanol was semi-quantified based on color sensing from green to orange, with corresponding concentration ranges. The limit of detection for both methanol and ethanol was determined to be 30% v/v. The developed method demonstrated an accuracy of 93%, with the error range of 1 − 10% v/v and standard deviation of 3.9% v/v, as confirmed by the analysis of 100 commercially available alcohol-based hand sanitizers. This methodology has the potential for further expansion to encompass a wide range of rapid colorimetric analyses of products containing alcohol, including food items, alcohol raw materials, and cosmetics.

GRAPHICAL ABSTRACT

KEYWORDS:

• Alcohol
• Food coloring
• Colorimetric analysis
• Quick test
• Alcohol-based hand sanitizer

Acknowledgments

The authors also express their gratitude to the Natural Products and Nanoparticles Research Unit (NP2), Faculty of Pharmaceutical Sciences, Chulalongkorn University, for their support to S.C.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Additional information

Funding

This research was supported by the Thailand Science Research and Innovation Fund (TSRI) (CU_FRB640001_23_33_8) to S.C. and the 90th Anniversary of Chulalongkorn University fund, No.GCUGR1125661019M (Ratchadaphiseksompot Endowment Fund) to W.S.