Colorimetric determination of ethanol percentage by volume in alcohol spray using the color comparison test
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Abstract
Determining the ethanol content in alcohol sprays was essential for evaluating the quality of disinfectant products. However, current methods require expensive scientific instruments and must be conducted in a laboratory. The objective of this research was to develop a simple method for determining the type and percentage by volume of
ethanol in alcohol sprays that can be used in the field. The method relies on comparing with a standard color strip without the need for scientific instruments. The study method has utilized the oxidation reaction of ethanol with potassium dichromate in sulfuric acid, examining the optimal temperature and reaction time. Interferences from
methanol and isopropanol were also investigated. A standard color strip was created based on the L*, a*, and b* color values of ethanol solutions. The results were compared with gas chromatography and color spectrophotometry. The experimental results revealed that the reaction at room temperature and 20 minutes resulted in a yellow-green or green solution in alcohol that met the quality standards with ethanol concentrations exceeding 70% by volume. In contrast, low-quality alcohol produced an orange or orange-yellow solution. There was no interference from methanol, but interference occurred from isopropanol. Ethanol concentrations could be visually distinguished at six levels 50%,
60%, 70%, 80%, 90%, and 99.7% by volume. B* values differed significantly at almost all concentrations (p<0.05). The findings were consistent with standard methods. The study results present a low-cost method, costing only 3 baht per sample. This approach is convenient, fast, and suitable for field applications, making it a viable alternative for
self-assessment of disinfectant product quality.
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