A simple and low-cost method for determination of methanol in alcoholic solutions

Abstract

Methanol poisoning can occur through consumption of methanol-containing alcohols, especially in areas where production, distribution, sale and consumption of alcohol is lawfully prohibited. Due to its toxic potency, determination of methanol in alcoholic solutions is important. The aim of the present study was to develop a rapid, simple and inexpensive method for quantification of methanol in alcoholic solutions that uses minimal equipment available in most laboratories. The method developed is based microdistillation and chromotropic acid, which can be conducted without sophisticated instruments or personal. The system consists of a micro-tube suspended in a falcon tube to function as a collector. Methanol is separated from wine by microdistillation at 90°C in water bath and converted to formaldehyde in the collector. The collector contains an acidic permanganate solution that converts methanol to formaldehyde. Formaldehyde was then quantified by use of chromotropic acid in concentrated sulfuric acid. Experimental variables were optimized by using central composite design (CCD). Method detection and quantification limits were 183 mg L−1 and 584 mg L−1, respectively. The percent relative standard deviation (RSD%) were between 6.4 and 7.9. Accuracies were between 89.6 % and 92.4 %. Concentrations of methanol in five alcoholic solutions were between 2.9×104 and 3.0×104, mg/L, v/v (ppm). Due to its simplicity and cost effectiveness, this method can be used for routine, real-time determination of methanol in alcoholic solutions.

Keywords

• Formaldehyde
• Chromotropic acid
• Experimental design
• Colorimetry
• Alcoholic beverage