Visual detection of methanol in alcoholic beverages using alcohol-responsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers as indicators

Abstract

A simple and visual method for quantitative detection of methanol in alcoholic beverages by using alcohol-responsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAM-co-DMAA)) linear copolymers as indicators is developed in this paper. The different number of carbon atoms in the alcohol molecules leads to the differential alcohol-responsive characteristics of the poly(NIPAM-co-DMAA) linear copolymer. With replacement of ethanol with an equal volume of methanol in alcoholic solutions, the poly(NIPAM-co-DMAA) copolymer chains change from the shrinking state to the stretching state isothermally. Therefore, the methanol concentration can be simply detected by observing the optical transmittance change of alcoholic beverages with poly(NIPAM-co-DMAA) linear copolymer as an indicator. The minimum methanol concentration that can be visually detected by using the poly(NIPAM-co-DMAA) linear copolymer containing 12.4 mol% of N,N-dimethylacrylamide is as low as 2.5 vol%. The presented detection method with the poly(NIPAM-co-DMAA) linear copolymer as indicator is quite simple and low-cost, and it is valuable for further design of simple and portable tools for home testing the general population, especially in developing countries.