Analysis of methanol–ethanol mixtures from falsified beverages using a dual biosensors amperometric system based on alcohol dehydrogenase and alcohol oxidase

A portable bienzymatic analytical system was developed for the chronoamperometric analysis of methanol–ethanol mixtures. The system consists of two biosensors, one based on alcohol dehydrogenase (ADH) that responds only to the ethanol and the second one based on alcohol oxidase (AOX) that responds to both methanol and ethanol. The transducers were screen-printed electrodes (SPEs) modified with mediators: Meldola blue for ADH and Co-phthalocyanine for AOX. The calibration graph of the ADH biosensor is linear between 0.3 and 8 mmol/L ethanol. The AOX biosensor is able to quantify both analytes in mixtures that contain methanol between 3 and 70 mmol/L and ethanol ranging from 15 to 110 mmol/L. Interferences due to non-specific oxidations from common oxidizable compounds like gallic acid and ascorbic acid were smaller in the case of transducer based on Meldola blue. The analytical system was successfully tested on real samples: non-alcoholised beer (NAB) spiked with ethanol or methanol and a falsified rose wine (FRW).