The results show that when the content of ethanol is lower than 5.0%, the measured concentration of sulfite is in good agreement with spiked value. But when the content of ethanol is over 10.0%, the measured values are significantly smaller than the spiked values. Fortunately, for many beers, the ethanol content is about 5% and therefore this method can give adequate results. In the case of ethanol, the interference does not contribute to the detector electrode current since no significant oxidation or reduction current is measured at +0.65Vversus Ag/AgCl. Thus, it appears the ethanol is influencing the enzyme activity [38]. When the enzyme activity is inhibited, less sulfite will be oxidized and less hydrogen peroxide will be produced and there will be a smaller current difference. Note that this type of interferent, one that interferes
with the enzyme reaction, cannot be compensated for
using the predictor electrode method [27,28].