Flow analysis with membrane separation and time based sampling for ethanol determination in beer and wine

Flow analysis with time based sampling (FA-TBS) applied for automated determination of ethanol is described. The use of immobilized alcohol oxidase (AOD) and a gas diffusion membrane enabled a highly specific determination of ethanol with amperometric detection of equimolar formed hydrogen peroxide. This flow analysis system had a linear range up to 15% (v/v) ethanol concentration and a detection limit of 0.0001% (v/v) ethanol. The range was adjusted by modified polytetrafluoroethylene (PTFE) membranes of different thickness and pore size as diffusion barrier. Real samples of beer and wine were analyzed without any sample pretreatment or dilution. The correlation with standard methods was very good (r = 0.9992, n = 49). The frequency of analysis was 30 samples h−1.