Two-parameter determination in vinegar by a flow injection-pervaporation system

A flow injection method (FI) for the sequential determination of ethanol an d acetic acid in vinegar is reported. The determination of ethanol is based on the oxidation of the pervaporated ethanol by K2Cr2O7. The acetic acid i s determined by an acid-base reaction with Thymol Blue as the indicator. Bo th reactions are monitored photometrically at 600 nm using a single detecto r. Optimisation studies and assessment of the sequential FI method are also reported. The linear determination range is 0-12% v/v for ethanol and 0-10 % (grams of acetic acid in 100 ml) for acetic acid. The sample throughput o f the sequential manifold is seven per hour. The new method was applied to vinegar samples and the results obtained were in excellent agreement with t hose from reference methods used in Spain.