Conductimetric and spectrophotometric determination of the volatile acidity of wines by flow injection

Abstract

Usual methods for the determination of the volatile acidity of wines are relatively slow, as about 40 min are necessary to perform one analysis. In this work, a method was developed which provides results in a much shorter time. About 60 analyses can be performed in 1 h. The conductimetric analysis consists of the injection of the wine sample into a de-ionized water stream which then flows past a poly(tetrafluoroethylene) membrane separator. The acetic acid diffuses through the membrane into another water stream that passes through a conductivity cell. The spectrophotometric method is similar. The acetic acid diffuses into a stream of Bromocresol Purple solution, at pH 7.0, which passes through a flow cell in a spectrophotometer set at 540 nm. For comparison, analyses were also carried out by the method of Jaulmes.