Determination of free and total sulphur dioxide in wine by use of an amalgamated piezoelectric sensor

A piezoelectric quartz crystal where the gold electrode is amalgamated with mercury is proposed as a sensor for sulphur compounds. The sensor is selective towards such compounds in both the vapour phase (particularly SO2 and H2S) and liquid phase. The dependence of its responsiveness to SO2 on the mercury concentration, amalgamation conditions and experimental procedure is discussed. The sensor is especially stable under continuous-flow conditions. For application to the determination of free and bound sulphur dioxide in wine, a continuous-flow manifold was developed with a view to combine sample treatment and detection on-line. The results thus obtained were favorably compared with those provided by the Ripper recommended method. The reproducibility of analyses of real wine samples was better than 3.5% and recoveries ranged from 98 to 103%.