Determination of total and free sulfur dioxide in wine by pervaporation-flow injection

A simple and interference-free method for the determination of SO2 in wine based on removal of the analyte by pervaporation is proposed. The sulfur dioxide is formed in an acidic stream and removed from the liquid sample at the donor chamber of the pervaporation unit, then collected in an acceptor solution containing p-rosaniline and formaldehyde. The typical coloured compound thus formed is monitored photometrically at 578 nm on passage through a flow cell. The linear determination range is between 2.0 and 20 mu g ml(-1) with a precision, expressed as relative standard deviation, lower than 3.0%. The method has been successfully applied to the determination of free and total sulfur dioxide in red and white wines and compares well with the standard iodimetric method.