Sequential determination of carbon dioxide and free sulfur dioxide in wine by flow-injection pervaporation with in series potentiometric-photometric detection

摘要

A method for the simultaneous determination of CO_2 and free SO_2 in wines based on the use of a continuous arrangement coupled to both a pervaporator and in series arranged potentiometric and photometric detectors is proposed. After pervaporation, both analytes give one common potentiometric signal and then the free SO_2 is photometrically determined via the colored compound formed with p-rosaniline and formaldehyde. The CO_2 content is determined by difference. The range of the method is linear between 2.0 and 20.0 mg/L for free SO_2 and 50.0 and 600.0 mg/L for CO_2, with a precision, expressed as relative standard deviation, of 7% in both cases. The method was applied to different Spanish wines and the results compare well with those obtained by the corresponding official methods.