A GC method for the determination of sulphur dioxide in food headspaces

A gas chromatographic procedure was developed to measure SO2 in the presence of water vapour up to saturation level in the headspace atmospheres of packaged food. A Teflon column packed with Chromosorb 108 was used to separate CO2, SO2, and H2O in that order, then SO2 was determined using an electrolytic conductivity detector operated in a non-catalytic mode. A permeation-tube apparatus, producing SO2 and modified to permit humidification of the effluent stream, was used to calibrate the instrument, and a heated syringe technique was devised which overcame problems of sampling low levels of SO2 in the presence of water vapour. In food headspaces the method was used to determine SO2 at the ng ml-1 level with relative deviations of less than 5%.