Gas-permeation continuous flow coulometric analysis: Determination of sulphur dioxide

A gas permeation system using two gaseous streams flowing on both sides of a membrane is developed. This gas permeation device and a coulometric detector are adapted for the continuous measurement of relatively high concentrations of sulphur dioxide. The interferences of other gases (NO2, NO and CO2) can be eliminated by using a scrubber behind the gas permeation device in the acceptor stream. The effects of the donor flow rates and gas pressure as well as the membrane thickness on the signal are discussed. The relative standard deviation is 1.3% (n = 7) for 2.002 x 10(-3) mol/mol certified sulphur dioxide.