Collect. Czech. Chem. Commun. 1986, 51, 2077-2082

Determination of subnanogram amounts of sulfur dioxide and sulfites by pneumatopotentiometry

Jan Langmaier and František Opekar

The UNESCO Laboratory of Environmental Electrochemistry, The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 110 00 Prague 1


Gold porous membrane electrode has been used for the potentiometric determination of small amounts of sulfur dioxide absorbed in the solutions of sodium tetrachloromercurate or sodium hydroxide. Sulfur dioxide is released by the reaction with an acid into a stream of nitrogen and led to the electrode immersed into the solution of iodine monochloride. Part of SO2 penetrates through the membrane pores into the solution where it is oxidized. The electrode redox potential change is a measure of the SO2 concentration in the absorption solution. In the solution of 1 . 10-5 M[ICl2]- in 0.02 M-HClO4 the limit of quantitation was found to be 0.07 ng SO2 . ml-1. The relative standard deviations of 1.4% and 2.5% were found for the determinations of 10 ng and 0.5 ng of SO2, respectively. Higher concentrations of H2S interfere only in the hydroxide solution. About 10 samples can be analyzed per one hour.