Pneumatopotentiometric determination of nanogram amounts of cyanide |
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Authors: | František Opekar |
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Affiliation: | The UNESCO Laboratory of Environmental Electrochemistry, J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, Jilská 16, 110 00 Prague 1 Czechoslovakia |
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Abstract: | Hydrogen cyanide is liberated from aqueous samples by reaction with sulphuric acid and transferred by a stream of nitrogen to a silver porous membrane electrode. Some HCN passes through the membrane into an alkaline dicyanoargentate solution; the cyanide ion produced causes a decrease in the equilibrium Ag+ concentration and the change of potential is related to the amount of cyanide in the sample. The detection limit is 3.0 ng ml?1 cyanide in the injected solution; the relative standard deviation is 0.82% for 17 ng of cyanide. Sulphide interferes (as H2S) but can be removed on a lead acetate column. |
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