Oxidation of polyacetylene in aqueous solutions containing sulphuric acid and selected supporting oxidants

It has been found that the addition of strong oxidants such as HNO₃, NaNO₂, KMnO₄, K₂Cr₂O₇ and NaIO₃ to an aqueous solution of sulphuric acid greatly facilitates the insertion of HSO₄^? ions into (CH)_x. [CH-(HSO₄)_y]_x formation occyrs even in less concentrated solutions in which sulphuric acid alone does not oxidize polyacetylene. Based on the above observation, a new analytical method for NO₃^? determination has been proposed. The method consists of acidification of any neutral, aqueous solution of a nitrate salt with sulphuric acid to 5.7 M. Although H₂SO₄ of such concentration does not oxideze polyacetylene, in the presence of NO₃^?, doping occurs due to the formation of free HNO₃ upon acidification. The doping reaction results in a significant increase of the electronic conductivity of the polyacetylene, σ. Log σ vs NO₃^? concentration plots are linear over a nitrate concentration range of 2 - 40 mM and can be utilized in chemical analysis. The selectivity of the proposed method is limited. Although the majority of common ions (HSO₄^?, Cl^?, PO₄^3?, etc. …) do not influence the measurements, the presence of other (than HNO₃) oxidants in the solution must be avoided.