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bThe interactions between rutin or the inclusion complex of rutin-Fcyclodextrin and DNA were investigated by means of cyclic voltammetry, W-vis absorption spectroscopy and fluorescence emission spec~oscopy. The apparent binding constant of rutin with DNA is found to be 2.9X lo4 LJmol. The results showed that the benzopyranic-4-one plane of rutin mainly intercalated into DNA in the absence of pcyclodextrin, while the catecholic portion of rutin was located in the double helix of DNA in the presence of pcyclodextrin.

Low cyanide concentrations are determined with a tyrosinase amperometric biosensor using enzyme immobilized on a preactivated polyamide membrane that is closely attached to the end of a wax-impregnated graphite electrode. The test is performed in the presence of the catechol substrate at -0.200 V versus SCE in 0.1 mol 1-1 phosphate buffer (pH 7.5) (the reduction current results from o-benzoquinone, derived from the tyrosinase driving the oxidation of catechol, which is being measured). The decrease in substrate response within the linear range 2.0 X 10-7-4.0 X 10-5 mol 1-1 is proportional to the square-root of cyanide concentration. This method is characterized by high selectivity and reproducibility.

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