<b>RUTHENIUM(III) DETERMINATION BY KINETIC-CATALYTIC METHOD USING THE NILE BLUE-ACIDIC CHLORITE REACTION</b>

Abstract

The mechanism of the Ru(III) catalysed oxidation of Nile blue (3-amino-7diethylamino-8,9-benzo-2-phenoxazine chloride, NB +) by acidic chlorite were investigated by kinetic approach and using the stopped flow technique at 633 nm. The catalysed reaction had a first-order dependence on the concentrations of NB + , H + , ClO 2 and catalyst. The pertinent mechanism, consistent with the experimental results is proposed. Based on the high sensitivity and selectivity of the reaction to the presence of Ru(III), using its catalytic efficiency on the oxidation of Nile blue (NB +) by acidic chlorite, a fixed-time kinetic method is reported for Ru(III) determination. Interference studies confirm that the proposed method allows determination of Ru(III) in presence of wide range of cations, including Pd(II), Rh(II), Fe(III) and Os(VIII). The lowest detection limit for Ru(III) ions is 0.2 nmoles L-1 (2.0 ng mL-1).

Oxidation and Reduction

“…The rate constants and activation parameters for the oxidation have been determined. 132 In the oxidation of alkanethiols to disulfides with chloramine-T (CAT), in alkaline solution, the proposed reactive species are hypochlorous acid and TsNCl − anion. A correlation of reaction rate with Taft's dual substituent parameter equation yielded ρ * = −5.28 and δ = −2.0, indicating the rate-enhancing effect of electron-donating substituents.…”