Selective Indicator Reaction for Kinetic Determination of Traces of Manganese(II), Ribavirin and Tiazofurin

 In this work it was established that, in the presence of ammonium carbonate, traces of manganese(II) catalyse the oxidation of Nile Blue A by hydrogen peroxide, which enables its kinetic determination in the concentration range from 6.6 to 65.9 ng cm⁻³, the detection limit being 8.0 × 10⁻² ng cm⁻³. Antiviral/antitumour substances modify the catalytic activity of manganese(II): 1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide, ribavirin, increases the catalytic effect of manganese(II), while 2-β-D-ribofuranosyl-thiazole-4-carboxamide, tiazofurin, acts as an inhibitor. On the basis of these effects, a kinetic method for determining ribavirin concentrations from 0.5 × 10⁻¹ to 4.0 × 10⁻¹ μg cm⁻³ and tiazofurin concentrations from 0.3 to 2.6 μg cm⁻³ is proposed. The kinetics of the indicator reaction were studied in the presence of the substances examined, the kinetic equations established, and the constants of the corresponding reaction rates calculated. The effect of temperature on these reactions was also investigated. The method was applied to the determination of manganese(II) in mineral water and ribavirin in pharmaceutical preparations. Received December 16, 1999. Revision June 6, 2000.