A model catalyst is described which has properties in common with carbonic anhydrase. The model demonstrates the availability of a mechanism, previously only hypothetical, for the action of the enzyme. It also shows, however, that this mechanism alone is not adequate to produce the high activity of the enzyme.

Models for metal ion function in carbonic anhydrase

Complexes of vanadium(V) with 8-quinolinolate and its substituted derivatives

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for vanadium(V) detection in mineral water samples

A novel sensitive and relatively selective kinetic method is presented for the determination of V(V), based on its catalytic effect on the oxidation reaction of Ponceau Xylydine by potassium bromate in presence of 5-sulfosalicylic acid (SSA) as activator. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Ponceau Xylydine at 640 nm between 0.5 to 7 min (the fixed time method) in H3PO4 medium at 25oC. The effect of various parameters such as concentrations of H3PO4, SSA, bromate and Ponceau Xylydine, temperature and ionic strength on the rate of net reaction were studied. The method is free from most interferences, especially from large amounts of V(IV). The decrease in absorbance is proportional to the concentration of V(V) over the entire concentration range tested (1-15 ng mL−1) with a detection limit of 0.46 ng mL-1 (according to statistical 3Sblank/k criterion) and a coefficient of variation (CV) of 1.8% (for ten replicate measurement at 95% confidence level). The proposed method suffers few interferences such as Cr(VI) and Hg(II) ions. The method was successfully applied to the determination of V(V) in tap water, drinking water, bottled mineral water samples and a certified standard reference material such as SRM-1640 with satisfactory results. The vanadium contents of water samples were also determined by FAAS for a comparison. The recovery of spiked vanadium(V) was found to be quantitative and the reproducibility was satisfactory. It was observed that the results of the SRM 1640 were in good agreement with the certified value.

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B.G. Jeliazkowa

Papers

Catalytic activity and complexation. II. Complex agents, affecting the entrance of the substrate into the coordination sphere of the catalyst☆

Reactivity of vanadium(V) polymeric and monomeric forms in complex formation with p-phenetidine

Catalytic activity and complexation. III. Kinetics of the Oxine activation of a catalytic reaction of vanadium(V)