Abstract: Modified electrodes, suitable for use in flow injection anal., were obtained by the electrostatic assembly of films constituted by 2 different porphyrins, namely, µ-meso(tetrapyridyl)porphyrinatecobalt(III)tetrakis[bis(bipyridine)(chloro)ruthenium(II)] and meso-tetra(4-sulfonatephenyl)porphyrinatezinc(II), forming alternating layers onto glassy carbon surfaces. The films were studied by cyclic voltammetry and proved to be strongly adherent and highly stable. They could be used for at least a week without loss of sensitivity. In addition, they exhibit an enhanced amperometric response and good protection against fouling, e.g., by phenol oxidation products. Their usefulness in flow injection analysis of NO2- and SO32- was demonstrated. Excellent signal to noise ratios were obtained for SO32- down to 10^-6 mol/L, and for NO2- down to 10^-7 mol/L.

Abstract: The build-up of polymetallic supermolecules based on porphyrins and ruthenium bipyridine complexes has been pursued with great interest. A relevant series of symmetric polynuclear species has been obtained by attaching four [Ru-II(bipy)(2)Cl] groups to the pyridyl substituents of meso-tetra(4-pyridyl)porphyrin and its metallated derivatives. These compounds display a rich electrochemistry and versatile catalytic and photochemical properties, associated with the ruthenium-bipyridine and metalloporphyrin complexes. The supermolecular species interact very strongly with DNA, yielding by irradiation with visible light, very efficient single-strand breaks and formation of 8-oxo-7,8-dihydroxo-2-deoxyguanosine. Another interesting property of the supramolecular porphyrins is their ability to form homogeneous and adherent molecular films by dip-coating. When combined with anionic porphyrins, self-assembled films can be generated, layer-by-layer, in a controlled way. Both types of films display photoaction response in the presence of visible light. The modified electrodes exhibit rectifying response in the presence of reducing species, demonstrating excellent performance as FIA detectors for biological and environmentally relevant substrates such as dopamine, NADH, ascorbic acid and sulfite ions.

Abstract: A glassy carbon electrode modified with a molecular film of tetraruthenated cobalt-porphyrin complex was used in a FIA system for the amperometric determination of NADH and dopamine. The working electrode was maintained at 0.85 V (for NADH) or 0.9 V (for dopamine) vs. a Ag/AgCl reference electrode with a steel auxiliary electrode. The carrier stream was 0.05 M acetate buffer at pH 4.7 at a flow rate of 0.8 ml/min and the injection volume was 130 µL. Calibration graphs were linear from 2-8 µM and 0.2-0.8 µM NADH and dopamine, respectively; detection limits were at the ppb level.