Amperometry coupled to flow injection analysis (FIA) and to batch injection analysis (BIA) was used for the rapid and precise quantification of ciclopirox olamine in pharmaceutical products. The favourable hydrodynamic conditions provided by both techniques allowed a very high throughput (more than 300 injections per hour) with good linear range (2.0–200 µmol L−1) and low limits of detection (below 1.0 µmol L−1). The results obtained were compared with titration recommended by the American Pharmacopoeia and also using capillary electrophoresis. Good agreement between all results were achieved, demonstrating the good performance of amperometry combined with FIA and BIA.
The structure of polytetraruthenated nickel porphyrin was unveiled for the first time by electrochemistry, Raman spectroelectrochemistry, and a hydroxyl radical trapping assay. The electrocatalytic active material, precipitated on the electrode surface after successive cycling of [NiTPyP{Ru(bipy)2Cl}4](4+) species in strong aqueous alkaline solution (pH 13), was found to be a peroxo-bridged coordination polymer. The electropolymerization process involves hydroxyl radicals (as confirmed by the characteristic set of DMPO/(•)OH adduct EPR peaks) as reaction intermediates, electrocatalytically generated in the 0.80-1.10 V range, that induce the formation of Ni-O-O-Ni coordination polymers, as evidenced by Raman spectroelectrochemistry and molecular modeling studies. The film growth is halted above 1.10 V due to the formation of oxygen gas bubbles.
A supramolecular Nickel (II) porphyrin complex containing four pyridyl‐bis(2,2′‐bipyridyl)chloro ruthenium meso substituents was submitted to successive voltammetric cycles in high alkaline media to produce a supramolecular matrix with Nickel centers linked by µ‐peroxo bridges, producing a highly stable thin film able to act as redox mediator for electrocatalytic oxidation of folic acid. The characterization of electrode surface material was performed by Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy. The modified electrode was inserted into a batch injection electrochemical cell used for the rapid and precise quantification of folic acid in pharmaceutical products. The favorable hydrodynamic conditions provided by amperometry‐BIA association allowed a very high throughput with good linear range (1 to 200 µmol L−1) and low detection limit (7.37×10−7 mol L−1). The electrochemical method was applied to the quantification of folic acid in different tablet samples. The results were comparable with values indicated by the manufacturer and those found using high HPLC according to the Brazilian Pharmacopoeia; commercial samples were submitted to a procedure in order to remove lactose of tablets, since carbohydrates act as interfering species. This procedure together with the electrochemical method showed to be simple, rapid, efficient and an appropriate alternative for quantifying this compound in real samples.
Mixed Ni−Co tetraruthenated porphyrin films were successfully electropolymerized on glassy carbon electrodes in alkaline solutions (pH=13) of NiTRP and CoTRP, giving excellent electrocatalytic responses for determination of the antibiotic drug chloramphenicol. Electrodes with four different compositions were obtained by varying the ratio of NiTRP and CoTRP in the deposition solution. For the characterization of these materials, SEM, ICP‐MS, EIS and CV were explored. The porphyrin modified glassy carbon electrodes presented two oxidation peaks for chloramphenicol (except for Ni‐25). The potential shifted to lower values as the percentage of CoTRP increased decreasing its oxidation potential in more than 200 mV for Ni‐50 as compared to Ni‐100. Interestingly, the materials with cobalt content larger than 50 % did not show the typical catalytic response of the NiIIIOOH species, but rather showed an increase in current at potentials larger than 0.4 V, demonstrating the key role played by nickel in this type of materials. The composition of polymeric mixed porphyrin materials influenced the oxidation current response of both redox waves, resulting in different sensitivities on the calibration curves.
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