[The role of halogenation in the electro-oxidation of halogenated anilines in acetonitrile as the solvent]. / A halogénezés szerepe halogén-anilinek elektrooxidációjában, acetonitril oldószerben.

The 4-halogeno-, 2,4-dihalogeno- and 2,4,6-trihalogenoanilines were the model substances of the research described. Acetonitrile being one of the most popular aprotic solvent was used. The halogeno monomers were chloro and bromoanilines. The electrodimerised substrate is stabilised by rejecting halogenide ion and protons. The rejected halogenide ions are oxidisable more easier compared to the substrate therefore the halogene formed substitutes both the substrate, and the dimer as well. The protons formed during the oxidation bind by the strong base monomer primary amine. Because of these not only a simple electrodimerisation will take place, but protonised monomers, higher halogenated monomers, and the corresponding dimer molecules are formed in the solution.

4-(1-Naphthylamino)-piperidines as inhibitors of lipid peroxidation.

Some analogues of (+/-)-N-methyl-N-¿1-[3-(4-fluorophenoxy)-2-hydroxy-propyl]-piperidin+ ++-4-yl¿ benzothiazol-2-amine (sabeluzole, CAS 104383-17-7), a series of 4-(l-naphthylamino)-piperidines (1a-1h), are potent inhibitors of both NADPH- and Fe(2+)-dependent lipid peroxidation (IC50 < 10 mumol/1). It was demonstrated that the naphthylaminopiperidine moiety is responsible for this effect due to its antioxidant property, verified by cyclic voltammetric studies.

The study of the differential pulse voltammetric behaviour of ergot alkaloids and their determination by DC amperometric detection in a FIA system.

The ergot alkaloids possess strong pharmacological effects and are important drugs with widespread clinical uses. The ergot alkaloid preparations manufactured by Gedeon Richter Chemical Works Ltd have a very low active substance content (e.g. 1.0 mg in each Secadol (0.4 g) coated tablet); therefore a sensitive method of determination must be used. Because of this constraint the differential pulse voltammetric behaviour of ergot alkaloids was studied in respect of the effects of pH and composition of media and an automated FIA system with amperometric detection has been used to develop a selective and sensitive method for the routine quantitative assay of these alkaloids. A short summary is given of the experimental evidence to substantiate the stoichiometric equation proposed for the electrochemical oxidation of the lysergic acid type of ergot alkaloids, the mechanism may be generally applicable for compounds having the ergoloid skeleton. In the course of the work it was concluded that a simple DC amperometric method of detection in a FIA system could be applied to determine the content of ergot alkaloids of different pharmaceutical preparations. A suitable method designed to meet current analytical requirements has been developed and validated.

Comparative study of a thin-layer cell for analysis of stationary and streaming solutions.

A comparative study with a home-built Kissinger-type twin-electrode thin-layer cell has been made, with the cell either filled with quiescent solutions or used as a flow-through detector. In both modes the cell was polarized by a slow linear potential sweep. The current-voltage curves recorded showed a limiting current region in both cases, in spite of the different types of transport process (steady-state diffusion caused by the redox cycling effect of the counter-electrode in the quiescent solution and convective diffusion in the flowing solution). The sensitivities and also the lower detection limits were found to be nearly the same for the two different modes of operation of the same cell, for which an explanation is given. The main analytical advantage of the thin-layer twin-electrode cell filled with quiescent solution is that only a few mul of analyte solution are necessary for the measurement. It was proved experimentally that this type of cell, used as a flow-through detector, gives the expected limiting current, but this current is dependent on the cube root of the linear flow-rate, in agreement with Weber's theoretical prediction, rather than on the square root of the flow-rate (commonly quoted in the literature).