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The renewable silver-amalgam film electrode (Hg(Ag)FE) was applied for voltammetric characterization and determination of semi-synthetic macrolide antibiotics azithromycin (AZI), clarithromycin (CLA) and roxithromycin (ROX) in the Britton-Robinson buffer as supporting electrolyte ranging the pH from 4.0 to 11.9. All three macrolides showed reduction signals in fairly negative potential range. During direct cathodic square wave voltammetric (SWV) investigations conducted over the potential range from −0.75 V to −2.00 V vs SCE, either one or two reduction peaks were obtained in the potential range from −1.5 to −1.9 V. The shapes and intensities of the signals depend on the applied pH values in wider pH ranges. For analytical purposes concerning the development of direct cathodic SWV and adsorptive stripping SWV (SW-AdSV) methods the neutral and slightly alkaline media were suitable as pH 7.2, pH 7.4 and pH 7.0 for AZI, CLA and ROX, respectively. Based on the cyclic voltammograms recorded at these pH values, adsorption-controlled electrode kinetics process can be proposed for all three macrolides. Furthermore, the water suppressed 1H NMR measurements in the pH range between 6.0 and 10.5 indicated that the macrolide molecules at the optimal analytical conditions are predominantly in protonated form via their tertiary amino groups which supported in all three cases their adsorption on the appropriately polarized Hg(Ag)FE electrode. The optimized direct cathodic SWV methods showed good linearity in concentration ranges 4.81–23.3 μg mL−1, 1.96–28.6 μg mL−1 and 1.48–25.9 μg mL−1 for AZI, CLA and ROX, respectively. The development of the SW-AdSV methods resulted in the linear responses at lower concentration ranges as 1.0–2.46 μg mL−1, 0.05–0.99 μg mL−1 and 0.10–0.99 μg mL−1, for AZI, CLA and ROX, respectively. The relative standard deviation for all developed methods was not higher than 1.0% except the SWV method for AZI with 4.7%. In the case of all three investigated macr

The electroreduction of cefetamet (CEF) using gold and platinum electrodes has been investigated in slightly alkaline medium (pH 8.40) where adsorption, previously observed at mercury electrode, was pronounced. This investigation was performed in order to determine whether the adsorption interferes with the reduction process even at solid electrodes and to compare with a mercury electrode., Redukcija cefetameta na elektrodama od zlata i platine je proučavana u slabo alkalnoj sredini (pH 8,40) gde je u prethodnim ispitivanjima na živinoj elektrodi u toku reakcije uočena adsorpcija antibiotika. Ovaj rad je posvećen ispitivanju uticaja adsorpcije na elektroredukciju cefetameta na čvrstim elektrodama i poređenju sa živom.

Newly synthesized oximes, mono and bis imidazole derivatives, which promise to be more effective acetylcholinesterase reactivators than standard antidotes used, were investigated by spectrophotometric and electrochemical methods. The electrochemical investigations confirmed the existence of overlapping equilibria, obtained by spectrophotometric methods. Dissociation constants of those oximes were also obtained by numerical treatment of overlapping equilibria, using the Lavendberg-Marquardt least square method, and when compared with the same for some similar compounds, were found to be very effective acetylcholinesterase reactivators. The distribution of ionic forms of the investigated oximes, as a dependence of pH values, was calculated from the obtained values of dissociation constants. The results indicated that many oxime anions will be available at physiological pH 7.4 and a relative increased ability to reactivate inhibited acetylcholinesterase could be expected.

Pulsation of potential of a gold electrode in the double-layer region, between the p.z.c. and a several hundred millivolts more positive value, was found to increase the rate of hydrolysis of tertiary butyl acetate. The homogeneous rate constant of hydrolysis at 35°C was found to be 1.4×10-6 s-1 in the absence of the electric field imposed by pulsation, while in the presence of the field at the ratio of the electrode surface area to the volume of reacting solution of 0.08 cm-1, it was found to be up to 7.2×10-5 s-1 indicating a heterogeneous rate constant of 9×10-4 s-1 cm-2. Effects of changing the potential limits, the frequency of pulsation and the ratio of time intervals during which the electrode has been maintained at one or the other potential limit have been recorded. The same effects are found when gold was replaced by silver. Tertiary butyl acetate is known to undergo hydrolysis by bond breaking between oxygen and tertiary carbon atom and the formation of a carb-cation radical intermediate. It is assumed that the catalytic effect is due to the polarisation of the adsorbed and suitably oriented molecules along the bond in the high electric field acting upon it in the Helmholtz layer during the potential pulse. The process is a non-faradaic one since no charge is transferred across the double layer. © 1979 Elsevier Sequoia S.A.

Pulsation of potential of a gold electrode in the double-layer region, between the p.z.c. and a several hundred millivolts more positive value, was found to increase the rate of hydrolysis of tertiary butyl acetate. The homogeneous rate constant of hydrolysis at 35°C was found to be 1.4×10-6 s-1 in the absence of the electric field imposed by pulsation, while in the presence of the field at the ratio of the electrode surface area to the volume of reacting solution of 0.08 cm-1, it was found to be up to 7.2×10-5 s-1 indicating a heterogeneous rate constant of 9×10-4 s-1 cm-2. Effects of changing the potential limits, the frequency of pulsation and the ratio of time intervals during which the electrode has been maintained at one or the other potential limit have been recorded. The same effects are found when gold was replaced by silver. Tertiary butyl acetate is known to undergo hydrolysis by bond breaking between oxygen and tertiary carbon atom and the formation of a carb-cation radical intermediate. It is assumed that the catalytic effect is due to the polarisation of the adsorbed and suitably oriented molecules along the bond in the high electric field acting upon it in the Helmholtz layer during the potential pulse. The process is a non-faradaic one since no charge is transferred across the double layer. © 1979 Elsevier Sequoia S.A.