Evaluation of the physico-chemical properties of chitosan as a potential carrier for rifampicin, using voltammetric and spectrophotometric techniques.

Rifampicin is an antibiotic which, on a carbon paste electrode, shows an oxidation response of 0.492 V (vs. Ag/AgCl) at pH 7.0, due to the electroactivity of the hydroquinone group. Interaction of rifampicin with chitosan is strongly dependent on pH, species concentrations and contact time between the latter. Compared to the carbon paste electrode, electrodes modified with chitosan showed greater sensitivity, with optimum voltammetric profile obtained at pH 8.0. Spectrophotometric measurements indicate that rifampicin is strongly absorbed by chitosan at pH less than the pKa of the pharmaceutical, such behaviour being favourable for the use of chitosan as a carrier for the controlled release of rifampicin in the intestinal tract.

Electroreduction of the antifouling agent TCMTB and its electroanalytical determination in tannery wastewaters.

The electrochemical reduction of antifouling agent 2-thiocyanomethylthiobenzothiazole (TCMTB) was investigated by cyclic and pulse differential voltammetry. The irreversible electrode reduction of TCMTB proceeded by ECEC reaction mechanism by two electrons transfer with one irreversible wave. Upon the basis of electrochemical evidence, the electrodic reaction mechanism was suggested to formation of mercaptobenzothiazole (MTB) in solution. Subsequently, a pulse differential method is described for the formation of TCMTB based on this electroreduction. Having been obtained a detection limit of 1.0 x 10(-7)mol L(-1) and recovery to 98% to concentration of 2.0 x 10(-6)mol L(-1). Therefore, the proposed method in this study is practical, sensitive and accurate for the analysis of TCMTB in tannery wastewater samples.