RESUMEN
The application of reverse pulse polarography to the determination of substances which form films electrochemically on the mercury electrode is illustrated with penicillamine and cysteine. The dependence of the peak current on several variables is reported and compared with theoretical predictions. It is shown that under optimal instrumental conditions (long drop times and short effective pulses) reverse pulse polarography compares favourably with both normal pulse polarography and differential pulse polarography for the determination of penicillamine and cysteine, concentrations of penicillanline as low as 5 x 10(-8)M being readily determined in the presence of copper(II).
RESUMEN
The reduction at mercury electrodes of a new 5-nitrofuran derivative with antibacterial activity, N2-(5-nitrofurfurylidene)formohydrazide-4-(3,5-dicyanophenyl)-6-ethoxy-2- pyridyl)imide, was studied by conventional, normal pulse, reverse normal pulse and differential pulse polarography in water-dimethylformamide (30%) buffered media. The waves observed, whose number depended on pH, are attributed to the reduction of the nitro group (6 electrons) and the azomethinic unit (4 electrons). The basic mechanisms of the electrode reactions have been deduced from the characteristics of the waves. Conditions for determining the formal potential of the nitroderivative/radical-anion system, a parameter related to pharmacological activity, are also reported.
Asunto(s)
Antiinfecciosos/química , Nitrofuranos/química , Piridinas/química , Concentración de Iones de Hidrógeno , Oxidación-Reducción , PolarografíaRESUMEN
Three lesions showing squamous cell carcinoma in situ (Bowen's disease) within seborrheic keratosis are reported: 2 were located symmetrically on the legs of one of the patients, with a lesion recurring after surgery. Nests of atypical cells were seen in the transitional zone between the 2 components of the third lesion.