Volume 2, Issue 1, 1984
24th September, 2022
Electrochemical removal of protecting groups of interest in peptide synthesis
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by Maia H.L.S. et al.
1-14
DOI: doi:10.4152/pea.198401001
O efeito de túnel na junção semicondutor-electrólito
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by da Silva A. M.
15-22
DOI: doi:10.4152/pea.198401015
A model -is presented of the space charge layer formed •in semiconductors deposited as a thin layer on an insula tor substrate.
The variations in charge transfer coefficients is stu died for tin oxide electrodes.
The anodic current density arising from a tunnel effect is calculated by a simplified expression, which considers the variation in barrier width with applied potential.
The use of a sulphur dioxide probe for measurements in gaseous streams
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by de Azevedo S. J. C. F.
23-27
DOI: doi:10.4152/pea.198401023
Resposta de eléctrodos selectivos de suporte de resina condutora com sensor de sulfureto de prata(I) a baixas concentrações de catião prata(I)
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by Silva M. G. P. et al
29-55
DOI: doi:10.4152/pea.198401029
Apresentam-se e discutem-se os resultados obtidos no estudo do comportamento de eléctrodos selectivos de suporte de resina condutora com sensor de sulfureto de prata (I) em resposta a baixas concentrações de catião prata(I).
As calibrações foram realizadas com soluções padrões de nitrato de prata(I) (>10 M), com soluções tampões de complexaçao obtidos com o sistema catiao prata(I)-EDTA (10 a ~ 10 M em catião prata(I) livre), com soluções tampões de precipitação obtidas com halogenetos de prata(I) (10 a 10 M em catião livre) e com soluções de sulfureto com concentração de anião sulfureto fixada por variação de pC (10
a 10 M em catião prata(I) livre). Observou-se resposta linear em toda a gama de concentrações de 10 a -22 10 M em catiao prata(I).
Preliminary studies on the redox properties of substituted ferrocene complexes
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by Herrmann R. et al.
57-66
DOI: doi:10.4152/pea.198401057
The electron donor/acceptor character of a variety of organic groups (X),-CH(R) (NR') ,-CH(R) (OR') ,-CH(R) (OCOR' ) ,-CH(R)N and ^C=Y, was Z X investigated by studying the redox properties (by cyclic voltammetry), the electronic absorption and the ''"H n.m.r. spectra of substituted ferrocene complexes (FcX) with those groups as substituents. An ordering of these groups(X) according to their electron acceptor character was proposed on the basis of the electrochemical data, and the results were discussed in terms of the energy dependence of the involved molecular orbitals of FcX on the electronic properties of the substituent group(X).
Electrochemical reduction of vitamin B1 on the mercury electrode
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by Lopes M. H. et al.
67-81
DOI: doi:10.4152/pea.198401067
The polarographic reduction of vitamin B1 was studied as a function of pH by using three different buffer solutions, namelly, acetate, phophate, and ammoniacal solutions. The results show the possibility of following electrochemical1y the transformations of thiamine in its yellow and thiole forms by measuring the height of the corresponding reduction waves for thiamine and its yellow form, and the height of the oxidation wave of the thiole form. A way of calculating the pK value of the transformation TH - YF is also suggested.
