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Chromatographia - A theoretical model is used to predict retention times of divalent metal cations in single-column ion chromatography using one or more ligands in the eluent. Stability constants... 相似文献
2.
J. Tamm A. Alumaa A. Hallik U. Johanson L. Tamm T. Tamm 《Russian Journal of Electrochemistry》2002,38(2):182-187
The influence of anions ClO4
–, NO3
–, Cl–, SO4
2–, and DDS– (dodecyl sulfate) on the cyclic voltammetric response of polypyrrole-modified electrodes is studied. The change in the film composition is examined by electron probe microanalysis. It is established that essential changes in the shape of voltammograms take place during cycling if the anions are not sufficiently freely mobile in the polymer film and insertion of cations from the solution is necessary to guarantee electroneutrality of the system. Some differences between the mobility of Cl– ions and ClO4
– or NO3
– ions are in good agreement with the results of semi-empirical quantum chemical calculations showing that the interaction of Cl– and Br– ions with pyrrole oligomers is stronger than that of NO3
– or ClO4
– ions. Nevertheless, it is established that the peak current determined from voltammograms increases linearly with the increase of the scan rate with very high correlation coefficient. It means that it is possible to describe the behavior of ClO4
–, NO3
– and Cl– ions in the framework of the model of free ions. The redox behavior of the PPy films doped with anions of low mobility such as SO4
2– and DDS– depends essentially on the nature of cations in the test solution. It is found that the mobility of cations increases in the row Li+ < Na+ < K+ < Cs+. The mobility of DDS– ions in the PPy in ethanolic solution is significantly higher and their electrochemical properties are quite similar to PPy|Cl or NO3
– film in aqueous solution. 相似文献
3.
Adsorption of naphthalene on a polarized bismuth electrode was studied from the ethanolic solutions of LiClO4 by means of differential capacity measurements. Two regions of adsorption of naphthalene (13.2 and ?1.3 μC cm?2) corresponding to different orientations of naphthalene molecules at the electrode surface were discovered. A sharp capacity maximum at far positive charges indicates that formation of a polymolecular adsorption layer consisting of the adsorbed naphthalene molecules in flat orientation occurs. By use of the Gibbs equation and of double layer theory the surface excess of naphthalene, adsorption energy, potential drop across the inner layer and some other adsorption parameters have been calculated for a wide range of charges. The π-oribital interaction energy of naphthalene with the bismuth surface has been estimated for various charges. A comparison of the adsorption behaviour of naphthalene in ethanolic and aqueous solutions was made. 相似文献
4.
Allan Hallik Ants Alumaa Väino Sammelselg Jüri Tamm 《Journal of Solid State Electrochemistry》2001,5(4):265-273
Polypyrrole/dodecylsulfate (PPy/DDS) films were synthesized in aqueous and ethanolic solutions and investigated in aqueous,
ethanolic, methanolic and acetonitrile solutions by cyclic voltammetry (CV). The amounts of anions and cations in the films
before and after electrochemical treatment were determined by electron probe microanalysis (EPMA); the film morphology was
studied by scanning electron microscopy (SEM). The results prove that the mobility of bulky DDS– ions in PPy increases in the order: water<acetonitrile<ethanol<methanol. It was found that dopant DDS– ions can be easily removed from PPy matrix swollen in alcohols or acetonitrile by electrochemical reduction or by soaking
in electrolyte solutions of these solvents. The influence of electrochemical treatment on the change of doping level in aqueous
solution is essentially less and depends on the cations in the test solution. Although the electroneutrality of PPy/DDS films
during redox cycling is realized mainly by movement of the cations in aqueous solution and by movement of the anions in organic
solvents, nevertheless the participation of anions in aqueous and cations in organic solvents is also established. The redox
properties of PPy/DDS are more dependent on the solvent of the test solutions than of the synthesis solutions.
Electronic Publication 相似文献
5.
Summary Ion chromatography and potentiometry were used for the determination of the stability constants Pb, Zn, Co, Ni, Mn tartrate
complexes at different ionic strengths. An extrapolation function based on the Debye-Hückel equation was applied to obtain
the thermodynamic stability constants. 相似文献
6.
The influence of different divalent cations (M2+) on the electrochemical charging/discharging process of polypyrrole/sulfate (PPy/SO4) films has been investigated. In principle, two different types of M2+ were found: (a) cations that cause the break-in phenomenon in the PPy film during electrochemical cycling with a gradual
increase of film electroactivity and (b) cations in whose solutions the PPy film remains mainly electroinactive. Certain correlations
have been drawn between several physico-chemical properties of the investigated cations and the break-in and passivation phenomena.
The break-in and passivation phenomena were found to be influenced by the size and deformability of the cation hydration shell,
ion covalent index and softness, as well as by the pH value of the test solution. 相似文献
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