Phase-selective anodic stripping analysis of micromolar cadmium(II) at the micrometer hanging mercury drop electrode in 0.1M potassium chloride

Abstract

0.061 ± 0.001 cm sec™1 with a transfer coefficient of 0.27. Note that the rate constant in this case does not change for a given potential step since the current and therefore the effective potential were almost constant during the time in which currents were measured. Each point on the plot represents one experiment.Attempts were also made to determine kinetic parameters for reduction of Cd(II) in 1.0M KNO3, Cd(II) in 1.0M KC1, and Co(III) tris(ethylenediamine) in 0.1M ethylenediamine/l.OM NaClO*. All three systems proved to have rate constants too large to be measured under the conditions of our experiments. As noted above, the shortest time at which meaningful data could be taken was 30 µ sec. For times of this order, the largest rate constant which could be determined, that is distinguished from diffusion control, is 0.8 cm sec™1. This lower limit of 0.8 cm sec™1 may be compared to the range of 0.6 to 5.0 cm sec™1 found by ac impedance methods for Cd(II) in nitrate and chloride media (11). Laitinen and Randles reported a rate constant of 0.13 cm sec™1 for Co(III) trisfethylenediamine) (12); however, Sluyters-Rehback and Sluyters demonstrated that the reduction of the similar system Co(III) in diethylenetriamine is diffusion controlled though complicated by adsorption of the cobalt complex (13).

Fundamental and second harmonic alternating current cyclic voltammetric theory and experimental results for simple electrode reactions involving amalgam formation

“…Several important observations become apparent on studying experimental data for the cadmium system in 0 Ei = -0.350 V, Es = -0.900 V, v = 50 mV s'1, = 5 mV, = 2 X 400 s'1, E°= -0.635 V, T= 298 K. Theoretical figures calculated using data from Reference 16. All potentials measured relative to Ag/AgCl (1 M NaCI).…”

“…A number of schemes for the attachment of a variety of molecules to electrode surfaces have been proposed and tested recently (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). In only a few instances have the attached molecules exhibited the long-lived, reversible electrochemical behavior that would be essential for effective catalysis of charge transfer reactions involving less reactive substrates to be realized.…”

Experimental factors affecting the phase-selective reversible anodic stripping determination of gallium from 1.0 molar ammonium thiocyanate electrolytes at 60.degree.C and collation of results with sodium thiocyanate/sodium perchlorate-based room temperature measurements

“…Inclusive equations describing the complete phase-selective anodic stripping cycle are probably unattainable and, for guidelines, one must stitch together the results of basic dc stripping studies (21,22), controlled-potential analysis (23), and ac polarography (20,(24)(25)(26)(27). The latter establishes useful guidelines for the appearance, size, shape, and rate dependence of PSAS peaks observed for the analysis step itself.…”

“…The latter establishes useful guidelines for the appearance, size, shape, and rate dependence of PSAS peaks observed for the analysis step itself. Relevant ac expressions for kinetically fast (in the ac sense), purely reversible reduction processes at the spherical mercury microelectrode have been included in discussions cited previously (12,20,(24)(25)(26)(27). Although these equations refer only to the simple, purely Nernstian charge transfer process at a spherical electrode, they are nonetheless moderately complex and are repeated here as Equation 2which depicts economically the expected effects of parameters included in the present study [the reader is referred to the comprehensive discussions of Smith and coworkers (24-26) for an analysis of reaction models that behave quasi-reversibly, or to systems where the interpretation of results is modified by the involvement of coupled chemical reactions.…”

Phase-selective cathodic stripping voltammetry for determination of water-soluble mercaptans

“…Differential pulse cathodic stripping voltammetry at a hanging mercury drop electrode (HMDE) has been employed to determine 2-mercaptopyridine-N-oxide ion with a sensitivity limit of 8 X -10 M (8). Several studies have been devoted to phase-selective anodic stripping (PSAS) (9)(10)(11); however, little attention has been given to the cathodic counterpart.…”