On the nature of polarographic waves in nickel and cobalt dimethylglyoximate solutions

Mairanovskii, S. G.; Prokhorova, G. V.; Осипова, Е. А.

doi:10.1016/0022-0728(89)85068-5

Cited by 18 publications

(9 citation statements)

References 31 publications

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“…28 It is worth recalling that the mechanism of electrode processes known under the generic designation of catalytic hydrogen evolution is elusive. For instance, it was recently proved that, despite the previous interpretation, 29 the cathodic peak occurring in the presence of dimethylglyoxime and Co(II) or Ni(II) is not due to catalytic hydrogen evolution but to the successive reduction of the metal ion and the ligand in an adsorbed complex. [30][31][32] On the other hand, catalytic hydrogen evolution was proposed as being responsible for the occurrence of the adsorptive cathodic stripping peaks of cobalt or nickel in the presence of quinolinethiol.…”

Section: Reaction Mechanismmentioning

confidence: 97%

Catalytic hydrogen evolution in cathodic stripping voltammetry on a mercury electrode in the presence of cobalt(ii) ion and phenylthiourea or thiourea

Spătaru

Bănică

2001

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The system Co(II)-phenylthiourea (PTU)-borax buffer was investigated by cathodic stripping voltammetry (CSV) at a hanging mercury drop electrode. The results of the voltammetric measurements showed that the presence of both PTU and Co(II) gives rise to a new irreversible peak at about -1.5 V. Based upon our previous results obtained in the study of other sulfur compounds and the sulfide ion itself, the peak was ascribed to the catalytic hydrogen evolution superimposed on the reduction of the coordinated Co(II) ion. The catalyst itself is a Co(II) complex with the sulfide ion produced by the decomposition of the analyte during the deposition step. The influence of PTU and cobalt concentration, accumulation conditions and stripping parameters was investigated and complementary data on thiourea are included. The results showed that the measurement of the catalytic hydrogen evolution peak current can be used as a basis for a simple, accurate and rapid method for the determination of PTU within the concentration range 10-100 nM. The catalytic method is relatively free of interferences and could be a suitable alternative for cases in which the stripping peak due to mercury ion reduction in the accumulated mercury compound is disturbed by some interference.

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Section: Reaction Mechanismmentioning

confidence: 97%

Catalytic hydrogen evolution in cathodic stripping voltammetry on a mercury electrode in the presence of cobalt(ii) ion and phenylthiourea or thiourea

Spătaru

Bănică

2001

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“…The enhancement of the limiting current of Co or Ni in the presence of DMG [21] was utilized many times for the determination of trace concentrations of these elements by AdSV methods [22,23]. The effect of an enhanced current of Co or Ni was attributed to catalytic reduction of the hydrogen ions [23] or exclusively to the adsorptive process [24].…”

Section: The Systems With Voltammetrically Active Ligandsmentioning

confidence: 99%

“…The effect of an enhanced current of Co or Ni was attributed to catalytic reduction of the hydrogen ions [23] or exclusively to the adsorptive process [24]. Detailed electrochemical [20,25] and spectroscopic studies [20] have shown that the electrochemical reduction of the Co-DMG and Ni-DMG complexes in aqueous media involves the overall reduction of both the central metal ion and the surrounding ligands, DMG in an overall 10-electron reduction process presented by Equations 11 and 12:…”

Section: The Systems With Voltammetrically Active Ligandsmentioning

confidence: 99%

Catalytic Systems in Adsorptive Stripping Voltammetry

2000

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“…1,12-14 Burger et al also have supported this general class of mechanism . The principal evidence supporting the thesis of the catalytic hydrogen reduction has been based on the reported formation of gas bubbles during reductive electrolysis on the HMDE surface by Prokhorova et al. , and the presence of the maxima on dc polarographic waves, which is consistent with catalytic reduction of hydrogen ions. ,− The mechanism described by eqs 13−16 has been modified several times by Russian investigators but is always based on the assumption of the catalytic reduction of hydrogen ions and no change in the redox state of dimethylglyoxime. However, the concept of a catalytic evolution of hydrogen has been widely criticized.…”

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confidence: 94%

Electrochemical and Spectroscopic Investigation of the Reduction of Dimethylglyoxime at Mercury Electrodes in the Presence of Cobalt and Nickel

et al. 1998

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Voltammograms (polarograms) obtained from solutions of cobalt and nickel containing dimethylglyoxime (dmgH(2)) are widely used for the trace determination of these metals. Detailed electrochemical and spectroscopic studies on the reduction process observed in the analytically important ammonia buffer media at mercury dropping, hanging, and pool electrodes are all consistent with an overall 10-electron reduction process, in which both the dmgH(2) ligand and cobalt ions are reduced in the adsorbed state: Co(II) + 2dmgH(2) ⇌ (solution) [Co(II)(dmgH)(2)] + 2H(+); [Co(II)(dmgH)(2)] + Hg ⇌ (electrode) [Co(II)(dmgH)(2)](ads)Hg; and [Co(II)(dmgH)(2)](ads)Hg + 10e(-) + 10H(+) → Co(Hg) + 2[2,3-bis(hydroxylamino)butane]. The limited solubility of the nickel complex in aqueous media restricts the range of studies that can be undertaken with this system, but an analogous mechanism is believed to occur. Low-temperature voltammetric studies in dichloromethane at a frozen hanging mercury drop electrode and in situ electron spin resonance electrochemical measurements on more soluble analogues of the dimethylglyoxime complexes are consistent with an initial one-electron reduction step being available in the absence of water. Deliberate addition of water to acetone solutions enables the influence of the aqueous environment on voltammograms and polarograms to be examined. The results of the present study are compared with the wide range of mechanisms proposed in other studies.

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On the nature of polarographic waves in nickel and cobalt dimethylglyoximate solutions

Cited by 18 publications

References 31 publications

Catalytic hydrogen evolution in cathodic stripping voltammetry on a mercury electrode in the presence of cobalt(ii) ion and phenylthiourea or thiourea

Catalytic hydrogen evolution in cathodic stripping voltammetry on a mercury electrode in the presence of cobalt(ii) ion and phenylthiourea or thiourea

Catalytic Systems in Adsorptive Stripping Voltammetry

Electrochemical and Spectroscopic Investigation of the Reduction of Dimethylglyoxime at Mercury Electrodes in the Presence of Cobalt and Nickel

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