Catalytic polarographic double wave of cysteine on a hanging mercury drop electrode

Anzenbacher, Pavel; Kalous, V.

doi:10.1135/cccc19723209

Cited by 13 publications

(9 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results of previous studies [11,12,15] and of the experiments represented in Figure 6 indicate that the primary condition for a compound to yield the catalytic peak P in presence of cobalt(II) ions at low scanning rates is the same as for the classical Brdic Ïka reaction [19], i.e., to contain a sulfhydryl (2 2SH) group. The same effect can be also expected for molecules with a disul®dic (2 2S2 2S2 2) group accessible to electroreduction to sulfhydryl.…”

Section: Discussionmentioning

confidence: 83%

“…Between scan rates of 20 and 10 mV s À1 the second peak becomes overlapped by a new more negative wide P peak due to catalytic evolution of hydrogen [11] which increases further when the rate of potential change slows down. The following drawn-out increase of current in the negative potential region signalizes another reaction of catalytic hydrogen evolution which is here at lower scan rates kinetically controlled while at higher rates (not shown in the ®gure) it is diffusion-controlled.…”

Section: Resultsmentioning

confidence: 99%

“…It was already shown [11,15] that the cathodic process in the P peak has an anodic counterpart at positive potentials. Cyclic voltammetry was applied to follow the reaction products in the P peak by polarizing HMDE from positive to negative potentials at the rate of 2 mV s À1 , reversing the scan in the potential region of the peak and returning back to positive potentials at different scanning rates.…”

Section: Resultsmentioning

confidence: 99%

“…With HMDE the reaction of catalytic evolution of hydrogen from slightly alkaline buffered solutions containing thiols and cobalt ions was found to take place in two potential ranges [11]: in addition to the known region around À1.7 V (vs SCE) it appeared also at potentials by some 0.4 V more positive. That more positive reaction, producing on the voltammogram a new peak denoted``P'' [12], becomes particularly prominent at low rates of potential scan [13].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

New Aspects of the Brdička Reaction of Low-Molecular Thiols; Voltammetry at Low Rate of Potential Scan

Heyrovský

2000

Electroanalysis

View full text Add to dashboard Cite

The catalytic evolution of hydrogen on mercury electrodes from solutions of thiols containing cobalt(II) ions can proceed in different ways according to the conditions of electrolysis: in the classical Brdička current at –1.7 V, at HMDE in the “P” peak, especially with low rate of potential scan, around –1.25 V, or at HMDE at –1.5 V after preelectrolysis at the foot of the Co(II) reduction step. The occurrence of the “P” peak is due to reaction in the adsorbed state, preceded by ligand catalytic reduction of the cobalt thiol complex; evolution of hydrogen is catalyzed by unstable intermediates of the surface process.

show abstract

Section: Discussionmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

New Aspects of the Brdička Reaction of Low-Molecular Thiols; Voltammetry at Low Rate of Potential Scan

Heyrovský

2000

Electroanalysis

View full text Add to dashboard Cite

show abstract

“…In polarography with the dropping mercury electrode (DME) a current increasing with decreasing mercury reservoir has been observed in cases of catalytic evolution of hydrogen [7] which was reported also in voltammetry with HMDE [8]; however, the appearance in voltammetry of a new peak at a slow scan rate is, so far, an unusual phenomenon. Anzenbacher and Kalous [9] described a catalytic double wave of cysteine in ammoniacal buffer containing Co(II) with HMDE polarized at the constant rate of 6.7 mV s À1 ; the ®rst wave of their double wave, at 7 1.3 V (SCE), is undoubtedly identical with the prominent peak in Figure 1; however, these authors did not check the character of their double wave by changing the rate of potential scan. In their later article [10] the same authors have shown that from ammoniacal buffer solutions containing thiols, cobalt(II) is electroreduced in various regions of potentials in various forms, some susceptible to irreversible electrooxidation.…”

mentioning

confidence: 94%

Anomalous Dependence of Peak Currents on Scanning Rate in Voltammetry of Co2+, Fe2+, and Ni2+Ions in Presence of Thiols

Heyrovský¹,

Vavřička

1999

Electroanalysis

View full text Add to dashboard Cite

In the voltammetry of complexes of substituted thiols with Co, Fe and Ni, in which the metals are deposited on the electrode, a new faradaic current appears which increases with decreasing rate of potential scan; it is apparently due to a catalytic evolution of hydrogen.Keywords: Thiol complexes, Iron group metals, Electrodeposition, Slow scan, Hydrogen catalysis Cations, which in the form of aquocomplexes are electroreduced in an irreversible reaction, undergo electroreduction at markedly less negative potentials after entering into complexes with particular ligands, e.g., substituted thiols [1,2]. The complexes are electroreduced in the adsorbed state. The electrode reactions of such complexes are of catalytic nature, as the ligands set free after the reduction combine readily with the aquoions prevailing in the solution and thus regenerate the electroactive form. The complexes of Fe(II), Co(II) and Ni(II) belong to this group. In our study of the voltammetric behavior of substituted thiols with hanging mercury drop electrode (HMDE) we observed an unusual phenomenon when the ions of iron group metals were added to the solutions containing thiols: at low rates of negative potential scans new reduction peaks appear which, contrary to the usual voltammetric experience, increase considerably with decreasing scan rate. These new peaks, presumably due to catalytic evolution of hydrogen on metals sparingly soluble in mercury and deposited on its surface [3], turned out to be to a certain extent speci®c for the ligands (e.g., there is a marked difference between the voltammetric reactions of cysteine and homocysteine in the presence of Co(II) [4]). In the light of the present results (cf. ®gures in this note) the catalytic evolution of hydrogen on mercury electrodes should not be considered as a nonspeci®c electrode reaction, as has been common till now.In Figure 1 it is shown how the``anomalous'' peak in linear voltammetry develops with decreasing rate of potential scan. The cobalt(II) cysteine complex is reduced in the current step around 7 1.0 V (SCE) which is preceded by an adsorption prestep at about 7 0.88 V. The small wave between 7 1.20 and 7 1.25 V belongs to the Co(II) ions complexed only by the borate anions from the buffer, and the strong current in the negative potential region is due to the``Brdic Ïka type'' catalysis of evolution of hydrogen on mercury by cysteine cobalt complexes [5,6]. When recorded with gradually slower rates of potential scan the voltammetric curve enclosing the described currents ®rst decreases in all its parts; at a scan rate of 20 mV s À1 a new current appears at 7 1.3 V which grows into an ever more prominent peak when the scan rate slows further down while the original currents continue to decrease. Also in other cobalt(II) solutions of thiols in general, between scan rates of 10 and 1 mV s À1 the new peaks increase up to 10 times. Obviously, when the potential changes suf®ciently slowly a new faradaic process can take place at the electrode. In polarography with the dro...

show abstract

ChemInform Abstract: KATALYTISCHE POLAROGRAPHISCHE DOPPELWELLE VON CYSTEIN AN DER HAENGENDEN QUECKSILBERTROPFEN‐ELEKTRODE

Anzenbacher¹,

Kalous²

1972

Chemischer Informationsdienst

View full text Add to dashboard Cite

show abstract

Catalytic polarographic double wave of cysteine on a hanging mercury drop electrode

Cited by 13 publications

References 0 publications

New Aspects of the Brdička Reaction of Low-Molecular Thiols; Voltammetry at Low Rate of Potential Scan

New Aspects of the Brdička Reaction of Low-Molecular Thiols; Voltammetry at Low Rate of Potential Scan

Anomalous Dependence of Peak Currents on Scanning Rate in Voltammetry of Co2+, Fe2+, and Ni2+Ions in Presence of Thiols

ChemInform Abstract: KATALYTISCHE POLAROGRAPHISCHE DOPPELWELLE VON CYSTEIN AN DER HAENGENDEN QUECKSILBERTROPFEN‐ELEKTRODE

Contact Info

Product

Resources

About