Influence of nonionic surfactants and water activity on to adsorption of 6-thioguanine at the mercury/chlorates(VII) interface

Abstract

The mixed adsorption layers of 6-thioguanine-TritonX-100 and 6-thioguanine-Tween 80 formed at the electrode/chlorate(VII) interface are discussed. The systems were characterized by measurements of differential capacity, zero charge potential, and surface tension at this potential. It was found that 6-thioguanine dominates in the formation of adsorption equilibria of the studied mixture. Competitive adsorption between 6-thioguanine-Triton X-100 and 6-thioguanine-Tween 80, ClO ions or mixed micelles cannot be excluded.

Influence of Mixed 6-Thioguanine-Nonionic Surfactant Adsorption Layers on Kinetics and Mechanism of Bi(III) Ion Electroreduction

“…Similar dependences were observed for the Bi-6-mercaptopurine-Tween 80 and Bi-6-mercaptopurine-Triton X-100 [6]. This was explained by the formed mixed adsorption layers whose presence changed evidently the dynamics of the Bi(III) ion electroreduction process rate [11,12].…”

“…Most probably, the molecules of surfactants start to block the electrode surface pushing out the earlier formed Bi-6TG active complexes from the adsorption layer. A similar situation was observed in the case of 6-mercaptopurine and the surface active substances [12].…”

“…For the same concentration of surfactants, the k s values are always lower in the presence of Tween 80, which proves that it is a more effective inhibitor of Bi(III) ion depolarization on the mercury surface. The studies of adsorption suggest stronger adsorption of Tween 80 compared with Triton X-100 which is explained by the size of surfactant molecules [12,18]. Tween 80 as a larger molecule favors larger electrode constraint making formation of a suitable number of the mentioned active complexes impossible.…”

“…It is worth mentioning that the Bi-6-thioguanine type complex plays a key role as 6-thioguanine dominates in reaching Table 2 The values of current and potential of SWV peaks of 1 × 10 −3 mol • dm −3 Bi(III) ion electroreduction in 2 mol • dm −3 chlorates(VIII) in the presence of 1 × 10 −3 mol • dm −3 6thioguanine and the increasing concentrations of Triton X-100 the adsorption equilibria of the studied mixtures, and what is more, it adsorbs specifically on the electrode surface [18], whereas Tween 80 and Triton X-100 adsorb physically [6,[19][20][21]. With the increasing concentration of surfactants in the electrolyte solution in the presence 1 × 10 −3 mol • dm −3 It should be also emphasized that the stages of dehydration and formation of active complexes in the multi-step Bi(III) ion electroreduction are much faster than those of electron transfer [22,23].…”

Electroanalysis of the Anthelmintic Drug Bithionol at Edge Plane Pyrolytic Graphite Electrode

“…Two distinct potential regions can be identified relative to the potential of about 0.2 V. In the first potential region ( E <0.2 V) one observes an adsorption‐desorption peak, which increases and shifts slightly toward more negative potentials in proportion to the bithionol concentration. In the region of more positive potentials ( E >0.2 V), an increase of the differential capacity at 0.1 μmol L −1 bithionol concentration was observed in comparison to the supporting electrolyte, indicating strong adsorption of bithionol, which predominantly exists as an anion at pH 7.0, considering its pK a =4.82 value; however, differential capacity decreased with further enhancement of bithionol concentration, most probably due to strong adsorption of neutral, polymeric electrochemical oxidation products on the EPPGE surface .…”