engleski

Square-wave voltammetry of 5-fluorouracil

The redox reaction of 5-fluorouracil (FU) at hanging mercury drop electrode (HMDE) is studied of square-wave volrammetry (SWV). It is demostrated that the redox raction proceeds according to the sheme L2-(aq) --- L2-(ads) + Hg(l) --Hg(s) + 2e-, which involves both chemosorption of FU on the electrode surface and creation of a sparingly soluble compound with the electrode material. The overall response exhibits properties of a surface process in which both the reactant and the product of the redox reaction are immobilized on the electrode surface. The SWV response of FU prossesses features typical of surface confined processes such as "split SW peks" and "quasi-reversible maximum". The proposed electrode mechanism is studies theoretically. The numerical calculated response under conditions of SWV is in qualitative agreement with the experimental data. Comparing the theoreticla and experimental data, the kinetic parameters of redox reaction investigated are esimated. The standard rate constant appears in interval 54 ks/s-1 to 108, the adsorption constant is K= 10 cm-1, and the transfer coefficient alfa = 54 +-0.01. The effect of the Cu(II) ions on the adsorptive SWV response of FU is discussed from an analtical point of view. It is demonstrated that SWV is appeling technique, which enables determination of FU at an ultar-trace concentration level. A linear calibration plot was established at 10-11 mol/l concentration level with coefficient of R2 = 0.992. The detection limit is 7.7 x 10-12 molL-1. The reproducibility of the results in terms of the relative standard deviation ranges from 0.9 to 3.2 %.

square-wave voltammetry ; 5-fluorouracil ; quasi-reversible maximum

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