RESUMO
A new nanocomposite (ZnO/Cysteic acid) was deposited on glassy carbon electrode by cyclic voltammetry. Uniform deposition of the nanocomposite was observed by scanning electron microscopy. The electron transfer characteristics of two food additives, sunset yellow and tartrazine, were greatly improved on the modified electrode. The prepared electrode was used in the sensitive simultaneous determination of sunset yellow and tartrazine by differential pulse voltammetry. Linear calibration curves were obtained in the concentration ranges of 0.1-3.0, and 0.07-1.86µM, and detection limits of 0.03 and 0.01µM for sunset yellow and tartrazine, respectively. The proposed method was evaluated by determination of the dyes in processed soft drinks with satisfactory results (recovery>95% and RSD%<5%).
Assuntos
Compostos Azo/análise , Corantes/análise , Ácido Cisteico/química , Técnicas Eletroquímicas/métodos , Aditivos Alimentares/análise , Nanocompostos/química , Tartrazina/análise , EletrodosRESUMO
An electrochemical sensor for the sensitive detection of acyclovir was developed by the electropolymerization of Eriochrome black T at a pretreated glassy carbon electrode. The surface morphology of the modified electrode was characterized by field emission scanning electron microscopy. Under the optimized conditions, a significant electrochemical improvement was observed toward the electrooxidation of acyclovir on the modified electrode surface relative to the unmodified electrode. The detection limit of 12 nM and two linear calibration ranges of 0.03-0.3 µM and 0.3-1.5 µM were obtained for acyclovir determination using a differential pulse voltammetric method in acetate buffer (0.1 M, pH 4.0). Real sample studies were carried out in human blood serum and pharmaceutical formulations, which offered good recovery (98-102%). The electrode showed excellent reproducibility, selectivity and antifouling effects.
Assuntos
Aciclovir/análise , Antivirais/análise , Técnicas Eletroquímicas , Polímeros/química , Aciclovir/sangue , Antivirais/sangue , Carbono/química , Eletrodos , Vidro/química , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Oxirredução , Reprodutibilidade dos Testes , Comprimidos/químicaRESUMO
Electrochemical deposition was used to prepare a glassy carbon electrode modified with multi-walled carbon nanotubes and the glycosidic compound, rutin (R/MWCNTs/GCE). Cyclic voltammetry of the modified electrode in aqueous solution (pH8) showed a pair of well-defined, stable and reversible redox peaks with surface confined characteristics. The catechol moiety of rutin produced the voltammetric peaks via a 2 electron, 2 proton mechanism in the range of 0.0-0.4V (vs. Ag/AgCl). The transfer coefficient (α), heterogeneous electron transfer rate constant (ks), and surface concentration (Γ) for R/MWCNTs/GCE were calculated by using the cyclic voltammetric data. The modified electrode showed excellent catalytic activity toward oxidation of methimazole. Fixed-potential amperometry was used for sub-micromolar determination of methimazole at pH8. Linear dependence of anodic current to methimazole concentration was obtained in the range of 0.1-26µM of the drug with a limit of detection at 18nM. The modified electrode retained its initial response for at least 2weeks if stored in dry ambient conditions. The electrode was used for the amperometric determination of methimazole in formulations and spiked blood serum samples, successfully.
Assuntos
Técnicas Eletroquímicas/métodos , Metimazol/análise , Nanotubos de Carbono/química , Calibragem , Catálise , Técnicas Eletroquímicas/instrumentação , Eletrodos , Desenho de Equipamento , Humanos , Limite de Detecção , Metimazol/sangue , Oxirredução , Reprodutibilidade dos Testes , Rutina/química , Comprimidos/análiseRESUMO
The interaction between gabapentin (GP), a neuroleptic drug, and calf-thymus DNA was investigated. Cyclic voltammetry and different spectroscopic methods (UV/vis spectrophotometry, spectroflourimetry and circular dichroism) were used to study the process. The oxidation current of GP was considerably decreased in the presence of calf-thymus DNA. The negative shift of the peak potential in cyclic voltammetry suggested an electrostatic interaction, while spectroscopic methods show minor groove binding as the predominant mode. The values of binding constants obtained from UV absorption, spectrofluorimetry and voltammetric measurements were in close agreement. Standard Gibbs free energy change, ΔG(0), of the interaction was calculated to be -21.99 kJ mol(-1) which indicated the spontaneity of the binding interaction. A hyperchromic effect in the maximum absorption band of DNA as well as quenching in fluorescence experiments were observed in the presence of GP.