Electrochemical determination of tryptophan, uric acid and ascorbic acid at a gold nanoparticles modified carbon paste electrode

Abstract

A carbon paste electrode (CPE) modified with gold nanoparticles was used as a selective electrochemical sensor for the determination of tryptophan (Trp), uric acid (UA) and ascorbic acid (AA). Cyclic voltammetric, chronoamperometric, and differential pulse voltammetric methods were used to investigate the electrocatalytic oxidation of Trp in aqueous solution. The Au nanoparticles modified carbon paste electrode (AuNPs/CPE) showed very efficient electrocatalytic activity for anodic oxidation of Trp, UA, and AA. The linear calibration range for Trp in the presence of 100 mM AA and 50 mM UA was 6-200 mM, with a detection limit of 0.65 mM (S/N ¼ 3). A linear relationship was found for UA in the range of 6-180 mM containing 100 mM AA and 25 mM Trp, with a detection limit of 0.71 mM. The linear calibration range for AA in the presence of 50 mM UA and 50 mM Trp was 20-250 mM, with a detection limit of 2.05 mM. The diffusion coefficient (D) for the oxidation of Trp at the modified electrode was calculated as 2.82 Â 10 À5 cm 2 s À1 . The modified electrode showed good sensitivity and selectivity, and was employed for the determination of Trp, UA, and AA in biological and pharmaceutical samples.

Enhancement of amperometric response to tryptophan by proton relay effect of chitosan adsorbed on glassy carbon electrode

“…3b. The increment of both the anodic potential and peak current for the electro-oxidation of Trp under more acidic conditions has been previously reported for different types of modified electrodes [13,14,28,29], suggesting the relevant role of protons in the electro-oxidation mechanism of Trp [21]. Furthermore, the E pa decreased linearly with pH according with …”

New Insight into the EC’ Mechanism of Uric Acid Regeneration in the Presence of Ascorbic Acid on a Poly(3,4‐ethylenedioxithiophene) Modified Gold Electrode

“…Most papers addressing their electrochemical analysis showed the variation of AA oxidation current in the presence or the absence of UA [27]. For those studying the influence of AA concentration on UA amperometric response, either the concentration of AA was kept constant [28][29][30][31] and/or the AA concentration range adopted was generally high compared to that of UA [32][33][34][35]. In such conditions it was therefore not possible to highlight any electrocatalytic effect even if the EC' mechanism was effective.…”

Synthesis, characterization, and application of silver nanoparticle‐thiophenol nanocomposite film on the glassy carbon surface

“…Because UA and ascorbic acid (AA) are oxidized at nearly the same potential standard on the bare electrodes, voltammetric responses are overlapped and create a real interference problem in simultaneous determination of each species . Because UA and AA are present in biological materials, it is significant to improve a selective method for the determination of UA in the presence of AA …”

“…[36] Because UA and AA are present in biological materials, it is significant to improve a selective method for the determination of UA in the presence of AA. [37][38][39][40][41][42][43][44][45] In this work, we modified the GC electrode with thiophenol (GC/TP) by the reduction of 4-thiophenol (TP) diazonium tetrafluoroborate for further immobilization of SNPs through formation of Ag-S bonds. Firstly, we report the modification of GC with 4-thiophenol and then the immobilization of the SNP to prepare GC/TP/SNP surface.…”