Electrocatalytic Characteristics of Ferrocenecarboxylic Acid Modified Carbon Paste Electrode in the Oxidation and Determination ofL-Cysteine

Abstract

The electrochemical behavior of l-cysteine studied at the surface of ferrocenecarboxylic acid modified carbon paste electrode (FCMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of l-cysteine is occurs at a potential about 580 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, a and catalytic reaction rate constant, K' h were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of l-cysteine showed a linear dependent on the l-cysteine concentration and linear calibration curves were obtained in the ranges of 10 À5 M -10 À3 M and 4.1 Â 10 À8 M -3.7 Â 10 À5 M of l-cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (2d) were determined as 2.4 Â 10 À6 M and 2.5 Â 10 À8 M by CV and DPV methods. This method was also examined for determination of l-cysteine in some samples, such as Soya protein powder, serum of human blood by using recovery and standard addition methods.

Electrocatalytic Determination of Ascorbic Acid at the Surface of 2,7‐Bis(ferrocenyl ethyl)fluoren‐9‐one Modified Carbon Paste Electrode

“…The comparison of figures 4d and 4c shows the anodic peak current of mediator was greatly increased in the presence of ascorbic acid over that ordinarily observed just for the Fc/Fc þ redox couple spiked in CPE, while the corresponding cathodic peak was disappear on the reverse scan of the potential. This behavior is typical of that expected for electrocatalysis at chemically modified electrodes [14,17,38]. The reaction scheme would probably via following mechanistic steps, which ascorbic acid can be oxidized by 2,7-bis(ferricenium ethyl)fluoren-9-one ion produced in the surface of electrode: …”

“…As can be seen in this figure, the cathodic current would increase with increasing the scan rate, because in short timescale experiments, there is no enough time for the catalytic reaction to take place completely. It can be noted from Figure 5A that, with an increase in the scan rate, the peak potential for the catalytic oxidation of ascorbic acid shifts to the more positive potentials, suggesting a kinetic limitation in the reaction between the redox sites of 2,7-BFEFMCPE and ascorbic acid [17,24,39]. However, the oxidation current for ascorbic acid increased linearly with the square Carbon paste electrode…”

“…Transition metal complexes such as phthalocyanines [4 -8], porphyrins [9], Schiff bases [10,11], hexacyanometallates [12], aquacobalamine [13], quinonic compounds [14,15] and ferrocene and its derivatives [16,17] are well known as electron mediators in the electrocatalytic oxidation of some biologically important compounds. Among these compounds, electrocatalytic oxidation of vitamins such as ascorbic acid (vitamin C, AA) has been more interested in medicine, veterinary science and toxicology, diagnosis of certain metabolic disorders and in the determination of nutritional value of foods [18 -20].…”

Carbon Paste Electrode Incorporating 1‐[4‐(Ferrocenyl Ethynyl) Phenyl]‐1‐Ethanone for Electrocatalytic and Voltammetric Determination of Tryptophan

“…However, some authors have emphasized the instability of the attached materials on the electrodes as a problem arising in the utilization of chemically modified electrodes [17]. It seems that the incorporation of electrocatalysts into the electrode matrix can, even partly, help to solve these problems, and carbon paste electrodes (CPEs), due to their ease and speed of construction, obtaining a new reproducible surface, low residual current compared to the other solid electrodes, porous surface, compatibility with various types of modifiers and low cost have been widely used as a suitable matrix for preparation of CMEs [18,19].…”

Crystal structure of bis(μ2-ferrocenecarboxylato-κ2 O:O′)-bis(1,10-phenanthroline-κ2 N,N′)-(μ2-methanolato-κ2 O,O)dicopper(II) tetrafluoroborate – acetonitrile (1/1), C49H40BCu2F4Fe2N5O5

“…Since its discovery, ferrocene has proven to be a versatile backbone for various ligands because of its rich chemistry, stability and redox properties [9]. Ferrocenecarboxylic acid is the mono-carboxylated ferrocene [10] and widely used in the modification of electrode for biosensors and electrocatalytic oxidation [11][12][13]. As a versatile functionalized ligand, ferrocenecarboxylate is widely used for the construction of heterometallic complexes with other metals.…”