A polymeric thin film modified electrode, that is, poly(niacinamide) modified carbon paste electrode (MCPE), was developed for the electrochemical determination of catechol (CC) by using cyclic voltammetric technique. Compared to bare carbon paste electrode (BCPE), the poly(niacinamide) MCPE shows good electrocatalytic activity towards the oxidation of catechol in phosphate buffer solution (PBS) of physiological pH 7.4. All experimental parameters were optimized. Poly(niacinamide) modified carbon paste electrode gave a linear response between concentration of CC and its anodic peak current in the range within 20.6–229.0
Electrochemically controlled formation of thin polymer films at surface of the electrode is one of the sensible techniques to determine new functional active species. Their uses as a monomer or a polymer for modification of several electrodes have been increasingly used in analytical applications [
Structure of catechol.
An assessment of the literature revealed that there are only rare analytical methods for the determination of CC, such as clay-modified electrode [
Cyclic voltammetry (CV) is a powerful analytical technique that provides information about the undergoing characteristic electrochemical processes of an analyte in solution, which is used to diagnose mechanisms of electrochemical reactions, for detection of the species present in solution [
Niacinamide is one of the derivatives of pyridine and readily soluble in water. It is also a main constituent of B-vitamin, required for mammalian daily diet. Due to its significant biological activity, it is widely investigated over the last few decades [
Structure of niacinamide.
The CV response of CC at modified electrode shows some major advantages like high sensitivity, stability, reproducibility, and comparatively lower detection limit. Overall, the modification procedure reported in this article was modest, efficient, and sensitive in the electrochemical detection of CC.
Electrochemical studies were carried out by using an electrochemical work station CHI-660c (CH Instrument-660 electrochemical analyser) coupled with a conventional three-electrode cell comprised of saturated calomel electrode (SCE) as a reference, a platinum wire as a counter electrode, and bare carbon paste electrode (BCPE) or poly(niacinamide) modified carbon paste electrode (MCPE) as working electrode. All the voltammograms were recorded at an ambient temperature of
All chemicals were of analytical grade and used without additional purification. Catechol (CC) was purchased from Himedia (molecular weight = 110.1, purity 99%). Niacinamide was obtained from Sigma Ltd., India (molecular weight = 122.12, purity 99.5%). A stock solution of CC (25 × 10−4 M) was prepared by dissolving in double distilled water (18 MΩ cm). Phosphate buffer solution (PBS) of same ionic strength was prepared (0.2 M) by mixing appropriate ratio of NaH2PO4·H2O and Na2HPO4. Graphite powder of average particle size 50
The BCPE was prepared by hand mixing of 70% graphite powder and 30% silicone oil in an agate mortar and grinded for about 45 min until a homogeneous paste was formed. The paste was packed into a homemade cavity of Teflon tube of 3 mm internal diameter and the surface was smoothened on a weighing paper. Unless otherwise stated, the paste was carefully removed prior to pressing a new portion into the electrode after every measurement. The electrical contact was provided by a copper wire connected to the end of the tube.
Electrochemical polymerisation of niacinamide at the BCPE was carried out using cyclic voltammetric technique. The BCPE was scanned for 10 multiple cycles in an electrochemical cell containing aqueous solution of 1 mM niacinamide monomer in 0.2 M PBS of pH 7.4. The electropolymerisation was achieved by successive cyclic voltammetric sweep between −0.8 V and +1.8 V with the scan rate of 0.1 Vs−1. After that, the polymeric thin film modified electrode, that is, poly(niacinamide) MCPE, was rinsed thoroughly with double distilled water and used for the determination of CC.
The poly(niacinamide) MCPE was fabricated by CV technique in between the potential window −0.8 V to +1.8 V with scan rate 0.1 Vs−1 for 10 multiple cycles in 0.2 M PBS of pH 7.4 until a stable cyclic voltammogram was obtained. In this process of multiple cycles, the voltammogram was slowly descended with increasing in cyclic times as shown in Figure
Mechanism of electropolymerisation of niacinamide on the surface of BCPE.
Cyclic voltammograms of preparation of poly(niacinamide) MCPE and 1.0 mM of aqueous solution of niacinamide in 0.2 M PBS of pH 7.4 at 10 cycles with scan rate of 0.1 Vs−1.
Figure
Cyclic voltammograms of 1.0 mM potassium ferrocyanide at BCPE (dashed line) and poly(niacinamide) MCPE (solid line) at scan rate of 0.05 Vs−1.
An approximate surface coverage of the poly(niacinamide) layer formed on the surface of carbon paste electrode (CPE) was calculated by [
Figure
Cyclic voltammograms for 0.2 mM CC at BCPE (dashed line) and poly(niacinamide) MCPE (solid line) in 0.2 M PBS of pH 7.4 at scan rate 0.05 Vs−1.
In this proposed method, the oxidation steps of CC were located on benzene ring containing two hydroxyl groups, which represents a typical redox system with two-electron oxidation process taking place. In this mechanism, CC (4a) loses two electrons and also loses two protons, forming a cation radical (4b), which further takes place in delocalization of electron (4c). Thus, the resulting 1,2-benzoquinone or cyclohexa-3,5-diene-1,2-dione compound was formed (4d). The mechanism is shown in Scheme
Oxidation mechanism of catechol (CC).
The effect of scan rate for the oxidation of 0.2 mM CC in 0.2 M PBS of pH 7.4 was studied by CV technique at poly(niacinamide) MCPE. According to Randles-Sevcik equation, the peak current is directly proportional to scan rate. Figure
(a) Cyclic voltammograms for 0.2 mM CC at poly(niacinamide) MCPE in 0.2 M PBS of pH 7.4 at different scan rate (
The effect of solution pH has a significant contribution on the electrochemical oxidation and was carefully investigated by CV technique. Figure
(a) Cyclic voltammograms of 0.2 mM CC at poly(niacinamide) MCPE in 0.2 M PBS solution of different pH values (
The electro oxidation of CC was carried out by varying its concentration at poly(niacinamide) MCPE from 20.6
Comparison of linear range and detection limits for catechol with different classical methods and electrodes.
Classical methods | Electrode/modifier biosensors | Detection limits ( | Detection Potential (V) | Refs. |
| ||||
DPV | Bare indium tin oxide electrode | 1.0 | 0.26 | [ |
DPV | DL-norvaline modified GCE | 0.8 | 0.37 | [ |
DPV | [Cu(Sal- | 1.46 | 0.07 | [ |
DPV | GCE/with a composite consisting of silver nanoparticles (AgNPs), polydopamine, and graphene | 0.1 | — | [ |
DPV | PASA/MWNTs composite film modified GCE | 1.0 | — | [ |
CV | Poly-NA modified CPE | | | |
DPV: differential pulse voltammetry; CV: cyclic voltammetry; GCE: glassy carbon electrode; Sal: salicylaldehyde;
(a) Cyclic voltammograms of CC in 0.2 M PBS solution of pH 7.4 at poly(niacinamide) MCPE at scan rate of 0.05 Vs−1 with different concentrations (
In the present work the poly(niacinamide) MCPE was fabricated for the electrooxidation of CC in PBS of pH 7.4 by CV technique. The modified electrode shows a detection and quantification limit of 1.497
The authors declare that there are no competing interests regarding the publication of this paper.
The authors wish to express their gratitude to the Department of Science and Technology and Science and Engineering Research Board, Ref. no. SERB/F/1217/2014-15, Dated 28-05-2014, New Delhi, for financial support of this work.