Herein, we report a simple electroanalytical detection method based on ultra-low cost pencil graphite as an elegant sensor for simultaneous and separation-free detection of Hx, X and UA.

M Gandhi

VIT School of Law

Chennai Campus

Rajagopal D

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Senthil Kumar Annamalai

Vishnu N

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Analytical Methods

Pencil lead is composed of clay and graphite and it has been widely used as a low-cost electrode system in electrochemistry. There are a few reports on chemical modification of PGE as oxygen functionalized surface that has been prepared via a pre-anodization technique for electro-analytical applications. For the first time in this work, we introduce a new strategy for electrochemical derivatization of PGE as Prussian blue (PB) and Fe(bpy)32 + functionalized PGEs (i.e., PGE-PB and PGE-Fe(bpy)32 +), utilizing its intrinsic iron (1.31 wt.%), in 0.1 M KCl-HCl medium. Potential cycling of the PGE with Fe(CN)63 − (as solution phase system) and bipyridyl (as surface adsorbed system) resulted in a facile formation of the hybrid complexes on the PGE surface. Physico and electrochemical characterization of PGE-PB and PGE-Fe(bpy)32 + modified electrodes by Raman, FT-IR and UV–Vis spectroscopies, cyclic voltammetry and several control experiments (graphite nano powder, clay, Fe2O3 modified electrodes) evidenced the formation of surface confined complexes on PGE. It was found that the intrinsic iron in clay is responsible for the complexation reactions. Selective electrocatalytic function for the H2O2 reduction reaction was demonstrated as an application of the PGE-PB system. © 2017 Elsevier B.V.

Journal of Electroanalytical Chemistry

Development of Prussian Blue and Fe(bpy)32+ hybrid modified pencil graphite electrodes utilizing its intrinsic iron for electroanalytical applications

Ellagic acid (EA) is a lactone and polyphenolic functional groups-containing phyto-chemical that has been widely used as an anti-oxidant, anti-cancer and anti-aging cosmetic agent. EA is known as a stable redox active system only in organic medium, but irreversibly oxidized with coupled chemical reactions showing ill-defined redox peaks in aqueous solutions. Interestingly, we report here that electro-oxidation of EA tethered multiwalled carbon nanotube-modified glassy carbon electrode (GCE/MWCNT@EA) showed a well-defined pair of redox peaks with a surface-confined characteristics at Ef = 0.020 V vs Ag/AgCl corresponding to ortho-quinone moiety of oxidized EA in pH 7 phosphate buffer solution (PBS). No such behavior was noticed with EA adsorbed GCE. The GCE/MWCNT@EA was characterized by cyclic voltammetery (CV) and the transfer coefficient (α) and electrode to redox surface layer electron transfer rate constant (ks) were calculated. Physicochemical characterization of MWCNT@EA by FTIR, XRD and Raman Spectroscopy techniques revealed immobilized EA in its native form on MWCNT. Effect of various CNTs on EA electro-immobilization and the features that distinguish each other was highlighted. The GCE/MWCNT@EA showed excellent electrocatalytic activity toward N2H4 oxidation. The mechanism and kinetics of the catalytic reaction was investigated by CV, and the kinetic parameters ca., number of electrons in the rate determining step (na′), total number of electrons (n′), reaction order with respect to N2H4, catalyst reaction rate constant (kchem) were evaluated. Finally, amperometric i-t and flow injection analysis for highly selective sensing of hydrazine without any interference from other biochemicals were validated. © 2016 Elsevier B.V.

Fulltext

Electrochemical immobilization of ellagic acid phytochemical on MWCNT modified glassy carbon electrode surface and its efficient hydrazine electrocatalytic activity in neutral pH

A low-cost pre-anodized 6B-pencil graphite (6B-PGE*) is shown as a fouling-free and renewable electrochemical sensor for mono-phenols and can be used for the detection of mono-phenolic preservatives in pharmaceutical insulin formulations.

A preanodized 6B-pencil graphite as an efficient electrochemical sensor for mono-phenolic preservatives (phenol and meta-cresol) in insulin formulations

An efficient electrochemical sensor for simultaneous electrochemical sensing of three purine compounds, uric acid (UA), xanthine (X) and hypoxanthine (HX), using a graphitized mesoporous carbon (GMC) modified glassy carbon electrode (GCE/GMC) has been demonstrated in pH 7 phosphate buffer solution without any enzyme, prior to electrode activation, surfactant and sample pre-concentration step. Electrochemical investigation of the GCE/GMC with [Fe(CN) 6] 3- indicates metallic conductor like surface features of the modified electrode. A diffusion controlled reaction mechanism was identified for the electro-oxidation of the three purine compounds with an electrocatalytic pathway, except for the UA, where it shows a surface area effect with a mixed-diffusion and adsorption controlled mechanism at higher scan rates (&gt;70 mV s -1). Calculated full-width of the half maximum values for the simultaneous detection of the three purine compounds are 42, 53 and 64 mV respectively and these are the lowest values ever reported in the literature, suggesting effective electron-transfer behaviour of the modified electrode for the purine oxidations. Calibration plots for the simultaneous detection of the purine compounds were linear in the concentration range of 20-400 μM, 20-320 μM and 20-240 μM for UA, X and HX with detection limit values of 110 nM, 388 nM, and 351 nM respectively. Selective sensing of the purine compounds in human blood-plasma, urine and fish samples was successfully demonstrated with recovery values ∼100%. © 2012 The Royal Society of Chemistry.

Graphitized mesoporous carbon modified glassy carbon electrode for selective sensing of xanthine, hypoxanthine and uric acid

A simple electrochemical sensor was designed, based on a glassy carbon electrode modified with "as commercially received" multiwalled carbon nanotubes (GCE/MWCNT), for the simultaneous detection of three purine bases: uric acid (UA), xanthine (X) and hypoxanthine (Hx) by differential pulse voltammetry (DPV). Comparison amongst various carbon nanotubes viz.; as commercially received-MWCNT, functionalized-MWCNT, purified-MWCNT and single walled carbon nanotubes for modified electrode preparation, and in turn for the simultaneous electrochemical detection of the purines by DPV, the "as received MWCNT" modified GCE showed the best performance in terms of well-separated peaks and higher peak current values. Scan rate experiments on discreet oxidations of UA, X and Hx suggested that the electron-transfer mechanism for both UA and X follows a mixed diffusion-adsorption controlled pathway, while in the case of Hx, a diffusion controlled route is followed. Calibration responses for the simultaneous detection of UA, X and Hx were linear up to 700, 200 and 150 μM respectively. Corresponding detection limit values were 141 nM, 134 nM and 2.87 μM. Finally analysis of UA, X and Hx content in three different fresh dead fish samples was successfully demonstrated with recoveries of around 100%. © The Royal Society of Chemistry 2011.

Simple method for simultaneous detection of uric acid, xanthine and hypoxanthine in fish samples using a glassy carbon electrode modified with as commercially received multiwalled carbon nanotubes

Pencil graphite as an elegant electrochemical sensor for separation-free and simultaneous sensing of hypoxanthine, xanthine and uric acid in fish samples

Journal	Data powered by TypesetAnalytical Methods
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	1759-9660
Open Access	0