Electrodeposition of 4-Benzenesulfonic Acid onto a Graphite-Epoxy Composite Electrode for the Enhanced Voltammetric Determination of Caffeine in Beverages

Caffeine is widely present in food and drinks, such as teas and coffees, being also part of some currently commercialized medicines, but despite its enhancement on several functions of human body, its exceeding use can promote many health problems. In order to develop new fast approaches for the caffeine sensing, graphite-epoxy composite electrodes (GECE) were used as substrate, being modified by different diazonium salts, synthetized as their tetraflouroborate salts. An analytical method for caffeine quantification was developed, using sware wave voltammetry (SWV) in Britton–Robinson buffer pH 2.0. Detection limits for bare electrode and 4-benzenesulfonic modified electrode were observed circa 145 µmol·L−1 and 1.3 µmol·L−1, respectively. The results have shown that the modification shifts the oxidation peaks to lower potential. Kinetics of the reaction limited by diffusion was more expressive when caffeine was added to the solution, resulting in decreases of impedance, characterized by lower Rct. All results for caffeine determination were compared to a reference chromatographic procedure (HPLC), showing no statistical difference. Analytical parameters for validation were suitably determined according to local legislation, leading to a linear behaviour from 5 to 150 µmol·L−1; precision of 4.09% was evaluated based on the RDC 166/17, and accuracy was evaluated in comparison with the reference method, with recovery of 98.37 ± 2.58%.

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Square-wave voltammetric determination of rutin in pharmaceutical formulations using a carbon composite electrode modified with copper (II) phosphate immobilized in polyester resin

Brazilian Journal of Pharmaceutical Sciences ◽

10.1590/s1984-82502012000400007 ◽

2012 ◽

Vol 48 (4) ◽

pp. 639-649 ◽

Cited By ~ 9

Author(s):

Kellen Heloizy Garcia Freitas ◽

Orlando Fatibello-Filho ◽

Ivanildo Luiz de Mattos

Keyword(s):

Modified Electrode ◽

Composite Electrode ◽

Polyester Resin ◽

Pharmaceutical Formulations ◽

Carbon Composite ◽

X Ray ◽

Square Wave ◽

Wave Voltammetry ◽

Carbon Composite Electrode

A carbon composite electrode modified with copper (II) phosphate immobilized in a polyester resin (Cu3(PO4)2-Poly) for the determination of rutin in pharmaceutical samples by square-wave voltammetry is described herein. The modified electrode allows the determination of rutin at a potential (0.20 V vs. Ag/AgCl (3.0 mol L-1 KCl)) lower than that observed at an unmodified electrode. The peak current was found to be linear to the rutin concentration in the range from 9.9 × 10-8 to 2.5 × 10-6 mol L-1, with a detection limit of 1.2×10-8 mol L-1. The response of the electrode was stable, with no variation in baseline levels within several hours of continuous operation. The surface morphology of the modified electrode was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) system. The results obtained are precise and accurate. In addition, these results are in agreement with those obtained by the chromatographic method at a 95% confidence level.

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Characterization of graphite-epoxy composite electrodes for free electrochemical detection of adenine and guanine in DNA

Journal of Electrochemical Science and Engineering ◽

10.5599/jese.1005 ◽

2021 ◽

Author(s):

Abel Ibrahim Balbin Tamayo ◽

Leodanis Correa Fajardo ◽

Ana Margarita Esteva Guas

Keyword(s):

Square Wave Voltammetry ◽

Construction Materials ◽

Composite Electrodes ◽

Single Chain ◽

Electron Transfer Rate ◽

Redox Probe ◽

Wave Voltammetry ◽

Electron Transfer Rate Constant

Graphite-epoxy composites (GECs) are alternative construction materials for electrochemical sensors. For these materials, the electron transfer rate constant of some redox reaction depends additionally on the stoichiometric relationship between the insulating and conducting phases of the composite. In this work, the influence of different ratios of araldite/hardener/graphite on the electrochemical properties of GEC electrodes is evaluated for the simultaneous determination of adenine and guanine in the single chain DNA, using the square wave voltammetry technique. Six GEC electrodes were prepared with different ratios of components, and electrochemically characterized by cyclic voltammetry in the presence of ferri/ferrocyanide redox couple as a redox probe. GEC electrodes that showed the best electrochemical responses of redox probe were characterized by thermogravimetric analysis (TGA) and used for the simultaneous determination of free adenine and guanine in a solution, and DNA oligonucleotides. The best results were obtained for GEC electrodes containing twice higher volume of araldite resin with respect to the hardener. TGA analysis revealed presence of 15-26 % of resin for these GEC electrodes. The obtained results revealed potential application of these GEC electrodes as DNA sensors based on the oxidation signal of guanine.

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Determination of atenolol in environmental water samples and pharmaceutical formulations at a graphite-epoxy composite electrode

International Journal of Environmental & Analytical Chemistry ◽

10.1080/03067310903582358 ◽

2012 ◽

Vol 92 (5) ◽

pp. 561-570 ◽

Cited By ~ 1

Author(s):

Carolina M.F. Calixto ◽

Priscila Cervini ◽

Éder T.G. Cavalheiro

Keyword(s):

Water Samples ◽

Composite Electrode ◽

Epoxy Composite ◽

Pharmaceutical Formulations ◽

Environmental Water ◽

Environmental Water Samples

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Determination of hydroquinone in a square wave voltammetry procedure using a graphite-polyurethane composite electrode

Eclética Química ◽

10.1590/s0100-46702006000400009 ◽

2006 ◽

Vol 31 (4) ◽

pp. 59-62 ◽

Cited By ~ 3

Author(s):

P. Cervini ◽

E.T.G. Cavalheiro

Keyword(s):

Confidence Level ◽

Square Wave Voltammetry ◽

Composite Electrode ◽

Limit Of Detection ◽

Voltammetric Sensor ◽

Square Wave ◽

Polyurethane Composite ◽

Wave Voltammetry

In order to a better characterization of a graphite-polyurethane composite intended to be used as a voltammetric sensor, the performance in a square wave voltammetric procedure was investigated. Using hydroquinone (HQ) as a probe, the electrode showed to be useful in square wave voltammetry with limit of detection of 0.28 µmol L-1, with recoveries between 99.1 and 101.5%. The results of the proposed method agreed with HPLC ones within 95% confidence level.

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