University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Manuel Chicharro

Abbrev:
Chicharro, M.
Other Names:
Chicharro Santamaría, Manuel
Address:
Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Madrid, Spain
Phone:
+34-91-397-40-41
Fax:
+34-91-397-49-31

Citations 6

"Dopamine And Glucose Sensors Based On Glassy Carbon Electrodes Modified With Melanic Polymers"
Electroanalysis 2004 Volume 16, Issue 15 Pages 1244-1253
Rosa González, Alberto Sánchez, Manuel Chicharro, María D. Rubianes, Gustavo A. Rivas

Abstract: This work deals with the study of polymers electrogenerated from different catechols at glassy carbon electrodes and the analytical applications of the resulting modified electrodes for dopamine quantification and glucose biosensing. The electropolymerization was performed from a 3.0 x 10 -3 M catechol solution (catechol, dopamine, norepinephrine, epinephrine or L-dopa in a 0.050 M phosphate buffer pH 7.40) by applying 1.00 V for 60 min. The properties of the polymers are very dependent on the nature of the catechol, L-dopa being the best. Glassy carbon electrodes modified with melanic polymers electrogenerated from L-dopa and norepinephrine were found to be suitable for dopamine determinations in flow systems, although the behavior was highly dependent on the nature of the monomer. Detection limits of 5.0 nM dopamine and interferences of 9.0 and 2.6% for 5.0 x 10^-4 M ascorbic acid and 5.0 x 10^-5 M dopac, respectively, were obtained at the glassy carbon electrode modified with a melanin-type polymer generated from L-dopa (using 1.0 x 10^-3 M AA in the measurement solution). The advantages of using a melanin-type polymer generated from dopamine to improve the selectivity of glucose biosensors based on carbon paste electrodes containing Pt and glucose oxidase (GOx) are also discussed. The resulting bioelectrodes combines the high sensitivity of metallized electrodes with the selectivity given by the polymeric layer. They exhibit excellent performance for glucose with a rapid response (around 10 seconds per sample), a wide linear range (up to 2.5 x 10^-2 M glucose), low detection limits (143 ?M) and a highly reproducible response (R.S.D of 4.9%). The bioelectrodes are highly stable and almost free from the interference of large excess of easily oxidizable compounds found in biological fluids, such as ascorbic acid (AA), uric acid (UA) and acetaminophen.

"Flow Injection Analysis Of Aziprotryne Using An Electrochemical Sensor Based On Cobalt Phthalocyanine Modified Carbon Paste Electrode"
Electroanalysis 2002 Volume 14, Issue 13 Pages 892-898
Manuel Chicharro, Antonio Zapardiel, Esperanza Bermejo, Elena Madrid, Cristina Rodríguez

Abstract: The detection and determination of aziprotryne in flow injection analysis with an amperometric method based on a carbon paste electrode modified with phthalocyanine is described. The concentrations of herbicide in acidic solutions were determined using the electrocatalytic reduction signal corresponding to herbicide reduction at this kind of electrode. A detection limit of 9 ng/mL (0.9 ng aziprotryne) was obtained for a sample loop of 100 µL at a fixed potential of - 130 mV (vs. Ag/AgCl) in 0.1 M perchloric acid and a flow rate of 4.0 mL/min. The developed method was applied to determine aziprotryne in environmental and tap water samples; using a prior solid-phase extraction step, aziprotryne concentrations lower than 0.2 ng/mL could be measured. Furthermore the modified carbon paste electrodes offered reproducible responses in such system, and the relative standard deviation was 3.1% using the same surface and 4.6% for different surface. The response of the electrodes was stable, with more than 98% of the initial retained activity in the first 35 minutes of continuous use.
Graphite

"Carbon Nanotubes Paste Electrodes As New Detectors For Capillary Electrophoresis"
Anal. Chim. Acta 2005 Volume 543, Issue 1-2 Pages 84-91
Manuel Chicharro, Alberto Sánchez, Esperanza Bermejo, Antonio Zapardiel, María D. Rubianes and Gustavo A. Rivas

Abstract: Carbon nanotubes paste electrodes (CNTPE) prepared with short (1-5 ?m length) and long carbon nanotubes (5-20 ?m length) of 20-50 nm diameter have demonstrated to be highly useful as detectors in flow injection analysis and capillary electrophoresis. Compared to the classical graphite paste electrode, CNTPE improved the detection limits of dopac, ascorbic acid, dopamine, norepinephrine and epinephrine. The content of agglutinant has shown to be an important variable in the preparation of these carbon nanotubes composites. Even when no substantial differences were observed between the electrodes, those prepared with long carbon nanotubes (55.0%, w/w) and mineral oil (45.0%, w/w) have allowed us to obtain less noisy and more reproducible signals. In this article we also report the successful use of a new electrochemical cell for the detection in capillary electrophoresis that allows an easier handling and more reproducible responses. Therefore, the combination of the carbon nanotubes electrocatalytic activity with the known advantages of composite materials, the efficiency of the new electrochemical cell and the excellent separative properties of capillary electrophoresis represents a very important alternative for new electroanalytical challenges. © 2005 Elsevier B.V. All rights reserved.

"Simultaneous UV And Electrochemical Determination Of The Herbicide Asulam In Tap Water Samples By Micellar Electrokinetic Capillary Chromatography"
Anal. Chim. Acta 2002 Volume 469, Issue 2 Pages 243-252
M. Chicharro, A. Zapardiel, E. Bermejo and A. Sánchez

Abstract: A simple end-column electrochemical detector was designed and attached to an available commercial capillary electrophoresis instrument with UV detection to detect different kind of herbicides and to determinate methyl-4-aminophenyl-sulfonylcarbamate (asulam) in water samples. The designed cell is very easy to assemble and disassemble in a short period of time; the working electrode positioning is also quickly achieved without micropositioners. The alignment between working electrode and capillary outlet was very reproducible for the all checked electrodes; the RSD obtained was lower than 6.0% for 100 µm gap distance. In this mode, the non-electroactive and electroactive compounds could be detected by UV and electrochemical detection, respectively at the same time. The electrochemical determination of asulam using micellar electrokinetic capillary chromatography (MEKC) is the first time that is reported. In both detection systems, a linear range was obtained for asulam concentrations lower than 25.0 mg l-1, in boric acid 0.020 mol L-1 at pH 8.20 and containing 0.025 mol L-1 of sodium dodecyl sulfate, to obtain selectivity additional separation by the micellar distribution process. Under these conditions, an experimental detection limit of 0.4 mg L-1 was achieved. A new experimental scheme is also described for asulam determination in tap waters with a previous pre-concentration step. Using both, UV and electrochemical detection, with a previous extraction procedure, the detection limits of asulam in tap water samples were of 1.0 and 0.8 µg l-1, respectively.

"Amperometric Determination Of Sympathomimetic Drugs By Flow Injection Analysis With A Metallic Copper Electrode"
Anal. Chim. Acta 1999 Volume 379, Issue 1-2 Pages 81-88
M. Chicharro, A. Zapardiel, E. Bermejo, J. A. Pérez and L. Hernández

Abstract: The detection and determination of sympathomimetic drugs in flow injection systems with an amperometric method based on a metallic copper wire electrode is described. The copper electrode is shown to give sensitive response toward sympathomimetic drugs, especially for norephedrine in flow injection analysis. The copper electrodes require no pretreatment except polishing before use. Furthermore, the copper working electrode shows stable response in such a system and the relative standard deviation is only 4.6% for 30 consecutive norephedrine injections at a 0.15 mM level. A detection limit of 10^-9 mol (0.15 µg norephedrine) for a sample loop of 0.1 mi was obtained at a fixed potential of +0.6 V (vs. Ag/AgCl) in NaOH 0.1 M and a Bow rate of 2.0 ml/min.
Drugs Norepinephrine Amperometry Electrode

"Electrocatalytic Amperometric Determination Of Amitrole Using A Cobalt-phthalocyanine-modified Carbon Paste Electrode"
Anal. Bioanal. Chem. 2002 Volume 373, Issue 4-5 Pages 277-283
Manuel Chicharro, Antonio Zapardiel, Esperanza Bermejo, Mónica Moreno, Elena Madrid

Abstract: Cobalt-phthalocyanine-modified carbon paste electrodes are shown to be excellent indicators for electrocatalytic amperometric measurements of triazolic herbicides such as amitrole, at low oxidation potentials (+0.40 V). The detection and determination of amitrole in flow injection analysis with a modified carbon paste electrode with Co-phthalocyanine is described. The concentrations of amitrole in 0.1 M NaOH solutions were determined using the electrocatalytic oxidation signal corresponding to the Co(II)/Co(III) redox process. A detection limit of 0.04 µg mL-1 (4 ng amitrole) was obtained for a sample loop of 100 µL at a fixed potential of +0.55 V (vs. Ag/AgCl) in 0.1 M NaOH and a flow rate of 4.0 mL min-1. Furthermore, the modified carbon paste electrodes offers reproducible responses in such a system, and the relative standard deviation was 3.3% using the same surface, 5.1% using different surface, and 6.9% using different pastes. The performance of the cobalt-phthalocyanine-modified carbon paste electrodes is illustrated here for the determination of amitrole in commercial formulations. The response of the electrodes is stable, with more than 80% of the initial retained activity after 50 min of continuous use.