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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Christopher M. A. Brett

Abbrev:
Brett, C.M.A.
Other Names:
Address:
Departamento de Química, Universidade de Coimbra, 3049, Coimbra, Portugal
Phone:
NA
Fax:
351 39 27703
Email:

Citations 8

"Electroanalytical Techniques For The Future: The Challenges Of Miniaturization And Of Real-Time Measurements"
Electroanalysis 1999 Volume 11, Issue 14 Pages 1013-1016
Christopher M. A. Brett

Abstract: A brief survey of electrochemical methods which can be employed to respond to the challenge of measuring electroactive species in untreated solutions in real-time is made. Particular attention is given to the advantages that can be obtained from miniaturization and protection of the electrode surface against fouling with polymers, together with employment of novel instrumentation techniques. The merits of the batch injection analysis approach in addressing these questions are discussed and illustrated.

"Square-wave Adsorptive-stripping Voltammetry Of Nickel And Cobalt At Wall-jet Electrodes In Continuous-flow"
Electroanalysis 1996 Volume 8, Issue 12 Pages 1169-1173
Christopher M. A. Brett*, M. Beatriz Quinaz Garcia, José L. F. C. Lima

Abstract: The wall-jet cell was equipped with a glassy C working electrode, a Pt tube counter electrode placed in the cell exit and a Ag/AgCl reference electrode placed in a compartment separated by a porous glass frit. Before determination, a Hg thin film was deposited onto the working electrode surface by passing a solution containing 0.1 mM Hg2+ in 0.1 M KNO3/5 mM HNO3 or in the carrier solution used for the determination; a potential of -1 V was applied for 300 s. The analyte solution was added to the carrier solution consisting of 30 mM sodium N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonate]/ 0.1 M NaClO4 and the mixture was pumped at 0.045 ml/s through the system. Determination was effected by applying a deposition potential of -0.7 V for 60 s, followed by scanning to -1.2 V, operated in the square wave mode with an amplitude of 30 mV and a frequency of 100 Hz. Detection limits were 1 nM for both analytes. Calibration plots were linear up to 0.1 µM in both instances.
Cobalt Nickel Voltammetry Voltammetry

"Amperometric Batch Injection Analysis: Theoretical Aspects Of Current Transients And Comparison With Wall-jet Electrodes In Continuous-flow"
Electroanalysis 1995 Volume 7, Issue 3 Pages 225-229
Christopher M. A. Brett, Ana Maria Oliveira Brett, Lucian Costel Mitoseriu

Abstract: Amperometric detection using the batch injection analysis technique has been studied and compared with the current obtained at the wall-jet electrode under similar conditions using the oxidation of potassium ferrocyanide and the injection of samples of volume 10 to 100 µL. The form of the current transients has been analyzed and compared with the steady-state response at wall-jet disk electrodes. Good agreement is found at high dispension rate, differences at lower dispension rates being ascribed to radial diffusion effects. The importance of tip-electrode distance and injection volume have been evaluated; it is shown that the optimum distance is 3 mm and that maximum sensitivity requires a minimum injection volume of 14 µL. A detection limit of 50 µM using simple amperometric detection is estimated. Implications of these results for the efficient application of amperometric batch injection analysis are discussed.
Amperometry Electrode Theory

"Adsorptive Stripping Voltammetry Of Cobalt And Nickel In Flow Systems At Wall-jet Electrodes"
Electroanalysis 1991 Volume 3, Issue 7 Pages 683-689
Christopher M. A. Brett*, Ana Maria C. F. Oliveira Brett, Jorge L. C. Pereira

Abstract: Adsorptive stripping voltammetry of cobalt and nickel in flow systems at wall-jet mercury thin-film electrodes has been investigated and assessed. A HEPES biological buffer with sodium perchlorate electrolyte was employed with excess nioxime, or dimethylglyoxime, ligand, and the accumulated complex on the mercury film surface determined by differential pulse reduction. Concentrations down to 1 nM can be routinely measured. Results at the wall-jet electrode, supported by evidence from LSV and impedance measurements at rotating and stationary electrodes respectively, show the viability of the method.

"Determination Of Chromium(VI) By Batch Injection Analysis And Adsorptive Stripping Voltammetry"
Anal. Lett. 2003 Volume 36, Issue 5 Pages 955-969
Christopher M. A. Brett, Olga M. S. Filipe, C. Susanna Neves

Abstract: A new sensitive voltammetric method is presented for the determination of trace levels of Cr(VI). The method is based on square wave adsorptive stripping voltammetry (AdSV) in conjunction with the electrochemical batch injection analysis technique at mercury thin-film electrodes. The determination of chromium is made in the presence of cupferron as ligand. Relevant experimental parameters are explored and optimized, such as injection mode, cupferron concentration, accumulation potential and time, and square wave parameters. A pre-concentration time of 20 s at -;0.8 V vs. SCE results in a detection limit of 32 nM. The relative standard deviation for 12 measurements of 0.12 µM was 6.5%. Possible interferences by other trace metals are considered.

"On The Suppression Of Zinc-copper Interactions In Square Wave Anodic-stripping Voltammetry In Flowing Solution By Addition Of Gallium Ions"
Anal. Chim. Acta 1997 Volume 339, Issue 1-2 Pages 167-172
Christopher M. A. Brett*, M. Beatriz Quinaz Garcia and José L. F. C. Lima

Abstract: The use of Ga3+ to suppress the formation of Cu-Zn intermetallic compounds during square wave anodic-stripping voltammetry in continuous-flow systems was investigated. The study was carried out using a three-electrode assembly consisting of a Hg thin film electrode on a vitreous C substrate (3 mm diameter), a Ag/AgCl (3 M KCl) reference electrode and a Pt counter electrode. The recommended procedure for determining Zn in the presence of Cu used a supporting electrolyte containing 40 µM-Ga3+ in 0.1 M acetate buffer of pH 4.75 or in 0.1 M sodium perchlorate of pH 3. A deposition potential of -1.4 V was applied for 120 s and the stripping voltammogram was recorded in the square-wave mode after the flow was stopped for 20 s. Under these conditions, a linear calibration graph was obtained for 5-20 nM-Zn and the detection limit was ~20 pM. To analyze mixtures of Cu, Zn, Pb and Cd, two two-stage procedures were recommended, namely, (i) the measurement of Cd, Pb and Cu after deposition at -0.9 V followed by the addition of Ga3+ solution and the depoon of Zn at -1.4 V or (ii) the measurement of Cu after deposition at -0.5 V followed by the addition of Ga3+ solution and the deposition of Zn, Cd and Pb at -1.4 V.
Copper Zinc Lead Cadmium Voltammetry Electrode Interferences

"Anodic-stripping Voltammetry Of Trace Metals By Batch-injection Analysis"
Anal. Chim. Acta 1996 Volume 322, Issue 3 Pages 151-157
Christopher M. A. Brett*, Ana Maria Oliveira Brett and Laura Tugulea

Abstract: Trace metals in sample volumes of 100 µL were determined by square wave anodic-stripping voltammetry using a batch-injection procedure. The measurements were carried out at a Hg film deposited on a vitreous C electrode with a Pt gauze counter electrode and a SCE as the reference electrode. Injections were performed using a programmable motorized electronic micropipette for the accurate additions of 10^-100 µL. Optimum experimental parameters were determined for the in situ formation of the Hg film, the pre-concentration time and the injection rate and injection volume of analyte. These values were used to determine Pb, Cd, Zn and Cu. Detection limits of 2-3 nM were achieved for Pb and Cd in a background electrolyte of 0.1 M KNO3/2 mM HNO3 with an injection volume of 50 µL at 24.5 µL/s, a deposition time of 30 s at -1.3 V and a potential scan in the positive direction with square wave parameters of 25 mV amplitude, 2 mV scan increment and 100 Hz frequency. The linear range extended to 1 µM. The results obtained by the proposed batch-injection procedure were compared to those obtained by FIA and a continuous-flow system with a wall-jet electrode.
Metals Cadmium Copper Lead Zinc Voltammetry Preconcentration Batch injection analysis

"Determination Of Mercury(II) By Invertase Enzyme Inhibition Coupled With Batch Injection Analysis"
Analyst 2002 Volume 127, Issue 8 Pages 1088-1093
Hasna Mohammadi, Mama El Rhazi, Aziz Amine, Ana Maria Oliveira Brett and Christopher M. A. Brett

Abstract: The determination of mercury(II) ions at the trace level by inhibition of the invertase enzyme-catalyzed hydrolysis of sucrose into glucose and fructose coupled to electrochemical batch injection analysis was investigated using two approaches. In the first, the glucose produced was detected by injection of 100 µL samples into the batch injection cell containing a platinum electrode modified by immobilized glucose oxidase. In the second, the glucose and fructose present in injected samples were oxidized directly at a copper-modified glassy carbon electrode. The experimental parameters were optimized and the degree of enzyme inhibition by mercury(II) ions under both conditions was measured. Mercury concentrations in the ng mL-1 range were determined by these two techniques with low sample and reagent consumption. Comparison is made between the two methods and perspectives as a screening test for field application are indicated.