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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Cristina Delerue Matos

Abbrev:
Delerue Matos, C.
Other Names:
Cristina Delerue-Matos
Address:
CEQUP/Departamento de Química-Física, Faculdade de Farmácia (U.P.), Rua Aníbal Cunha 164, 4050 Porto, Portugal
Phone:
+351-22-834-0500
Fax:
+351-22-832-1159

Citations 10

"Electroanalytical Determination Of Paroxetine In Pharmaceuticals"
J. Pharm. Biomed. Anal. 2006 Volume 42, Issue 3 Pages 341-346
Henri P.A. Nouws, Cristina Delerue-Matos, Aquiles A. Barros and José A. Rodrigues

Abstract: Electroanalytical methods based on square-wave adsorptive-stripping voltammetry (SWAdSV) and flow-injection analysis with SWAdSV detection (FIA-SWAdSV) were developed for the determination of paroxetine (PRX). The methods were based on the reduction of PRX at a mercury drop electrode at -1.55 V versus Ag/AgCl, in a borate buffer of pH 8.8, and the possibility of accumulating the compound at the electrode surface. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was also possible to determine PRX using FIA-SWAdSV. This method enables analysis of up to 120 samples per hour at reduced costs. Both methods developed were validated and successfully applied to the quantification of PRX in pharmaceutical products.

"Electroanalytical Study Of The Antidepressant Sertraline"
J. Pharm. Biomed. Anal. 2005 Volume 39, Issue 1-2 Pages 290-293
Henri P.A. Nouws, Cristina Delerue-Matos, Aquiles A. Barros and José A. Rodrigues

Abstract: A flow injection square wave cathodic stripping voltammetric method has been developed for the determination of sertraline in a pharmaceutical preparation. The method shows linearity between peak current intensity and sertraline concentration for the interval between 0.20 x 10^-6 and 1.20 x 10^-6 mol L-1. Limits of detection and quantification were found to be 1.5 x 10^-7 and 5.0 x 10^-7 mol L-1, respectively. Up to 70 samples per hour can be analyzed with a good precision (RSD = 2.5%). The proposed method was successfully applied to the determination of sertraline in a commercial product. In the voltammetric determination of sertraline in flow, a high sample rate is obtained at reduced costs, opening the possibility to compete with the chromatographic methods generally used for this analysis. © 2005 Elsevier B.V. All rights reserved.

"Development Of Electrochemical Methods For Determination Of Tramadol--analytical Application To Pharmaceutical Dosage Forms"
J. Pharm. Biomed. Anal. 2003 Volume 32, Issue 4-5 Pages 975-981
E. M. P. J. Garrido, J. M. P. J. Garrido, F. Borges and C. Delerue-Matos

Abstract: A square-wave voltammetric (SWV) method and a flow injection analysis system with amperometric detection were developed for the determination of tramadol hydrochloride. The SWV method enables the determination of tramadol over the concentration range of 15-75 µM with a detection limit of 2.2 µM. Tramadol could be determined in concentrations between 9 and 50 µM at a sampling rate of 90 h-1, with a detection limit of 1.7 µM using the flow injection system. The electrochemical methods developed were successfully applied to the determination of tramadol in pharmaceutical dosage forms, without any pre-treatment of the samples. Recovery trials were performed to assess the accuracy of the results; the values were between 97 and 102% for both methods.

"Flow Injection System With Potentiometric Detection For The Determination Of Urea Content In Milks"
J. Agric. Food Chem. 1998 Volume 46, Issue 4 Pages 1386-1389
José L. F. C. Lima, Cristina Delerue-Matos, and M. Carmo V. F. Vaz

Abstract: Two variant manifolds of a flow injection analysis (FIA) system are described for the determination of urea content in milks. This determination consists of the enzymatic reaction of urea with urease in which ammonium ion is formed. Ammonium is converted to ammonia by adding a NaOH solution and then led to a gas diffusion unit in which it diffuses to an acceptor channel (Tris/HCl, pH 7.5). Here, it is reconverted to ammonium ion and determined by a tubular configuration electrode sensitive to this ion. One of the FIA manifolds is based on the merging zones technique, whereas the other uses an immobilized enzyme. The results obtained were compared with those given by the Boehringer UV test and by the Official Method of Analysis of the Association of Official Analytical Chemists which can be applied to animal feed and adapted to the matrix studied. The relative deviation was less than 5%, and the precision of the developed methodologies considering RDS (%) was always less than 2%.
Urea Milk Feed Electrode Electrode Potentiometry Immobilized enzyme Gas diffusion Merging zones Volatile generation Method comparison Standard method

"Electroanalytical Study Of The Pesticide Asulam"
Int. J. Environ. Anal. Chem. 2002 Volume 82, Issue 2 Pages 69-76
Henri P A Nouws, Cristina Delerue-Matos, José L F C Lima, E Manuela Garrido, Pieter Vincke, Noel A Maes

Abstract: The electrochemical behavior of the herbicide Asulam was studied by cyclic and square wave voltammetry. Asulam may be irreversibly oxidized at a glassy carbon electrode. Maximum currents were obtained at pH = 1.9 in aqueous electrolyte solution. Based on the electrochemical behavior of Asulam, two analytical methodologies were developed for its determination in water samples, using square wave voltammetry (SWV) and flow injection analysis (FIA) coupled with an amperometric detector. Limits of detection of 7.1 x 10^-6 mol L-1 and 1.2 x 10^-8 mol L-1 for SWV and FIA respectively, were achieved. Repeatability was calculated by assessing the relative standard deviation (%) for 10 consecutive determinations of one sample. The found values were 2.1% for SWV and 5.0% for FIA. Validation of the results provided by SWV and FIA methodologies was performed by comparison with results from an HPLC-DAD technique. Good relative deviations were found (< 5%). Recovery trials were performed to assess the accuracy of the results and the obtained values were between 84% and 107% for both methods.

"Determination Of Citric Acid In Soft Drinks Using Flow Injection With Potentiometric Detection"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 3 Pages 266-269
Jos&eacute; L. F. C. Lima, C. Delerue-Matos, M. Carmo, M. C. V. F. Vaz, Jeanine Silva

Abstract: A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with copper(II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations of citric acid in the range of 1 x 10^-3 mol/L -1 x 10^-2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0% to 101.0%. The system allows a sampling frequency of 60 samples/h.

"Automation Of Iron And Copper Determination In Milks Using FIA Systems And Colorimetric Detection"
Food Chem. 1998 Volume 62, Issue 1 Pages 117-121
Jos&eacute; L. F. C. Lima, Cristina Delerue-Matos* and M. Carmo V. F. Vaz

Abstract: This paper describes a flow injection manifold with a colorimetric detection system that enables the determination of iron and copper in different types of milks, namely cow milk and infant formula powd. milks. The methodology used is based on the formation of colored complexes produced by the reaction of iron (II) with 1,10-phenanthroline and copper(II) with 1,5-diphenylcarbazide. The samples were digested with nitric and sulfuric concentrated acids and inserted in the FIA system without additional treatment. The pH adjustment was carried out inside the manifold including the addition of the reagents needed to form the absorbing species. The sample rate of both species was never lower than 120 determinations h-1. The results obtained were compared with those given by the reference methods, and the relative deviation was less than 5 and 4% for the determinations of iron and copper respectively. The precision of the results evaluated by the relative standard deviation (RSD%) was less than 0.5% for iron and 2% for copper determinations
Iron(2+) Copper(II) Cows Milk Powder Spectrophotometry Sample preparation Complexation pH Method comparison

"Electroanalytical Study Of The Pesticide Ethiofencarb"
Anal. Lett. 2006 Volume 39, Issue 12 Pages 2387-2403
M. F&aacute;tima Barroso; M. Carmo; V. F. Vaz; M. Goreti; F. Sales; Paula Pa&iacute;ga; Cristina Delerue-Matos

Abstract: A detailed study of voltammetric behavior of ethiofencarb (ETF) is reported using glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). With GCE, it is possible to verify that the oxidative mechanism is irreversible, independent of pH, and the maximum intensity current was observed at +1.20 V vs. AgCl/Ag at pH 1.9. A linear calibration line was obtained from 1.0 x 10^-4 to 8.0 x 10^-4 mol L-1 with SWV method. To complete the electrochemical knowledge of ETF pesticide, the reduction was also explored with HMDE. A well-defined peak was observed at -1.00 V vs. AgCl/Ag in a large range of pH with higher signal at pH 7.0. Linearity was obtained in 4.2 x 10^-6 and 9.4 x 10^-6 mol L-1 ETF concentration range. An immediate alkaline hydrolysis of ETF was executed, producing a phenolic compound (2-ethylthiomethylphenol) (EMP), and the electrochemical activity of the product was examined. It was deduced that it is oxidized on GCE at +0.75 V vs. AgCl/Ag with a maximum peak intensity current at pH 3.2, but the compound had no reduction activity on HMDE. Using the decrease of potential peak, a flow injection analysis (FIA) system was developed connected to an amperometric detector, enabling the determination of EMP over concentration range of 1.0 x 10^-7 and 1.0 x 10^-5 mol L-1 at a sampling rate of 60 h-1. The results provided by FIA methodology were performed by comparison with results from high-performance liquid chromatography (HPLC) technique and demonstrated good agreement with relative deviations lower than 4%. Recovery trials were performed and the obtained values were between 98 and 104%. Copyright © Taylor & Francis Group, LLC.

"Study Of The Voltammetric Behaviour Of Metam And Its Application To An Amperometric Flow System"
Anal. Bioanal. Chem. 2005 Volume 383, Issue 5 Pages 880-885
M. F&aacute;tima Barroso, Paula Pa&iacute;ga, M. Carmo V. F. Vaz, Cristina Delerue-Matos

Abstract: The electrochemical behavior of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17-29 mg L-1. Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at -0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition -0.20 V for 10 s), calibration curves was measured in the concentration range 2.5 x 10^-1 to 1.0 mg L-1 using SWV. The electrochemical behavior of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 µL and an overall flow rate of 2.4 mL min-1. Real samples were analyzed via calibration curves over the concentration range 1.3 x 10^-2 to 1.3 mg L-1. Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L-1), and the value obtained was 1.5%.
Methylcarbamodithioic acid Environmental Electrode Electrode Electrode Voltammetry Voltammetry Electrochemical analysis Amperometry Optimization Calibration pH Linear dynamic range Precision

"Electroanalytical Study Of Fluvoxamine"
Anal. Bioanal. Chem. 2005 Volume 382, Issue 7 Pages 1662-1668
Henri P. A. Nouws, Cristina Delerue-Matos, Aquiles A. Barros, Jos&eacute; A. Rodrigues and Alice Santos-Silva

Abstract: Fluvoxamine (FVX) can be reduced at a mercury-drop electrode, with a maximum peak current intensity being obtained at a potential of -0.7 V vs. Ag/AgCl, in an aqueous electrolyte solution of pH 2. The compound was determined in a pharmaceutical product and in spiked human serum by square-wave adsorptive-stripping voltammetry (SWAdSV) after accumulation at the electrode surface, under batch conditions. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was also possible to determine FVX in the pharmaceutical product by use of a flow-injection analysis (FIA) system with SWAdSV detection. The methods developed were validated and successfully applied to the quantification of FVX in a pharmaceutical product. Recoveries between 76 and 89% were obtained in serum analysis. The FIA-SWAdSV method enabled analysis of up to 120 samples per hour at reduced cost, implying the possibility of competing with the chromatographic methods usually used for this analysis.