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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Anastasios Economou

Abbrev:
Economou, A.
Other Names:
Address:
Department of Chemsitry, Aristotelian University of Salonika, GR-54006 Salonika Greece
Phone:
+30-2310-997728
Fax:
+30-2310-997719

Citations 12

"Sequential-injection Analysis (SIA): A Useful Tool For On-line Sample-handling And Pre-treatment"
Trends Anal. Chem. 2005 Volume 24, Issue 5 Pages 416-425
A. Economou

Abstract: In this article, sequential-injection analysis (SIA) is reviewed as a tool for on-line sample manipulation and sample pre-treatment. Although SIA is an established technique for performing solution chemistry, its great potential lies in the scope it offers for the more complicated on-line sample-manipulation stages before the measurement step. This review will demonstrate the scope of SIA in complex sample-handling procedures with examples of on-line sample dilution, dialysis and gas diffusion, extraction (liquid/liquid, gas/liquid and solid-phase), enzymatic and immunological assays, and various other on-line operations. © 2005 Elsevier Ltd. All rights reserved.

"On-line Stripping Voltammetry Of Trace Metals At A Flow-through Bismuth-film Electrode By Means Of A Hybrid Flow-injection/sequential-injection System"
Talanta 2007 Volume 71, Issue 2 Pages 758-765
Anastasios Economou and Anastasios Voulgaropoulos

Abstract: In this work, we describe an automated stripping analyzer operating on a hybrid flow-injection/sequential-injection (FIA/SIA) mode and utilizing a bismuth-film electrode (BiFE) as a flow-through sensor for on-line stripping voltammetry of trace metals. The instrument combines the advantages of FIA and SIA and is characterized by simplicity, low-cost, rapidity, versatility and low consumption of solutions. The proposed analytical flow methodology was applied to the determination of Cd(II) and Pb(II) by anodic stripping voltammetry (ASV) and of Ni(II) and Co(II) by adsorptive stripping voltammetry (AdSV). The steps of the rather complex experimental sequence (i.e. the bismuth-film formation, the analyte accumulation, the voltammetric stripping and the electrode cleaning/regeneration) were conducted on-line and the critical parameters related to the respective analytical procedures were investigated. In ASV, for a accumulation time of 180 s the limits of detection for Cd(II) and Pb(II) were 2 and 1 ?g l-1, respectively (S/N = 3) and the relative standard deviations were 5.3% and 4.7%, respectively (n = 8). In AdSV, for a total sample volume of 1000 µL, the limits of detection for Ni(II) and Co(II) were 1 ?g L-1 (S/N = 3) and the relative standard deviations were 5.5% and 6.2%, respectively (n = 8). The measurement frequency ranged between 15 and 20 stripping cycles h-1. The results indicate that the BiFE is well suited as a flow-through detector for on-line stripping analysis and, by virtue of its low toxicity, can serve as a viable alternative to mercury-based flow-through electrodes. © 2006 Elsevier B.V. All rights reserved.

"Rapid Enzymatic Chemiluminescent Assay Of Glucose By Means Of A Hybrid Flow-injection/sequential-injection Method"
Talanta 2005 Volume 67, Issue 3 Pages 603-609
Polyxeni Panoutsou and Anastasios Economou

Abstract: This work reports a hybrid flow-injection analysis (FIA)/sequential- injection analysis (SIA) method for the rapid enzymatic assay of glucose with soluble glucose oxidase (GOD). The method relies on the sequential injection of segments of the sample and of a solution of enzyme by means of a multi-port selection valve in a flowing water stream. As the two zones are swept downstream, they overlap and merge so that the glucose in the sample is enzymatically oxidized. The generated hydrogen peroxide is merged with an alkaline luminol solution and the chemiluminescence (CL) intensity is monitored and related to the glucose concentration in the sample. The linear range of the method for glucose determination is 0.01-1 mmol L-1, the relative standard deviation is 3.9% at the 0.08 mmol L-1 level (n = 8), the limit of detection at the 2? level is 4 ?mol L-1 glucose and the injection rate is 80 h-1. The method was applied to the analysis of energy drinks and honey with relative errors in glucose determination in the range 100 ± 4.3%. The advantages of the proposed method are the wide linear range, the simple instrumentation used, the low consumption of sample and reagents, the elimination of catalysts and immobilized enzymes and the high sample throughput. © 2005 Elsevier B.V. All rights reserved.

"Selective Determination Of Nickel(II) And Cobalt(II) By Flow Injection Analysis And Adsorptive Cathodic Stripping Voltammetry On A Wall Jet Mercury Film Electrode"
Talanta 1998 Volume 46, Issue 5 Pages 1137-1146
A. Economou* and P. R. Fielden

Abstract: Ni(II) and Co(II) were determined simultaneously by adsorptive cathodic stripping voltammetry (AdCSV) in a computerized flow injection system. The working electrode was a glassy C disk that was fitted in a wall-jet flow cell. The electrode was initially electrochemically coated with a Hg film at -1.0 V by injecting a Hg(II) solution in the flow stream. Then, the sample, containing Ni(II) and Co(II), was mixed online with a solution containing dimethylglyoxime (DMG) at pH 9 to selectively complex the metal ions and was injected in the flow system. After a number of successive injections during which accumulation took place under controlled potentiostatic conditions, the surface-bound complexes were reduced in NH3 buffer at pH 9 by a cathodic scan of the potential of the working electrode in the square wave mode and the current-potential response was recorded. Finally, the electrode surface was regenerated by a potentiostatic polarization at -1.4 V in the same buffer. The app. could be easily converted for continuous-flow accumulation to increase the sensitivity; in this mode of operation, instead of performing discrete injections, the sample was continuously pumped through the cell. Various parameters associated with the pre-concentration, stripping and regeneration steps were optimized for the determination of Ni(II) and Co(II). The selectivity of the method was demonstrated for the anal. of high purity Fe; the accuracy for the determination of Ni(II) and Co(II) was 11 and 3%, respectively while the coefficient of variation was 10 and 8%, respectively.
Nickel(II) Cobalt(II) High purity Voltammetry Voltammetry Electrode Electrode Simultaneous analysis Computer Complexation pH Optimization

"Sequential-injection Analysis: Principles, Instrument Construction, And Demonstration By A Simple Experiment"
J. Chem. Educ. 2005 Volume 82, Issue 12 Pages 1820-1822
A. Economou, P. D. Tzanavaras, and D. G. Themelis

Abstract: Sequential-injection analysis (SIA), an approach to sample handling, enables the automation of the manual wet chemistry procudures in a rapid, precise and efficient manner. The SIA apparatus is constructed and automated using the graphical programming language of LabVIEW. This approach of using the same basic hardware for both flow-injection analysis and SIA is advantageous in terms of pedagogical value, cost-effectiveness, ease of operation and an opportunity to compare the two techniques. Experimental equipment and procedures including chemical measurements, analysis and hazards are outlined.

"Automated Flow-injection Instrument For Chemiluminescence Detection Using A Low-cost Photodiode Detector"
J. Chem. Educ. 2004 Volume 81, Issue 3 Pages 406-410
A. Economou, D. Papargyris, and J. Stratis

Abstract: An overview is given of the development of an FI analyzer for CL detection using a low-cost photodiode. This work demonstrates in a single project how different aspects in chemical instrumentation fit together to produce a working analytical system.

"Polymer-coated Bismuth-film Electrodes For The Determination Of Trace Metals By Sequential-injection Analysis/anodic Stripping Voltammetry"
Anal. Chim. Acta 2006 Volume 576, Issue 2 Pages 283-289
Georgia Kefala and Anastasios Economou

Abstract: In this work, the utility of polymer-coated bismuth film electrodes (BiFEs) was assessed for the simultaneous on-line determination of Cd(II), Pb(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV) in the sequential-injection analysis (SIA) mode. The polymeric Nafion coating was initially plated on a glassy carbon electrode forming part of the flow-through electrochemical cell. The subsequent steps of the bismuth layer generation, analyte pre-concentration, voltammetric measurement and electrode cleaning were conducted on-line. For a sample volume of 1.2 mL, the limits of detection (at S/N = 3) were 2 µg L-;1 for Cd(II) and Pb(II) and 6 µg L-;1 for Zn(II), the coefficients of variation at 20 µg L-;1 were 5.1% for Cd(II), 5.9% for Pb(II) and 6.2% for Zn(II) and the measurement frequency was between 10 and 20 h-;1 (depending on the sample volume aspirated). It is demonstrated that the polymer-coated BiFEs, combined with SIA, can provide an environmentally friendly, sensitive and robust tool to perform rapid and cost-efficient on-line monitoring of trace metals by ASV, even in the presence of surface-active compounds.

"Enzymatic Chemiluminescent Assay Of Glucose By Sequential-injection Analysis With Soluble Enzyme And On-line Sample Dilution"
Anal. Chim. Acta 2006 Volume 572, Issue 1 Pages 140-147
Anastasios Economou, Polyxeni Panoutsou and Demetrius G. Themelis

Abstract: This work reports a sequential-injection analysis (SIA) method for the enzymatic assay of glucose with soluble glucose oxidase (GOD) and on-line sample dilution with chemiluminescence (CL) detection. A zone of sample was aspirated in the holding coil of the SIA manifold and, if necessary, was diluted on-line by means of an auxiliary dilution conduit. Then, a zone of GOD was aspirated adjacent to the sample zone and a stopped-flow period was applied to allow the enzymatic reaction to proceed with production of hydrogen peroxide. Then, zones of a catalyst (Co(II) solution) and alkaline luminol were aspirated into the holding coil. Finally, the flow was reversed and the stacked zones were sent to a flow-cell located in front of a photomultiplier tube (PMT) that monitored the CL intensity. The linear dynamic range was 1 x 10^-5-1 x 10^-3 mol L-;1 glucose, the coefficient of variation at 8 x 10^-5 mol L-;1 of glucose was sr = 3.1% (n = 8), the limit of detection at the 3s level was cL = 1 x 10^-6 mol L-;1 and the sampling frequency was 28 h-;1. With on-line dilution by a factor of 1/200, the linear range could be extended up to 0.2 mol L-;1 glucose. The advantages of the proposed method are the simple manifold and instrumentation used, the scope for automated on-line dilution, the low consumption of sample and reagents and the elimination of enzyme immobilization procedures. The method was applied to the analysis of commercial drinks and honey with percent relative errors in glucose determination in the range 100 ± 6.1%.

"Determination Of Boron In Water And Pharmaceuticals By Sequential-injection Analysis And Fluorimetric Detection"
Anal. Chim. Acta 2004 Volume 510, Issue 2 Pages 219-224
Anastasios Economou, Demetrius G. Themelis, Helen Bikou, Paraskevas D. Tzanavaras and Pantelis G. Rigas

Abstract: This work reports the application of a sequential-injection analysis (SIA) method for the determination of boron. The method relies on the enhancement of the fluorescence (λex=313 nm, λem=360 nm) of chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulphonic acid-CA) as a result of its complexation with boric acid (BA). Individual zones of the sample, the CA solution in a suitable buffer and a NaOH solution were aspirated in the holding coil of the SIA apparatus. As the zones were propelled towards the detector, zone penetration in the sample-CA interfaces occurred resulting in the formation of the strongly fluorescent BA-CA complex. The native fluorescence of the CA was quenched by the alkaline environment established as a result of the mixing at the CA-NaOH interface. The chemical and instrumental parameters affecting the fluorescence intensity were investigated and the influence of potential interferents was investigated. After selecting the most suitable conditions, the calibration plot for boron was linear in the range of 8-350 µg L-1 with a 3s limit of detection of 3 µg L-1 and a relative standard deviation of 2.7% at the 90 µg L-1 boron level (n=8). Finally, the method was applied to the determination of boron in natural waters and pharmaceutical products with revoveries in the range of 96-106%.

"Determination Of Methimazole And Carbimazole By Flow-injection With Chemiluminescence Detection Based On The Inhibition Of The Cu(II)-catalysed Luminol–hydrogen Peroxide Reaction"
Anal. Chim. Acta 2004 Volume 505, Issue 1 Pages 129-133
Anastasios Economou, Paraskevas D. Tzanavaras, Maria Notou and Demetrius G. Themelis

Abstract: This paper reports an indirect flow-injection (FI) method for the determination of the anti-hyperthyroid drugs methimazole and carbimazole in pharmaceuticals. The method was based on the inhibition that these thioimidazole drugs caused on the Cu(II)-catalyzed chemiluminescence (CL) reaction between luminol and H2O2. The CL reaction was induced on-line and injection of the sample produced negative peaks as a result of the Cu(II) complexation by the analytes. The height of the FI peaks was proportional to the drug concentration in the sample. The linear range was 2-100 and 3-120 mg L-1 for methimazole and carbimazole, respectively. The relative standard deviation was 1.9% for methimazole and 2.1% for carbimazole at the 50 mg L-1 level (n=10). Common excipients present in pharmaceutical tablets were found not to interfere with the analysis. The method was applied to the determination of methimazole and carbimazole in pharmaceutical formulations with recoveries in the range 100±4%.

"Sensitive Determination Of Captopril By Flow Injection Analysis With Chemiluminescence Detection Based On The Enhancement Of The Luminol Reaction"
Anal. Chim. Acta 2002 Volume 463, Issue 2 Pages 249-255
Anastasios Economou, Demetrius G. Themelis, Georgios Theodoridis and Paraskevas D. Tzanavaras

Abstract: This work reports a novel flow injection (FI) method for the determination of captopril, 1-[(2S)-3-mercapto-2-methyl-propionyl]-L-proline (CPL), based on the enhancement CPL affords on the chemiluminescence (CL) reaction between luminol and hydrogen peroxide. For this purpose alkaline luminol and hydrogen peroxide solutions were mixed online, the sample containing CPL was injected into an aqueous carrier stream. mixed with the luminol-hydrogen peroxide stream and pumped into a glass flow cell positioned in front of a photomultiplier tube (PMT). The increase in the CL intensity was recorded in the form of FI peaks, the height of which was related to the CPL mass concentration in the sample. Different chemical and instrumental parameters affecting the CL response were investigated. Under the selected conditions, the log-log calibration curve was linear in the range 5-5000 µg L-1 of CPL, the limit of detection was 2 µg L-1 (at the 3s level), the RSD, s(tau) was 3.1% at the 100 µg L-1 level (n = 8) and the sampling rate was 180 injections h-1. The method was applied to the determination of CPL in pharmaceutical formulations with recoveries in the range 100±3%. (C) 2002 Elsevier Science B.V. All rights reserved.
Derivatization

"Determination Of Co(II) By Chemiluminescence After In Situ Electrochemical Pre-separation An A Flow-through Mercury Film Electrode"
Analyst 2001 Volume 126, Issue 1 Pages 109-113
A. Economou, A. K. Clark and P. R. Fielden

Abstract: A novel method of electrochemical pre-separation of Co(II) before detection by chemiluminescence is reported together with the associated instrumentation. The Co(II) ions were selectively pre-separated on a mercury film electrode (MFE) by on-line reduction, then the accumulated metal was oxidized and selectively stripped back into the flowing solution as Co(II). These secondary ions were quantified as a result of their catalytic activity on the chemiluminescent reaction between luminol and hydrogen peroxide that was also induced on-line. The whole sequence was carried out in an automated flow-through system, in which the electrochemical pre-separation of metals was performed in either continuous flow or flow injection analysis (FIA) regimes. The scope of the method, both in terms of selectivity and sensitivity, has been demonstrated and the quantitative determination of Co(II) by the proposed method has been investigated. For a period of continuous flow pre-separation of 4 min, the calibration curve for Co(II) was linear up to a concentration of 100 µg L-1, the relative standard deviation was 4% at the 20 µg L-1 level and the limit of detection was 0.5 µg L-1 (at the 3s level). The method was applied to the determination of the cobalt content in a high purity iron sample.