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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Polymer

Classification: Solid phase -> Polymer

Citations 12

"Modified Microelectrodes And Multivariate Calibration For Flow Injection Amperometric Simultaneous Determination Of Ascorbic Acid, Dopamine, Epinephrine And Dipyrone"
Analyst 2000 Volume 125, Issue 11 Pages 2011-2015
Renato C. Matos, Lúcio Angnes, Mário C. U. Araújo and Teresa C. B. Saldanha

Abstract: Flow injection amperometric quantification of ascorbic acid (AA), dopamine (DA), epinephrine (EP) and dipyrone (DI) in mixtures (in the µg g-1 range) was successfully performed by using an array of microelectrodes with units modified by the electrodeposition of different noble metals, together with multivariate calibration analysis. The four groups of microelectrodes utilized included a pure gold electrode and electrodes modified by electrodeposition of platinum, palladium or a mixture of platinum + palladium. The array of microelectrodes was inserted in a flow cell and the amperometric data acquisition was performed with a four-channel potentiostat. The analysis of the resulting signals was carried out by a multivariate calibration method, using a group of 16 standard mixtures selected by a two-level factorial design. The analysis of synthetic samples and pharmaceutical compounds containing AA and DI led to very similar values to those obtained by the classical iodimetric analysis. The average absolute errors (in µg g-1) calculated for each analyte were 0.3, 0.2, 0.4 and 0.4 for AA, DA, EP and DI, respectively.

"Evaluation Of Glucose Biosensors Based On Prussian Blue And Lyophilised, Crystalline And Cross-linked Glucose Oxidases (CLEC (R))"
Talanta 2001 Volume 54, Issue 5 Pages 963-974
Ivanildo Luiz de Mattos, Lilia V. Lukachova, Lo Gorton, Thomas Laurell and Arkady A. Karyakin

Abstract: Glucose biosensors based on lyophilised, crystalline and cross-linked glucose oxidase (GOx, CLEC(R)) and commercially available lyophilised GOx immobilized on top of glassy carbon electrodes modified with electrodeposited Prussian Blue are critically compared. Two procedures were carried out for preparing the biosensors: (1) deposition of one layer of adsorbed GOx dissolved in an aqueous solution followed by deposition of two layers of low molecular weight Nafion(R) dissolved in 90% ethanol, and (2) deposition of two layers of a mixture of GOx with Nafion dissolved in 90% ethanol. The performance of the biosensors was evaluated in terms of linear response range for hydrogen peroxide and glucose, detection limit, and susceptibility to some common interfering species (ascorbic acid, acetaminophen and uric acid). The operational stability of the biosensors was evaluated by applying a steady potential of -50 mV versus Ag/AgCl to the glucose biosensor and injecting standard solutions of hydrogen peroxide and glucose (50 muM and 1.0 mM, respectively, in phosphate buffer) for at least 5 h in a flow-injection system. Scanning electron microscopy was used for visualisation of the Prussian Blue redox catalyst and in the presence of the different GOx preparations on the electrode surface. (C) 2001 Elsevier Science B.V. All rights reserved.
Glucose

"Mediated Electron Transfer For Electroanalysis: Transport And Kinetics In Tin Films Of [Ru (bpy)(2)PVP10] (ClO4)(2)"
Anal. Chim. Acta 1999 Volume 396, Issue 1 Pages 13-21
Conor F. Hogan and Robert J. Forster

Abstract: Thin films of the redox polymer, [Ru(bpy)(2)PVP10] (ClO4)(2), deposited on electrode surfaces are effective mediators for the oxidation of oxalate, bpy is 2,2-bipyridyl and PVP is poly-4-vinylpyridine. The effects of systematically Varying the electrode rotation rate, the film thickness and the electrode potential, on the modified electrode rate constant reveal that the catalytic current is limited by the kinetics of the cross-reaction and that the reaction takes place throughout the layer (Lk mechanism). The rate constant for the cross-reaction of the Ru3+ centres with oxalate is 3.1 x 10(2) M-1 s-1. Diffusion of the analyte through the layer is relatively unimpeded and a value of 3.3 x 10^-6 cm(2) s-1 is observed for the diffusion coefficient. In sulfuric acid electrolyte, charge transport through the film is a diffusion Like process and the charge transport diffusion coefficient, D-CT, as measured by both cyclic voltammetry and chronoamperometry is 2 x 10^-11 cm(2) s-1. This charge transport rate is independent of the concentration of sulfuric acid as supporting electrolyte indicating an open porous layer structure in this medium. The application of the layers for amperometric detection of oxalate is demonstrated using a flow injection analysis system. A linear response range extending from 2 x 10^-5 to 6 x 10^-3 M was obtained with a detection limit of 0.35 ppm. The precision of the response of the system is evaluated (1.53% RDS for 10 repeated injections), as is the response time (9.8 s for 98% of the maximum response). The possibility of using the layers for simultaneous detection of current and electrogenerated chemiluminescence is considered.

"Integration Of Enzymes And Electrodes: Spectroscopic And Electrochemical Studies Of Chitosan-enzyme Films"
Anal. Chem. 2002 Volume 74, Issue 19 Pages 5039-5046
Xin Wei, Juan Cruz, and Waldemar Gorski

Abstract: A new film-forming solution was developed for the efficient immobilization of enzymes on solid substrates. The solution consisted of a biopolymer, chitosan (CHIT), that was chemically modified with a permeability-controlling agent, Acetyl Yellow 9 (AY9), using glutaric dialdehyde (GDI) as a molecular tether. A model enzyme, glucose oxidase (GOx), was mixed with the CHIT-GDI-AY9 solution and cast on the surface of platinum electrodes to form robust CHIT-GDI-AY9-GOx films for glucose biosensing. UV-visible and infrared spectroscopies were used to determine the composition of the films. The optimized films contained on average 1 molecule of AY9/3 glucosamine units of chitosan and 25 free GDI tethers/1 molecule of GOx. The electrochemical assays of the films indicated both a very high efficiency of enzyme immobilization (similar to99%) and large enzyme activity (60 units cm-2). The latter translated into a high sensitivity (42 mA M-1 cm-2) of the Pt/CHIT-GDI-AY9-GOx biosensor toward glucose. The biosensor operated at 0.450 V, had a fast response time (t(90%) less than or equal to 3 s), and was free of typical interferences, and its dynamic range covered 3 orders of magnitude of glucose concentrations. The lowest actually detectable concentration was 10 muM glucose. In addition, the biosensor displayed a practical shelf life and excellent operational stability; e.g. its response was stable during 24-h testing under continuous polarization and continuous flow of 5.0 mM glucose solution. The proposed approach to enzyme immobilization is simple, efficient, and cost-effective and should be of importance in the development of biosensors based on other enzymes that are more expensive than glucose oxidase.

"A Polyaniline-modified Electrode-based FIA System For Sub-ppb-level Chromium(VI) Analysis"
Anal. Chem. 2001 Volume 73, Issue 6 Pages 1377-1381
Yun-Jung Yang and Hsuan-Jung Huang

Abstract: By taking advantage of the electrocatalytic effect of polyaniline, a polyaniline/polystyrene composite electrode was prepared and used as a sensitive FIA detector for the analysis of Cr(VI). Optimal conditions, such as applied potential, pH, and now rate of carrier for flow injection analysis, were studied. A linear dynamic range from 0.08 to 32.00 ppb with a linear correlation coefficient of 0.9999 and a relative standard deviation (n = 17) of 1.67% for successive injection of 2.0 ppb Cr(VI) were obtained. By incorporating a Dowex 1 x 4 anion-exchange column into the FIA system, interference to the Cr(VI) analysis can be eliminated and the detection limit for Cr(VI) analysis can be lowered to 0.004 ppb. The contents of Cr(VI) in seawater samples were analyzed to demonstrate the capability of the developed system.

"A Chemically Modified Carbon Paste Electrode With D-lactate Dehydrogenase And Alanine Aminotranferase Enzyme Sequences For D-lactic Acid Analysis"
Talanta 2001 Volume 54, Issue 2 Pages 361-368
Hun-Chi Shu and Ning-ping Wu

Abstract: An amperometric biosensor was constructed for the analysis of D-lactic acid based on immobilizing D-lactate dehydrogenase(D-LDH), alanine aminotransferase (ALT), NAD(+), a redox polymer and polyethylenimine in carbon paste. The effect of addition of ALT in the paste, using enzyme sequences of ALT/D-LDH, was insignificant for D-lactic acid analysis. The responses of D-lactic acid in ALT/D-LDH paste electrode are the same as those in D-LDH paste electrode. However, the interference effect of pyruvate in the sample can be substantially reduced if sodium glutamate was applied in the carrier solution. When ALT immobilized in control porous glass as an immobilized enzyme reactor (IMER) was mounted in flow injection analysis system with the D-LDH paste electrode as detector for D-lactate analysis, the interference of the pyruvate can be significantly eliminated. The adverse effect of pyruvate in the samples for D-lactic acid analysis was reduced more effectively in ALT IMER with D-LDH electrode than in ALT;D-LDH electrode. (C) 2001 Elsevier Science B.V. All rights reserved.

"Development Of An Electrochemical Flow Injection Immunoassay (FIIA) For The Real-time Monitoring Of Biospecific Interactions"
Anal. Chim. Acta 1999 Volume 400, Issue 1-3 Pages 109-119
Anthony J. Killard, Shanqing Zhang, Huijun Zhao, Richard John, Emmanuel I. Iwuoha and Malcolm R. Smyth

Abstract: Not only are sensors a revolution in analysis; they themselves are also experiencing a revolution brought about by parallel developments in sensor fabrication techniques and materials, polymer chemistry, signal processing methodologies, the increased use of biomolecular processes as a means of analyte detection, and the coupling of sensors to other techniques such as flow injection analysis. Many of these developments have been incorporated into the present study, which we are undertaking in the development of our immunosensor technology. The system described here utilises screen-printed electrodes which are low-cost, disposable devices that are simple to fabricate. Incorporated into our sensor is the electroactive polymer, polyaniline, which brings about mediatorless redox coupling between the electrode and biomolecular components attached to the polymer surface. This system also utilises enzyme-labelled antibodies as the biomolecular recognition component for the analysis of the test analyte, biotin. The system has also been integrated into a flow injection system. This has led to the monitoring of real-time antibody-antigen interactions using electrochemical methods and foreshadows the development of single-step immunosensors.

"In Situ Preparation Of Overoxidized PPy/oPPD Bilayer Biosensors For The Determination Of Glucose And Cholesterol In Serum"
Sens. Actuat. B 1999 Volume 57, Issue 1-3 Pages 219-226
J. C. Vidal, E. García and J. R. Castillo

Abstract: Overoxidized polypyrrole (PPy)/poly(o-phenylenediamine) (oPPD) bilayer biosensors have been developed with the enzymes glucose oxidase or cholesterol oxidase entrapped within an inner PPy layer onto which a non-conducting oPPD film was then electrodeposited. Electrosynthesis of the polymer layers was carried out in situ in a flow injection system with continuous circulation of a solution containing the monomer (plus the enzyme in the case of pyrrole). The analytical performance of this type of biosensor in the amperometric determination of glucose and cholesterol was compared with that of a PPy single layer sensor and their selectivity against electroactive substances frequently present in biological media was assessed by using them to determine both substrates in reference artificial serum.
Glucose

"Glucose-sensing Electrode Based On Glucose Oxidase-attached Polyion Complex Membrane Containing Peroxidase And Ferrocene"
Electroanalysis 2001 Volume 13, Issue 5 Pages 380-383
Soichi Yabuki, Fumio Mizutani, Yoshiki Hirata

Abstract: A glucose oxidase (GOD)-attached polyion complex membrane containing peroxidase (POD) and ferrocene was prepared by two steps on a glassy carbon electrode. First, a polyion complex membrane containing POD and ferrocene was prepared: a poly-L-lysine solution, a POD solution, a ferrocene dispersion and a poly(styrenesulfonate) solution were successively dropped on an electrode, and the electrode was allowed to dry. Then GOD was attached by the use of glutaraldehyde: GOD and glutaraldehyde solutions were dropped on the membrane. and the electrode was dried. Current response to glucose for the enzyme electrode was measured at a potential of -0.2 V (vs. Ag/AgCl). The 100 % response time was ~20 s. The current was proportional to the glucose concentration up to 0.1 mM. The lower detection limit was 1 muM (signal-to-noise ratio. S/N = 5). The enzyme electrode was used for the glucose measurements in beverages. The results obtained agreed well with those obtained by Boehringer F-kit method. The electrode would be useful as a glucose biosensor for beverages.

"Preparation Of A Glucose-sensing Electrode Based On Glucose Oxidase-attached Polyion Complex Membrane Containing Microperoxidase And Ferrocene"
Electrochemistry 2000 Volume 68, Issue 11 Pages 853-855
Soichi YABUKI, Fumio MIZUTANI, Yoshiki HIRATA

Abstract: A glucose oxidase-attached polyion complex membrane containing microperoxidase and ferrocene was formed on a carbon electrode. The enzyme electrode gave a reductive current response (100% response time, within 20 s), and steady-state response was proportional to the glucose concentration up to 0.2 mM. Lower detection limit was 1 µ-M The current response decreased gradually, owing to the loss of the microperoxidase activity. The enzyme electrode was used for the detection of glucose concentration in beverages. The results obtained agreed well with those obtained by Boehringer F-kit method. The electrode would be useful as a glucose biosensor for real samples.
Glucose

"Development Of Organic Solvent Carrier System For Flow Injection - Chemiluminescence Analysis And Its Application"
Bunseki Kagaku 1992 Volume 41, Issue 9 Pages 433-440
Ishii, M.;Ito, K.

Abstract: The cited organic solvent carrier system was applied to the chemiluminescent determination of THF; the carrier system was protected from destruction by organic solvents by a joint to another water introduction line. The system comprised three flow lines: an acetonitrile solution line for chemiluminescent reagents, equipped with a light introduction system, a sample solution line and a protection line. Reaction between THF and methylsilicone solid polymer (used for the flow cell) produced the chemiluminescence, which was enhanced with dye-sensitizer, surfactant and visible light. As chemiluminescence was weakly and slowly produced, THF was determined by the stopped-flow method. The lower detection limit was 1 mM by the continuous sample flow method. The coefficient of variation (n = 7) was 6.2% for 1 M THF solution Sampling was at 72 h-1. Interference was observed with samples containing 10% toluene, cyclopentane or 1,2,4-trimethylbenzene in 1 M THF. In order to expand solution chemiluminescence (CL) anal. in organic solvents, an organic solvent carrier system applicable to FIA was developed and applied to the CL determination for THF. The carrier system is protected from destruction by organic solvents by a joint to another water introduction line. The proposed FIA/CL system is comprised of three flow lines; the CH3CN solution line for CL reagents equipped with a light introduction system, the sample solution line and the protection line. The CL for the THF determination is essentially produced by the reaction between THF and the methylsilicone solid polymer used for the flow cell and enhanced with dye-sensitizer, surfactant and visible light. Since the CL is weakly and slowly produced, THF is determined by the stopped-flow method. The lower detection limit is 1 x 10^-3 M by the continuous sample flow method. Relative standard deviation is 6.2% for 7 repeated runs of the 1 M THF solution Sampling rate is 72 per h. In terms of relative error, the samples containing 10 (by volume) % of toluene, cyclopentane or 1,2,4-trimethylbenzene in 1 M THF showed 100% interference of the CL intensity for 1 M THF alone.
Tetrahydrofuran Chemiluminescence

"Studies On The Determination Of Heavy Metal Ion By Flow Injection, The Photochemical Characterization And Polymerization Of Eight-coordinated Complex. 2. Synthesis Of W(IV) Eight-coordinate Polymer"
Pollimo 1994 Volume 18, Issue 6 Pages 922-928
Chang, C.;Jo, C.;Park, K.;Sung, H.;Kim, H.

Abstract: The eight-coordinate tungsten(IV) complex has been synthesized from the 4-amino-3,5,6-trichloropicolinic acid(apic) and tungsten hexacarbonyl at a mole ratio of 5:1, respectively. A new eight-coordinate W(IV) polymer was prepared by condensation polymerization of eight-coordinated W(IV) complex and carbonyl substituted aromatic compounds. Structure of the complex was determined by the spectroscopic methods and elemental analysis. Solubilities, viscosities and thermal stabillties for the polymer have been investigated.
Metals, heavy Polymer Spectrophotometry