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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Canadian Journal of Chemistry

  • Publisher:
  • FAD Code: CAJC
  • CODEN: CJCHAG
  • ISSN: 0008-4042
  • Abbreviation: Can. J. Chem.
  • DOI Prefix: 10.1139/cjc
  • Language: English
  • Comments: Fulltext from 1951 V29

Citations 11

"Comparison Of Supported Liquid Membranes And Solid-phase Extraction For Quantitative Removal Of Lead From Aqueous Solutions"
Can. J. Chem. 2003 Volume 81, Issue 10 Pages 1061-1069
Emily R. Yourd and Julian F. Tyson

Abstract: The selective transport of a target metal ion across a membrane from a donor to an acceptor solution is an attractive concept for pre-concentration or separation in a flow injection (FI) system. However, we found that the transport of lead across a supported liquid membrane consisting of dicyclohexano-18-crown-6 in decanol embedded in Celgard 2400 was too slow to be practical for an FI atomic spectrometry system. On the other hand, the same chemistry in an on-line, solid-phase reactor (a mini-column containing Pb-Spec resin) gave a satisfactory performance. In an attempt to understand the kinetics of the system, we have calculated the rate of transport across the membrane. As flux is proportional to concentration on the donor side - which decreases with time - we performed a series of numerical simulations involving fixed time intervals of decreasing values. These calculations show that for the sizes of membranes in a typical FI system, transport is very slow compared with the adsorption of lead by the Pb-Spec resin: it takes about 100 min for the concentration in a 0.06 mL donor solution to decrease by a factor of 1000. The time required for the same decrease in concentration for a membrane having the same surface area and ligand concentration as the Pb-Spec column was calculated as approximately 9 s.

"Electrocatalytic Oxidation And Flow Amperometric Detection Of Hydrazine On A Dinuclear Ruthenium Phthalocyanine-modified Electrode"
Can. J. Chem. 2003 Volume 81, Issue 2 Pages 161-168
Mehrdad Ebadi

Abstract: Electrocatalytic oxidation of hydrazine on a dinuclear ruthenium phthalocyanine ((RuPc)2) modified electrode was studied using cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques. At pH = 13, a four-electron oxidation of hydrazine to N2 was observed. A suitable mechanism was proposed by analyzing the rate equation and the Tafel slope. The flow injection analysis was performed to characterize the (RuPc)2-modified electrode as an amperometric sensor for the detection of hydrazine. The electrode displays an excellent accuracy and precision in phosphate solution at pH 12 and 13. The linearity range was from 30 nM to 1 mM with a correlation coefficient of 0.9998.

"Amperometric Cholinesterase Biosensors For The Determination Of Organophosphorus Pesticides"
Can. J. Chem. 2002 Volume 80, Issue 3 Pages 315-331
Graziella Turdean, Ionel Catalin Popescu et Liviu Oniciu

Abstract: The purpose of this study is a comparative presentation of the different types of the amperometric biosensors based on cholinesterases for the determination of organophosphorous pesticides using the bibliographical information of the last 20 years. The study contains the presentation of the structure and properties of the cholinesterases, the main reactions implied in the functioning of the amperometric biosensors, their applications and factors influencing the detection or (and) the inhibition process. The detection limit of the mono- or bi-enzymatic amperometric biosensors are relatively higher than those corresponding with the immunobiosensors or with gas and liquid chromatography, which are still considered as the reference methods. As shown, for many other amperometric biosensors, the Michaelis-Mentens kinetic treatment used for reactions catalyzed by free enzymes can be extended to describe the response of amperometric biosensors based on immobilized cholinesterases. The positive compromise between advantages and drawbacks, as well as the soft experimental conditions, point to the amperometric monoenzymatic bioelectrode, as an attractive analytical tool for the detection of organophosphorous pesticides.
Kinetic Immobilized enzyme

"Flow Injection-chemiluminescent Assay For The Determination Of Superoxide Dismutase Activity"
Can. J. Chem. 2001 Volume 79, Issue 3 Pages 337-341
Hong Yeob Choi, Jin Hyang Song, Yong Sung Park, Gabriel Lord, and Dong Ki Park

Abstract: Superoxide dismutase (SOD) activity was measured using a flow injection-chemiluminescent assay (FI-CLA) based on xanthine-xanthine oxidase dependent superoxide (O-2(.-)) formation. The mobile phase consists of 50 mM potassium phosphate buffer (pH 7.4) containing lucigenin (5 muM) and xanthine (0.3 mM). Under optimum conditions, bovine albumin did not affect chemiluminescence at concentrations of 1-1000 µg mL-1 and KCN inhibited 100% of the Cu, Zn-SOD activity using 5 µL of a 0.23 mM concentration. The analysis of one sample was done in less than 30 s with a relative standard deviation of±3.1%. SOD activity in the biological samples was correlated to the amount of exogenously applied SOD. The FI-CLA method reported here appears to be one of the faster and more useful tools used to assay SOD activity.

"New Chaotic Behavior And Its Effective Control In Belousov-Zhabotinsky Reaction"
Can. J. Chem. 2001 Volume 79, Issue 1 Pages 29-34
Yan-Ni Li, Hao Song, Zun-Sheng Cai, Lan Chen, Zhe Hou, Qing-Li Wei, Ben-Xiang Wu, and Xue-Zhuang Zhao

Abstract: A new spiral-in-to-spiral-out mixed-mode type chaos of the Belousov-Zhabotinsky (BZ) reaction in a continuous flow stirred tank reactor (CSTR) is observed. We discussed its evolution and characterization in detail. We controlled the new chaos into steady periodic behavior by two control methods: (i) a self-adaptive delayed feedback controlling scheme; and (ii) a linear self-interacting feedback controlling scheme.

"Partial Leaching As An Aid To Slurry Nebulization For The Analysis Of Soils By ICP-MS With Flow Injection And Mixed-gas Plasmas"
Can. J. Chem. 1999 Volume 77, Issue 4 Pages 409-415
Anthony Treveidi Persaud, Diane Beauchemin, Heather Edith Jamieson, and Robert J.C. McLean

Abstract: Acid leaching (with 1 mol L-1 HNO3) was combined with slurry nebulization in inductively coupled plasma mass spectrometry, with mixed-gas plasmas and flow injection, in an attempt to facilitate the quantitative analysis of heterogeneous materials such as soils. Matrixes analyzed ranged from marine sediment to metal-contaminated soil, and were chosen for their variety in elemental composition and matrix structure. Slurries were prepared by first grinding the material to <3 µm in high-purity water and then diluting to 0.1% (w/v) with 1 mol L-1 HNO3, which served as both a dispersing and a leaching agent. The resulting slurries were injected (0.25 mL) into a deionized distilled water carrier. Under these conditions, the sensitivity was ~85% of that achieved by continuous nebulization. Multivariate optimization of the N percentage, forward torch power, and aerosol carrier gas flow rate was conducted to find conditions maintaining sensitivity constant between different slurries. Since no set of conditions was optimal for all elements, a compromise set was selected, which resulted in accurate results for La and Pb in reference materials, by calibrating with aqueous standards. However, the results for V and Cr were almost systematically low, indicating that the compromise plasma conditions did not allow complete atomization/ionization of these elements.

"Adsorption Of Tetrahexylammonium - Bromothymol Blue Ion-pairs At The Chloroform-water Interface"
Can. J. Chem. 1991 Volume 69, Issue 1 Pages 88-93
Lawrence Amankwa and Frederick F. Cantwell

Abstract: Porous membrane phase separators are used to study the adsorption of the cation tetrahexylammonium (Q+) of the anion bromothymol blue (HB-) and of the ion-pair formed between them (QHB) at the liq.-liq. interface in a rapidly stirred mixture of CHCl3 and aqueous buffer. Adsorption isotherms in all 3 cases follow the Langmuir equation. The anion HB- is much more strongly adsorbed than the ion-pair QHB. The porous membrane technique readily permits measurement of simultaneous adsorption of the 2 species HB- and QHB, and thereby allows a study of their competitive adsorption. When WHB is adsorbed in the presence of an excess of HB- both the saturated (monolayer) interfacial concentration. of QHB and the logarithm of the adsorption equilibrium. constant for QHB decrease linearly with an increase in interfacial concentration. of HB-. This shows quant. that coadsorption of QHB and HB- involves a direct competition for space at the interface and also that the presence of adsorbed HB- changes the adsorbent properties of the interface. Anal. implications for solvent extraction are discussed.
Tetrahexylammonium ion Bromothymol blue Sample preparation Ion pair extraction Kinetic Phase separator Solvent extraction Surfactant

"Spectrophotometric Determination Of Peroxydisulfate With O-dianisidine By Flow Injection"
Can. J. Chem. 1990 Volume 68, Issue 10 Pages 1750-1756
Paul M. Shiundu, Adrian P. Wade, and S.B. Jonnalagadda

Abstract: The method is based on the Cu(II)-catalyzed oxidation of o-dianisidine (I) by S2O82- (II) in the flow injection system of Wentzell et al. (J. Autom. Chem., 1989, 11, 227) to give a product with λmax = 450 nm. The sample (e.g., 100 µL) was injected into a stream of 0.5 mM Cu(II) (1.5 mL min-1) and mixed with a stream of 10 mM I (0.5 mL min-1) in aqueous 40% acetone in a 50-cm coil before being mixed with a stream of 0.1 M 3,3-dimethylglutaric acid (0.5 mL min-1) in 1 M NaCl (pH adjusted to 7.0 with NaOH) in a further 50-cm coil. The manifold was constructed from PTFE tubing (i.d. 0.5 mm). Calibration graphs based on the absorbance at λmax were rectilinear for 25 to 750 µM-II; the detection limit was 0.5 µM. In the determination of 25 µM-II the coefficient of variation was 1.5% (n = 10). There was little interference from 2.5 M methanol, 1.0 M ethanol or 0.25 M prop-2-en-1-ol, some interference from 0.25 M prop-2-enyl acetate and 0.5 M ethyl acetate and serious interference from formaldehyde.
Peroxydisulfate Polymer Spectrophotometry Catalysis pH Interferences

"Pulse Cyclic Voltammetry. 2. Flowing Solutions"
Can. J. Chem. 1987 Volume 65, Issue 8 Pages 1795-1799
Gordon N. Eccles and William C. Purdy

Abstract: By the use of pulse cyclic chronovoltammetry, better anal. data are sometimes obtained during the reverse scans. This is demonstrated by a chronovoltammetric flow-injection anal. (FIA) study of the quinone-hydroquinone couple. A quant. FIA pulse cyclic chronovoltammetric investigation of the ferri-ferrocyanide reversible couple showed linearity for time-integrated Fourier-smoothed data for reduction scan currents as well as the total of the forward and reverse scan peak currents. The detection limit was found to be 2 x 10^-6M.
Voltammetry

"Nafion-coated Mercury-coated Glassy-carbon Electrodes For Metals Analysis And Speciation"
Can. J. Chem. 1987 Volume 65, Issue 5 Pages 1133-1138
Robert D. Guy and Sarath Namaratne

Abstract: The properties of mercury-coated glassy carbon electrodes coated with a thin membrane of Nation 117 were studied to evaluate the potential analytical applications in metal ion analysis. The Nation membrane was found to contain two types of binding sites - a strong site that bound metal ions in a nonelectroactive form and cation exchange sites that were useful for pre-concentrations prior to differential pulse voltammetry. The exchange constants for the weak sites ranged from 0.413 for copper to 12.5 for methyl viologen. The differential pulse currents were increased by a factor of 75 to 100 and a linear calibration curve was observed from about 25 n M to 1000 n M for copper, lead, cadmium, and zinc. The ion exchange reaction is very sensitive to ionic strength and significant enrichments occur only in solutions of ionic strength below 0.10. The Nafion-coated glassy carbon electrode in a flow cell can be used to determine the free copper ion concentration in samples by a combination of ion exchange and differential pulse voltammetry. The flow-through system required about 15 mL of sample solution and an analysis time of about 10 min. The ion exchange measurement gave a linear calibration from 40 nM to 10 µM for free copper.
Cadmium Copper Lead Metals Zinc Electrode Electrode Ion exchange Voltammetry Preconcentration Speciation

"Use Of Peak Height For Quantification In Solvent Extraction/flow Injection Analysis"
Can. J. Chem. 1985 Volume 63, Issue 9 Pages 2559-2563
Jamal A. Sweileh and Frederick F. Cantwell

Abstract: An equation is presented which expresses peak height in terms of the concentration. of sample injected, detector sensitivity, dilution due to band dispersion, the fraction extracted, the flow rates of carrier, organic phase and compensating solvent and the flow rate of the organic extract through the membrane phase separator. Each term in the equation was evaluated experimentally with the determination of Zn, by AAS or UV detection, after solvent extraction of Zn(SCN)2.
Zinc Spectrophotometry Spectrophotometry Sample preparation Dispersion Theory Solvent extraction Phase separator Membrane