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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Quality

Classification: Feature -> Quality

Citations 11

"Rapid Approach To The Quantitative Determination Of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose Sulfamate) In Human Plasma By Liquid-liquid Extraction And Flow Injection Negative-ion Electrospray Mass Spectrometry"
Rapid Commun. Mass Spectrom. 1999 Volume 13, Issue 20 Pages 1980-1984
Su Chen, Paul M. Carvey

Abstract: Topiramate, a sulfamate-substituted monosaccharide (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopy-ranose sulfamate), is a new antiepileptic drug, which has been approved for adjunctive therapy in adult patients with partial-onset seizures, Liquid-liquid extraction followed by flow injection negative-ion electrospray mass spectrometry was evaluated as a means for the quantitative analysis of Topiramate in human plasma. Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trione [15 µg/mL]) was used as the internal standard because its solubility and molecular weight are similar to those of Topiramate, Calibration curves for Topiramate were linear over a range of 1 to 30 µg/mL plasma (signal-to-noise ratio >4) and were highly reliable (r2 = 0.994), This approach offers several advantages: (i) the extraction of Topiramate from human plasma using chloroform is simple and reproducible; (ii) the quantitative determination of Topiramate, in the presence of an internal standard, by blow-injection negative-ion electrospray mass spectrometry with selected-ion recording, is rapid and accurate and does not require chromatographic separation; (iii) the assay possesses adequate sensitivity (2-25 µg/mL) for the quantitative analysis of Topiramate in plasma from patients.

"Flow Techniques In Water Analysis"
Talanta 1999 Volume 50, Issue 4 Pages 695-705
V. Cerdà, J. M. Estela, R. Forteza, A. Cladera, E. Becerra, P. Altimira and P. Sitjar

Abstract: In the present work the main flow techniques for the analysis and monitoring of several parameters of interest in the quality control of different types of waters are reviewed. Firstly, a review involving the advantages and disadvantages of flow techniques, from those currently out-dated, such as segmented flow analysis (SFA), to the most modern techniques, such as flow injection analysis (FIA), sequential injection analysis (SIA) and multi-commutation techniques (MCFA), is carried out. On the other hand, a new technique, the multi-syringe flow analysis (MSFA) is hereby described for the first time as both a fast and robust alternative. Its possibilities, limitations and potential advantages when using this technique either on its own or coupled to SIA, which carries out a previous sample handling, are outlined.

"Photocatalytic Sensor For The Determination Of Chemical Oxygen Demand Using Flow Injection Analysis"
Anal. Chim. Acta 2001 Volume 432, Issue 1 Pages 59-66
Yoon-Chang Kim, Satoshi Sasaki, Kazuyoshi Yano, Kazunori Ikebukuro, Kazuhito Hashimoto and Isao Karube

Abstract: A photocatalytic sensor for the determination of chemical oxygen demand (COD) with flow injection analysis (FIA) based on the photocatalysis of organic compounds in the presence of titanium dioxide (TiO2) beads in a photochemical column is described. The sensor was developed in conjunction with TiO2 beads in the photochemical column and with an oxygen electrode as the sensing part. The sensor signal was observed as a result of the detection of dissolved oxygen changes due to photocatalytic oxidation of organic compounds in the sample solution. This sensor responded linearly to the CODMn of artificially treated wastewater (AWW) in the range of 0.12-8 ppm. A complete analysis, including sampling and washing, took about 10 min. The sensor was stable for over 15 days and has successfully been applied to the determination of COD in lake samples.

"Characterization And Meat Freshness Application Of A Serial Three-enzyme Reactor System Measuring ATP-degradative Compounds"
Anal. Chim. Acta 2000 Volume 404, Issue 1 Pages 75-81
In-Seon Park, Yong-Jin Cho and Namsoo Kim

Abstract: A serial three-enzyme reactor system which measures hypoxanthine (H-x), inosine (HxR) and inosine 5-monophosphate (IMP) simultaneously was prepared, characterized for its properties and applied to freshness evaluation of meats. The biosensor system was operated as a flow injection analysis mode and the reactor length combination of 15, 12 and 7 cm for H-x, HxR and IMP, respectively, was selected for a complete reaction between substrate and enzyme. The sequential enzymatic reactions by the system were performed best at 0.05 M phosphate buffer, pH 7.5 and 35°C. The effects of various possible interferants such as amino acids and sodium chloride on the system were investigated. When applied to meat freshness evaluation, the K-i- and H-values obtained by the system agreed well with those obtained by a conventional method (liquid chromatography (LC)).
Hypoxanthine Inosine Inosine 5'-phosphate Meat Sensor

"Rapid Determination Of Lactulose In Milk By Microdialysis And Biosensors"
Analyst 1999 Volume 124, Issue 3 Pages 325-329
D. Moscone, R. A. Bernardo, E. Marconi, A. Amine and G. Palleschi

Abstract: A simple and rapid flow system for the determination of lactulose in milli samples was developed. It is based on the hydrolysis of lactulose to galactose and fructose by the enzyme β-galactosidase immobilized in a reactor. The amount of fructose produced was measured with an electrochemical biosensor based on the fructose dehydrogenase enzyme, K-3[Fe(CN)(6)] as mediator and a platinum based electrochemical transducer. Parameters such as the enzyme immobilization in the reactor and under the electrode surface, the lifetime of the β-galactosidase reactor and of the dehydrogenase biosensor and the flow parameters were studied and optimized. Fructose was determined in the range 1 x 10^-6-5 x 10^-3 mol L-1 with an RSD of about 2% and a detection limit of 5 x 10^-7 mol L-1. The use of a microdialysis probe as the sampling system permitted the direct measurement of lactulose in milli samples without pre-treatment in the range 1 x 10^-5-5 x 10^-3 mol L-1. The sensitivity of the procedure allowed pasteurised, UHT and in-container sterilised mill, to be distinguished.

"Urbanizations Impact On Timber Harvesting In The South Central United States"
J. Environ. Manage. 2002 Volume 64, Issue 1 Pages 65-76
Ian A. Munn, Stephen A. Barlow, David L. Evans and David Cleaves

Abstract: The impact of urbanization on timber harvesting in the south central United States was investigated. Geo-referenced Census and Forest Inventory Analysis (FIA) data were combined using a geographic information system (GIS) in order to examine the effects of various demographic and biophysical forest inventory characteristics on timber harvesting. These effects were estimated for intermediate and final harvests using a multinomial logit model. The probability for both types of harvests decreased with increasing population density, decreasing forest size, and decreasing distance to urban areas; however, the reduction in intermediate harvests was greater for each variable. Harvesting rates decreased by as much as 19% as population densities increased or distance to urban areas decreased. The results indicated that active forest management is curtailed far beyond the urban boundary. In order to model the impact of urbanization adequately, timber supply projections must also account for its impact on harvesting frequencies in surrounding areas.

"Development Of A System With Enzyme Reactors For The Determination Of Fish Freshness"
Talanta 1998 Volume 47, Issue 2 Pages 335-342
M. -A. Carsol and M. Mascini*

Abstract: A continuous system for the determination of fish freshness with double enzyme reactors was developed and applied to the determination of the freshness indicator K K = 100(HxR + Hx)/(IMP + HxR + Hx), where IMP, HxR and Hx are Inosine monophosphate, Inosine and Hypoxanthine, respectively. The system was assembled with a three electrode screen-printed element (graphite as working electrode, silver as counter and silver, silver chloride as reference electrode) placed in a flow cell, a sample injection valve and two enzyme reactors. The determination of the total amt. of HxR and Hx is realized by flowing the sample through two reactors in series: one reactor was packed with nucleoside phosphorylase (Np) and the other with xanthine oxidase (XO) immobilized on aminopropyl glass. Similarly, the other term of the equation was evaluated by flowing through the two reactors the sample treated by Alkaline phosphatase (AlP) for 5-10 min at 45°C. One assay could be completed within 5 min. The system for the determination of fish freshness was reproducible within 2-3% (n = 4). The immobilized enzymes were fairly stable for at least three months at 4°C. More than 200-300 samples could be analyzed in about one month by using these enzyme reactors provided the disposable screen-printed electrode should be changed every 30-40 real samples. The results obtained suggest that the proposed sensor system provides a simple, rapid and economical method for the determination of fish freshness (K). We applied the present system with two reactors for the determination of K values in fish samples and compared the results with those obtained by the XO-reactor. Correlation factor and regression line between the two methods were 0.992 and Y = -3.14+1.03X respectively. We concluded that the present flow injection analysis (FIA) system with XO and Np reactors was suitable as a simple, easy to handle and reliable instrument for quality control in the fish industry.
Inosine monophosphate Inosine Hypoxanthine Marine Electrode Amperometry Electrode

"Assessment Of Quality Of Flow Injection Methods Used In Food Analysis"
Analyst 1995 Volume 120, Issue 9 Pages 2393-2400
J. M. López-Fernández, A. Ríos and M. Valcárcel

Abstract: A review is presented of the quality of flow injection (FI) methods used in food analysis. Over 200 FI methods are evaluated for quality in terms of accuracy, applicability, precision, selectivity, sensitivity, determination range and sample throughput. A quality scale is proposed that enables the most appropriate method to be chosen for a given type of food analysis. (129 references).
Food

"Assessment Of Analytical Quality In Automatic Flow Systems"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 140-149
Juliana Marcos, Angel Ríos, Miguel Valcárcel

Abstract: Flow systems employed most frequently for the automatic photometric determination of elementary parameters incorporate a single channel manifold, a dual channel manifold or a merging-zones manifold (illustrated). Each type of manifold was characterized in terms of precision, sensitivity and throughput with bromocresol green in 0.01 M sodium tetraborate buffer of pH 10 and the dual channel manifold was further studied with the reaction of Fe(II) as (NH4)2SO4 with 0.01 M 1,10-phenanthroline and 0.1 M hydroxylamine hydrochloride in 0.1 M sodium acetate. The uncertainty introduced by each flow unit in a manifold was assessed in standard deviation units. Systems were also tested for ruggedness of both flow injections and chemical variables. A number of papers in the literature were evaluated with the data obtained.
Spectrophotometry

"Fast Online Data Evaluation Of Flow Injection Analysis Signals Based On Parameter Estimation By An Extended Kalman Filter"
J. Biotechnol. 1998 Volume 62, Issue 1 Pages 11-28
X. Wu and K. -H. Bellgardt*

Abstract: The present paper is concerned with the fast evaluation of the flow injection analysis (FIA) signals and the automatic correction of the analytical values interfered by systematic and stochastic disturbances. With the application of the extended Kalman filter, the highest amount of information for the data evaluation of analytical signals can be estimated from FIA peaks. The concentration of the analyte and the offset of the baseline are estimated as time-variable parameters by filtering. The results of the application to simulated and real FIA data show that the parameters corresponded to the evaluation of the analytical data, but is already available before the maximum of the FIA peak, i.e. the evaluation of the data with the Kalman filter can be done during the running peak. Good estimates of the measured values are already obtained short after start of the peak. For this reason, the measuring dead-time of the FIA system can be reduced by the use of this method. The evaluation of FIA signals disturbed often by fluctuation of the baseline and other noise can be corrected by estimation of the offset of FIA peaks and smoothing of real FIA signals. Therefore, the application of the extended Kalman filter can also improve conventional evaluation methods.
Fermentation broth

"Correlation Of Wine Phenolic Composition Versus Cyclic Voltammetry Response"
Am. J. Enol. Vitic. 2002 Volume 53, Issue 4 Pages 294-302
Paul A. Kilmartin, Honglei Zou, and Andrew L. Waterhouse

Abstract: Cyclic voltammetry has been used to quantify antioxidants at a carbon electrode in white wines diluted to 10% and red wines diluted to 0.25% in a model wine solution (12% ethanol, 0.033 M tartaric acid adjusted to pH 3.6). The first peak near 400 mV (versus Ag/AgCl) was due to phenolic compounds with an ortho-diphenol group or to gallic acid, while a small feature at 300 mV was seen in red wines containing higher levels of myricetins (triphenol on the flavonoid B-ring), and a peak or shoulder at 470 mV was ascribed to quercetin glycosides. The integral of the current to 500 mV was then used as a measure of the lower oxidation potential phenolics, reported as gallic acid equivalents, and compared to traditional measures of total phenols in wines. A peak at 640 mV in red wines was associated with malvidin anthocyanins and was smaller in an older red wine sample, while further oxidation current beyond 700 mV prominent in white wines was due to meta-diphenol or isolated phenol groups and other oxidizable compounds. Simulated voltammograms constructed from high-pressure liquid chromatography results for six monomeric phenolics were in good agreement with the experimental voltammograms for the white wines, while a higher proportion of the current for the red wine samples was due to oligomeric phenolics.
Antioxidants Phenol Wine Red Wine White Voltammetry