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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R. Alan Wheatley

Abbrev:
Wheatley, R.A.
Other Names:
Address:
Department of Chemistry, University of Hull, Hull HU6 7RX, UK
Phone:
+44-1482-465484
Fax:
+44-1482-466416

Citations 5

"Some Recent Trends In The Analytical Chemistry Of Lipid Peroxidation"
Trends Anal. Chem. 2000 Volume 19, Issue 10 Pages 617-628
R. Alan Wheatley

Abstract: The analytical chemistry of lipid peroxidation is reviewed with special attention to literature that has appeared in the last four years. The pathways of the cascade of reactions are first described and current analytical practice discussed. Selected assays, classified by analyte, are then considered as indices of lipid peroxidation; these mainly involve ultraviolet and visible spectrophotometry, fluorescence and chemiluminescence.

"Evaluation Of The Antioxidant Effect Of Melatonin By Flow Injection Analysis-luminol Chemiluminescence"
Pharmacol. Res. 2003 Volume 48, Issue 4 Pages 361-367
M. Sariahmetoglu, R. A. Wheatley, Ý. Çakýcý, Ý. Kanzýk and A. Townshend

Abstract: The antioxidant effect of melatonin was evaluated by using a flow injection analysis chemiluminescence (FIA-CL) method to measure alone its direct antioxidant behavior in aqueous solutions. Inhibition by melatonin, -tryptophan or serotonin (5-hydroxytryptamine, 5-HT) of the steady CL emissions of various oxidants with luminol was measured. Log IC50 values of melatonin were calculated: -2.6±0.1 M for superoxide (O2.-), -3.0±0.02 M, for hydrogen peroxide (H2O2), -4.7±0.04 M, for hypochlorous anion (-OCl), -2.8±0.1 M, for hydoxyl (.OH) and -2.0±0.03 M, for peroxynitrite (ONOO-). Thus melatonin exerted a limited direct antioxidant activity towards reactive oxygen species (ROS) in aqueous solutions, broadly comparable to that of tryptophan, but less than that of serotonin and of major antioxidants such as ascorbic acid. This suggests that where the benefits of melatonin are correctly attributed to antioxidant behaviour, this is mediated largely through antioxidant enzymes. The pharmacological implications are discussed.

"Using Flow Injection Analysis To Time-resolve Rhythmic And Pulsatile Signals"
Analyst 2002 Volume 127, Issue 5 Pages 588-590
R. Alan Wheatley

Abstract: Continuous monitoring can be used to detect rhythms, an important aspect of biology. But peaks of concentration are broadened by dispersion so that they overlap their neighbours and obscure high frequency chemoperiodicities. In this study, flow injection was found experimentally to be useful in resolving these. A rhythmically varying pattern of permanganate concentration was measured spectrophotometrically. The rhythm (frequency 0.08 Hz) was observable at a dispersion coefficient of 3.0 but not at 3.9 (when only a single peak was recorded). It was again observable using the same high dispersion manifold but positioned after an injection valve that subsampled the stream at intervals. A design based on this work is proposed for an automated instrument that outputs a time series of concentration measures.

"Determination Of Carbonyl Compounds By The Oxidative Chemiluminescence Of 2,4-dinitrophenylhydrazine"
Analyst 1998 Volume 123, Issue 5 Pages 1047-1051
Alan Townshend and R. Alan Wheatley

Abstract: The oxidative chemiluminescence of phenylhydrazines can be applied to the determination of carbonyl compounds by utilizing the attenuation of the signal which occurs on conversion to the corresponding phenylhydrazone. Using an assay for 2,4-dinitrophenylhydrazine, off-line derivatization for a period of 2 h is optimized for a temperature of 30°C and for a sulfuric acid concentration. of 0.05 M. The optimum conditions for 2,4-dinitrophenylhydrazone formation can be understood in terms of a stepwise mechanism of carbinolamine formation via a zwitterion intermediate. The log-log calibration for the combined derivatization/assay of hexanal in optimized conditions is linear (r = 0.9931, n = 5) from 1 x 10^-6 to 2 x 10^-5 M. The limit of detection calculated as above was 1.7 x 10^-7 M (1.7 pmol of hexanal). Applications to the oxidative deterioration of linoleic acid and to the effect of lipoxygenase on linoleic acid are described.
Carbonyl compounds Linoleic acid Chemiluminescence Indirect Optimization Heated reaction

"Oxidative Chemiluminescence Assay Of 2,4-dinitrophenylhydrazine"
Analyst 1998 Volume 123, Issue 5 Pages 1041-1046
Alan Townshend and R. Alan Wheatley

Abstract: This paper describes the development of an assay for 2,4-dinitrophenylhydrazine suitable for application to the determination of carbonyl compounds Complete factorial design was used to study the effects of solvents and carrier on the oxidative chemiluminescence of phenylhydrazines in flow injection analysis 2,4-Dinitrophenylhydrazine gave a better analyte:blank signal ratio than other phenylhydrazines. Aqueous propan-2-ol is the preferred solvent and aqueous formic acid containing no sensitizer the preferred carrier solution Rhodamine B sensitizer enhanced all signals but, by its effect on blank signals, reduced the signal to blank ratio. Simplex optimization was carried out on six variables. The criterion was (A-B)/B, where A and B are the analyte and blank signals, respectively; conditions giving analyte signals of relative standard deviation >10% were eliminated whatever the value of (A-B)/B. The effects of formic acid carrier and propan-2-ol solvent are best understood in terms of their effects of enhancing the signal by energy transfer and diminishing it by competition for permanganate. The log-log calibration for 2,4-dinitrophenylhydrazine in optimum conditions was linear (r = 0.9972, n = 10) from 1 x 10^-7 to 2 x 10^-5 M; the detectivity calculated at three standard deviations above blank was 1.1 x 10^-7 M (1.1 pmol analyte). The method is subject to interference from common metal ions from V to Zn in the periodic table, especially Fe(II), though EDTA largely corrected this latter effect.
2,4-Dinitrophenylhydrazine Carbonyl compounds Chemiluminescence Interferences Simplex Optimization EDTA Factorial design