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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Dirk Janasek

Abbrev:
Janasek, D.
Other Names:
Address:
Institute for Biotechnology, University Halle Wittenberg, Kurt Mothes Str 3, D-06120 Halle, Germany
Phone:
+49-345-55-24871
Fax:
+49-345-55-27013

Citations 6

"A Chemiluminometric FIA Procedure For The Enzymatic Determination Of L-aspartate"
Sens. Actuat. B 2001 Volume 74, Issue 1-3 Pages 163-167
Dirk Janasek and Uwe Spohn

Abstract: An enzymatic FIA procedure was developed for the chemiluminometric determination of L-aspartate in a medium for mammalian cell cultivation. Packed bed flow reactors containing aspartate:aminotransferase and L-glutamate oxidase, respectively, immobilized on sieved porous glass beads were combined with a peroxidase modified fiber optic sensor to detect the produced hydrogen peroxide. Peroxidase from Arthromyces ramosus was immobilized on a preactivated microporous nylone membrane and catalyzes the light generating oxidation of luminol by hydrogen peroxide. To improve the selectivity of the L-aspartate determination a L-glutamate eliminating reactor was prepared by coimmobilization of L-glutamate oxidase and catalase in a packed bed enzyme reactor. Under FIA conditions at least 0.5 mM L-glutamate can be quantitatively eliminated from the preconditioned sample solution. L-Aspartate can be determined in the range between 5 and 1000 muM under FIA conditions. The determination of L-aspartate was optimized with respect to pH, cosubstrate concentration and residence time in the packed bed enzyme reactors. The proposed procedures show high recoveries between 96 and 100% for the L-aspartate determination in a medium for mammalian cell cultivations after the elimination of L-glutamate. (C) 2001 Elsevier Science B.V. All rights reserved.

"Novel Chemiluminometric H2O2 Sensors For The Selective Flow Injection Analysis"
Sens. Actuat. B 1998 Volume 51, Issue 1-3 Pages 107-113
D. Janasek*, U. Spohn and D. Beckmann

Abstract: H2O2 can be detected chemiluminometrically in the presence of luminol at Co and Cu foils. The chemiluminescence signal can also be induced electrochemistry. The linear determination ranges are 0.1-200 µM on Co and 5-2000 µM on Cu under flow injection conditions. To improve the selectivity the chemiluminescence detector was combined with a thin layer gas dialysis cell. H2O2 was detected at 0.5-100 mM. The interference by a >100-fold excess of EDTA, α-ketocarboxylic acids and peroxodisulfate can be excluded. Peroxomonosulfate concentrations greater than a 10-fold excess of H2O2 cause a significant bias, which resulted from the hydrolysis of peroxomonosulfate.
Hydrogen peroxide Chemiluminescence Chemiluminescence Sensor Sensor Interferences EDTA Dialysis Gas diffusion

"An Enzyme-modified Chemiluminescence Detector For Hydrogen Peroxide And Oxidase Substrates"
Sens. Actuat. B 1997 Volume 39, Issue 1-3 Pages 291-294
D. Janaseka,* and U. Spohna

Abstract: Enzyme-modified silica and graphite pastes were used to construct chemiluminescence detectors for hydrogen peroxide, glucose and L-lactate. The pastes for H2O2 detection were prepared by mixing a solution containing 1-5 mg fungal peroxidase in 2.9 mL 0.1 M Tris buffer with 100-300 µL 0.32% polyethyleneimine and 100 mg fumed silica, LiChrospher Si 100, Li-Chrospher NH2 100 or graphite powder. The mixtures were dried under vacuum and then dispersed in 2 µL octadecane/paraffin oil (9:1). The resulting paste was packed into a cavity (0.32 mm x 7 mm i.d.) in the flow-through detection cell (total volume 2.2 µL) in a FIA system. The stability of the graphite paste detector was improved by coating with electropolymerized o-phenylenediamine. The FIA system was equipped with a 30 µL injection loop and was operated with 0.5 mM luminol/0.2 M Na2CO3 at pH 9.2 as the reagent stream and 0.1 M potassium phosphate buffer at pH 7.4 as the carrier stream (both at 0.2 ml/min). H2O2 was injected into the buffer carrier stream which was then merged with the reagent stream. The chemiluminescence signal was detected with a photodiode. Bienzyme optrodes for the detection of glucose and L-lactate were prepared by immobilizing glucose oxidase and lactate oxidase, respectively, in a poly(carbamoylsulfonate) hydrogel adsorbed onto the graphite-paste H2O2 detector.
Glucose Hydrogen peroxide Lactate Chemiluminescence Optrode Immobilized enzyme Buffer Silica Graphite Photodiode

"Chemiluminometric Flow Injection Analysis Procedures For The Enzymatic Determination Of L-alanine, α-ketoglutarate And L-glutamate"
Biosens. Bioelectron. 1999 Volume 14, Issue 2 Pages 123-129
D. Janasek and U. Spohn

Abstract: Chemiluminometric Flow Injection Analysis (FIA) procedures were developed for the enzymatic determination of L-alanine, α-ketoglutarate and L-glutamate in the cultivation medium of mammalian cells. A packed bed flow microreactor containing alanine aminotransferase and glutamate oxidase immobilized on sieved porous glass beads was combined with a chemiluminescence detector for the generated hydrogen peroxide. To catalyse the indicator reaction between luminol and hydrogen peroxide both Co(II) ions and immobilized peroxidase from Arthromyces ramosus were used in a fiber optic detector cell. L-alanine, α-ketoglutarate and L-glutamate can be detected over two decades of concentration magnitudes with detection limits of 2, 5 and 1 µM, respectively. The FIA procedure was applied to determine L-alanine and a-ketoglutarate in cell cultivation media.
Reactor

"An Enzymic Chemiluminescence Optrode For Choline Detection Under Flow Injection Conditions"
Anal. Lett. 1996 Volume 29, Issue 1 Pages 1-17
Lapp, H.;Spohn, U.;Janasek, D.

Abstract: A chemiluminometric bienzyme membrane-based optrode was developed for the detection of choline (I). Choline oxidase and fungal peroxidase were immobilized on a nylon (biodyne) membrane preactivated with 25% glutardialdehyde for 12 h. The addition of polyethylenimine to the mixed enzyme solution before glutardialdehyde crosslinking improved the sensitivity and the long-term stability of the membrane. Up to 200 determinations were possible with an RSD of 0.8%. The calibration graph was linear from 0.1-2 mM I with a detection limit of 1 µM.
Choline Chemiluminescence Optrode

"Ruthenium/rhodium Modified Gold Electrodes For The Amperometric Detection Of Hydrogen Peroxide At Low Potentials"
Anal. Bioanal. Chem. 2002 Volume 374, Issue 7-8 Pages 1267-1273
Dirk Janasek, Walter Vastarella, Uwe Spohn, Nico Teuscher, Andreas Heilmann

Abstract: Electrodes of ruthenium/rhodium deposited as thin layers on gold foils were investigated. Ruthenium layers were radio frequency (r.f.) magnetron sputtered and the rhodium layers were made by vacuum evaporation. Hydrogen peroxide could be detected using the cathodic reduction at potentials lower than +170 mV or the anodic oxidation at higher potentials. Under flow injection conditions, H2O2 was detected between 1 and 1000 µM at a potential of -100 mV and between 2 and 500 µM at a potential of +250 mV vs. Ag/AgCl/0.4 M KCl. The electrodes also showed high operational stability and selectivity against many electroactive substances. The selectivity against dissolved oxygen was investigated.