Electrochemical characterization of screen-printed carbonaceous electrodes for the determination of peroxidase activity in novel screen-printed flow-through modules

A novel totally screen-printed flow-through cell for immunoanalysis is presented. It contained screen-printed carbonaceous electrodes, which allowed the determination of peroxidase activity through the electrochemical reduction of p-benzoquinone. As different electrode materials differ strongly in their electrochemical properties, electrodes resulting from various screen-printable carbonaceous pastes were characterized using the hydroquinone/ p-benzoquinone redox couple. For most of the electrodes, cyclic voltammogram peak separations of between 550 and 670 mV were observed indicating only quasi-reversible electrochemical behavior. This was confirmed by variation of the peak separation with scan rate. Heterogeneous electron transfer rates of ca. 0.5 - 1 x 10(-3) cm s(-1) and electrochemical activation energies of ca. 20 kJ mol(-1) were found. These flow-through cells were not only applied to electrochemical peroxidase activity determinations but also, in combination with a separate detector, as affinity reactors. After biotinylation of screen-printed layers, streptavidin and then biotinylated peroxidase could be bound. However, as signals were only 10-20% of those obtained with a column filled with biotinylated glass beads, only the screen-printed electrochemical detector was applied to the detection of antibodies against the African Swine Fever Virus.     

Direct potentiometric immunoelectrodes

Summary The selective binding of 3-indole acetic acid (IAA) alkali phosphatase (AP) to respective antibodies immobilized on pretreated titanium wires as electrodes (40×0.8 mm ø) is studied and the conditions are optimized with respect to selectivity and sensitivity, and the cross-reactivity of some related compounds is determined. Using these experiences, such wires are used as electrodes to detect selectively the methylester of IAA (IAA-Me). They are shown to behave best when the change of the electrode potential is measured against a similar reference electrode, coated with immobilized immuno globulin G (IgG) of the respective pre-immuno serum. A second coating with bovine serum albumin (BSA) is shown to prevent unspecific binding of IAA-Me. The sensitivity goes down to around 100 pmol/ml. Part I: Fresenius J Anal Chem (1992) 343:541     

A one-step route to 4-hydroxy-2,3-diaryl-3,4-dihydro-1 (2 )-isoquinolones

A new procedure for the synthesis of 2,3-diaryl-3,4-dihydro-4-hydroxy-1 (2 )-isoquinolones is described in which the -isomer predominates. Dehydration leads to 2,4-diarylisocarbostyrils.     

Eine Halbmikromethode zur Bestimmung von Carboxyh?moglobin durch Mikrodiflusion, Reduktion von Palladiumionen und Jodtitiation

Ohne Zusammenfassung     

Die fluorimetrische Bestimmung des Gesamtcatecholamingehaltes im Urin

Ohne Zusammenfassung