Milk lactate determination with a rotating bioreactor based on an electron transfer mediated by osmium complexes incorporating a continuous-flow/stopped-flow system

Organometallic polymers for electrode decoration in sensing applications

Macromolecules containing metals combine the processing advantages of polymers with the functionality offered by the metal centers. The developments in the area of electrochemical chemo/biosensors based on organometallic polymers are reviewed.

Penicillamine determination using a tyrosinase micro-rotating biosensor

Tyrosinase [EC 1.14.18.1], immobilized on a rotating disk, catalyzed the oxidation of catechols to o-benzoquinone, whose back electrochemical reduction was detected on glassy carbon electrode surface at -150mV versus Ag/AgCl/NaCl 3M. Thus, when penicillamine (PA) was added to the solution, this thiol-containing compound participate in Michael type addition reactions with o-benzoquinone to form the corresponding thioquinone derivatives, decreasing the reduction current obtained proportionally to the increase of its concentration. This method could be used for sensitive determination of PA in drug and human synthetic serum samples. A linear range of 0.02-80 microM (r=0.999) was obtained for amperometric determination of PA in buffered pH 7.0 solutions (0.1 M phosphate buffer). The biosensor has a reasonable reproducibility (R.S.D.<4.0%) and a very stable amperometric response toward this compound (more than 1 month).

Sensitive determination of ciprofloxacin and norfloxacin in biological fluids using an enzymatic rotating biosensor

The high sensitivity that can be attained using an enzymatic system and mediated by catechol has been verified by on-line interfacing of a rotating biosensor and continuous-flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in the presence of hydrogen peroxide catalyzed the oxidation of catechol, whose back electrochemical reduction was detected on glassy carbon electrode surface at -200mV. Thus, when ciprofloxacin (CF) or norfloxacin (NF) was added to the solution, these piperazine-containing compounds participate in Michael addition reactions with catechol to form the corresponding aminoquinone derivative, decreasing the peak current obtained in proportion with the increase of its concentration. CF was used as the model piperazine-containing compound for the study. The influence of indicator composition on the nature of the analytical response has been assessed through examining the electrochemical properties of three derivatives. Interference by electroactive species (ascorbate, urate, and tyrosine) and other physiological constituents (cysteine, glutathione) has also been assessed.