Screen-printed enzymatic biosensor modified with carbon nanotube for the methimazole determination in pharmaceuticals formulations

NOELIA A. MARTINEZ; GERMÁN ALEJANDRO MESSINA; FRANCO A. BERTOLINO; ELOY SALINAS; JULIO RABA

SENSORS AND ACTUATORS B-CHEMICAL

Año: 2008

0925-4005

This paper describes the development of a screen-printed sensor, modified with carbon nanotubes for therapid and sensitive quantification of methimazole (MT) in pharmaceuticals formulations. Tyrosinase [EC1.14.18.1], immobilized on a rotating disk, catalyzed the oxidation of catechols to o-benzoquinone, whoseback electrochemical reductionwas detected on graphite screen-printed electrodes modified with carbonnanotubes at −150 mV. Thus, when MT was added to the solution, this thiol-containing compound participatein Michael type addition reactions with o-benzoquinone to form the corresponding thioquinonederivatives, decreasing the reduction current obtained proportionally to the increase of its concentration.This method could be used to determine MT concentration in the range of 0.074–63.5M (r = 0.998). Thedetermination of MT concentration was possible with a detection limit of 0.056M in the processing ofas many as 25 samples per hour. The biosensor has a reasonable reproducibility (R.S.D. < 3.50%) and avery stable amperometric response toward this compound (more than 1 month). The application of thisanalysis to different pharmaceutical samples containing MT supports the utility this biosensor.