Horseradish peroxidase covalent grafting onto screen-printed carbon electrodes for levetiracetam chronoamperometric determination.

A new enzymatic electrochemical biosensor based on disposable transducers, namely screen-printed carbon electrodes, has been developed for the determination of the antiepileptic drug levetiracetam. Horseradish peroxidase was immobilized onto the carbon working electrode previously modified by an aryl diazonium salt. The formation of amide bonds between the amino and carboxylic groups of the enzyme surface, catalyzed by hydroxysuccinimide and carbodiimide, leads to the electrode functionalization. This orientated enzymatic modification results in high reproducibility, with an associated relative standard deviation of 6.21% for the slopes of several calibration curves in the calibration range from 0.10 to 0.83mM. Experimental variables that can affect levetiracetam chronoamperometric response, such as hydrogen peroxide concentration, pH, and applied potential, were optimized to perform a selective determination. An average limit of detection of 1.75x10(-5)M (alpha=beta=0.05) was obtained. The biosensors were finally applied to the determination of levetiracetam in complex matrices such as pharmaceutical drugs, yielding successful results.