ABSTRACT
A biosensor based on vaseline/graphite modified with avocado tissue (Persea americana) as the source of polyphenol oxidase was developed and used for the chronoamperometric determination of paracetamol in pharmaceutical formulations. This enzyme catalyses the oxidation of paracetamol to N-acetyl-p-benzoquinoneimine whose electrochemical reduction back to paracetamol was obtained at a potential of -0.12 V. After addition of paracetamol reference solutions in glass cell and stirring for 60 s for the accumulation of N-acetyl-p-benzoquinoneimine at the electrode surface under open-circuit conditions, the current response was monitored by 120 s without stirring. The currents obtained at 70 s were proportional to the paracetamol concentration from 1.2x10(-4) to 5.8x10(-3) mol l(-1) (r=0.9927) with a detection limit of 8.8x10(-5) mol l(-1). The recovery of paracetamol from two samples ranged from 97.9 to 100.7% and a relative standard deviation lower than 0.5% for a solution containing 5.0x10(-3) mol l(-1) paracetamol in 0.10 mol l(-1) phosphate buffer solution (pH 7.0; n=10) was obtained. The results obtained for paracetamol in pharmaceutical formulations using the proposed biosensor and those obtained using a pharmacopoeial procedure are in agreement at the 95% confidence level.
