Chronoamperometric determination of paracetamol using an avocado tissue ( Persea americana) biosensor

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 1.2×10 −4 to 5.8×10 −3 mol l −1 ( r=0.9927) with a detection limit of 8.8×10 −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 5.0×10 −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.