Evaluation of a simple and low cost potentiometric biosensor for pharmaceutical and in vivo adrenaline determination

In this work the polyphenol oxidase (PPO) was the main component of a biosensor for adrenaline determination. The activity of this enzyme was measured in several vegetables. Banana (Musa sp.) extracts presented better results with 974 UA (units of activity). The biosensor was constructed with a polyethylene tube (0.8 mm i.d.) filled with: carbon paste containing 50 UA of the PPO in phosphate buffer (pH = 7.00) solution and vaseline as agglutinant. When the biosensor was applied in medicine samples it provided a linear range from 8.00 × 10−9 to 8.00 × 10−4 mol L−1; the results obtained with the proposed method and the Brazilian Pharmacopoeia method were in agreement (t-test). When it was applied in blood samples, the matrix-matching calibration was used, and the linear range was from 8.00 × 10−7 to 8.00 × 10−3 mol L−1. In vivo studies were also done. The obtained results for those electrodes, which were inserted in the jugular vein of Wistar rats, were very promising.