tModern researches and also the laboratories increasingly need the methods to measure the small volumesas microliter of analytical samples for determination of various analytes with a high accuracy. An electro-chemical biosensor based on a modified carbon paste electrode with hydrogel as an absorbent polymericmatrix and banana as a source of polyphenol oxidase was constructed and it was used for determinationthe concentration of paracetamol in one microliter volume of solution. The electrochemical oxidationof paracetamol was studied by cyclic voltammetry and square wave voltammetry. The effective param-eters on the voltammetric response of the constructed biosensor were optimized. The results obtainedby cyclic voltammetry revealed that the banana-hydrogel carbon paste electrode shows a higher currentresponse compared to a banana carbon paste electrode and hydrogel carbon paste electrode. Because ofhigh absorption property of hydrogel, the proposed electrode has the capability to measure only one Lof sample solution, which is very important and considerable property for limited volumes of samplesolutions. The modified electrode also exhibits a low detection limit (1.6 M) with a good linear range(10–250 M) and it has a good reproducibility and stability in both basic and acidic environments even inthe presence of the enzyme and a long life time (20 days) for measurement of paracetamol in solutions.

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