Aazam Aliabadi - Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Iran
Gholam Hossein Rounaghi - Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Iran
Mohhamad Hossein Arbab Zavar - Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Iran

Modern researches and also the laboratories increasingly need the methods to measure the smallvolumes as microliter of analytical samples to identify various analytes with the high accuracy.An electrochemical biosensor based on a modified carbon paste electrode with hydrogel as anabsorbent polymeric matrix and banana as a source of polyphenol oxidase was constructed and itwas used for determination of paracetamol. The ability of the hydrogel to absorb and retain theliquids, allows us to insert only 1 mL of standard paracetamol solution into the surface of theelectrode, in fact we measure the concentration of paracetamol which is at the surface of theelectrode, not in solution. The electrochemical oxidation of paracetamol was studied by cyclicvoltammetry and square wave voltammetry. The effective parameters on the voltammetricresponse of the constructed biosensor were optimized. The results obtained by cyclicvoltammetry revealed that the banana-hydrogel carbon paste electrode shows a higher currentresponse compared to a banana carbon paste electrode and hydrogel carbon paste electrode. Theproposed electrode shows excellent capability to measure only one mL of sample solution, whichis very important and considerable property for limited samples in volume. The modifiedelectrode also exhibits an excellent sensitivity (1.6 picomole), a good linear range (10-250picomole), good reproducibility and stability in both basic and acidic environments even in thepresence of the enzyme and a long life time (20 days) for measurement of paracetamol insolutions.

Banana biosensor, Carbon paste, Polyphenol oxidase, Hydrogel, Paracetamol, Lowvolume consumption sensor