A novel electrochemical sensor was fabricated for measurement the concentration of morphine in very low volume of solution. This paper introduces a new approach for sensing of morphine (MP) in sub microliter of the solution using a modified carbon paste electrode. The electrode was prepared simply by mixing a hydrogel as an absorbent polymeric matrix with a carbon paste. Unlike the conventional electrochemical methods, a drop of morphine solution was absorbed into the surface of the electrode, and then the electrode was immersed into an electrochemical cell. The electrode showed a dynamic concentration range from 5.0 to 200 μM with a detection limit of 1 μM at pH 7 with respect to the concentration of morphine. The electrode successfully applied for determination of morphine in a drop of urine sample.

Keywords