Browsing by Author "Bekele, Tesfaye"

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    Analytical Application of the Membrane-Stabilized, Enzyme-Modified Interface Between two Immiscible Electrolyte Solutions
    (Addis Ababa Universty, 1995-06) Bekele, Tesfaye; Hundhammer, B.(PhD)
    An amperometric urea biosensor based on facilitated transfer of urease-generated ammonium ion by a neutral carrier (ionophore) dibenzo-18-crown-6 across the polarizable membrane-stabilized interface between water and nitrobenzene is described and discussed. The enzyme urease employed for the investigation was immobilized on the sensor surface by physical entrapment as a gel between dialysis membranes. The current response of the anlperometric sensor was found to be directly proportional to the concentration of urea in the sample solution. In addition, correction for residual current due to interfering (residual) substances is relatively easy. The sensor gave a linear response to urea in the concentration range 5 x 10" to 5 x 10.3 M. The response time of the sensor was I min. The sensitivity appeared to be dependent on the conditions of immobilization of the enzyme. The effect of the thickness of the enzyme layer on the sensor response has been discussed. The life time of the sensor was more than 3 weeks when stored in the buffer solution at room temperature