Analytical Application of the Membrane-Stabilized, Enzyme-Modified Interface Between two Immiscible Electrolyte Solutions
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Date
1995-06
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Addis Ababa Universty
Abstract
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
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Keywords
Enzyme-Modified Interface