Fabrication of Quinine-Sensitive Membrane Electrodes and Their Properties

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Abstract
The fabrication and performance characteristics of quinine-sensitive membrane electrodes based on the ion-association complex of quinine with tetraphenylborate are described. The electrodes showed a near-Nernstian response over the range of about 5×10-5-1×10-1M quinine concentration. The potentiometric response of the electrodes was satisfactorily fast above a concentration of 1×10-5M, though below this level a longer time was required to attain the steady state-potential. The effects of ion-association complex concentration in the membrane and the membrane thickness on the potentiometric response were small. The electrodes showed good selectivity for quinine relative to several inorganic and organic ions, though the response was interfered with alkaloids. The electrodes can be used in the pH range of 5.3-7.3. Direct potentiometry and potentiometric titration were applicable for the determination of quinine concentration.