536
Anal. Chem. 1087, 5 9 , 536-537
Donnan dialysis with dual ion exchange permits the determination of anions in polyelectrolytes by subsequent ion chromatography. The results suggest that this general approach shouId be applicable to a wide variety of complicated matrices.
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RECEIVED for review July 24,1986. Accepted October 21,1986. The work was supported in part by the National Science Foundation under Grant CHE-8215371.
Highly Stable Biosensor Using an Artlflclal Enzyme M. Y.K. €Io and G. A. Rechnitz* Department of Chemistry, University of Delaware, Newark, Delaware 19716 Enzyme electrodes based on the coupling of immobilized enzymes with electrochemical sensors continue to play an important role in meeting the analytical measurement needs of biotechnology and biomedicine (1). Practical limitations, e.g., insufficient lifetime or cofactor requirements, of natural enzymes used for this purpose, have led to the use of whole cells (2) or tissue sections (3) as alternate biocatalysts. Such materials are not readily suited, however, for routine production of biosensors outside of the research laboratory or for use in conjunction with ion-selective field effect transistors ( 4 ) ,where time stability is a cardinal requirement. We now report on the construction and properties of a new type of electrochemical biosensor where an artifcial enzyme is coupled to a potentiometric gas-sensing membrane electrode. It will be seen that the use of the artificial enzyme results in highly stable sensor response characteristics with attractive analytical operating limits. Artificial enzymes (synzymes) are synthetic polymer chains having functional groups that mimic the biocatalytic activity of natural enzymes. Such synzymes have been extensively studied by Klotz's group (5) who kindly provided several artificial enzymes for the purposes of the present investigation. In order to make use of the potentiometric pC02 electrode and to provide a comparison with a natural enzyme, we chose the synzyme PEIQ-NH2 which catalyzes the decarboxylation of oxalacetate according to
HOOCC(=O)CH&02-
+ H+
----*
HOOCC(=O)CH3
+ C 0 2 (a)
Table I. Performance Comparison of Artificial and Natural Enzyme Electrodes for Oxalacetate artificial enzyme electrode
natural enzyme electrode
amt of catalyst lifetime cofactor requirement
13 IU 4 mg at least 6 monthsa
