ELSEVIER Biosensor~" & Bioelectronics Vol. 13. No. 3-4, pp. 371-382, 1998 © 1998 ElsevierScience S.A. All rights reserved Printed in Great Britain PII: S0956-5663(97)00116-4 0956-5663/98/$19.00 Electropolymerization of pyrrole and immobilization of glucose oxidase in a flow system: influence of the operating conditions on analytical performance Juan-C. Vidal,* Esperanza Garcia & Juan-R. Castillo Department of Analytical Chemistry, GEAS, Faculty of Sciences, University of Zaragoza, Pza. San Francisco s/n, E-50009 Zaragoza Spain (Received 24 June 1997; revised form received 24 June 1997; accepted 15 October 1997) Abstract: The in situ potentiostatic electropolymerization of pyrrole (Py) on a Pt electrode in a thin-layer amperometric cell and the entrapment of the enzyme glucose oxidase (GOx) for the determination of glucose are reported. Polypyrrole (PPy) is directly formed by continuous passage of a buffered solution of the monomer (0.4 M) and enzyme (250 U mL -~) at pH 7 at a flow rate of 0.05- 0.1 mL rain -~ under a constant applied potential of + 0.85 V vs Ag/AgCII. The electrosynthesis of PPy by injection of 500/xL of a Py + GOx solution in a carrier electrolyte consisting of 0.05 M phosphate buffer and 0.1 M KCI at pH 7.0 was also assayed. The influence of the electropolymerization conditions on the analytical response of the sensor to glucose was investigated. The analytical performance of the PPy/GOx sensor was also studied in terms of durability and storage life, as well as selectivity against electroactive species such as ascorbic acid and uric acid as a function of the thickness of the polymer film formed. © 1998 Elsevier Science S.A. All rights reserved Keywords: polypyrrole, electropolymerization in flowing solutions, FIA, glucose oxidase, glucose determination INTRODUCTION Amperometric chemical sensors based on con- ducting and non-conducting polymers have aroused increasing interest in the last few years (Bartlett and Birkin, 1993). This type of sensor consists essentially of a polymer film formed by *To whom correspondence should be addressed. electrochemical oxidation on the surface of a working electrode from a monomer solution. The incorporation of biological reagents by physical entrapment is one of the most interesting applications in this field on account of their sim- plicity and analytical efficiency (Bartlett and Cooper, 1993). This type of immobilization, which is widely documented, usually involves physical entrapment of an enzyme within a poly- mer film as it grows from an aqueous solution 371