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A highly permeable film of the condensation a-qclodexrin polymer (a-CDP) was used as a membrane for fabricating a "second-generation" glucose amperometric biosensor. Glucose oxidase (GOD) was covalently immobilized, whereas 1,4-benzoquinone (BQ), or tetrathiafulvalene (TTF) mediator molecules were included in the membrane by the a-cyclodextrin sites. A simple one-step procedure for the biosensor preparation was developed. It consisted of casting the membrane onto the surface of a glassy carbon, gold, or platinum disk substrate from an aqueous solution, pH 2.0 (HCl), containing equimolar quantities of a water-soluble a-cyclodextrin prepolymer. a glutaric dialdehyde cross-linlung reactant, GOD, and the mediator. Cyclic voltammetn (0') limiting currents for glucose biocatalytic electrooxidation were measured for different enzyme loadings and mediator dosings inside the membrane as well as for different glucose concentrations in a (0.1 M phosphate buffer + 0.1 M NaC10J pH 7.0 solution. The limiting-electrocatalytic currents at the (a-CDP)-GOD-TTF electrode were pH independent and occurred at Ella = 0.03 1' (vs. SCE), i.e., at a favorably low potential value. The detectability of glucose was 10 p M for the (a-CDP)-GOD-BQ electrode at the 2 mg (18,s unit) GOD loading and a signal-to-noise ratio of 3. The values of apparent Michaelis constant for glucose and the maximum limiting electrocatalytic current density, determined from the MichaelisMenten analysis for the 1 mg (18.5 unit) GOD loading, were (4.5 ? 0.5) mM and (190 ? 20) pA cm-* for the (a-CDP)-GOD-BQ electrode, and (5.6 * 0.8) mM and (137 t 16) pA cm-' for the (a-CDP)-GOD-TTF electrode, respectively. The sensor performance was examined with respect to the method of membrane preparation, membrane composition, and long-term stability. Miniaturization of the biosensor is facile if, for instance, a 10 p m Pt disk microelectrode substrate is used.

Poly(m-chloroaniline) (PmClAn) was synthesized by emulsion polymerization. The in¯uences of reaction temperature and initiator concentration on polymerizations were studied. It was found that PmClAn with number-average molecular weight of 1.85 Â 10 3 g mol À1 was obtained by the following conditions: 80°C, [monomer] = 0.187 Â 10 À3 mol l À1 , [sodium lauryl sulfate] = 4.8 Â 10 À2 mol l À1 , [potassium peroxydisulfate] = 5.6 Â 10 À2 mol l À1 , reaction period = 2.0 h. 1 H NMR, FTIR, and transmission and scanning microscopy were used for structural characterization of PmClAn. It was shown that the ratio of benzoid to quinoid units in the macromolecular chain was respectively 3:2, and that PmClAn has a typical crystalline monoclinic form. A PmClAn molecular chain con®guration was also proposed on the basis of crystallographic data. Cyclic voltammetry experiments revealed the PmClAn membrane electrode electroactivity. This electroactivity increased when the polymer was proton-doped. When Pt particles were electrodeposited onto the polymer membrane electrode, they presented a preferred orientation. Isopropanol oxidation intensities with platinized PmClAn modi®ed electrodes were larger than with a platinized Pt electrode. We also found that oxidation occurred mainly on the Pt particles deposited on the polymer, and that the anodic peak potential changed with polymer and its doping level. These results indicated that the Pt particles interacted with the polymer and that catalytic properties could be observed.

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