Internal membranes and laminates for adaptation of amperometric enzyme electrodes to direct biofluid analysis

This study describes the use of discrete, highly selective covering inner membranes in amperometric enzyme electrodes for direct biofluid analysis. Such inner membranes when interposed between the enzyme layer and the electrode working surface has been found to be both selective, as well as biocompatible. Cellulose acetate or detergent (Triton X-100 and Tween 80) modified cellulose acetate and polyethersulphone polymeric membranes, were both found to be highly selective against electroactive solutes normally present in biofluids. The inclusion of such inner perm-selective membranes greatly enhanced the biocompatibility of the enzyme electrode and reduced the passivation of the working electrode on exposure to whole blood or serum. The study indicates that electrode drift in biological solutions may also be due to passivation of the working electrode by small diffusible surface active species.