Integration of compressed and composite immobilized enzyme membranes into an injection molded pin format by ultrasonic welding

Enzyme immobilization conditions were optimized using four commercially available pre-activated membranes and glucose oxidase. Compression of the immobilized enzyme membrane was used to reduce the recovery time of the sensor. Easily prepared composite membranes consisting of the pre-activated membrane with either a thin Nafion or cellulose acetate film were found to have better selectivities towards interfering species than unmodified membrane sensors. Thermoplastic was injection molded around platinum and silver chloride coated pins (1.2 mm diameter). Ultrasonic welding was then used to reliably attach an immobilized enzyme membrane over the working electrode. Flow injection measurements with the integrated sensor including an electropolymerized blocking layer on the working electrode gave peak heights for glucose, ascorbic acid and acetaminaphin of 26, 1.7 and 0.05 nA mM−1 mm−2 Pt, respectively, and a 95% recovery time of 90 s for glucose. These new methods and materials represent an option for batch processing of sensitive sensor components and low-cost electrode assembly.