Abstract: The cited sensor was fabricated by covalent immobilization of alcohol oxidase and α-chymotrypsin on to a polycarbonate membrane via glutaraldehyde. A cellulose acetate membrane was applied over the immobilized enzymes and used to attach the assembly to the surface of a Pt electrode. Amperometric measurements of aspartame (I) were performed in 0.1 M phosphate buffer of pH 7.5 with the Pt electrode polarized at +650 mV vs. Ag/AgCl. Calibration graphs were linear from 1-750 µM I using batch and flow-through methods, and up to 1 mM I using a flow injection method. Detection limits were 0.2-1 µM; RSD were 1.8-4% (n = 10). Different strategies for eliminating interfering compounds, including the use of an additional alcohol oxidase/catalase membrane and signal subtraction using an alcohol electrode, were employed. The sensor was applied to various foods; recoveries were 95-106%. An amperometric enzyme electrode for the determination of aspartame was developed by covalent immobilization of alcohol oxidase and α-chymotrypsin. A platinum based hydrogen peroxide electrode was used as the detector. Excellent sensitivity was obtained using batch, flow-through and flow injection methods with detection limits of 2 x 10^-7, 4 x 10^-7 and 10^-6 mol L-1, respectively. Different strategies for eliminating interfering compounds, including the introduction of an additional alcohol oxidase-catalase membrane and signal subtraction using an alcohol electrode, were employed. A recovery study on seven food samples was carried out and the results were satisfactory.

Abstract: The method and apparatus for the preparation of phosphatidylcholine/dipalmitoylphosphatidic acid membranes, containing enzymes or antibodies, cast on glass microfiber or polycarbonate ultrafiltration membranes are described [cf. Anal. Chem., 1995, 67, 936; Electroanalysis (N.Y.), 1995, 7, 531, 1082]. The membranes were used in flow injection amperometric determinations of (i) substrates (e.g., acetylcholine, penicillin and urea) of hydrolytic enzymes, and (ii) antigens (e.g., thyroxine and triazine herbicides).