Amperometric flow-injection determination of sucrose with a mediated tri-enzyme electrode based on sucrose phosphorylase and electrocatalytic oxidation of NADH

A new sucrose electrode is described for the determination of sucrose without interference from glucose or fructose. The sucrose electrode is based on the tri-enzymatic system of sucrose phosphorylase, phosphoglucomutase and glucose-6-phosphate 1-dehydrogenase. where NAD(P)H is produced from the last enzymatic reaction and recycled into NAD(P)(+) through its electrocatalytic oxidation by Os(4,4'-dimethvl-2.2-bypyridine)(2)(1, 10-phenanthroline-5.6-dione). The electrodes were optimised with respect to the various construction parameters and carrier composition in a FIA system and their response as a function of the pH and flow-rate was examined. The electrodes were suitable for operation in a FIA system and the analysis of real samples showed good agreement with the reference method. Typical optimised electrodes showed detection limits of 1 mM sucrose. response time of 5 min, sensitivity 1.010 nA mM(-1). and current density of 8.38 muA cm(-2), using 200 mM PIPES pH 7.25 with 10 mM phosphate and 5 mM MgCl2 as carrier. (C) 2001 Elsevier Science B.V. All rights reserved.