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'-dimethyl-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 microA cm(-2), using 200 mM PIPES pH 7.25 with 10 mM phosphate and 5 mM MgCl2 as carrier.