Simultaneous determination of glucose and galactose in dairy products by two parallel amperometric biosensors

A sensitive, specific and rapid procedure for the simultaneous determinatio n of glucose and galactose in dairy products based on biosensors is describ ed. The biosensing probes consisted in two electrodes operating in parallel in a Flow Injection Analysis (FIA) system. Both electrodes consisted of a 5% rhodium-on-carbon paste, one equipped with glucose oxidase (GOx) and the other with galactose oxidase (GAOx) and peroxidase (HRP) for the determina tion of glucose and galactose, respectively. The rhodium-on-carbon paste el ectrode shows enhanced selectivity (particularly discrimination against asc orbic acid) and electrocatalysis of the reduction at lower potential of hyd rogen peroxide produced by the oxidase, The response was linear from 250 to 4,000 mg L-1 with a detection limit of 45 for glucose and 98 mg L-1 for ga lactose. Compared with classical methods mainly based on HPLC, the proposed procedure features straightforward sample preparation and improved sensiti vity and selectivity, All results reported demonstrate that the rhodium-on- carbon paste/ enzyme electrode constitutes a robust amperometric biosensor which can be used for quality control in dairy industries.