Automated determination of glucose in soluble coffee using Prussian Blue-glucose oxidase-Nafion((R)) modified...

A highly selective, fast and stable biosensor for determination of glucose in soluble coffee has been developed. The biosensor electrode consist of a thin film of ferric hexacyanoferrate (Prussian Blue or PB) electrodeposited on the glassy carbon electrode (GCE) (to provide a catalytic surface for the detection of hydrogen peroxide) glucose oxidase immobilized on top of the electrode and a Nafion((R)) polymer layer. The stability of the PB film and the biosensor was evaluated by injecting standard-solution (50muM H(2)O(2) and 0.5mM glucose) during 4h in a flow-injection system with the electrodes polarized at -50mV versus Ag/AgCl. The system is able to handle about 60 samples per hour and is very stable and suitable for industrial control. Determination of glucose in the range 2.5 and 15% (w/v) in phosphate buffer with precision (r.s.d.<1.5%) has been achieved and is in agreement with the conventional procedures. Linear calibration in the range of 0.15 and 2.50mM with detection limits of ca. 0.03mM has been obtained. The morphology of the enzyme glucose oxidase on the modified electrode has been analyzed by scanning electron microscopy (SEM) measurements.