PREPARATION AND CHARACTERIZATION OF A FRAGILE ENZYME IMMOBILIZED CARBON PASTE ELECTRODE

Several modes of glutamate dehydrogenase immobilization on glassy carbon and carbon paste electrodes were investigated for the preparation of a glutamate biosensor. Better performances were obtained by incorporating the "fragile" enzyme into the electrode matrix of the carbon paste. The biosensor was characterized using hexacyanoferrate(III) as the electrochemical mediator and phenazine methosulphate as the enzyme (coenzyme) mediator. The electrochemical behaviour of the redox couple hexacyanoferrate(II)/(III) was improved by incorporating octadecylamine into the enzyme modified carbon paste. Higher operational stability as well as improved signals in terms of magnitude and stability were achieved owing to the immobilization technique and to the use of two redox mediators respectively. Linear calibration curves were obtained between 50-mu-M and 1.3 mM glutamate. The electrode remained stable for about 11 days.