Département de chimie moléculaire

In this present work, a highly reversible and sensitive amperometric biosensor, based on the immobilization of tyrosinase (Tyro) by calcium carbonate nano-materials (nano-CaCO3), was applied for detn. of food preservative, benzoic acid. The detection of benzoic acid was performed via its inhibiting action on the Tyro/nano-CaCO3 modified glassy carbon electrode. The effects of enzyme substrate type and substrate concn. on the inhibitory were investigated in detail. A potential value of -0.20 V vs. SCE, and a const. catechol concn. of 6 $μ$M were selective to carry out the amperometric inhibition measurement. The inhibitor biosensor had a fast response to benzoic acid ({\textless}5 s) with a wide linear range of 5.6 × 10-7 to 9.2 × 10-5 M and a high sensitivity of 1061.4 ± 13 mA M-1 cm-2. The inhibiting action of benzoic acid on the Tyro/nano-CaCO3 electrode was highly reversible (100{%}) and of the typical competitive type, with an apparent inhibition const. of 17 $μ$M. This inhibitor biosensor was successfully applied for the detn. of benzoic acid in some real beverage sample, such as Coca-Cola, Pepsi-Cola, Sprite and yogurt. Results were compared to those obtained using high performance liq. chromatog., showing a good agreement. [on SciFinder(R)]