A highly reversible and sensitive tyrosinase inhibition-based amperometric biosensor for benzoic acid monitoring

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 determination 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 concentration on the inhibitory were investigated in detail. A potential value of −0.20 V versus SCE, and a constant catechol concentration of 6 μM were selective to carry out the amperometric inhibition measurement. The inhibitor biosensor had a fast response to benzoic acid (<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 constant of 17 μM. This inhibitor biosensor was successfully applied for the determination of benzoic acid in some real beverage sample, such as Coca-Cola, Pepsi-Cola, Sprite and Yoghurt. Results were compared to those obtained using high performance liquid chromatography, showing a good agreement.