Bachelor of Science

This study has been undertaken to develop two new mediated amperometric biosensors for the determination of H202. The tissue-based biosensor was constructed by the incorporation of the Swede turnip tissue, rich in peroxidase, and ferrocene in a carbon paste matrix. The fabrication of another biosensor modified by the sol-gel immobilisation technique in a "sandwich" configuration was the other emphasis.

The detection principle of the biosensors was based on the enzymatic reduction of H202 by peroxidase and subsequently electron transfer from the electrode to the enzyme, via a redox mediator, ferrocene. The optimisation procedure for the fabrication and analytical performance of the biosensors were studied by amperometry. Possible interference and stability of the biosensors were evaluated The applicability of the biosensors was tested in recoveries of H202 in food and environmental samples.

The tissue composition and mediator loading were the primary parameters for the optimisation fabrication of the turnip tissue-based biosensor. This biosensor was endowed with an extended range of linearity from 0.06 mM to 0.68 mM and a detection limit of 0.015 mM. It exhibited a remarkable measurement reproducibility of 2.44% (n=15) and excellent stability, with no significant activity changes observed within six days of use.

The optimisation fabrication of the sol-gel modified horseradish peroxidase biosensor was focused on H20:Si (vlv), the outer and inner sol-gel film thickness, and the mediator concentration. The linear calibration range of the biosensor under optimised condition was 3 μm to 57 pM with a correlation of 0.996. Its good selectivity warranted a reasonable recovery in analytical applications. Its short response time of 16 seconds rendered it suitable for biosensing applications.