Investigation of organic phase biosensor for measuring glucose in flow injection analysis system

The aim of our present work was to develop a flow-through measuring apparatus for the determination of glucose content as model system in organic media and to compare the properties of the biosensor in organic and in aqueous solutions. Glucose oxidase (GOx) enzyme was immobilized on a natural protein membrane in a thin-layer enzyme cell, made of Teflon. The enzyme cell was connected into a flow injection analyzer (FIA) system with an amperometric detector. After optimizing the system the optimal flow rate was found at 0.8 ml min⁻¹. In this case 50-60 samples were measured per hour. Adding ferrocene monocarboxylic acid (FMCA) to acetonitrile and to 2-propanol the optimal concentration was 5 mg l⁻¹, while in the case of tetrabutylammonium-p-toluenesulfonate (TBATS) the optima were 2.7 and 8.0 mg l⁻¹, respectively. With 6% buffer in acetonitrile containing FMCA more than 100 samples could be measured with the enzyme cell without any loss of activity. Measuring the hydrogen peroxide content produced in 2-propanol, the optimal concentration of buffer solution was at about 20%. The linear measuring range was 0-0.5 mM glucose in acetonitrile and 0-1.0 mM in 2-propanol.Glucose concentration of oily food samples was measured and compared with results obtained by the reference UV-photometric method. The correlation between the results measured by the two methods was very good with correlation coefficient (r) as high as 0.976.