Catalase-based thin-layer enzyme cell used in organic-phase FIA system for determination of moisture in oily foods

The aim of our present work was to study the possibility of constructing a biosensor based on immobilized catalase enzyme (EC 1.11.1.6.) in organic-phase solutions. The catalase enzyme was immobilized by glutaraldehyde on a natural protein membrane in a thin-layer enzyme cell, connected to a stopped-flow injection analyser (SFIA) system with an amperometric detector. Adding FMCA to acetonitrile, the optimal concentration was 7.5 mg l(-1), while with TBATS it was 2.7 mg l(-1). The optimal pH value of the immobilized enzyme in buffer was about 6.0. On studying the role of the buffer solution used in the carrier solvent, the activity of the enzyme changed dramatically. The signal was highest when there was no buffer added to the carrier solution and decreased rapidly when the content increased (0-1.5%). Utilizing these results, a quick analytical method was developed to monitor indirectly the water content (activator) in various butter and margarine samples by maintaining a fixed substrate concentration. The water content of samples was compared with the results obtained by the gravimetric reference method (AOAC Method 920.116); the correlation coefficient (r) was 0.993.