Flow-injection analysis for hypoxanthine in meat with dissolved oxygen detector and enzyme reactor

A low cost flow-injection analysis (FIA) with a dissolved oxygen (DO) detector and a xanthine oxidase immobilized column for the analysis of hypoxanthine as an index to determine degree of aging in meat was developed for quality control in the food industry. In this system, hypoxanthine is oxidized by an enzyme reaction with xanthine oxidase immobilized on the column to produce xanthine. Then the catalytic reaction between hypoxanthine and DO with xanthine oxidase proceeds with the DO concentration decreasing in the stream of the flow system. Decrease in the DO concentration was monitored by a DO detector located downstream of the flow system. This decrease in DO concentration was proportional to the hypoxanthine concentration. For detecting the decreased DO concentration efficiently a flow-through cell with a polarographic-type DO sensor was specially designed. As a result, a linear working curve was obtained from 3.68 × 10⁻⁵ to 1.84 × 10⁻³ M hypoxanthine concentrations with this FIA system. We applied the present system with a DO detector for the determination of hypoxanthine in meat samples and compared the results with those obtained by the conventional HPLC method. The data obtained with the present FIA method were in fairly good agreement with those obtained by the conventional HPLC method for the meat samples. Correlation factor and regression line between the two methods were 0.998 and Y= 1.51X-32.64 respectively. We concluded that the present FIA system with a DO detector was suitable as a simple, easy to handle and reliable instrument for quality control in the food industry.