Microwave-Based Biosensor for Determination of Cholesterol in Food

Abstract

A new method for determination of cholesterol in food has been developed based on dielectric properties of the cholesterol in food after enzymatic reaction at microwave frequencies in the range of 0.2-20 GHz. The dielectric properties of cholesterol solution, enzyme and cholesterol-enzyme reaction were measured using the open ended coaxial probe coupled with computer controlled software automated network analyzer at room temperature (25 °C). At frequency 4.98 and 10.9 GHz the dielectric loss difference was obtain by subtracting the dielectric after the reaction with dielectric of cholesterol oxidase alone at 1:2 ratios. The relative standard deviation of the reproducibility was calculated to be 1.85 % for frequency 4.98 GHz and 2.06 % for frequency 10.9 GHz at cholesterol concentration of 38.67 ppm. The limit of detection was calculated to be 2.48 ppm at frequency 4.98 GHz and 3.53 ppm at frequency 10.9 GHz. Result obtained from the developed method was compared with the standard method of cholesterol determination (BOHAC extraction-HPLC). The comparison result shows an excellent agreement between the developed method and standard method. This indicates the results obtained from both methods are comparable. The good linear correlations, suggest that microwave di-electric properties could be used in developing sensors to determine cholesterol in food.