APPLICATION OF PAPER-BASED DEVICES AND SMARTPHONE FOR DETECTION OF BENZOIC ACID IN BEVERAGES

The purpose of this research was to design and apply paper-based devices and smartphone for quantitative analysis of benzoic acid. Based on the interactions between benzoic acid and methyl red indicator on the tetradecyltrimethylammonium bromide (TTAB) treated paper, the colors of methyl red modified paper changed from yellow to orange and pink, depending on benzoic concentration. In this research, the volume of TTAB, volume of benzoic acid, concentration of methyl red and time of detection were studied to obtain the optimum condition for preparing the paper-based devices. The digital images of paper-based devices were taken using a smartphone and using Color Grab application for RGB measurement. The ΔG intensity was linearly correspondign to the concentration of benzoic acid ranging from 20 to 200 mg/L (R² = 0.995) with the limit of detection (LOD) of 16.02 mg/L and limit of quantification (LOQ) of 48.54 mg/L. The Liquid-Liquid extraction technique was used to eliminate interferences including citric acid and ascorbic acid in sample preparation step. The proposed method was successfully applied to detect benzoic acid in beverage samples with recoveries of 101-109 %, and an acceptable relative standard deviation of 0.76-0.96%.