A portable electrochemical sensor for caffeine and (-)epigallocatechin gallate (EGCG) based on molecularly imprinted poly(ethylene-co-vinyl-alcohol) recognition element

The U.S. FDA allows a maximum of 72 mg of caffeine per 12 oz. serving (6 mg/oz) and the tolerance to sleep disruption effects of caffeine develops after consuming 400 mg/day of caffeine 3 times for a week. However, it is still hard for people to estimate how much caffeine is intake daily. On the other hand, (-)epigallocatechin gallate (EGCG) is studied a potent antioxidant that may have therapeutic properties for anti-aging and cancer. Conventionally, both caffeine and EGCG could be measured by the protocols of high performance liquid chromatography (HPLC); however, high precision instruments are required. In this work, the caffeine and EGCG are used as the target molecules and then imprinted into poly(ethylene-co-vinyl alcohol) via solvent evaporation. Target molecules on membrane are then removal, and the membrane is used as the sensing element for electrochemical urinalysis. From the cyclic voltammetry measurement of the caffeine, the peak oxidation potential is shifted from 0.36 to 0.38 V when the final concentration of caffeine is from 0.01 to 1 mg/mL, and the highest current density is about 0.18 ¿A/cm². This molecularly imprinted polymeric coated electrode is potential employed as a home-care system.