Extraction of caffeine and gallic acid from coffee by electrokinetic methods coupled with a hollow-fiber membrane

摘要

In this study the hollow fiber membrane coupled with electrokinetics was used, for the first time, for extraction and determination of caffeine and gallic acid from coffee prior to high performance liquid chromatography with photodiode array detection. Gallic acid (as an acid) and caffeine (as a base) were extracted from coffee at pH 5. In this work, several variables including applied voltage, coffee pH, acceptor phase pH, and extraction time were investigated. Our results showed that the extraction efficiency was increased when the applied voltage and extraction time were increased. The optimum conditions were pH 5 for the coffee, applied voltage of 20 V, and extraction time of 5 h. Gallic acid as an acid and caffeine as a base migrated to anode and cathode, respectively. Under the optimum conditions, gallic acid and caffeine were extracted with extraction efficiency of 21.3 and 23.4%, respectively. The intra-day and inter-day precisions (%) were found to be 7.6 and 4.8%, respectively. Therefore, this set-up for electrokinetics was potentially considered as a selective and simple preparation method for simultaneous extraction and analysis of basic and acid compounds in various matrices.