Polarographic determination of glycyrrhizic acid eased on double enhancement action of surfactant and dissolved oxygen

A method for the determination of glycyrrhizic acid (GA) is described based on polarographic current of GA enhanced doubly by both cation surfactant (cetyl trimethyl ammonium bromide (CTMAB)), and dissolved oxygen (including oxygen-derived species). The doubly enhanced current of GA includes two additional currents. One is the increased reduction current of adsorbed GA induced by CTMAB. The other is the catalytic current of GA caused by the dissolved oxygen molecule and its derived species. In 0.1 M NaAc-Hac (pH4.7+/-0.1) similar to 1x10(-5) M CTMAB supporting electrolyte without deoxygenation, the enhanced current of GA is linearly proportional to its concentration in the range of 4x10(-7) M similar to 4.0x10(-6) M. The detection limit is 1.8x10(-7) M. The double enhanced current of GA in sensitivity is about 15 times higher than its reduction wave in the same acetate buffer solution.