Determination of glycyrrhizic acid and 18-β-glycyrrhetinic acid in biological fluids by micellar electrokinetic chromatography

Abstract

A micellar electrokinetic chromatographic technique for determining glycyrrhizic acid (GZA) and 18β-glycyrrhetinic acid (GRA) in human plasma and urine was developed. Sample clean-up and analyte concentration were carded out by solid-phase extraction (with C18 sorbent). The buffer solution used for MEKC contained 20 mM sodium dihydrogenphosphate, 20 mM sodium tetraborate, 20 mM tetrabutylammonium bromide and 50 mM sodium dodecylsulphate, at a pH of 8.7. Good linearities for both GZA and GRA in plasma and urine were obtained. The recoveries of the method were in the range 86.5 to 107%. The detection limits for GZA in urine (0.5 ml) and plasma (1 ml) were 1.6 μg ml-1 and 0.8 μg ml-1, respectively, while for GRA in urine (0.5 ml) and plasma (1 ml) were 2 μg ml-1 and 1 μg ml-1, respectively.