Determination of glycyrrhizin in liqueurs by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

An on-line coupled capillary isotachophoresis-capillary zone electrophoresis method for the determination of glycyrrhizin in liqueurs is described. The optimised electrolyte system was 5 mM HCl + 11 mM ɛ-aminocaproic acid + 0.05% hydroxyethylcellulose + 30% methanol (leading electrolyte), 5 mM caproic acid + 30% methanol (terminating electrolyte) and 20 mM caproic acid + 10 mM histidine + 0.1% hydroxyethylcellulose + 30% methanol (background electrolyte). Method characteristics, i.e., linearity (20–500 ng/ml), accuracy (recovery 99 ± 4%), intra-assay repeatability (2%), intermediate repeatability (3.8%) and detection limit (8 ng/ml) were determined. Speed of analysis, low laboriousness, high sensitivity and low-running cost are the typical attributes of the capillary isotachophoresis-capillary zone electrophoresis method. Developed method was successfully applied to analysis of liqueurs with liquorice extract and some foods (sweets and food supplements) containing liquorice. Found levels of glycyrrhizin in liqueurs, sweets and food supplements varied between 1–16 mg/l, 850–1050 mg/kg and 1.6–1.8 g/kg, respectively.