The use of capillary electrophoresis with contactless conductivity detection for sensitive determination of stevioside and rebaudioside A in foods and beverages

- Capillary electrophoresis facilitates the determination of rebaudioside A and stevioside.
- Low LOD is achieved by contactless conductivity detection.
- Coated capillary with narrow inner diameter provides an efficient separation.
- Sample preparation is based only on its dilution and filtration.

Two electrophoretic methods with contactless conductivity detection have been developed for determination of the content of rebaudioside A and stevioside in samples of sweeteners and beverages prepared from extracts of the plant Stevia rebaudiana Bertoni. The total content of rebaudioside A and stevioside can be determined in a fused silica capillary with an inner diameter of 10 μm and total length of 31.5 cm in optimised background electrolyte with the composition 170 mM H3BO3/LiOH (pH 9.0). The combined peak of the two glucosides is characterised by a migration time of 54 s, which completely separates it from EOF. INST coating solution in an amount of 0.5% v/v, which effectively suppresses the electroosmotic flow, was added to the background electrolyte for mutual separation of rebaudioside A and stevioside. The CE method with suppression of EOF is characterised by complete separation of rebaudioside A and stevioside, LOD is 0.3 mg/L (0.1 μM).