HPLC determination of stevioside in plant material and food samples

An HPLC method for the determination of sweet-tasting stevioside (STS) in the leaves of the plant Stevia rebaudiana and in some beverages (e.g. tea, orange juice) was developed. The pre-separation procedure consisted of extraction of STS from the plant material using boiling water and a solid-phase extraction (SPE). Recovery rates of the SPE for the analysed matrices ranged from 92.8% to 97.8% (for concentrations of STS of 105, 210 and 300 mu g/ml; Relative Standard Deviation (RSD) less than or equal to 3.3%). The chromatographic separations were realized using a C-18 column, the mobile phase consisting of methanol and water, and with UV detection at 210 nm. The limits of determination of STS were 5 mu g/ml for the Leaf extracts and the tea sample and 8 mu g/ml for the juice sample.