Determination of Cinchona alkaloids and Vitamin B"6 by high-performance liquid chromatography with fluorescence detection [An article from: Analytica Chimica Acta]

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Description:
A simple and specific method has been developed for the simultaneous determination of the four major Cinchona alkaloids and their dihydroderivatives and pyridoxine hydrochloride (Vitamin B"6) by high-performance liquid chromatography (HPLC) with fluorescence detection (@l"e"m=420nm with @l"e"x=330nm). The chromatographic separation was performed on a Phenomenex Prodigy ODS column (5@mm, 250mmx3.2mm i.d.), recommended for basic compounds, under isocratic reversed-phase conditions. The method allowed a good peak shape and an effective resolution of the tested compounds. The extraction of alkaloids from the Cinchona succirubra bark was carried out in mild and fast conditions (ambient temperature, 20min) by ultrasonication. The procedure showed to be advantageous respect to a reference method, which involved Soxhlet extraction. The results were compared statistically by means of the Student's t-test and the variance ratio F-test; no significant difference was found. The method was reproducible (relative standard deviations in the range of 1.0-5.0% for the different alkaloids) and gave quantitative recovery of alkaloids added to bark samples (97.8-105%). For additional informations a photoreactor was arranged between the analytical column and the detector and the online post-column photochemical conversion (irradiation=254nm) was investigated. Vitamin B"6 was shown to be highly photosensitive, giving significantly different fluorescence spectra with and without UV irradiation. The proposed method was successfully applied to the quality control of Cinchona bark, liquid extract and cosmetics.