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Determination of ephedrine alkaloids and synephrine in dietary supplements by column-switching cation exchange high-performance liquid chromatography with scanning-wavelength ultraviolet and fluorescence detection

Niemann, R.A., Gay, M.L.
Journal of agricultural and food chemistry 2003 v.51 no.19 pp. 5630-5638
herbal medicines, dietary supplements, ephedrine, alkaloids, aromatic compounds, chemical analysis, cation exchange resins, high performance liquid chromatography, ultraviolet radiation, fluorescence, detection, detectors
An HPLC method with on-line cleanup coupled to the separation column is described for determination of (-)-norephedrine, (+)-norpseudoephedrine, (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine, (+)-N-methylpseudoephedrine, and (±)-synephrine in finished dietary supplement products. Test portions were extracted in acidified aqueous acetone. A filtered aliquot was cleaned up on a strong cation exchange (SCX) precolumn that later was automatically coupled to the SCX analytical column. Measurement was by full-scan UV spectra for confirmation of identity by spectral matching and real-time integration of three wavelength signals for multiple quantitation. (±)-Synephrine was also quantitated by native fluorescence. Recovery averaged 95-100%. Determination of the major ingredients (-)-ephedrine, (+)-pseudoephedrine, and (±)-synephrine compared favorably to findings by an independent LC-MS analysis for a set of 25 samples. The results of a survey were reported for total ephedrine alkaloid and synephrine content and were compared to content declaration, for approximately 48 finished products.