Separation of adrenergic amines in Citrus aurantium L. var. amara by capillary electrochromatography using a novel monolithic stationary phase.

ABSTRACT

This manuscript reports on the use of capillary electrochromatography for the determination of tyramine, (±) synephrine, and (±) octopamine, the major alkaloids in bitter orange peel. A novel methacrylate-based monolithic stationary phase was prepared by UV-photopolymerization in 100 µm id fused-silica capillaries. It facilitated the quantitative assessment of alkaloids with a mobile phase comprising aqueous 10 mM ammonium acetate in ACN and isopropanol. Applied voltage and temperature were 25 kV and 25°C, and samples were injected in electrokinetic mode. The method reported herein revealed adequate sensitivity (LOD ≤0.6 µg/mL), repeatability (σrel ≤4.1%), accuracy (recovery rates between 95.2 and 102.2%), and precision (intra-day variation ≤5.7%, inter-day variation ≤4.1%). The application of the CEC assay on C. aurantium var. amara plant material and dietary supplements, which usually are advertised for slimming properties, indicated that synephrine (0.17-0.82%) is the dominant alkaloid.