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

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 (σ rel ≤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.