Simultaneous determination of Ephedra sinica and Citrus aurantium var. amara alkaloids by ion-pair chromatography.

Ephedra sinica (Ma Huang) preparations have recently gained a lot of attention because of serious side effects associated with their prolonged consumption. Citrus aurantium var. amara is now used as an alternative, despite the fact that similar side effects are suspected. We have developed and validated the first analytical procedure for the simultaneous determination of all major alkaloids from both species. Using the ion-pairing reagent SDS, a C-18 stationary phase (3mum material) and a pH-gradient for elution enabled the baseline separation of six alkaloids ((+/-)-octopamine, (+/-)-synephrine, tyramine, (-)-norephedrine, (+)-pseudoephedrine and (-)-ephedrine) within less than 30min. The method is sensitive (LOD</=4.6ng and LOQ</=16.2ng on-column), selective (l-tyrosine and l-phenylalanine, two closely related amino acids did not interfere), accurate (recovery rates of spiked samples were between 97.5 and 102.0%), repeatable (sigma(rel)</=4.6%) and precise (intra-day variation </=7.7%, inter-day variation </=7.0%). Without the need of a special sample treatment different matrices (plant material, commercial products) were successfully analyzed for their alkaloid content. Dominant alkaloids were (-)-ephedrine (0.9-1.6%) and/or (+/-)-synephrine (0.1-3.0%). Whether a product contained Ephedra-alkaloids or not could be determined in all investigated samples unambiguously.