Determination of Ephedrine and Pseudoephedrine by Field-Amplified Sample Injection Capillary Electrophoresis

• Published in: Journal of chromatographic science 2014-04, Vol.52 (4), p.357-362
• Main Authors: Deng, Dongli, Deng, Hao, Zhang, Lichun, Su, Yingying
• Format: Article
• Language: English
• Subjects: Alkaloids; Capillarity; Chromatography; Electrophoresis; Electrophoresis, Capillary - methods; Ephedra sinica - chemistry; Ephedrine; Ephedrine - analysis; Ephedrine - chemistry; Hydrogen-Ion Concentration; Limit of Detection; Linear Models; Linearity; Mass spectrometry; Plant Extracts - chemistry; Pseudoephedrine - analysis; Pseudoephedrine - chemistry; Reproducibility of Results; Separation
• ISSN: 0021-9665; 1945-239X
• DOI: 10.1093/chromsci/bmt039

A simple and rapid capillary electrophoresis method was developed for the separation and determination of ephedrine (E) and pseudoephedrine (PE) in a buffer solution containing 80 mM of NaH2PO4 (pH 3.0), 15 mM of β-cyclodextrin and 0.3% of hydroxypropyl methylcellulose. The field-amplified sample injection (FASI) technique was applied to the online concentration of the alkaloids. With FASI in the presence of a low conductivity solvent plug (water), an approximately 1,000-fold improvement in sensitivity was achieved without any loss of separation efficiency when compared to conventional sample injection. Under these optimized conditions, a baseline separation of the two analytes was achieved within 16 min and the detection limits for E and PE were 0.7 and 0.6 µg/L, respectively. Without expensive instruments or labeling of the compounds, the limits of detection for E and PE obtained by the proposed method are comparable with (or even lower than) those obtained by capillary electrophoresis laser-induced fluorescence, liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. The method was validated in terms of precision, linearity and accuracy, and successfully applied for the determination of the two alkaloids in Ephedra herbs.