title: Field-amplified sample injection in capillary electrophoresis with amperometric detection for the ultratrace analysis of diastereomeric ephedrine alkaloids.
abstract: A coupling method of field-amplified sample injection (FASI) CE with amperometric detection is developed for ultratrace analysis of ephedrine alkaloids stereoisomers. FASI was introduced by injecting electrokinetically the sample solution for 10 s into the capillary filled with highly conductive background electrolyte (BGE). The diastereomeric selectivity and the detection sensitivity were improved by using borate buffer of high ionic strength as BGE. Parameters affecting FASI and CE separation were investigated to achieve the optimal conditions. Four analytes were separated within 15 min using 200 mmol/L borate buffer (pH 9.5) and separation voltage of +18 kV, with detection potential at +1.0 V (vs. Ag/AgCl) and carbon disc electrode as working electrode. Excellent linearity was observed between peak current and concentration of analytes in the range of 0.1-100 ng/mL. The LODs (S/N = 3) for (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (+)-N-methylpseudoephedrine were 39.3, 54.9, 30.8, and 44.1 pg/mL, respectively. The proposed method was successfully applied to the determination of alkaloids in Ephedra sinica, with results agreed well with HPLC method. Mean recoveries of 102.1-109.7% and RSDs less than 6% were found. And the merits of high sensitivity and selectivity, as well as a simple and stable operation, have been demonstrated.
authors: Ministry of Education and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.|Fujian Metrology Institute, Fuzhou, Fujian, P. R. China.
authors: Xiaoyan
authors: X
authors: Chen
authors: Ministry of Education and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.
authors: Yanxia
authors: Y
authors: Tang
authors: College of Biological Science and Technology, Fuzhou University, Fuzhou, Fujian, P. R. China.
authors: Shaoyun
authors: S
authors: Wang
authors: Ministry of Education and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.
authors: Yunping
authors: Y
authors: Song
authors: Ministry of Education and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.
authors: Fengxiang
authors: F
authors: Tang
authors: Ministry of Education and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.
authors: Xiaoping
authors: X
authors: Wu
mesh_terms: D000470:Alkaloids / Q000032:analysis* / Q000737:chemistry*; D004566:Electrodes; D019075:Electrophoresis, Capillary / Q000379:methods*; D004809:Ephedrine / Q000032:analysis* / Q000737:chemistry*; D057446:Hydrodynamics; D006863:Hydrogen-Ion Concentration; D015203:Reproducibility of Results; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D004809:Ephedrine
keywords: Capillary electrophoresis; End column amperometric detection; Ephedrine alkaloids diastereoisomers; Field-amplified sample injection; Ultratrace analysis