title: Capillary electrophoresis coupled with end-column electrochemiluminescence for the determination of ephedrine in human urine, and a study of its interactions with three proteins.
abstract: A tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)-based electrochemiluminescence (ECL) detection coupled with capillary electrophoresis (CE) method has been established for the sensitive determination of ephedrine for the first time. Under the optimized conditions [ECL detection at 1.15 V, 25 mmol/L phosphate buffer solution (PBS), pH 8.0, as running buffer, separation voltage 12.5 kV, 5 mmol/L Ru(bpy)₃²⁺ with 60 mmol/L PBS, pH 8.5, in the detection cell] linear correlation (r = 0.9987) between ECL intensity and ephedrine concentration was obtained in the range 6.0 × 10⁻⁸-6.0 × 10⁻⁶ g/mL. The detection limit was 4.5 × 10⁻⁹ g/mL (S:N = 3). The developed method was successfully applied to the analysis of ephedrine in human urine and the investigation of its interactions with three proteins, including bovine serum albumin (BSA), cytochrome C (Cyt-C) and myoglobin (Mb). The number of binding sites and the binding constants between ephedrine and BSA, Cyt-C and Mb were 8.52, 12.60, 10.66 and 1.55 × 10⁴  mol/L, 6.58 × 10³  mol/L and 1.59 × 10⁴  mol/L, respectively.
authors.affiliation: Department of Chemistry, Zhengzhou University, People's Republic of China.
authors.forename: Ran
authors.initials: R
authors.lastname: Yang
authors.forename: Hua-Jin
authors.initials: HJ
authors.lastname: Zeng
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shi-Jun
authors.initials: SJ
authors.lastname: Li
authors.forename: Ling-Bo
authors.initials: LB
authors.lastname: Qu
mesh_terms: D000818:Animals; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry*; D004365:Drugs, Chinese Herbal / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D029789:Ephedra / Q000737:chemistry; D004809:Ephedrine / Q000737:chemistry* / Q000652:urine; D006801:Humans; D057230:Limit of Detection; D008163:Luminescent Measurements / Q000379:methods*; D009211:Myoglobin / Q000737:chemistry*; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry*
chemical_list: D004365:Drugs, Chinese Herbal; D009211:Myoglobin; D012710:Serum Albumin, Bovine; D045304:Cytochromes c; D004809:Ephedrine