Enantioseparation of dopa and related compounds by cyclodextrin-modified microemulsion electrokinetic chromatography.
A chiral microemulsion electrokinetic chromatography method has been developed for the enantiomeric separation of 3,4-dihydroxyphenylalanine (dopa), its precursors phenylalanine and tyrosine, and the structurally related substance methyldopa. The separations were achieved using an oil-in-water microemulsion, which consisted of the oil-compound ethyl acetate, the surfactant sodium dodecylsulfate (SDS), the co-surfactant 1-butanol, the organic modifier propan-2-ol and 20mM phosphate buffer pH 2.5 or 2.0 as aqueous phase. For enantioseparation sulfated beta-cyclodextrin was added. The resolution of each racemate was optimized by varying the concentration of the buffer and all components of the microemulsion. Enantioseparation could be achieved for dl-dopa, dl-phenylalanine and dl-tyrosine within 13 min with a resolution of 4.3, 3.1 and 3.3, respectively, and for methyldopa in 17 min (Rs: 1.4). The established methods allowed the detection of dopa, phenylalanine, tyrosine and methyldopa with a limit at 0.5, 1.0, 0.2 and 2.0 microg/ml.
Borst
Claudia
C
Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
Holzgrabe
Ulrike
U
D024322:Amino Acids, Aromatic / Q000737:chemistry*; D002845:Chromatography; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D003505:Cyclodextrins / Q000737:chemistry*; D004295:Dihydroxyphenylalanine / Q000032:analysis* / Q000737:chemistry* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D008750:Methyldopa / Q000032:analysis / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry; D015203:Reproducibility of Results; D013237:Stereoisomerism; D014443:Tyrosine / Q000032:analysis / Q000737:chemistry
D024322:Amino Acids, Aromatic; D003505:Cyclodextrins; D014443:Tyrosine; D010649:Phenylalanine; D008750:Methyldopa; D004295:Dihydroxyphenylalanine