title: High speed liquid chromatography of phenylethanolamines for the kinetic analysis of [11C]-meta-hydroxyephedrine and metabolites in plasma.
abstract: A method is developed and described for analysis of [11C]-meta-hydroxyephedrine, [11C]MHED, a tracer of cardiac function, and its metabolites in plasma samples. The method combines on-column solid-phase extraction and separation on a single weak cation-exchange column. Phenylethanolamines were used to develop the separation method that concentrates the analytes on-column from physiological saline and then elutes them by changing to an acidic mobile phase. Hydrophobic interactions determine the selectivity, and elution order is the same as for reversed-phase liquid chromatography on a C1 stationary phase. The mechanism of separation is mixed mode, with ion-exchange coupled with a reversed-phase liquid chromatography mechanism. Each sample analysis requires only 10 min and does not require deproteinization or the use of organic solvents. In human samples, a single plasma metabolite of [11C]MHED along with the parent compound were observed using this method. The method was sufficiently rapid so that in 70 min seven samples were assayed, providing a well-defined time course for MHED and its metabolites in blood. The metabolite concentration increased with time to approximately 85% of the plasma activity 50 min after administration. The results with the developed method are comparable to those described for reversed-phase separations, with the advantage that our method does not require deproteinization, reducing sample analysis time by a factor of two.
authors.affiliation: Department of Radiology, University of Washington, Seattle 98195-6004, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Link
authors.forename: R E
authors.initials: RE
authors.lastname: Synovec
authors.forename: K A
authors.initials: KA
authors.lastname: Krohn
authors.forename: J H
authors.initials: JH
authors.lastname: Caldwell
mesh_terms: D002250:Carbon Radioisotopes; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004809:Ephedrine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D004983:Ethanolamines / Q000032:analysis*; D006801:Humans
chemical_list: D002250:Carbon Radioisotopes; D004983:Ethanolamines; C065363:3-hydroxyephedrine; D004809:Ephedrine