High speed liquid chromatography of phenylethanolamines for the kinetic analysis of [11C]-meta-hydroxyephedrine and metabolites in plasma

J Chromatogr B Biomed Sci Appl. 1997 May 23;693(1):31-41. doi: 10.1016/s0378-4347(97)00040-6.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Carbon Radioisotopes
  • Chromatography, Gas
  • Chromatography, High Pressure Liquid
  • Chromatography, Ion Exchange
  • Ephedrine / analogs & derivatives*
  • Ephedrine / blood
  • Ephedrine / pharmacokinetics
  • Ethanolamines / analysis*
  • Humans


  • Carbon Radioisotopes
  • Ethanolamines
  • 3-hydroxyephedrine
  • Ephedrine