Application of capillary electrochromatography to the separation of phenylthiohydantoin-amino acids

The applicability of capillary electrochromatography with 1.5-mu m ODS-modi fied non-porous particles for the separation of phenylthiohydantoin (PTH)-a mino acids was investigated. The effect of the pH, organic solvent content and ion concentration of the mobile phase on the separation was investigate d. On a 34-cm column, plate numbers in the order of 60 000-180 000 were obt ained for the neutral and acidic PTH-amino acids. The required presence of sodium dodecyl sulfate (SDS) in the mobile phase led to broad asymmetric pe aks and long retention times for the three basic PTH-amino acids (Arg, His, Lys). With a mobile phase containing a phosphate buffer with a pH of 7.2, 5 mM SDS, and 5% (v/v) of both acetonitrile and tetrahydrofuran, an isocrat ic separation in less than 8 min could be realized for all PTH-amino acids with the exception of PTH-Arg. (C) 1999 Published by Elsevier Science B.V. All rights reserved.