Capillary electrochromatography with thermo-optical absorbance detection for the analysis of phenylthiohydantoin-amino acids

Capillary columns were packed with 3 mu m C-18,, stationary phase, interfaced with an ultraviolet-laser based thermo-optical absorbance detector, and evaluated for separation of a mixture of phenylthiohydantoin-amino acids. These columns demonstrated consistent performance with a relative standard deviation (RSD) for migration time of less than 1.5% and a separation efficiency of 216 000 plates/m for the electroosmotic flow marker, thiourea. The thermo-optical absorbance detector was based on a 248 nm krypton-fluoride excimer laser. Detection limits (3 sigma) ranged from 1.6 to 4.8X10(-7) M phenylthiohydantoin (PTH)-amino acid injected onto the column, which is a factor of three superior to those obtained in micellar electrokinetic chromatographic analysis of these compounds. A mixture of 17 PTH amino acids was injected onto the capillary; 13 components were nearly baseline resolved in 14 min. (C) 1999 Elsevier Science B.V. All rights reserved.