An excellent separation of the N-TFA N-butyl esters of seventeen of the protein amino acids was achieved with acid washed Chromosorb W as the support material mesh, dried at 140~ for 12 h). In these experiments, the liquid phase, stabilized EGA, was used at loadings of from 0.325 w/w o/0 to 0.65 w/w o/o on both dried and non-dried acid washed Chromosorb W. The best separation was obtained with Chromosorb W dried for IZ h at 140~. Cysteine and methionine were not well resolved on any of the columns prepared with the non-dried acid washed Chromosorb W. A slightly poorer separation was obtained with the non-dried Chromosorb W, and there was a little skewing of the threonine and serine peaks on the 0.325 w/w o/o EGA columns, This was apparently due to an interaction of the threonine and serine derivatives with the water adsorbed on the surfaces of the Chromosorb W support material. At heavier loadings, of ca. 0.65 w/w %, these interactions were reduced, apparently due to the thicker layer of stationary phase.
Different mesh sizes of the dried support phase, 60/80, 80/1oo, and 100/120 were found to give quite similar results. Resolution improved only slightly with smaller particle size. Thus, mesh size in this range contributed only slightly to the elution properties of the column for the amino acid derivatives.