SEPARATION OF AMINO-ACIDS DIMETHYLAMINOBENZENE-THIOHYDANTOIN DERIVATIVES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The reversed-phase high-performance liquid chromatography (RP-HPLC) separation of dimethylaminobenzenethiohydantoin (DABTH) amino acids is improved by optimizing ionic strength and the mobile phase. The selectivity and the efficiency of the column depends on the rate change of acetonitrile and on buffer concentration, which affect the resolution and the elution order of DABTH-derivatives-Tyr,-Ala,-Cys,-Trp,-Val,-Pro,-Lys(K2) (see Appendix for amino acid abbreviations), and particularly of basic derivatives, DABTH-His and DABTH-Arg. These effects were utilized to produce an optimum gradient of acetonitrile and sodium acetate. The technique separates 22 of the 24 derivatives in 20 min and permits the identification of all amino acids found in proteins.