Analytical Laboratory, Department of Applied Chemistry, Faculty of Engineering, Aligarh Muslim University, Aligarh-202 002, India Manuscript received 3 May 1999, accepted 5 May 1999 Thin layer chromatographic behavior of twentyfour amino acids has been examined on plain silica gel as well as silica gel layers impregnated with cationic and anionic aqueous solutions using water-in-oil microemulsion as mobile phase. The impregnated plates were stable and gave well-formed spots. Silica gel impregnated with 2% CuSO4 solution was found most suitable layer material for selective separation of DL-phenylalanine from other amino acids. The limit of detection of some amino acids has also been deter­mined.