My dear freind Surjit. You are asking a classical, basic physical chemistry question. First of all try to understand the physical properties of the class of molecules (like dipole moment, polarity of the solvent in which these will dissolve etc) then design a solvent system with certain polarity(from your observation in the previous studies) and try separating them on TLC. The antibiotic molecules are a world by themselves so do not try to embrace that large world with 2 of your hands. You will make a huge mistake in trying to do so. Restrict your study to a certain class of molecules (as per their similar/dissimilar molecular behaviour). Good luck.