Abstract: The conditions of HPIECseparation of Cl^-, Br^- and I^- were studied. The ions were separated within 35minutes by using NaNO₃ as an eluent. the chloride and bromide contents of.some samples were determined. The trace amounts (ppb order) of chloride in pure water were determined by using a pre-column without a four or six way valve.The IECbecaviouf of Cl^-, Br^- and I^- was interpreted from the theory of hard and soft acids and bases. The following experimental formula was obtained.lgD= 0.24φlg[B]-lg[B] + 0.490 + 0.61 where Dis the distribution coefficient of an anion, [B] is the concentra-tion of the eluent, φ is the softness of the anion as a base.