“…The terms "apparent" and "equivalent" can be extended to other measures of efficiency or performance (e.g., the separation number (13)) in order to clearly distinguish Ligand Interference Preventive Buffer in Determination of Copper(ll) by a Cupric Ion Selective Electrode Sir: In the determination of copper(II) by means of a cupric ion selective electrode, the problems encountered are variation of activities caused by complexation of copper(II) with ligands in samples and the abnormal response of the electrode in the presence of some ligands such as NTA and EDTA (1). In addition, interferences of halide ions limit its application or practical analysis (2,3).…”