the protonation of different species of glycylisoleucine were studied in the ph range of 1.5 - 10 at25 °c using potentiometric technique. investigations were performed in sodium perchlorate andtetraethylammonium iodide as background electrolytes at i (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) moldm-3. the parameters based on the protonation constants were calculated, and their dependenceson ionic stren...