Protonation Constants of Glycylisoleucine at Different Ionic Strengths and Various Ionic Media

Document Type : Research Paper




The protonation of different species of glycylisoleucine were studied in the pH range of 1.5 - 10 at
25 °C using potentiometric technique. Investigations were performed in sodium perchlorate and
tetraethylammonium iodide as background electrolytes at I (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) mol
dm-3. The parameters based on the protonation constants were calculated, and their dependences
on ionic strength are described by a Debye-Huckel type equation. The dependence on ionic
strength of the protonation constants was also analyzed by the specific ion interaction theory (SIT)
model. The constants at infinite dilution, obtained using this model, are logK°1 = 2.72 and logK°2
= 8.24. The specific interaction coefficients are also reported.