title: Determination of the Acid-Base Dissociation Constant of Acid-Degradable Hexamethylenetetramine by Capillary Zone Electrophoresis.
abstract: The acid-base equilibrium of hexamethylenetetramine (hexamine) was analyzed with its effective electrophoretic mobility by capillary zone electrophoresis. Although hexamine is degradable in a weakly acidic aqueous solution, and the degraded products of ammonia and formaldehyde can be formed, the effective electrophoretic mobility of hexamine was measured in the pH range between 2.8 and 6.9. An acid-base dissociation equilibrium of the protonated hexamine was analyzed based on the mobility change, and an acid dissociation constant of pKa= 4.93 ± 0.01 (mean ± standard error, ionic strength: 0.020 mol dm-3) was determined. The monoprotic acid-base equilibrium of hexamine was confirmed through comparisons of its electrophoretic mobility with the N-ethylquinolinium ion and with the monocationic N-ethyl derivative of hexamine, as well as a slope analysis of the dissociation equilibrium.
authors.affiliation: Graduate School of Science and Technology, Tokushima University.
authors.forename: Toshio
authors.initials: T
authors.lastname: Takayanagi
authors.forename: Natsumi
authors.initials: N
authors.lastname: Shimakami
authors.forename: Masashi
authors.initials: M
authors.lastname: Kurashina
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Mizuguchi
authors.forename: Tomoki
authors.initials: T
authors.lastname: Yabutani