Analytical Sciences

Determination of Acid Dissociation Constant of Degradable Tetrabromophenolphthalein Ethyl Ester by Capillary Zone Electrophoresis AUTH: Toshio TAKAYANAGI, Ayumi TABARA, and Takashi KANETA AFFL: Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita, Okayama 700-8530, Japan ABST: An acid dissociation constant of tetrabromophenolphthalein ethyl ester (TBPE) was determined through the measurement of electrophoretic mobility by capillary zone electrophoresis (CZE). Although TBPE is degradable in acidic pH region and it gradually degraded at pH conditions around and below its pK_a values in the time scale of the CZE measurement, equilibrium species of interest were detected as a peak-shaped signal with tailing of the degraded species. Changes in electrophoretic mobility of the equilibrium species of TBPE were analyzed at its detectable pH range in the presence of phenol red as a mobility standard. An acid dissociation constant of 3.47 ± 0.06 (pK_a, I = 0.01, 25°C, standard error) was determined for TBPE.

J-STAGE: View this article in J-STAGE