Determination of acid dissociation constant of degradable tetrabromophenolphthalein ethyl ester by capillary zone electrophoresis

Toshio Takayanagi, Ayumi Tabara, Kaneta Takashi

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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 pKa 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 fo TBPE.

Original languageEnglish
Pages (from-to)547-552
Number of pages6
JournalAnalytical Sciences
Issue number5
Publication statusPublished - 2013


ASJC Scopus subject areas

  • Analytical Chemistry

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