Acid-base equilibrium constants and distribution coefficients of aminopyrene between the surface and bulk of liquid water as studied by a laser two-photon ionization technique

Miki Sato, Akira Harata, Yoshihiko Hatano, Teiichiro Ogawa, Takeshi Kaieda, Kohshin Ohmukai, Hirofumi Kawazumi

    Research output: Contribution to journalArticle

    2 Citations (Scopus)

    Abstract

    The pH-dependent amount of aminopyrene adsorbed at the water surface was measured using a laser two-photon ionization technique. The distribution coefficients of neutral and cationic aminopyrene between the surface and bulk of liquid water were determined to be 9.6 × 10 -6 m and 2.5 × 10 -7 m, respectively, The acid-base equilibrium constant, pK a, of aminopyrene on the water surface was determined to be 2.0, while that of the same molecule in bulk water was 3.6 × 0.1. These results show that neutral aminopyrene tends to stay on the water surface, resulting in equilibrium shifts toward the neutral form. It is demonstrated that laser two-photon ionization is a powerful method to analyze the equilibria of a small amount of molecules, 0.17pmol/cm 2, adsorbed at the water surface.

    Original languageEnglish
    Pages (from-to)12111-12115
    Number of pages5
    JournalJournal of Physical Chemistry B
    Volume108
    Issue number32
    DOIs
    Publication statusPublished - Aug 12 2004

    All Science Journal Classification (ASJC) codes

    • Physical and Theoretical Chemistry
    • Surfaces, Coatings and Films
    • Materials Chemistry

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