Highly Sensitive Determination of Aromatic Molecules at the Interface Region of an Oil-Water system using Laser Two Photon Ionization

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The laser multi photon ionization technique has been applied to an interface region in two phase sys tems(n-octane/water). The Laser irradiated the interface at total reflection condition from oil phase, and the photo-ionization signal was caused by water region. Pyrene stayed at oil/water interface, and the concentration of Pyrenesulfonic acid at that interface was very small and increased along inside of water region. Other aromatic molecules, naphthalene derivatives and benzene derivatives, also were applied to this technique. The pH and surfactant dependence also exhibited that the non-ionic molecules stayed at oil/water interface. Lowering the pH, the protonated aromatic molecules increased and overall dissolving process decelerated. With increasing the anionic and cationic surfactant concentration, the photo-ionization current gradually decreased. The surfactant and aromatic molecules formed into micelles in the deep water region. The photo-ionization is potential tool for investigating the phenomena of a two-phase system.