ION-ASSOCIATION ADSORPTION OF WATER-SOLUBLE PORPHYRIN AT A LIQUID-LIQUID INTERFACE AND AN EXTERNAL ELECTRIC-FIELD EFFECT ON THE ADSORPTION

Citation
R. Okumura et al., ION-ASSOCIATION ADSORPTION OF WATER-SOLUBLE PORPHYRIN AT A LIQUID-LIQUID INTERFACE AND AN EXTERNAL ELECTRIC-FIELD EFFECT ON THE ADSORPTION, Analytical sciences, 12(3), 1996, pp. 393-397
Citations number
13
Categorie Soggetti
Chemistry Analytical
Journal title
ISSN journal
09106340
Volume
12
Issue
3
Year of publication
1996
Pages
393 - 397
Database
ISI
SICI code
0910-6340(1996)12:3<393:IAOWPA>2.0.ZU;2-I
Abstract
By using total internal-reflection fluorescence (TIRE) spectroscopy it was shown that an unprotonated form of water-soluble porphyrin (5,10, 15,20-tetraphenyl-21 H, 23 H-porphinetetrasulfonic acid, TPPS) is pref erentially adsorbed over the diprotonated one by the toluene-water or di(2-ethylhexyl)phthalate (DEHP)-water interface in the presence of a cationic surfactant (cetyltrimethylammonium bromide, CTAB). The pH dep endencies of the TIRF intensity were satisfactorily analyzed by a simp le adsorption model, including the protonation equilibria in the bulk aqueous phase and the adsorption equilibrium at the interface of TPPS. Further, it was found that applying an electric field across the DEHP -water interface significantly changed the ion-association adsorption equilibria. This result was explained in terms of the electrophoresis of TPPS in the interfacial region.