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Fluorescence quenching of β ‐carboline alkaloids in micellar media. A study to select the adequate surfactant to use in analytical techniques
Author(s) -
Martín Laura,
Olives Ana I.,
del Castillo Benito,
Martín M. Antonia
Publication year - 2005
Publication title -
luminescence
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.428
H-Index - 45
eISSN - 1522-7243
pISSN - 1522-7235
DOI - 10.1002/bio.812
Subject(s) - micelle , chemistry , quenching (fluorescence) , aqueous solution , pulmonary surfactant , fluorescence , micellar solutions , cationic polymerization , bromide , inorganic chemistry , photochemistry , organic chemistry , biochemistry , physics , quantum mechanics
The study of fluorescence quenching of the fluorophores allows the localization of the alkaloids (harmane and harmine) in the micelles (SDS, CTAB, Brij‐35) to be established. In aqueous micellar solutions (SDS and Brij‐35) at pH 13.0, emission corresponding to the neutral or zwitterionic forms can be observed. In the presence of CTAB (pH = 13.0) it was possible to observe the emission of anionic form. These species are not present in buffered aqueous solutions at these pH values. Bromide ion was added to the different surfactant solutions and the quenching effect was studied according to the Stern–Volmer equation. In the presence of SDS the quenching effect is considerably reduced compared to the aqueous solutions without surfactants, while for Brij‐35 micelles were similar to those observed in homogeneous aqueous solution. For CTAB micelles a notable fluorescence quenching was observed for the different pH values studied. The fluorescence quenching studies show that the neutral species are associated inside the micelles, instead of the ionic species (cationic, zwitterionic or anionic) remaining on the surface of the micelles. The anionic surface of SDS micelles prevents the quenching effect by anionic quenchers for both neutral and charged species. Copyright © 2005 John Wiley & Sons, Ltd.