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|Title:||Characterization of Surfactant Effects on the Visible Spectroscopy of Lanthanide Metal Ion-Triphenylmethane Dye Complexes (Microscopy, Polyvinylidene Fluoride, Electron, Polymethylmethacrylate, Blends)|
|Author(s):||Klopf, Gary James|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The sensitivity of spectrophotometric methods used for determining metal ion concentrations is often improved by adding a surfactant to the metal-dye complex. The resultant sensitization is characterized by increased molar absorptivities and red-shifted absorbance maxima. To better define the mechanism responsible for sensitization, the interactions of representative cationic, anionic, and nonionic surfactants with several lanthanide metal ion-triphenylmethane dye complexes, particularly the gadolinium (Gd('+3))-Chromeazurol S (CAS) complex, were characterized.
Only cationic surfactants induced sensitization when added to the Gd('+3)-CAS complex. Sensitization induced by cetylpyridinium chloride (CPC) occurred at submicellar concentrations and was attributed to the formation of a 1:2:4 Gd('+3)-CAS-CPC ternary complex. Additional ternary complexes evidently form if excess CAS is present. Other sufficiently hydrophobic quaternary ammonium salts (quats) also induced sensitization. As with CPC, sensitization was attributed to the formation of stoichiometric ternary complexes.
High concentrations of each quat considered induced dissociation of the Gd('+3)-CAS complex. Dissociation induced by CPC was attributed to displacement of Gd('+3) from the ternary complex by excess CPC. When dodecyltrimethylammonium bromide and tetramethylammonium chloride were considered, competition for CAS between cationic micelles and Gd('+3), and the formation of Gd('+3)-chloro species, respectively, were responsible.
High concentrations of anionic surfactants also induced dissociation due to competition for Gd('+3) between CAS and anionic micelles. Adding inorganic salts and increasing the binary complex stability constant inhibit this process. In fact, in solutions of high ionic strength, micellar sodium dodecyl sulfate concentrations sensitized, rather than dissociated, the strong Gd('+3)-Xylenol Orange complex.
Although both micellar and submicellar concentrations were considered, adding the nonionic surfactant Triton X-100 to the Gd('+3)-CAS complex had little effect.
This work also examined cold-stage transmission electron microscopy as a potential tool for characterizing aqueous micellar solutions. Attempts to visualize micelles were unsuccessful, but the utility of the instrumentation constructed was demonstrated by determining the crystallization temperature of poly(vinylidene fluoride) (PVF(,2)) in several PVF(,2)-poly(methyl methacrylate) polymer blends.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-15|