Fluorescence in Organized Assemblies

Abstract

This article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) and cyclodextrins (CDs) and summarizes their utilization to enhance the performance of analytical fluorescence measurements. In many instances, organic molecules and metal complex species, when included within a CD cavity or solubilized and bound to surfactant aggregates, exhibit enhanced fluorescence. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve the selectivity of the analytical method. These benefits of improved sensitivity and selectivity arise from the compartmentalization, isolation and shielding of the excited singlet state of the guest analyte from quenching and nonradiative decay processes as well as prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for the use of an aqueous medium to perform the procedure. The possibility of conducting reactions and forming fluorescent organic or metal chelates in micellar (or other organized) media that are not observed in a bulk homogeneous solvent system serves to expand the scope of chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative examples of fluorescent methods for determination of both organic and inorganic analytes are provided which serve to illustrate the advantages and benefits accrued from the use of the micelles, vesicles, liposomes or CDs in such procedures. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.

Indirect Atomic Absorption Determination of Cocaine via Formation and Liquid‐liquid Extraction of the Iron(III)‐cocaine Complex

“…The preliminary data obtained suggests that this method could be extended to the on-line determination of cocaine and possibly other alkaloids too. Besides, the analytical utilities of micellar media [39][40][41][42][43][44] can also be incorporated for the trace level analysis using a chemiluminescence detection system. These will be included in our future work.…”

Reatividade química e fotoquímica em agregados de tensoativos em água/acetonitrila

“…Com essas propriedades interessantes de solubilização, as micelas são capazes de afetar velocidades de reações, deslocar equilíbrios, controlar regiosseletividades e modificar o comportamento de espécies geradas fotoquimicamente (Fendler, 1982;Chaimovich et aI., 1982;Kalyanasundaram, 1987;Tachiya, 1987;Bunton et aI., 1991;Pramauro & Pelizzetti, 1996 (Hinze, 2000).…”