In-situ Fluorescence Studies of Aluminum Ion Complexation by 8-Hydroxyquinoline Covalently Bound to Silica

摘要

Much interest has been generated by the development of immobilized chemical reagents for preconcentration of metal ions and optically based chemical sensing. Devices related to the latter application, called optrodes, have potential uses in remote sensing in hazardous or inaccessible environments, such as monitoring groundwater contaminants, industrial chemical processes, or in vivo biological systems. Investigations of interfacial effects on an immobilized reagent response was undertaken by using in situ fluorescence spectroscopy and flow injection methods. A procedure to immobilize 8-hydroxyquinline by an alkyl siloxane linkage to silica gel was used to produce a chemically stable material, capable of producing fluorescent complexes with a number of metal ions. Reactions of this reagent with aluminum ion were studied by using flow injection methods to control the solution conditions and the exposure of the reagent to metal ion samples, providing some insight into the chemical interactions that affect the equilibrium behavior. Surface equilibrium constants were calculated and compared to the free solution values for the aluminum quinolate complex. Differences in the behavior of the free solution and immobilized reagent under flow injection and steady-state conditions could be related to changes in the surface potential of the silica gel. The pH and ionic strength dependence of the reaction and saturation of the immobilized ligand response further point out the important role that the double-layer potential plays in the reactivity of surface bound reagents for ionic species. Keywords: Reprints; Optical detectors; Optrodes. (KT)