Demonstration of an integrated capillary electrophoresis-laser-induced fluorescence fiber-optic sensor

A unique integrated separation-based fiber-optic sensor for remote analysis, that incorporates capillary electrophoresis (CE) directly at the fiber sensing terminus is described for the first time. Based on laser-induced fluorescence detection, the sensor offers the potential for high sensitivity. Although the broad-band nature of fluorescence spectra limits selectivity, the high separation power of CE provides a unique dimension of selectivity, while permitting a design of diminutive size. Previously reported fluorescence-based sensors that utilize a chemical reagent phase to impart selectivity tend to be inflexible (not readily adaptable to the detection of different species) and "one-measurement-only" sensors. Conversely, the CE-based fiber-optic sensor described here is both versatile and reusable. The analysis speed and the potential for remote control are further attributes which make the system amenable to remote sensing. A "single-fiber" optical detection arrangement and a "single-reservoir" CE system with the fiber-optic probing the outlet of the separation capillary are employed. A preliminary evaluation of the separation characteristics of this CE-based sensor is presented. Highlights include an observed separation efficiency of up to 3000 theoretical plates (8 cm separation capillary) and migration time reproducibility of less than 10% for frontal mode CE separations. The potential utility of the sensor for remote analysis is demonstrated with separations involving the CE analysis of charged fluorescent dyes, CE analysis of metal complexes based on in situ complexation and micellar electrokinetic capillary chromatographic analysis of neutral fluorescent compounds.