Capillary Electrophoresis−Fluorescence Line-Narrowing System for On-Line Structural Characterization of Molecular Analytes

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Abstract
We have demonstrated, for the first time, that capillary electrophoresis (CE) can be interfaced with low-temperature fluorescence line-narrowing (FLN) spectroscopy for on-line structural characterization. Detection by laser-induced fluorescence spectroscopy, under fluorescence non-line-narrowing and line-narrowing conditions, provides three-dimensional electropherograms and FLN spectra, which lead to significantly improved overall resolution and allow for structural characterization (“fingerprinting”) of molecular analytes. This novel CE−FLN system consists of a modular CE system, instrumentation for FLN spectroscopy, and a specially designed capillary cryostat (CC). An absorbance detector serves to determine the migration rates of analytes. After the 77 K fluorescence-based electropherogram is generated, the temperature of the capillary is lowered to 4.2 K for high-resolution FLN characterization. Automated translation of the CC and capillary in the direction of the capillary axis allows the separated analytes to be sequentially characterized by fluorescence spectroscopy as the capillary is translated through the laser excitation region. Detection of fluorescence from stationary CE-separated analytes significantly improves the accuracy of quantitation and structural characterization. We believe that this interfacing represents an exciting addition to the rapidly evolving field of CE, providing a new and powerful tool for chemical analysis. The first application of the CE−FLN system to a mixture of polycyclic aromatic hydrocarbons is presented; prospects and future applications of CE−FLN are briefly addressed.