Development of a new capillary electrophoresis-based fibre optic sensor
A new fluorescence-based fibre optic sensor is described which combines the sensitivity offered by laser-induced fluorescence with the selectivity offered by capillary electrophoresis (CE). A single optical fibre directly probes the terminus of a 5-8 cm separation capillary. The linear geometry associated with this sensor necessitates a 'single reservoir' design, thus presenting major challenges to overcome in comparison to the conventional two-reservoir configuration common to a typical laboratory setup. Some of the challenges confronted by the design features presented in this work include the reduction of gravity-driven hydrostatic flow, the ejection of electrolytic gases evolved at the detection-side electrode and the establishment a suitable compromise between detectability and separation performance. The success of such design features demonstrates the feasibility of a CE-based sensor which offers several amenities particularly useful for in situ sensing. Such attributes include selectivity, diminutive size, flexibility, reusability, high sensitivity, speed, and remote control. Detailed descriptions of sensor fabrication are included, including two variations on a general design concept. In addition, the single-fibre optical detection system is described. Separation characteristics of the new CE-based sensor are presented, highlighted by an observed separation efficiency of up to 8000 theoretical plates (for a 5 cm capillary). The separation of a three-component mixture of the laser dyes, Rhodamine 6G, fluorescein isothyocyanate and sodium fluorescein, is demonstrated.
Stokes, DL; Sepaniak, MJ; Vo-Dinh, T
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