Evaluation of a separation-based fiber-optic sensor in a micellar electrokinetic capillary chromatography mode of operation

The research presented in this thesis involves the evaluation of a separation-based fiber-optic sensor (SBFOS) for remote analyses, that combines the selectivity of capillary electrophoresis with the sensitivity provided by laser-induced fluorescence detection. The performance of the sensor is shown in a micellar electrokinetic capillary chromatography mode of separation which extends capillary electrophoresis to neutral analytes. The design and construction of the sensor are demonstrated which is based on a single-reservoir, linear configuration. The gravity-driven hydrostatic flow resulting from nonlevel positioning of the separation capillary ends is reduced by incorporating a narrow-bore restrictor capillary. A single fiber optic is used in the optical detection arrangement of the SBFOS to transmit both the laser excitation and sample fluorescence signal to and from the sensor side of the separation capillary. The evaluation experiments are performed in a frontal mode of operation which at some point results in the displacement of the micellar phase in the capillary by the sample (reagent depletion). Studies involve varying the composition of the sample matrix with regard to buffer and surfactant, measuring signal over applied voltages in 2.0-4.0 kV range, as well as constructing linear calibration curves for single- and multi- component mixtures. The results of the SBFOS evaluation include observed separation efficiencies of 10^{3 -104 theoretical plates for an 8-cm separation capillary, migration time and bandfront height reproducibilities of less than 10%, low-mid nanomolar limits of detection, and a linear response over two orders of magnitude in concentration. A preliminary SBFOS-MECC separation and detection of important pollutants, aflatoxins G₁ and G_{2, demonstrates the potential of the sensor for environmental monitoring}}