| The improvement of the detection limit is a fundamental goal of analytical chemistry. The recent achievement of a one-molecule mass detection limit in capillary electrophoresis (CE) is one instance where this goal appears to have been achieved. However, because of the small injection volume, the impressive mass detection limit of CE does not translate to concentration detection limits that are adequate for trace analysis.; This thesis presents methods that improve the concentration detection limit by using off-line and on-line concentration techniques. The first section introduces CE and presents methods for peptide analysis and the second section presents methods for protein analysis.; For peptides, two methods based on solid-phase extraction (SPE) are presented. In the first method, peptides are preconcentrated and fluorescently labelled on an SPE material and then analyzed by CE with laser-induced fluorescence (LIF) detection. This method provides nanomolar detection limits, a 1 000-fold improvement over UV absorbance detection. In the second method, peptides are preconcentrated using SPE and then analyzed by capillary isotachophoresis (CITP) with mass spectrometric (MS) detection. This method provides picomolar detection limits, an improvement of four orders of magnitude over standard CE-UV methods. SPE-CITP-MS analysis of peptides in human plasma is shown.; Proteins have many derivatizable groups; therefore, reactions between proteins and fluorescent dyes usually produce heterogeneously labelled samples. These samples, when analyzed by CE, usually result in poor separation efficiency. This thesis presents the first application of protein labelling in which high separation efficiency is maintained. Detection limits in the in the mid-picomolar range and efficiencies of 180 000 theoretical plates are obtained. When the labelling is performed in the capillary and combined with on-capillary stacking, the separation efficiency rises to 350 000 theoretical plates and the detection limit decreases 15 fold.; These techniques bring the concentration detection limit of CE-LIF within the range required for real-world samples. |
