Sample introduction and separation in capillary electrophoresis, and combination with mass spectrometric detection

Capillary-electrophoresis methods are attracting interest owing to the ability to yield rapid high-resolution separations, but many aspects, such as sample injection, separation conditions and detection, need further development. Effects related to sample injection and buffer composition have been investigated. Automated methods for electromigration injection of nl-size sample volumes are shown to give a precision of approximately +/-1%. Problems encountered with manual injection procedures have been examined by an electric field reversal technique. The effect of buffer pH on capillary zone-electrophoresis (CZE) separations can be attributed to changes in electro-osmotic flow velocities and to changes in the isoelectric points of analytes. The interfacing of capillary electrophoresis with mass spectrometry is described and demonstrated for a range of conditions, with a quaternary phosphonium salt mixture. Separations obtained by CZE and capillary isotachophoresis are compared and the relative advantages of the two techniques discussed.