On-line mass spectrometric detection for capillary zone electrophoresis

The authors have developed a viable alternative to capillary zone electrophoresis (CZE) detection based on mass spectrometric interfacing. A capillary zone electrophoresis-mass spectrometry (CZE-MS) interface obviously requires a substantial departure from the conventional CZE arrangement; it is clear that the interface design and ionization method are crucial to success. The liquid flow rate in CZE (approx.1 ..mu..L/min) is highly compatible with conventional mass spectrometers even if the total column effluent was introduced directly. The direct liquid introduction interfaces developed for LC-MS suffer from orifice plugging at low flow rates and the thermal degradation of high mass-low volatility components. Thermospray ionization, though attractive, has not been shown to be effective for liquid flow rates below a few tenths of a mL/min. Therefore, the authors evaluation of the requirements for a mass spectrometer interface suggested an approach that incorporates the electrospray ionization technique developed by Dole et al. and the more recent work reported by Fenn and co-workers. In this communication, the authors report the successful development of CZE-MS instrumentation for the separation and analysis of ionic species in aqueous solutions.