Separation of metal ions by capillary electrophoresis--diversity, advantages, and drawbacks of detection methods

Capillary electrophoresis (CE) has been applied to metal-ion analysis during the last 10 years. To improve sensitivity and selectivity different modes of detection have been adapted or developed. The selection of commercially available detection systems for metal-ion analysis is still primarily limited to UV-Vis detection, although other commercial systems, e.g. fluorescence, conductivity, or interfaces for coupling to mass spectrometry (MS) or inductively coupled plasma mass spectrometry (ICP-MS) are becoming available. High demands are made on any detector used in CE, because the analytical signal has to be extracted from less than 1 nL of sample, which corresponds to a total amount of < or = 10(-12) to 10(-15) mol analyte. This paper compares currently available and recently developed detection methods for CE as applied to the analysis of metal ions. Commercially available techniques, for example UV-Vis, fluorescence, or mass spectrometry, and other new detection methods including electrochemistry, radioactivity, and XRF, are discussed and future trends are anticipated.