A comparison of capillary electrophoresis using indirect UV absorbance and ICP-MS detection with a self-aspirating nebulizer interface

A comparison of capillary electrophoresis (CE) migration times using standard on-column UV detection and inductively coupled plasma mass spectrometry (ICP-MS) is presented for two different CE separations. The first is a separation of five arsenic compounds, four anionic species and one neutral, using reverse polarity in a chromate buffer with an electroosmotic flow modifier. The second CE separation employs normal polarity for the separation of eleven lanthanide cations using a hydroxyisobutyric acid (HIBA) buffer with an indirect UV detection reagent. The CE-ICP-MS interface is based on a tee design which introduces a sheath flow around the CE capillary using a self-aspirating make-up electrolyte with a microconcentric nebulizer (MCN-100). Migration times observed for CE-ICP-MS electropherograms are comparable to migration times acquired with UV detection, and may be adjusted by changes in the make-up liquid level position. The precision of peak areas (< 2%) and migration times (< 4%) obtained using CE-ICP-MS is comparable to that obtained using online UV absorbance detection. CE-ICP-MS limits of detection are in the low ng ml(-1) range for the analytes studied.