Capillary Electrophoresis Coupled Online with Inductively Coupled Plasma Mass Spectrometry for Elemental Speciation

Abstract

A novel interface to connect a capillary electrophoresis (CE) system with an inductively coupled plasma mass spectrometric (ICPMS) detector is reported here. The interface was built using a direct injection nebulizer (DIN) system. In this interface, the CE capillary was placed concentrically inside the fused-silica DIN sample introduction capillary. A makeup liquid was pumped at a flow rate of 15 μL/min into the fused-silica DIN sample transfer capillary via a connector. The makeup liquid flowing outside the CE capillary served two purposes : (a) it established continuous and stable electrical contact at the exit (grounding) terminus of the CE capillary, and (b) it allowed the DIN system to be optimized independently of the CE system for efficient sample introduction to the ICPMS system. The makeup liquid along with the liquid from the electroosmotic flow generated inside the CE capillary was nebulized by the DIN system directly into the ICP torch. The CE/DIN-ICPMS system was evaluated using test samples containing selected alkali, alkaline-earth, and heavy metal ions, as well as selenium [Se(IV) and Se(VI)], and various inorganic and organic arsenic species. The preliminary results show that the CE/DIN-ICPMS system can be used to determine metal species at parts-per-trillion to parts-per-billion levels.