Abstract

An interface between capillary zone electrophoresis and inductively coupled plasma mass spectrometry (CZE-ICP-MS) based on a self-aspirating total consumption micronebulizer was evaluated for a study of metal complexation by metallothionein. The elimination of the nebulizer suction (and thus of the laminar flow) allowed a separation efficiency comparable with that reachable with on-capillary UV detection whereas the low (6 µl min⁻¹) nebulizer aspiration rate allowed the minimization of the post-capillary dilution effect, and thus maximization of the CZE-ICP-MS sensitivity. Operating conditions were optimized with the natural rabbit liver metallothionein preparations allowing detection limits of ca. 10 ng mL⁻¹ (as MT-bound Cd) to be obtained within 10 min at quasi-baseline resolution. Recombinant (mouse liver MT-1-Zn₇) and natural (rabbit liver MT-1-Cd₇ and MT-2-Cd₇) proteins were then titrated with Cd(II) and Cu(I), and Cu(I), respectively. A number of mixed metal complexes with different migration times were observed as a function of the Cu∶Cd ratio in the system.