Investigation of metal binding by recombinant and native metallothioneins by capillary zone electrophoresis (CZE) coupled with inductively coupled plasma mass spectrometry (ICP-MS) via a self-aspirating total consumption micronebulizer

An interface between capillary zone electrophoresis and inductively coupled plasma mass spectrometry (CZE-ICP-MS) based on a self-aspirating total con sumption 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 reachabl e with on-capillary UV detection whereas the low (6 mul min(-1)) nebulizer aspiration rate allowed the minimization of the post-capillary dilution eff ect, and thus maximization of the CZE-ICP-MS sensitivity. Operating conditi ons were optimized with the natural rabbit liver metallothionein preparatio ns allowing detection limits of ca. 10 ng mL(-1) (as MT-bound Cd) to be obt ained within 10 min at quasi-baseline resolution. Recombinant (mouse liver MT-1-Zn-7) acid natural (rabbit liver MT-1-Cd-7 and MT-2-Cd-7) proteins wer e 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 fu nction of the Cu:Cd ratio in the system.