Design and characterisation of a microconcentric nebuliser interface for capillary electrophoresis-inductively coupled plasma mass spectrometry

Abstract

An interface for capillary electrophoresis (CE) and inductively coupled plasma mass spectrometry (ICP-MS) is reported. The interface was constructed using a commercial microconcentric nebuliser and home-built cyclonic spray chamber. Isoforms of the heavy metal binding protein, metallothionein, were separated and the bound metals detected to characterise the interface. Nebuliser suction was identified as the principal factor controlling separation resolution in the CE-ICP-MS system. Two methods for counterbalancing the nebuliser suction were investigated: in the first method an optimised make-up flow was employed, and in the second a negative pressure was applied to the inlet vial. Negative pressure was the preferred method for counterbalancing the nebuliser suction because sensitivity was not compromised. Separation resolution, under negative pressure conditions, was improved compared with that achieved using on-capillary UV detection. Absolute metal detection limits for¹¹⁴Cd, ¹¹¹Cd, ⁶⁶Zn and ⁶⁴Zn were 2.09, 3.42, 8.93 and 9.12 fg, respectively.