On-line cleanup of blanks by electrochemically modulated liquid chromatography for inductively coupled plasma-mass spectrometry

Electrochemically modulated liquid chromatography (EMLC) is used on-line to remove metal ions from the blank solution and improve detection limits in inductively coupled plasma-mass spectrometry (ICP-MS). The EMLC column contains glassy carbon particles held at an appropriate negative applied potential (Eapp). The supporting electrolyte and reference electrode are outside the porous stainless steel column to minimize contamination of the blank flow stream. Various metal ions, such as Tl+ and Pb2+, are retained at cathodic values of Eapp with an efficiency of 99% or better at liquid flow rates of 50-80 μl min−1. Other metals are retained at an Eapp that is moderately positive with respect to their standard reduction potentials. This latter observation suggests that surface functional groups on the carbon stationary phase are also important. The column can be cleaned easily by stripping the deposited metal at high anodic values of Eapp.