Removal of metallic impurities from mobile phases in reversed-phase high-performance liquid chromatography by the use of an in-line chelation column

An in-line stripper column packed with iminodiacetate chelation resin is placed between the pump and injection valve and shown to remove metallic impurities from an HPLC system. We used a test procedure based on assessing the relative peak asymmetries of 2,2'-bipyridyl, a chelating analyte and 4,4'-bipyridyl, a non-chelating analyte. Results from use of polyether ether ketone (PEEK) and stainless steel pumps are evaluated. Analytical columns with titanium/PEEK and stainless steel frits are used to assess the role of frits in metallic contamination. We demonstrated that although metal-free pumping systems contribute significantly lower metallic impurities than stainless steel systems, metal is nevertheless present in the mobile phase and the chelating stripper columns were found useful in protecting the analytical columns from contamination. The stainless steel frits were not found to be significant contributors to the contamination.