Development of mini column experiments (MCE) by coupling microliter flow HPLC with ICP-MS for the analysis of metal retention under conditions close to nature

Abstract

The development and implementation of mini column experiments (MCE) can be of great importance to improve existing analytical methods such as highly standardised but unrealistic batch laboratory experiments or lengthy long-term diffusion experiments to study metal sorption/desorption properties. One envisaged application would be to test the retention of repository-relevant metals in claystone, which is a promising candidate for the host rock of a final repository site for high-level radioactive waste (HLW). The used MCE setup is derived from classical high performance liquid chromatography (HPLC). On this basis, coupling of MCE to ICP-MS (inductively coupled plasma mass spectrometry) detection was realised. This online separation enables the dynamic monitoring of metal sorption and desorption experiments on clay minerals (kaolinite), natural clay (Opalinus Clay) and mixtures with quartz sand in background solutions close to nature, and without the common use of metal complexing ligands, other reaction partners or buffers for the analysed metal ions. The optimised method allows the analysis of the retention of various contaminants in real groundwater solutions and compact clay samples in a reasonable amount of time and a small amount of sample. In addition, the coupling to the unspecific mass detector of ICP-MS enables the study of different radionuclides and homologues rather than the limited UV detection of a common HPLC.