Copyright 1982 by Elsevier Science Publishing Co SCIENTIFIC BASIS FOR RADISACTIVE VIA=1E 9ASACOoIT- V Werner. Iaze, editor LIQUID CHROMATOGRAPHY IN MIGRATION STUDIES LARS CARLSEN and WALTHER BATSBERG Chemistry Department, Ris0 National Laboratory, DK-4000 Roskilde, Denmark INTRODUCTION A detailed knowledge of the geochemical environment of a site for the dispo- sal of radioactive waste is of fundamental importance. To evaluate the migration behaviour of radionuclides in geological media a series of data are needed, amongst others a number of physico-chemical properties of the media, such as permeability, porosity, dispersion-, diffusion-, and sorption characteristics. In this connection liquid chromatography appears to be advantageous as a facile experimental technique to obtain relevant data for these physico-chemical pro- perties. The capabilities of the liquid chromatography technique in connection with migration studies are in the following illustrated by examples from recent stud- ies on the cretaceous formation overlying the Erslev salt dome (North Jutland, Denmark). 1,2 BASIC PRINCIPLES OF THE LIQUID CHROMATOGRAPHY TECHNIQUE Liquid chromatography is a column technique normally used for the separation of different organic as well as inorganic components in a solution. A typical experimental set-up for a liquid chromatographic separation is shown in figure 1. The pump delivers a solvent (eluent) flow at a preset, con- stant flow rate. Samples of known volume are injected into the column via the injection port and the eluate from the column is continuously monitored by a de- tector. For a given column material, e.g. chalk, the separation mechanism will be controlled by the physical and chemical nature of the interaction between the molecules present in the injected sample and the column material. Adsorption-, partition-, substitution-, and ion exchange processes, separately or in combi- nation, can occur in the columns, being responsible for the actual shape of the chromatogram. Figure 2 depicts a typical chromatogram used for the determination of the different physico-chemical characteristics of the columns. The shape of the peak corresponding to an unretarded solute characterizes the flow dispersion in the column (vide infra), whereas the elution volume (or time)