“…Different in vitro techniques, like Caco-2 membrane permeability, Parallel Artificial Membrane Permeability Assay (PAMPA) and animal tissue based methods, have been discussed by several authors [1,2] but these techniques are not very valuable in the high-throughput screening of diverse candidate drug molecules. Next to these techniques based on artificial membranes, isolated gut-segments or cultivated intestinal cells, HPLC-methods were developed, using either classical reversed-phase conditions [3], special stationary phases or special mobile phases [1,2,4,5]. A method with a special stationary phase is immobilized artificial membrane (IAM)-chromatography [1,2], which uses a stationary phase containing fosfatidylcholine groups, to mimic the lipophilic environment of the celmembranes [4].…”