Whereas with ion exchangers (mainly) charged molecules can be adsorbed and/or separated, neutral adsorbent resins (Polymeric ADsorbents: SERDOLIT^® PAD Resins) can be used for the extraction and in some cases even for separation of neutral, basic and acidic substances. This adsorption process often is performed with compounds which are dissolved in water or in a solution which does not contain too much of an organic solvent that might prohibit the interaction (van der Waals forces, hydrophobic, hydrogen bridges) between adsorbent and adsorbate.
The apolar resins SERDOLIT^® PAD I - III bind organics from water. Unwanted substances (impurities, salts) are eluted with water, the enriched compound(s) with water mixable organic solvents. Their eluotropic forces are known from chromatographic experience. Acidic molecules are best eluted with basic eluents, basic molecules under acidic conditions.