Matériel pour la chromatographie en couche mince

A thin layer chromatographic element comprises a flexible support bearing a layer containing a chromatographically active adsorbent and a polymeric binder, the weight of the binder being from 2-65% of the total weight of the adsorbent and binder, the binder causing the adsorbent to adhere to the support while permitting access of an elutant to the absorbent when the element is in use. The support may be dimensionally stable polyester films such as polyethylene, terephthalate, polyvinyl, polyolefin, cellulose or polyamide films, metal foils such as aluminium foil. Suitable adsorbents are alumina, silica gels, diatomaceous earth, titanium dioxide, kieselguhr, polyamide powders, ion exchange resins and cellulose. The polymeric binders may be: hydrophilic polymers such as polyvinyl alcohol, gelatin-polyvinyl alcohol mixtures, gelatin derivatives; cellulose derivatives such as carboxymethylhydroxyethyl cellulose; thermosetting polymers such as melamine-formaldehyde, polyvinyl formal, acetal, butyral, ureaformaldehyde, polyisocyanate, polyhydroxy ether, epoxy and other cross-linking resins and mixtures thereof; polyolefine resins such as polyethylene and polypropylene in emulsion and non-emulsion form. A sub-layer may be provided on the support e.g. a layer of a terpolymer of methyl acrylate, vinylidene chloride, and itaconic acid. Where polyvinyl alcohol is used as binder, the support may be first treated with a solution of trichloroacetic acid. Phosphor or fluorescing compounds may be present, and also silver nitrate incorporated by dipping the element into alcoholic silver nitrate solution and then drying the element. Any conventional coating method may be used e.g. doctor blades, air knives, roll coating, hopper coating. A solution of the polymeric binder in a solvent e.g. water, ethanol-water mixtures, containing the adsorbent in powder form may be coated on the support. A reticulating agent may be added to the polymer solution before coating so that the polymer becomes insoluble after coating and before use; e.g. a solution of polyvinyl butyral and urea-formaldehyde resin modified by aliphatic alcohols in methyl isobutyl ketone. The elements may be activated by heating before use.