A direct-elution technique for the recovery of thin-layer samples.

The separation of compounds by chromatography is often followed by the need to separate the compounds from the stationary phase for quantification, rechromatography, or other analytical procedures. In thin-layer chromatography compounds are usually separated from the adsorbent by removal of the layer from the backing by scraping or suction, followed by elution of the compounds in columns or by centrifugation (l-4). These procedures are generally quite time-consuming, and care is needed to prevent cross-contamination or loss of sample by air currents. Kirchner (5) stated that these problems could be alleviated if the compounds were eluted directly off the plate. Recently, Falk and Krummen (6) designed such a direct-elution apparatus, which is now marketed by Camag. They point out the following advantages of their instrument over the usual elution methods: (i) Time and money are saved; (ii) only small volumes of solvent are required; (iii) no centrifugation or filtration step is needed; (iv) elution is automatic once the apparatus is set up; (v) adsorbent remains unchanged in the eluted area. In this report we describe a simple, direct-elution technique for flexible, thin-layer plates, which is based on the conventional methods for elution from paper chromatograms by descending solvent flow (73). This device can be made from inexpensive and easily obtained materials and has the same advantages that were listed above for the more complex instrument.