Removal of Separated Compounds from the Plate

Examination of the plates nnder UV light and by the application of general and specific spray reagents as described in the previous section will usually provide full information regarding the Rf values in different development solvents of the various components of the original additive mixture applied to the plate and, possibly some information regarding 

It is emphasised here that, in order to avoid missing any sample components it is highly advisable to apply the sample location techniques described in the last section to chromatograms of the sample obtained using several plate materials such as silica gels and alumina, and with each adsorbent to use as wide a variety as possible of different types of development solvents. 

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Note 4. Removal of separated compounds from the plate. The extraction solvent must (1) be a good solvent for the additive, (2) be sufficiently polar to desorb the additive from the absorbent (successive desorption with different solvent may be necessary at this stage), (3) have a low boiling point to facilitate subsequent removal of solvent and reduce to a minimum evaporation losses of any volatile sample constituents, and/or, (4) not interfere in the subsequent spectroscopic examination of extracts. 

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