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Discussion

In this example, the material being analyzed was colored. Most material is colorless and it will be necessary to treat the plate in some way to see the spots. A common method of analysis uses a combination of observation under ultraviolet light and staining with iodine vapor. Ultraviolet light is nondestructive to the compounds on the plate and can be used immediately. Be careful. Never look directly at the light source.

Narrative

Frequently, an inorganic fluorescer, zinc sulfide, is added to the TLC adsorbents. When viewed under short wavelength light, the zinc sulfide in the adsorbent will fluoresce green. Consequently a TLC plate possessing fluorescer will show a series of dark spots on a bright green background when viewed under short wavelength light. While the TLC plate is under UV light, note the positions of any spots you see by drawing around them lightly with a pencil.