VIEWING A SLIDE
Staining with Iodine
The iodine staining technique allows
us to carry around a marked version of our TLC run rather than having
to pencil sketch our spots in the UV viewer. The iodine vapors
chemically attach to analytes on the TLC plate. While this makes the
samples unrecoverable for future use (usually you will not need to
recover your sample from a TLC plate), it makes analysis easier.
Some compounds might not even appear under UV light, making other
visualization techniques such as iodine staining necessary.
- Properly develop a TLC plate.
- Obtain another developing jar.
Operating under a
hood and wearing gloves (the iodine is corrosive and toxic), use a
spatula to place 5-6 iodine chips into the bottom of the
developing jar. Replace the lid.
- After the developing solvent
has completely evaporated, place the TLC slide in the developing
jar containing the iodine. Replace the lid.
- Continuously monitor the
development of your slide. Typically, the staining process takes
a couple of minutes. You should see the analyte begin to take on
a yellowish color. Be sure not to allow the silica on the plate
itself to begin staining. This will happen after the slide has
been exposed to the iodine fumes for too long.
- Once the analytes are
sufficiently visible (if they stained at all) and before the slide
begins to stain, remove the slide from the developing jar. The
iodine chips may be reused and you may place them back in their