Homemade TLC Plate - need instructions

[jmcsmith]

Does anyone have an idea on making homemade TLC plates. I have one recipe for using cornstarch and water that is not working too well.

[tom jupille]

The first chromatography I ever did "on the job" (circa 1968) was done using quick-and-dirty TLC plates to follow organic synthesis reactions.

TLC-grade silica from Merck was slurried with chloroform. Microscope slides were dipped into the slurry and then waved around (under a hood!) to air-dry. A bit of the reaction mixture was spotted on a slide using a melting-point capillary drawn out to a fine tip in a Bunsen burner flame. The plates were run in baby-food jars. The first time on any reaction they ran a battery of jars with hexane, benzene, chloroform, ethyl acetate, and ethanol. The developed plates were air-dried and then put into a covered beaker with iodine crystals on the bottom; the beaker was then placed on a warm hot plate to sublime the iodine and visualize the spots.

The old organic chemists (well, they *seemed* old; they must have been in their thirties!) would prepare the slurry by "seat of the pants" to get just the right consistency.

[SVRChari]

Triturate 30gm silica gel G with 60ml water, till you get a smooth gel. Pour slowly onto a 20x20cm glass TLC plate. You can use a glass rod to obtain an even coat, or carefully tilt the plate up and down until the gel coats evenly. To activate the plate for use, heat it in a hot-air oven at 160 deg C for 30 minutes, remove from the oven, cool it off in a fume hood. And it's ready to use. TLC plates made from silica gel G need to be activated before use, to remove any last traces of water from the gel.

30gm silica gel G is enough for one 20x20 cm plate or four 5x20 plates or about 20 microscope slides. For best results, the proportion of silica gel G to water is 1:2. Dipping slides into the slurry is ok, for quick tlc analyses. But you'll get best results when you arrange the slides on a horizontal surface (like a 20x20 glass plate) and pour the gel on them.

Always use silica gel G TLC grade only. You can of course use chloroform or benzene slurries to make your plates, but usually the coating peels off such plates. Water slurries yield more rugged tlc plates, because the gypsum binder in the silica gel binds best when water is used.

I've been making my own TLC plates since 1986, and I still teach chemists how to make TLC plates during my training programs.

Hope this is useful.

SK Srinivas

[aalbre]

I understand that this topic is quite old, but maybe I will be successful in reviving it

Like the gentleman before me, I too would like to know how to prepare my own TLC plates because I didn't get any usuful literature so far. I tried suspending silica gel + binder (CuSO4 anhydrous) in water in approx. 1:2 ratio. I stirred rigurousely and then quickly applied the slurry onto a glass plate, which was previousely washed extensively with detergent, miliQ water, and finally acetone. The problem I encounter is that the slurry is just "dancing" around the plate when I try to evenly spread it out on the plate to get a uniform and thick film. It is just like pouring water in teflon frying pan, it just won't stick!

Do you have any idea what am I doing wrong?

[Peter Apps]

Unless the acetone is very pure it is probably leaving a residue of something organic and hydrophobic on the glass. Try it without the acetone.

Peter

[aalbre]

So you suppose the detergent and subsequent exhaustive rinsing with milliQ should suffice? Will try... thx...

[Fernando]

Hi aalbre

Consult this book:

THIN-LAYER CHROMATOGRAPHY (A LABORATORY HANBOOK) by Egon Stahl (1965)

Best luck

Fernando

[Peter Apps]

So you suppose the detergent and subsequent exhaustive rinsing with milliQ should suffice? Will try... thx...

Yes, if the detergent washing and rinsing is thorough then there is nothing on the glass that an acetone rinse can remove. Of course, the rinse water should wet the glass evenly - has it been doing that ?

Peter

[aalbre]

No it didn't I see your point... Do you think I should activate the glass surface in some way? How?
Or ordinary detergent simply doesn't suffice?

[Peter Apps]

What detergent are you using ? Ordinary kitchen detergent has all sorts of other stuff in it.

Peter

[aalbre]

You pretty much guessed it... what kind of detergent did you have in mind? SDS or something similar?

[Peter Apps]

You can get a range of lab detergents specifically for cleaning lab glassware. I doubt that there is much to choose between them for what you need to do.

Peter

[aalbre]

Has anyone ever tried making hard layer TLC plates with polyvinyl alcohol or polyvinyl pyrrolidon as binder for example? I tried with both in the range of 1-5% addition to silicagel, but the layer is even softer compared to the one I prepare with gypsum :/

Procedure I use:
- Dissolve 1-5% w/w PVA or PVP in water
- Add silicagel, mix rigorously
- Apply the slurry onto a clean glass plate
- heat for approx 15 min at 200°C or 150 °C or 100°C, respectively

After this, the layer sort of just peels/slides of the plate.

Does anyone have any experience with this?

Cheers...