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Author: Subject: Learn using TLC for analysis
Mateo_swe
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[*] posted on 5-10-2022 at 14:57
Learn using TLC for analysis


I want to try learn using TLC plates to analyze various compounds (compare them to a known substance)
Now i wonder what is the best TLC plates to get when starting this learning experience.
I have no specific type of compounds to analyze in mind, it will be used on many things so a plate that is usable on a broad spectrum of compounds is best if that is possible.

Would the standard silica based plates be good choice and should i get 20x20cm or smaller size?
I see there are glass, aluminum or plastic backed plates.
I have read some TLC plates can be cut or divided into smaller sections and that might be good when learning.
Witch type of plates can be cut into smaller sections?

Also one can get the plates with or without F254.
If i understood this correctly this is a additive to the plate that makes it glow under UV to enhance the visibility of the spots.
Should i use F254 plates?
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[*] posted on 5-10-2022 at 16:07


The Home Scientist on YT (Robert Bruce Thompson RIP) has a video showing how to make your own TLC plates very cheaply. He has follow up videos showing how to use them.
You might be interested in these.
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AvBaeyer
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[*] posted on 5-10-2022 at 18:59


1. Use F254 dopped plates and get a short wavelength uv source for visualization. Keep in mind that iodine is usually good for visualization. There are also many kinds of sprays and "dips" used.

2. I recommend getting commercial glass microscope slide size silica plates if you can afford them. These are typically about 2.5 cm x 7.5 cm in size. I cut these in half to get a 2.5 x 3.75 cm miniplate which I use for all initial solvent selection experiments as well as other uses. A good glass cutter is essential. To spot these miniplates you need a very fine capillary so that you typically spot 1 -2 microliters of sample. Experience will teach you how to do this effectively. You can note the size of your spot under uv before the plate is developed and add more if necessary. I can easily run 3-4 spots side by side on these plates (in the long direction) which is very useful for following reactions or column separations. When required you can use the full-length plate.

3. Buying very large plates and trying to cut them will result in considerable waste. Believe me on this. There used to be plates sold that were prescored to easily break into smaller plates. Perhaps these are still offered somewhere (Analtech comes to mind.)

4. My experience with plastic and aluminum plates is minmal. I really do not like them for a variety of reasons. Their only attraction is that they are relatively cheap.

5. Making your own plates is an art form not easily mastered. Also getting your hands on useful TLC adsorbents formulated for plate making is not easy. I guess it just depends on how deeply you want to learn the technology.

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[*] posted on 6-10-2022 at 03:20


Now whats a "good glasscutter"? You talk about the expensive diamond tipped ones or those with the wheels?



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Mateo_swe
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[*] posted on 6-10-2022 at 05:58


OK, thanks for all info.

Ill check out The Home Scientist on YT and the TLC videos.

So, F254 plates is good, use smaller glass backed variants, pre-scored if avaliable otherwise small 2.5 x 7.5cm.
Get some capillary tubes for spotting and a 245nm UV source.
I have Iodine i can use and i think i stick with purchased plates and look at homemade plates later if i use it a lot.

I have one of those glass cutters/scorers with a small wheel on the top, will it do the scoring job or do i need a more proffesional one?
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AvBaeyer
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[*] posted on 6-10-2022 at 15:48


Some further comments-

Good glass cutter: I use a wheel type which I bought at Ace hardware. It is one of the more expensive ones made in Germany. I also use a diamond stylus but I prefer the wheel cutter. When cutting plates, they need to be face down. I recommend a clean, thick piece of glass as a work surface.

TLC plates: I use Whatman silica gel plates although several reputable brands can be had on Ebay. I do not recommend Chinese plates. My experience with these several years ago showed inconsistent quality from plate to plate. Perhaps they have improved over the years.

TLC spotting: I use Drummond 2 microliter "disposable" micropipettes. They are somewhat expensive but can easily be cleaned and reused. A vial of 100 has been recycled several times and has lasted for several years. I found them on Ebay. You can also pull your own capillaries from disposable glass pipettes. The secret to a good TLC experiment is a very small tight spot of a not so concentrated sample. Good spotting is an art form easily learned from experience.

Other TLC methods: Paper chromatography using Whatman products can be very useful for a variety of analytical methods. Water based eluents can be used whereas standard silica plates do not fare too well with aqueous eluents. The paper can also be chemically modified to change its properties. For example, it can be acylated with activated carboxylic acids to make it more lipophilic or give it an "aromatic surface" with, for example, benzoic acid. This is somewhat analogous to reverse-phase silica plates.

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[*] posted on 6-10-2022 at 21:29


Quote: Originally posted by AvBaeyer  

TLC spotting: I use Drummond 2 microliter "disposable" micropipettes. They are somewhat expensive but can easily be cleaned and reused.


That looks nice.

At university I used to make my own spotters from Pasteur pipette using Bunsen burner. At my home lab I am sometimes using melting point capillary tubes but those are not as thin as stretched glass fibre and require more caution as they can produce larger spots
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Mateo_swe
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[*] posted on 10-10-2022 at 01:58


I see the glass TLC plates on Ebay are expensive, very expensive if its a known good brand.
400Euros for 20pcs of Merck glass silica F254 20x20cm plates, ouchh...

The chinese plates are much cheaper, about 100Euros for 80pcs, 2.5x7.5cm similar to the ones below, but they are no good you say, or can they be used?
Chinese plates

Found these plates for about 160Euros with shipping, 80pcs/box
Glass Backed TLC Classical Silica Plate - Silica Gel 60 F254 2.5 X 7.5Cm
Glass backed TLC classical silica plates, silica gel 60, F254, 2.5x7.5cm

Manufacturer is Lichen cottage, shipped from Florida US.
Maybe an option.

[Edited on 2022-10-10 by Mateo_swe]
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[*] posted on 10-10-2022 at 18:21


Mateo_swe,

I did not say the chinese plates were no good. I said that several years ago plate to plate quality was inconsistent. They were useable but with some caution. If you want to learn silica gel based tlc, the chinese plates should work ok for you. And yes, commercial plates are very expensive, but you really cannot run organic chemistry reactions without them. Perhaps you might try paper chromatography first. Whatman chromatography paper strip is sold as a roll, or you can sometimes buy sheets. I noticed some products available on Amazon searching for "Whatman chromatography paper." Also, a really good office supply store just might still have high quality blotter paper which can be used for chromatography.

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[*] posted on 11-10-2022 at 04:15


Hmm, i think i have to pay up for some at least decent plates as i really would like to learn TLC analysis.
I take my chances on the plates made by Lichen cottage.
80pcs will last a while for me, hopefully enough to learn the basics.
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[*] posted on 11-10-2022 at 19:17


Quote: Originally posted by Mateo_swe  
Hmm, i think i have to pay up for some at least decent plates as i really would like to learn TLC analysis.
I take my chances on the plates made by Lichen cottage.
80pcs will last a while for me, hopefully enough to learn the basics.

That will be definitelty enough noto only for learning but for some concrete application as well. If you cut them in a half you get 160 2.5 X 3.75 which should last you for a while (depending on what you do)
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[*] posted on 12-10-2022 at 12:21


I have ordered TLC plates, two 270nm UVC diodes with a power supply (to build a TLC UV visualizer device) and i think i have the rest needed.
Thanks for all info.
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