Home Made TLC plates

hmm, good point on the UV indicator. I have a set of lab quality silica plates with the florescent indicator, I wonder what It would take to incorporate the same function onto homemade plates. (project # 6241.. there are several texts on TLC at my university library so I'll take a look next time I'm there.

As far as coating is concerned, yes, the uniformity of the layers is going to be an issue. perhaps there is a DIY method that could be developed. with a ball mill one should be able to get a fine enough grind which is key. Instucatables has a few DIY ball mills that can be fashioned from a power drill and HDPE bottle. Maybe take a look at commercial coating system and see if we could copy one...maybe ultrasonic agitation of the sullery?

That looks very nice. Couple of problems with that kinda rig:

> Hard to get replicable uniformity
>Will work rather badly using a rectangular substrate? In which case a circular disk should be used, meaning waste as you trim it to the proper shape.

But it is a very attractive idea and can't be that hard to set up

Quote: Originally posted by DJF90

> Hard to get replicable uniformity >Will work rather badly using a rectangular substrate?

Quote: Originally posted by Dr.3vil

Spin coating is great for fluids of low viscosity, but will it be able to handle the thick slurry?

I don't have any experience with spin coating but I accept your reasoning. Looking back DJF90 mentioned a bit about milled aluminum templates, I could see that as being a viable means to build a spin coat rig. round rig with a cut-out for the substrate. It would be conceivable to have several rigs for various sizes of plates. time to build something i guess..

Quote: Originally posted by Dr.3vil

DJF90 mentioned a bit about milled aluminum templates, I could see that as being a viable means to build a spin coat rig. round rig with a cut-out for the substrate.

Take your time. Really, if you want to get a glass cutter and practice on some glass panes before you commit to buying these, go for it.

Let me tall you a little more about these:
I bought them for $30 dollars from a vendor selling surplus lab stuff on ebay over a year ago. It was a box of 25 plates, 5 have been used. The plates are in good shape.The glass is about as thick as a quarter. Their dimensions are 20x20 cm; they are alumina coated, with a 254nm fluor and the stationary phase is 1000 microns thick.

Most standard TLC plates have ~250 micron stationary phase, these plates have a thicker stationary phase, for prep use. They will preform equally well as standard plates, again the only difference is they allow more product to be loaded before they start streaking/giving poor seperations. As an aside, for prep work you could purify of about 1-2g of material per plate (assuming 5mg per sq cm which is about the loading ceiling for a 1000u plate). Pics attached.

Also: I have never heard of adding ferric chloride for amine detection, but in the past in order to determine what spot is an amine, I have taken my TLC sample, and seperated an aliquot. This aliquot I treated with a tiny amount of HCL gas (taken by using a pipet to suck a couple of times some HCl vapor from the head-space of a conc. HCL bottle). Run the HCl treated and stock sample side by side. In the HCl treated sample the HCl salt will stay at baseline except in VERY polar solvent systems (eg neat methanol or water). So whatever spots are missing or have become very faint (from incomplete neutralization of the amine) when comparing the two samples are very likely amines (or compounds that could react with HCl...).




[Edited on 2-9-2011 by smuv]

This is a great thread!

I was thinking of spin coating as well. I've seen people doing it, not with TLC's but with other thin films, using a computer fan - which is easy to control and smooth running, and cheap, or free. I was also thinking, like Smuv says, that it's not such a bad thing if they're a bit thicker, since they can be useful for preparative. The PDF is very nice. Although yes, spotting with a pasteur, as it is, is likely going to make a mess. You can see in the last picture, the plate on the left is not the eluted plate on the right - which he does mention.

There is a thread going here which discusses spotting tools and gathering results with software.

The only drawback to DIY plates or column packing is the difficulty in comparing them with the Rf results you'll find quoted, which are all on standardised grain sizes, purities, layer thicknesses and uniform.

250 microns though... you can get a rough check of that with a cheapo micrometer.

If you had access to a microscope, you could have a peak at the grains through that. Alternatively, there are quite a few places online selling foot square swatches of micronic weave cloth - including stainless. Attach a big vibrating sex toy, and you've got a screen for the particle size.

I have posted a photo of it before, but I have made a little ball mill using Lego alone. The uses of Lego never end. It was simply a medicine bottle sat on top of some of the rubber wheels and driven by a motor. Marbles inside provided the grinding action. You will certainly want it running from a power supply, because it's going to be on for a looooooooong time to get it that finely divided and homogenised. Maybe go the whole hog and build a Lego spin coater whilst at the forge. You could use the MindStorm controllers to produce repeatable results.

For the price of the TLCs new, if you've got a micrometer and a bit of Lego handy, it's worth doing!

Try new micronic stainless weave bedding! Pressure cleaner friendly. I was going to suggest stockings, or silk, but those will probably deform too much and the stainless is going to have a better rating on it, as it's usually going into a filtration system of some sort to begin with.


[Edited on 9-2-2011 by peach]

I'm not sure what precisely is used on the commercial plates to make them glow, only that it's usually a 254nm fluorophor.

There are a number of alternatives to UV glows, alternatives which can be beneficial in that they will show specific functional groups, as opposed to anything that quenches the UV dye.

Have a look at these for some examples.

Here's curly arrow talking about vanillin stain.

And Hanessian's stain.

Very pretty!

Quote: Originally posted by HexJam

Ah ha! Apparently the chemical they add to make it UV active is "... usually manganese-activated zinc silicate". This doesn't really help me much, but I thought I'd included it for completeness ;-)

sorry to bump an old thread but I had a go at this and it works like a charm.

My only complaint is drawing on the plates must be done VERY gently. It is too easy to go through the solid-phase. Perhaps one of those chalk line markers(for marking wood) would be more ideal depending on the eluent of course.

edit - the silica I used was Sigma brand for column chromatography(too lazy to read off the size). The CaSO4 I used was from a brew-store(gypsum). Which was dehydrated in an oven for 1 hour at I believe 350*F to form the proper hydrate("plaster of paris").

Here are the results:



A harmine/harmaline extraction, eluted with HEET(methanol) no other additives. My spotting was done very poorly and it was not fully developed, but this was my very first plate. A 5 and 3/4 inch pasteur pipet has a very small mouth that can be used instead of a thin capillary if one is VERY careful(which I obviously was not).

[Edited on 16-8-2011 by smaerd]

Quote: Originally posted by Paddywhacker

The only problem is that powder for making TLC media is pretty well unobtainable.

I bought a Kg of silica media for column chromatography for I think 40 USD on an auction site. Worked pretty good for TLC plate making and for column chromatography .

Quote: Originally posted by Paddywhacker

Silica gel G? The stuff for plates contains binder and a fluorophor, which shouldn't be in the stuff for columns, and different mesh sizes too.

Quote: Originally posted by Paddywhacker

The problem is making a mixture that actually works for TLC, with reasonable adherence to the glass. I have tried but was never happy with the result. It was always a pathetic imitation of the real thing. [...] Grinding up up kitty litter is a better proposition than grinding up desiccant silica gel. Sure, there is plenty of that available, but I recon it to be too hard. If anybody has actually cracked the formulation of these products then please post a photo essay in the prepublications forum.

Quote: Originally posted by watson.fawkes

Quote: Originally posted by Paddywhacker   The problem is making a mixture that actually works for TLC, with reasonable adherence to the glass. I have tried but was never happy with the result. It was always a pathetic imitation of the real thing. [...] Grinding up up kitty litter is a better proposition than grinding up desiccant silica gel. Sure, there is plenty of that available, but I recon it to be too hard. If anybody has actually cracked the formulation of these products then please post a photo essay in the prepublications forum. At least we're out of the realm of "unobtainable" into "I didn't make it work". The photo essay you're looking for is in the very first post of this thread. The author uses desiccant silica gel, although he did grind it with a ball mill.

I tried making plates today following the original process in the first post of this thread. It was a failure. I used silica gel desiccant beads, crushed to a very fine powder along with the plaster of paris in a 4:1 ratio. The plates were easy enough to coat, dried nicely and then oven dried. They looked great (for a first try anyways) but the layer wiped off with the touch of a finger, almost like a compact layer of talc- shit.

Before scrapping it all, a small dog of methylene blue was applied and the plate placed into some solvent. The solvent started to climb the plate quickly, but stopped because the phase immersed in solvent fell off. I'm thinking the only fix to this would be to try adding more calcium sulfate next time, any ideas? Has anyone tried the above prep with reasonable luck?

Attached photos...




[Edited on 13-2-2013 by Mailinmypocket]

Quote: Originally posted by Mailinmypocket

I tried making plates today following the original process in the first post of this thread. It was a failure. I used silica gel desiccant beads, crushed to a very fine powder along with the plaster of paris in a 4:1 ratio. The plates were easy enough to coat, dried nicely and then oven dried. They looked great (for a first try anyways) but the layer wiped off with the touch of a finger

Quote: Originally posted by watson.fawkes

Quote: Originally posted by Mailinmypocket   I tried making plates today following the original process in the first post of this thread. It was a failure. I used silica gel desiccant beads, crushed to a very fine powder along with the plaster of paris in a 4:1 ratio. The plates were easy enough to coat, dried nicely and then oven dried. They looked great (for a first try anyways) but the layer wiped off with the touch of a finger What drying schedule did you use? Plaster of Paris starts to calcine at 100 °C, which is easy to exceed in an oven.

Has anyone had some reasonable luck in making TLC plates? Again I followed the OP's attached procedure without luck. I think it would be nice to make a visual guide on how to make them so that TLC can be available to more amateurs (Rf values might be hard to determine with the variable grain sizes but that's another issue).

I ground up more silica desiccant beads in a large mortar and pestle, this creates a lot of airborne dust that is dangerous to inhale, use a mask or do it outside. After about 10 minutes it was the consistency of talcum powder. Then the plaster was mixed in and ingredients were ground together for an additional 10 minutes. Then I followed the procedure but once the plates dried I baked them for an hour at only 90c to avoid calcining the plaster, which was a suspected problem in my last attempt.

Again, they came out fragile as hell. Not as much so as last time but the layer can easily be wiped off instead of blown off- I guess that's a small success. A dab of sharpie marker was placed on the plate, which removed some of the coating... Surprise surprise there! An attempt was made to elute with ethyl acetate and it did manage to carry some ink up with it but then the immersed portion of the plate started to disintegrate. Any ideas on how to improve this?

Looks like this...(the top of the plate is bare because I wiped it with a finger :S)

Quote: Originally posted by Mailinmypocket

Then I followed the procedure but once the plates dried I baked them for an hour at only 90c to avoid calcining the plaster, which was a suspected problem in my last attempt. [...] Any ideas on how to improve this?

That is very interesting! Thanks for sharing!

Up until now (since smaerd's experiment results) I have been messing around with polyvinyl alcohol(PVA) and etched plates hoping for better adhesion. Had to put it on hold due to some pretty nasty burns from saturated ammonium bifluoride.... Just kidding!

Haven't had the time to experiment lately... Only had time to etch the plates and prepare the PVA solution. This method with methyl cellulose and talc intrigues me, I have methyl cellulose but no talc yet, have you any experience using unscented baby powder? Or have you only used pure talc powder?

I just used what I found in the bathroom. Imperial leather original talc. I mixed it with methanol (2 g talc to 3 ml methanol, stoppered and shaken for 1 minute in a 4 ml volumetric flask), poured onto a glass plate, and left it to dry overnight. The layer adheres to the glass when held vertically (and up side down), but I have been using horizontal development so far, just to test the resolution. To get a consistent thin (250 um) layer, the dipping method described in the porphyrin paper seems suitable, but I will get some pure talc before I try that. Hopefully I can remove commercially prepared plates from my shopping list entirely. The method that I described is amply suitable for solvent selection experiments using radial chromatography, though, and the results translate onto commercially prepared silica plates. It depends on one's intended use. I do more qualitative tests than quantitative. I am going to try to impregnate a piece of chromatography paper with talc, using a methanol suspension. I also bought some cab-o-sil fumed silica for this purpose, but I have a feeling that talc will better-adhere. Another paper on preparing talc TLC plates (using ethanol): http://link.springer.com/article/10.1007/BF02330381
I should mention that, in contrast to silica plates, talc does not need to be activated prior to using. It is debatable whether silica plates need activation, I suppose, but that's a different matter. A picture of one of the plates used either for radial chromatography or drop chromatography (10 cm diameter plate). This one was left nearest the window in my shed, so there are a few more minor ripples than on the others, which were almost entirely flat:



[Edited on 31-8-2013 by sonogashira]

I could only find two samples to test. I was a little heavy-handed, but the resuls are good, regardless. There are two samples in the picture: the yellow one to the left is just-about visible, and the orange one was developed with two different solvents (IPA and ethyl acetate respectively, from left to right). I've scraped some of the talc off so that the uniform thickness may be seen, as well as the ease with which one may make clean edges due to the softness of the talc, especially compared with silica.

As mentioned above, this is common bathroom talc (scented!). I used 2 g of talc, 3 ml of methanol (giving 4 ml of talc-slurry), air-dried on a flat plate for only 30 minutes before spotting.

Completely forgot to update my experimental efforts here.

I have tried a few variations with polyvinyl alcohol(PVOH). I have gotten close but nothing quite there.

I experimented with sillica to 5-10% by mass hydrolyzed polyvinyl alcohol. The basic procedure so far has been as follows:

*Abrade microscope slides with sandpaper(also tested without abrasion without much effect). Clean microscope slides with acetone and oven dry.
*Add PVOH to a small volume of distilled water. Warm water to about 70-80*C until complete dissolution.
*Oven dry silica gel for column chromatography. Let cool, and then weigh appropriate proportion.
*Made slurry with silica gel by adding the PVOH solution and mixing. Think this is where things go wrong...
*Apply slurry too microscope slides so there is no drips over-hanging (Important)
*Let the slides sit, then oven dry gently(have experimented with this a bit).


Now the problem I have been having is a bit unexpected. I appear to get a great TLC plate. Well until I touch it. It seems as though the PVOH forms a 'bubble'. Meaning The outer edge is dry and bonded exactly how I would like. Even a crusty polymeric film layer exists on the face of the plate. When touched with a pencil or similar however, this 'bubble' shatters to reveal dry mobile silica gel underneath.



It's as if the PVOH concentrates to the outer edges of the TLC plate and does not fully mix with the sillica slurry no matter how much it is mixed. I'm not sure why this may be the case. I'm wondering if it has to do with hydrogen bonding being more favorable to the silica surface from the water, rather then PVOH to the the silica. I think trying isopropanol as a solvent may then prove to be more fruitful? Another alternative would be to do something similar to PCR's thermal phase. Warm the slurry to 80-90*C so the thermal motion over-comes the strength of the hydrogen bonding, then allow the solution to cool. I will try in the future and update if there is success. Acquiring some input would be fantastic.

I think PVOH would be a great layer if it does work. PVA(polyvinyl acetate) would be great as well, but it may pollute the plate with acetates? Probably be preferred to use lab-grade PVA and not the yellow gunky stuff. Might be cross-linkable in an easy way to get a nice firm PVOH/PVA layer.

[Edited on 26-5-2014 by smaerd]

[Edited on 26-5-2014 by smaerd]

From the book - Thin Layer Chromatography in Chiral Separations and Analysis by Teresa Kowalska, I found another recipe for TLC plates used in chiral analysis. I'd imagine this could be substituted for regular silica gel rather then the chiral one.