Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  2  
Author: Subject: Home Made TLC plates
Paddywhacker
Hazard to Others
***




Posts: 478
Registered: 28-2-2009
Member Is Offline

Mood: No Mood

[*] posted on 5-3-2011 at 19:44


What part of the world are you? Overseas shipment is probably not worth the hassle.
View user's profile View All Posts By User
Chordate
Hazard to Others
***




Posts: 108
Registered: 23-2-2011
Member Is Offline

Mood: No Mood

[*] posted on 5-3-2011 at 23:46


In the states.
View user's profile View All Posts By User
HexJam
Harmless
*




Posts: 25
Registered: 29-9-2008
Member Is Offline

Mood: Steady

[*] posted on 6-7-2011 at 15:43


Does anyone know what the UV reactive material is that they mix in? Or some suitably available substitute?
View user's profile View All Posts By User
chemrox
International Hazard
*****




Posts: 2961
Registered: 18-1-2007
Location: UTM
Member Is Offline

Mood: LaGrangian

[*] posted on 6-7-2011 at 16:18


Really good set of posts.. outstanding. I look for bargains on the commercially made ones but for slide sized I might try again. I didn't add enough binder to the last .. also filter paper has a virtue or two.



"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
View user's profile View All Posts By User
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 6-7-2011 at 19:16


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!




View user's profile View All Posts By User
HexJam
Harmless
*




Posts: 25
Registered: 29-9-2008
Member Is Offline

Mood: Steady

[*] posted on 6-7-2011 at 23:33


Hey, great links, thanks! I have some of those chemicals so I think I might have a go at doing some staining after I've made my plates.

I take it that a plate isn't reusable once you've used a stain on it though? (I've never done TLC before, excuse my noobness).

I was going to have a go trying to TLC an aspirin / paracetamol (acetaminophen) tablet to see if I could separate the two, a KMnO4 stain aught to do the trick on those right?

One last thing... I notice lots of TLC experiments use hexane as the solvent, which is proving difficult to get a hold of. Is there some common use/source of hexane I'm overlooking? If I use a different set of solvents is there some way/formula to convert the Rf values I'd calculate to the same kind of scale as the reference ones that use hexane/other solvents?

View user's profile View All Posts By User
HexJam
Harmless
*




Posts: 25
Registered: 29-9-2008
Member Is Offline

Mood: Steady

[*] posted on 6-7-2011 at 23:45


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 ;-)

(source: http://en.wikipedia.org/wiki/Thin_layer_chromatography#Analy... )

[Edited on 7-7-2011 by HexJam]
View user's profile View All Posts By User
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 7-7-2011 at 12:07


Funnily enough, manganese activated zinc SULPHIDE is what I've been trying to make for a while. It illuminates when exposed to electric fields. I think UV may make it glow as well, but haven't tried it myself.

Plates aren't really reusable, particularly once they've been stained.

Really, you don't even want your finger prints on the surface. So you should handle them by their sides and most definitely wear some gloves, or you'll end up ruining your kick ass results with contaminants.

If you look at this page on wiki, scroll down to the table of solvents and look in the none polar section for possible alternatives.

Hexane is used as an ideal none polar as it is incredibly simple in terms of functional groups (it has none) and has zero polarity to it. Cyclohexane is even better, since it doesn't even have ends to the molecule. Benzene used to be used, but has double bonds and is of coarse carcinogenic.

In answer to the calculating part, if you were planning to do preparative chromatography, to prepare a sizeable mass, I would recommend you instead give it a test yourself with your solvent mix and plates of choice.

[Edited on 7-7-2011 by peach]




View user's profile View All Posts By User
not_important
International Hazard
*****




Posts: 3873
Registered: 21-7-2006
Member Is Offline

Mood: No Mood

[*] posted on 7-7-2011 at 12:12


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 ;-)


AKA Willemite

View user's profile View All Posts By User
smaerd
International Hazard
*****




Posts: 1262
Registered: 23-1-2010
Member Is Offline

Mood: hmm...

[*] posted on 15-8-2011 at 17:07


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:

TLC.JPG - 40kB

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]




View user's profile View All Posts By User
smaerd
International Hazard
*****




Posts: 1262
Registered: 23-1-2010
Member Is Offline

Mood: hmm...

[*] posted on 7-12-2012 at 15:23


So I've been trying to read up on making better TLC plates. Trying to think of better ways to get the silica onto microscope slides and I ran into this article saying some people use silicic acid rather then gypsum?

I don't know much about silicic acid or how to use it in this context I was wondering if anyone had any experience?


It also gives some pretty nice tips such as using methanol instead of water so the slurry can be stored rather then having to use it all and use it quick.

It also says that the freshly made plates should be tapped against a table gently to remove air-bubbles, which I didn't know was good practice. As well as air-drying prior to oven heating another mistake I've made in the past.

Another nice hint I've read about was wrapping two ends of a stir bar(kind of like a dumbell the width of a microscope slide) with masking tape or similar to the desired height(above a microscope slide) and rolling over the silica slurry to give an even uniform coating.

It's definitely a bit of an art, I'd like to hear more discussion and or experiences about.

Attachment: 061009_Making_TLC_Plates_from_Bulk_TLC_Silica_Gels.pdf (93kB)
This file has been downloaded 4470 times





View user's profile View All Posts By User
Paddywhacker
Hazard to Others
***




Posts: 478
Registered: 28-2-2009
Member Is Offline

Mood: No Mood

[*] posted on 27-1-2013 at 02:01


Here is an interesting technique that I came across today, involving depositing the thin layer on the outside of a glass rod or test tube.

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

Attachment: test tube TLC.pdf (128kB)
This file has been downloaded 1426 times

View user's profile View All Posts By User
watson.fawkes
International Hazard
*****




Posts: 2793
Registered: 16-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 27-1-2013 at 08:58


Quote: Originally posted by Paddywhacker  
The only problem is that powder for making TLC media is pretty well unobtainable.
Unobtainable? Why do you think that?
View user's profile View All Posts By User
smaerd
International Hazard
*****




Posts: 1262
Registered: 23-1-2010
Member Is Offline

Mood: hmm...

[*] posted on 27-1-2013 at 09:05


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 :).



View user's profile View All Posts By User
Paddywhacker
Hazard to Others
***




Posts: 478
Registered: 28-2-2009
Member Is Offline

Mood: No Mood

[*] posted on 27-1-2013 at 11:28


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.

Sure, silica flour can be had from the pottery suppliers, but it make muster.
View user's profile View All Posts By User
watson.fawkes
International Hazard
*****




Posts: 2793
Registered: 16-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 27-1-2013 at 13:32


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.
Silica gel (if you don't want to make it) is readily available as a desiccant. All it needs is crushing. The G is for gypsum (CaSO4), that is, plaster of paris. The F in silica gel GF is the fluorophore. Water tracing dyes are all fluorescent; they're used with portable black light lamps. Fluorescein, originally trade named Uranine (and still sold under that name), remains one of the most common such dyes.
View user's profile View All Posts By User
Paddywhacker
Hazard to Others
***




Posts: 478
Registered: 28-2-2009
Member Is Offline

Mood: No Mood

[*] posted on 27-1-2013 at 15:54


I believe the best fluorophors are inorganic, but that isn't the problem. 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.

Column material is also another difficulty. In order to get uniform grain sizes of the right mesh size for reasonable flow rates it is necessary to mix the silica gel with water and a binder, let it set, then grind and sieve it. My formulations, using gypsum as the binder were always too fragile and crumbled to sub 200 mesh ... useless.

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.
View user's profile View All Posts By User
watson.fawkes
International Hazard
*****




Posts: 2793
Registered: 16-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 28-1-2013 at 05:17


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.
View user's profile View All Posts By User
Mailinmypocket
International Hazard
*****




Posts: 1351
Registered: 12-5-2011
Member Is Offline

Mood: No Mood

[*] posted on 12-2-2013 at 15:54


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...


image.jpg - 62kB image.jpg - 67kB

[Edited on 13-2-2013 by Mailinmypocket]
View user's profile View All Posts By User
watson.fawkes
International Hazard
*****




Posts: 2793
Registered: 16-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 12-2-2013 at 16:21


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.
View user's profile View All Posts By User
Mailinmypocket
International Hazard
*****




Posts: 1351
Registered: 12-5-2011
Member Is Offline

Mood: No Mood

[*] posted on 12-2-2013 at 16:47


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.


Ah... I think that might be the problem then. Calcining never occurred to me - I let the plates air-dry for an hour, and then oven dried as per the article, at 120c for 45 minutes.

The lowest my makeshift lab oven (toaster oven) goes is 90c, I have to try again and use a digital thermometer to monitor the T as I doubt the thermostat on a 19$ toaster oven is "lab grade", and if I'm going to crush more of those damned stubborn silica beads I want it to work.

[Edited on 13-2-2013 by Mailinmypocket]
View user's profile View All Posts By User
Mailinmypocket
International Hazard
*****




Posts: 1351
Registered: 12-5-2011
Member Is Offline

Mood: No Mood

[*] posted on 15-8-2013 at 09:42


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)


image.jpg - 86kB
View user's profile View All Posts By User
watson.fawkes
International Hazard
*****




Posts: 2793
Registered: 16-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 15-8-2013 at 10:22


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?
Given that you've got some adhesion now (rather than none), I'd guess you've still got a problem with the temperature of the TLC plate.

Since you're using a toaster oven, if there's a direct optical path to the heating elements, it's likely that the TLC plates surface is sitting at a temperature above 90 °C because of radiative heat transfer. Think of the oven as a steady-state heat flow device, rather than a constant temperature device. The latter is what you want ideally, but the former is what you actually get. The easiest intervention is to make your actual oven more like an ideal oven.

Just putting a couple of layers of metal separated by an air gap will do a lot to even out the radiative inhomogeneities in your rig. (Incidentally, this is the insulation technique that the Webb space telescope uses to reject radiative heat load.) Put these layers between the heating element and your plates.
View user's profile View All Posts By User
sonogashira
National Hazard
****




Posts: 555
Registered: 10-9-2006
Member Is Offline

Mood: No Mood

[*] posted on 15-8-2013 at 12:44


Maybe scratch the glass with sand paper?
View user's profile View All Posts By User
smaerd
International Hazard
*****




Posts: 1262
Registered: 23-1-2010
Member Is Offline

Mood: hmm...

[*] posted on 15-8-2013 at 13:10


I'll do some experiments this weekend and report back. I did have some success but it wasn't anything too impressive. I could write on the plates if I was very gentle. I have a few ideas now that I've matured in my knowledge base and experimental technique a bit.



View user's profile View All Posts By User
 Pages:  1  2  

  Go To Top