I will not be using any chemical catalysts to aid in visualization along with the charring, i.e., sulfuric acid. I was hoping to get some details, the very least of which include the temp and minimum number of hours. Also if anyone has a paper where this method is used (I have been looking but have been unsuccessful so far)
Normally one hour in atmosphere of few ml of SO2Cl2 vapors (milder agent than spraying with methanolic H2SO4) is enough - in a closed chamber, without immersing the plate in the charring agent. Then heating on a temperature controlled plate - spots begin to appear about 110oC. 180oC is enough for good charring. Some precoated TLC plates may darken at such temperatures, so above 100oC you'll observe which temperature is optimal. 50% H2SO4 in methanol (or water) is widely used. Always use fume hood!
may be burning in furnace will help. temp between 200 to 250 deg C fr 30 to 60 min.
Thanks for the responses.
Just to reiterate: I am referring to charring in the absence of charring agents. Literally I want to just run the the plate and put it into an oven. Never heard of this before (prior to my advisor). I know that the prolonged exposure to heat will result in a carbon imprint. I was just curious if anyone had every used this method before and if so , any pointers?
Cheers
Never heard of charring lipids without charring agents. I guess if you don't break the bonds in the hydrocarbon chains you will need very long time to burn lipids only heating the TLC plate... But, please let me ask you, why do you want to know this? Just curiosity? Have you ever tried to use iodine vapour (reversible) or primuline (not reversible) to stain lipids? If you are interested I can suggest you some protocols...
Currently, I am just working with what we have (and my adviser suggested it). I also visualized the bands by UV shadowing but a permanent record would be nice. I am going to try and petition for Iodine vapor. If you have a protocol I would appreciate it. Thanks Roberto.
Sorry for my late answer. In order to have a permanent record using primuline (i.e. UV) you can use a VersaDoc imager. Do you have one? This instrument is commonly used for recording images given by chemoluminescent or fluorescent probes in blotting techniques such as western blotting. If you do not have it you could use iodine vapour staining and then you can easily scan the TLC before the staining disappear. You only have to buy some crystal iodine and then expose the developed plate to iodine vapor (in a closed chamber), then if you like you can spray it with a suitable solvent to prevent halogen evaporation, but this is not strictly necessary.
If you need a protocol for primuline staining (more efficient) you can find it following the references in the paragraph 2 of this review about TLC of lipids:
http://www.sciencedirect.com/science/article/pii/S0021967310016547#
Please, read this review carefully because all these methods I cited have important limitations.
regards