Chromatography Forum

hello all

i wish that any can provide me suitable way to exract polar lipids after from these non-polar.. and if possible how to exctract if from the TLC plate.

I think you need to make your question more clear. Can you specify any analyte?

Hello Waleed,

you should not try to extract your sample from your TLC plate. use small amounts in order to find chromatographic ocnditions.
after you have found the critiria for separation on your plate, move to flash chromatography with either glass columns or instruments like the ones from ISCO. see http://www.isco.com.

Possibly, because it´s so simple to scratch spots off TLC plates nobody answered on this.
Especially since there are also prep TLC plates used extensively I am a bit surprised at your suggestion, unmgvar, not to do "hyphenated" TLC. Could there be reasons that have not been discovered before in millions of applicatons?

HW Mueller it is only because for prep purposes all the organic chemist that i work with almost entirely use flash chromatogrpahy because it is easier, especially if you use instrumentation. Isco instrumentation also permit the use of gradient elutions which increases the separation power.

have yet to be a part of a project were we did choose prep TLC.

anyway we will have to wait and hear what Waleed needs to do with is sample and how much he has of it

That´s a relief to know, just feared that I did a bodge job the last 40+ years.

Jokes aside, so it´s a matter of what you want to do, and $. Just one example where TLC is hard to beat: It´s used extensively to do rough and quick quality control in radiolabeling. There are some methods were you know, with an acceptedly (I admit that sometimes I disagree) accurate %, the yield of radiolabeling within about 5 minutes, test preparation (actually just pouring a few drops of mobile phase into a vial), developing, and quantitation inclusive.
The other extreme, if you read material by mabufacturers of TLC equipment you get the impression that HPLC practitioners are fools.

well... to make it clear .. i hve a sample with polar and non-polar lipids. ok? i want t use TLC to separate it. no any other techniuqu an provide me better reults. i hve tried solid phase extractio with aminoprpyl columns. but i want to use TLC now. i want t measure the concentartions of the polar lipids using HPLC.. so my question is how to extract it from the silica gel itsef.? do i need to make dervatization? and what i need?
ok?
i wish that become clear now.
thnx by the way.

Dear unmgvar:
i dont have any alternate way you know why? because i dont find any other way rather than extracion of the oplar lipids spots from the TLC plate..
i cant get these polar lipids by any other technique,, ok? i want to inject these polar lipids sample in the HPLC instrument... so how can i get it out of the silica?
ok?

Thank you unmgvar and thank u WH mueller ...
well i think that i have to explain everything now..
i want t seprate polar lipids such as " phosphatidylecholine" from those nonpolar lipids and the best way is using TLC .. and as u know its concentrations from the sample is so little. i want to quantify its concentrations and its type through HPLC. all what i need to get is few microliters of it.. i already have standerds to held the calibration curve and just want to extract it from the silica gel plate after sepration to inject it directly in the HPLC after dilution with the mobile phase ... and the problem is that thses phospholipids contain fatty acid resdue , so i think it will be kind of hard to seprat it with polar-nonpolar extraction, and on the other hand maybe it will be bounded to the surface silica molcules,,, wish that its now clear,, if there s any correction of what i said it will be of my pleasure to hear it,,, i

Dear Waleed:
I do not have experience with phosphatidylecholine but I will believe it can wash off silica easily. To quantification you need TLC working curve, good luck

You got your answer from ym 3142 and me already....OK?

Dear HW Mueller- ym3142.
thank you very much for your reply ,,, but really i wish to find that procedure that i can apply to extract it out of silica gel..
there is the esterification method - i dunno wether you know it or not- but i wish to find alternate way rather than that.. because esterfecation will measure the the taffy acid composition ...
the other way is to direct hot of the silica spots with acids at high temp about 180 0c....
but actulay i ddnt tried it ...
anyway.. thank you for your suggestions

How about scratching off the silica gel, placing it in a vial and shaking it with a solvent (literally)? You moved the spots with a liquid also, didn´t you?

Thank you HW Mueller. i think thats what shall i do... on at least am not in a situation that what i need in the lab can be avilabe anytime...
thnx alot... would you plz tell me if i can keep phospholipids stock solution in the freezer or not? is it will stay stable that long time?
thnx for your time...