i have a bacterial crude extract soluble only in water .........what solvent system i should use to run TLC or column
If using silica, you can use acetonitrile or methanol or THF with water, if the TLC binding material permits it. Start with the organic solvent and use increasing amounts of water- this is called HILIC ( Hydrophilic Interaction LIquid Chromatography, aqueous normal phase). This can be run in a small silica column as well- the sample needs to be dry-loaded. If you need a solvent modifier, keep the solvent acidic or neutral. Polar basic solvents (>pH 7.5) dissolve silica! You may also try dichloromethane/methanol or DCM/acetonitrile since the compound may only be very polar, but able to run with organic solvents.
Alternatively, try C18 or diol TLC plates and columns.
The links below demonstrate HILIC with silica (and other packings) for flash column chromatography:
http://www.teledyneisco.com/Documents/Liquid%20Chromatography/Application%20Notes/HILIC%20Purification%20Strategies%20App%20Note.pdf#search=HILIC
http://www.teledyneisco.com/Documents/Liquid%20Chromatography/Application%20Notes/RediSep%20Rf%20Gold%20Silica%20and%20Highly%20Polar%20Solvents%20App%20Note.pdf#search=HILIC
http://www.teledyneisco.com/Documents/Liquid%20Chromatography/Posters/Strategies%20for%20Flash%20Purification%20of%20Highly%20Polar%20Compounds%20Poster.pdf#search=HILIC
Hi Renu
n-butanol:acetic acid:water (4:1:3) is good for aqueous extracts.
Try this and it's different combinations for better resolution.
In the case of polar compounds, it is advisable to perform reverse-phase TLC, ie. on RP-18 TLC plates.
The solvent should be polar, i.e. mixtures of water and methanol or CH3CN. If the compounds are acidic (i.e. phenols), a small amount (i.e 0.1%) of formic acid can be added to the eluent
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