Hi everyone,
I recently performed TLC experiments using extracts from coffee leaves, cherries, and blossoms, prepared with hot water, ethanol, ethyl acetate, and hexane. I used the following mobile phases:
1. Toluene:Ethyl acetate:Formic acid:Water (10:30:5:3)
2. Ethyl acetate:1-Propanol:Water:Formic acid (10:10:4:2)
The TLC plates were silica gel 60 with a fluorescent indicator. Unfortunately, the separation was not satisfactory.
Does anyone have suggestions for improving my results, such as alternative mobile phases or other adjustments?
Thank you for your insights!
1. If the concentration of the sample solution is too high and exceeds the sample loading capacity of the silica gel plate, part of the sample cannot be adsorbed, which will cause tailing. The solution is to dilute the sample solution before spotting.
2. When the product contains strong polar groups, the adsorption force with the silica gel plate is strong, which may also cause tailing. The solution is to add a drop of weak acid (such as formic acid or acetic acid) or weak base (such as triethylamine or ammonia water) to the developing agent, which usually has a significant improvement.
3. If the developing agent has poor solubility in the product, it may also cause tailing. The solution is to replace the developing agent, such as replacing petroleum ether/ethyl acetate with petroleum ether/dichloromethane.
4. If the homemade silica gel plate is left for too long or in a humid environment, it may contain water, resulting in tailing. The solution is to re-dry and activate the silica gel plate. If the entire batch of silica gel plates has tailing, there may be a problem with the quality of the silica gel plate.
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