[Chromatography Q & A] Differences between silica gel plate and amino silica gel plate used in thin-layer chromatography (TLC)
Thin-layer chromatography (TLC) is a thin layer of silica gel, amino silica gel, alumina, polyamide resin, etc. applied on a glass plate. It is mainly used for simple and rapid confirmation of the progress of reaction, examination of separation conditions for column chromatography.
Silica gel is applied in silica gel TLC and amino silica gel is applied in amino silica gel TLC. The silica gel surface has a "silanol group" with one or two hydroxyl groups (OH) on silicon (Si) and a compound is separated by adsorption to the silanol group. However, since this silanol group adsorbs basic compounds strongly, the tailing of the spot or the adsorption without developing may not be improved even if the developing solvent is changed and good separation may not be obtained in the separation of strongly basic compounds by silica gel TLC.
Amino silica gel is effective in reducing ionic binding interactions with basic compounds by modifying the silanol groups with amine. In the separation of basic compounds, addition of ammonia solution, amines, etc. to the developing solvent is required by the TLC with silica gel, but with amino silica gel TLC (NH2 Silica Gel 60F254 Plate Wako), basic substances such as 2,4,6-trimethylpyridine and 4-dimethylaminopyridine can be separated without the addition of base.
NH2 silica gel TLC is more expensive than silica gel TLC. Therefore, we recommend to first separate with silica gel TLC and, if separation seems to be difficult, consider separation with NH2 silica gel TLC.
For strongly basic compounds and highly polar substances regardless whether acidic, neutral or basic, silica gel TLC may not give clear spots due to tailing, which is often improved by the use of amino silica gel TLC.
First try silica gel TLC and, if it is difficult to obtain a good result, shift to "NH2 silica gel 60F254 Plate Wako."
Advantages of NH2 Silica Gel 60F254 Plate Wako
- It is suitable for isolation of moderately or highly polar substances.
- It is effective for isolation of strongly basic substances.
- It is also effective for separation of acidic substances as a TLC of weak anion exchange system when a developing solvent containing water, such as a buffer solution, is used.
- Many detection methods can be used as the product is a TLC of glass plate.