Silica with F254 has an flourescent material that absorbs light at 254 nm (hence the 254 name) and emits in the visible spectrum. It works because many compounds also have some absorbance at 254 nm; this absorbance blocks a portion of the UV light from reaching the plate causing reduced fluorescence where the compound is located, making dark spots that we see.

I generally find the F254 plates are pretty universal. If the compound doesn't absorb at 254 (even weakly), other methods work well with these plates such as charring with a sulfuric acid spray, or simply spraying with water (lipophilic compounds keep water from reaching the plate so the compound shows as white, while the rest of the plate is grey). The F254 compound is zinc orthosilicate, if anyone is curious.

I tend to just only keep the F254 plates as I've not had an issue with the F254 compound interfering with other spray reagents,.

Silica gel 60F254 is for fluorescence, i.e. for UV visualization of separation performed over thin-layer.

The use of both of these depends on the type of compounds you are expecting in your TLC plate. Certain compounds are UV fluorescent i.e. they themselves are indicator of their presence in UV exposure. So in these cases you should use the Silica gel G F254 so that you can get a glimpse of thee compounds at the very first visualization. Mostly such compounds include flavonoids, coumarins, furanocoumarins, carotenoids and sometimes steroids also.

Other compounds which are not visualised in UV and those which require a derivatization by a spraying reagent can be analysed on a silica gel G plate. You can use the proper spraying reagent and get the result in the form of spots visible under daylight with naked eyes.

Now-a-days TLC plates with a specialization of UV 254+366 are also available which allow you to scan the plate at the long and short UV both at the same time. Hence increasing the area of your analysis and hence the results also.

I would suggest you to always have a UV scan of your developed plate, whether you are any type of silica gel because inherent fluorescence will be seen in UV light if present in the compound.

Gud Luck

Regards

Good Answer by Dr. Alok Nahata.

Silica with F254 has an flourescent material that absorbs light at 254 nm (hence the 254 name) and emits in the visible spectrum. It works because many compounds also have some absorbance at 254 nm; this absorbance blocks a portion of the UV light from reaching the plate causing reduced fluorescence where the compound is located, making dark spots that we see.

I generally find the F254 plates are pretty universal. If the compound doesn't absorb at 254 (even weakly), other methods work well with these plates such as charring with a sulfuric acid spray, or simply spraying with water (lipophilic compounds keep water from reaching the plate so the compound shows as white, while the rest of the plate is grey). The F254 compound is zinc orthosilicate, if anyone is curious.

I tend to just only keep the F254 plates as I've not had an issue with the F254 compound interfering with other spray reagents,.

So, you mean it's ok if we use spraying reagent on TLC plate F254 to visualize the compound?

@Nor Syafirah Zambry

It is perfectly OK to use spray reagents on F254 plates. There might be some exception (a chemically specific reagent of some sort), but I've used it with the common ones (sulfuric acid, water, molybdate spray reagent, and  iodine chembers too) with no issues. I've also used some of the chemically specific reagents for alcohols and other functional groups too, without issues.

Thank you Jack Silver for sharing your experience and knowledge.