[yedwards12]

Hi,

I am seperating amino acids using a Flash system. To start I am using C18 Tlc plates but am having a problem getting the amino acids solutions to spot to the plate. They do not absorb onto the plates. The amino acids solutions are made in water. Any suggesstions on how to make the plate take the solution. I tired silica plates but am getting the same Rf values.

[discodermolide]

May be better to use normal TLC plates and a chloroform/methanol/water solvent system. You can probably find solvent systems via a google search.
C18 TLC may be too non polar for the amino acids, you didn't mention the solvent system you are using for the C18 plates?

[Babcock_Hall]

Are you running free amino acids?  Stahl's book (which is quite old but still useful) on TLC gives five solvent systems for amino acids (acidic, basic, and neutral).  I have used water/ethanol on occasion.