Dissolving Amino Acids in Scintillation Fluid

[harald at mol.univie.ac.at]

In article <calvert-ya02408000R1208970149370001 at taco.cc.ncsu.edu>, calvert at eos.ncsu.edu says...
>
>I hydrolyzed some protein with HCl and passed the hydrolyzate through a
>small ion-exchange column.  The amino acids were then eluted with 4M
>ammonium hydroxide.  When I tried mixing this with scintillation fluid
>(Ultima Gold) it became very cloudy.  I figured it must be the ammonia, so
>I blew it down to dryness with nitrogen.  Well, I still couldn't get it to
>dissolve properly.  This makes sense because amino acids don't dissolve
>very well in organic solvents, generally speaking.  Is there a trick to
>this?  I was thinking that maybe using a co-solvent like DMSO, DMF,
>pyridine, etc. might work, but this is just a hunch.  Any suggestions?


Sure. I suggest using Dioxan or a commercially available Szintillation cocktail (I don t recall 
the name) which allows mixing with water. Also, you could try to bring the AA in the salt form by 
adding a small amount of e.g. NaOH in order to make them dissolve better in water, since amino 
acids sometime just refuse to dissolve, but the salts should not. DMSO is a common solvent for 
both inorganic and organic salts and is definitely worth a try.

hope this helps, Harald