Re: Brown Stains during FMOC assembly...

Angela c. Murphy (acmurphy@helix.nih.gov)
Thu, 25 Mar 1999 12:32:24 -0500

>From what I can see on the lines of the ABI 430A peptide synthesizer, the
culprit may be the DIEA. The line from the 2M DIEA in NMP bottle has
turned a reddish-brown color, and that seems to be permanent. Although my
HBTU/HOBt in DMF solution turns yellow in a few days, it doesn't affect
the lines. My piperidine line is OK also. I don't know why you have more
problems with aliphatic amino acids. You might try distilling the DIEA
from ninhydrin before use.
As for the glass frits, in our lab, any frit that sees resin is routinely
cleaned with 3:1 concentrated sulfuric/nitric acids.
Hope this helps.
Angela C. Murphy

On Wed, 24 Mar 1999 Steven.Johnson@biomeasure.com wrote:

> Hello...this is my first foray into this forum, so please be
> gentle... =-}
>
> Here is my question:
>
> I'm sure that I'm not the only one who has seen the brown staining
> of the glassware and teflon lines during FMOC synthesis.
>
> I am using an HOBt/TBTU/DIEA in DMF activation protocol for my
> assembly.
>
> I would like to retain this protocol as it is relatively
> inexpensive and gives great peptides on larger scale with little or
> no racimization, and I need to keep away from the chlorinated
> solvents as this protocol will eventually be a manufacturing
> process.
>
> The brown staining seems to occur most prevalently with the
> aliphatic amino acids, and is not noticeable with the other types
> of amino acids.
>
> Has anyone figured out 1) what is that brown staining (that can
> only be removed from the glassware by elbow grease or harsh acid
> treatment) and 2) how to eliminate or minimize this phenomenon...as
> it is more difficult to clean the tubing.
>
> It also seems to plug the glass frits (removable by treating them
> with 10% peroxide in sulfuric acid) after a few complete assemblies
> and is quite the nusiance.
>
> Thoughts and advice???
>
> Regards,
> Steven
>
> Steven.Johnson@Biomeasure.com
>

*******************************************
Angela C. Murphy, Chemist
Lab. of Cell Biology, NHLBI, NIH
3 Center Drive, MSC 0301, Rm. B1-22
9000 Rockville Pike
Bethesda, MD 20892-0301 USA
tel.: (301) 496-2324
fax: (301) 402-1519
email: acmurphy@helix.nih.gov
*******************************************