Clogged G-amidite lines

gustilo at pobox.upenn.edu gustilo at pobox.upenn.edu
Tue Nov 29 02:02:29 EST 1994


In article <KU-281194183230 at ku.niddk.nih.gov>, KU at helix.nih.gov (Karen) wrote:

> Apparently this is a well known and widespread problem. We have tried a
> number of things based on the advice of the ABI people. All to no avail. We
> were optimistic a while back that diluting the phosphoramidate when we
> switched to the 0.04nmole columns might help a bit, but no such luck. We
> also tried using only phosphoramidites synthesized since Jan of this year
> when some new trick was apparently tried with the synthesis but also no
> luck. We have tried the low temperature hypothesis, the humidity hypothesis
> etc etc but found no consistent factors that we could identify. The last
> advice ABI gave us was to take the bottle off the machine if the machine
> was going to be idle for any length of time [The remaining solution can be
> stored in a dessicator at -20C until needed].

We have this problem too. We are now stuck to using 250 mg bottles of G
and changing it 2-3 times/week and our lines still get clogged.

I thought that it could be the grade of Argon gas we are using (99.99%). I
looked at the specs for the gas and there is about 0.0001% H20 (as vapor)
in the tank.

I was never able to test my hypothesis that putting a gas dessicator
between the tank and the synthesizer, or using gas of a higher purity,
would solve the problem.

--

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gustilo at pobox.upenn.edu



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