On Fri, 23 Apr 1999, Kenneth Williams wrote:
> A triplet of peaks has suddenly appeared on the HPLC chromatogram from our
> HS Procise 494 that we cannot seem to rectify - any help/ideas would be
> greatly appreciated. Here are the clues to this puzzle:
>
> 1. the first two peaks co-elute with Pth-Gly and Pth-Glu with the third
> eluting between Pth-His and Pth-Ala. By comparison to the standards the
> relative "pmol" amounts of these peaks are about 0.5 pmol (Gly), 2 pmol
> (Glu) and 1 pmol (X).
>
> 2. these peaks appeared following addition of several new reagents to the
> instrument - all of which have subsequently been changed again.
>
> 3. the peaks are present at the same level in all cycles and the instrument
> is still sequencing normally.
>
> 4. the peaks are present also in the blank cycle.
>
> 5. the flask has been KOH washed and the column guard has been changed
> without effect
>
> 6. the Pth column is 4 weeks old while this problem occurred suddenly a few
> days ago
>
> Currently, our efforts are directed towards watching a blank cycle to be
> sure all wash steps are indeed occurring and then, to deleting steps from
> the wash cycle program until we isolate the step or reagent causing these
> peaks.
>
> If you have seen these peaks previously and/or have any ideas on their
> origin or how to more effectively diagnose the problem please respond.
>
> Thanks very much,
> Ken Williams
>