I have just run into a similar loss of lys signal problem. The lys in the
PTH stds are as you would expect but in the middle of a run - blank cycles.
I have recently changed from PE Biosytems TFA (R3) to Auspep synthesis
grade TFA. The problem appeared to have arisen when the sequencer was left
unattended for seven days (we all know how they require human attention
around the clock seven days a week). I replaced the TFA with a new aliquot
from an Auspep bottle which had been opened for sometime and the lys
returned. I would have thought the bottle on the sequencer under argon
would have been more stable than the bottle sitting on the shelf!?
Hope this may be of some help.
Trudy Bond
Centre for Drug Design and Development
The University of Queensland
Brisbane Australia.