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- Posts: 33
- Joined: Wed Mar 18, 2009 12:15 am
Main problem is that DFTPP will not pass--low mass ions are too high relative to base peak and high mass ions are too low relative to base peak.
This 5972 SVOC MS had been tuning at EMV of about 1800 and experienced abrupt loss of high mass ion response and will not tune at less than 2700 EMV. No matter how I play with target tune ratios 219 will not exceed about 28% of 69 and 502 is about 1% which is workable. Same thing with Dftpp autotune.
Ion gauge is reading 1.5 x 10-4 while foreline is mid 60s @ 1ml/min.
When I tune, I target tune at the following ion ratios--normally passes every time and holds tune awhile.
131 40% vs. 69
219 32% vs. 69
502 0.8 % vs 69
Tune parameters currently:
EMV 2700
Xray 102
Emission 35
Ion Focus 90
Repeller 22
Ent Lens 0
Ent Offs Var
Column Flow is 1ml/min
Foreline pressure is 60
Ion gauge reading is 1.5 x 10-4 which is high
Cal gas peaks are all visible during full scan
Air/water peaks are almost entirely absent
All isotope peaks visible
Source cleaned on 5/19
Rough pump oil replaced on 5/20
Checked diff pump oil and it was low, refilled and the baffle was abrasively cleaned on 5/20--baffle was black with lots of char.
Ion gauge traded out--same reading.
I've removed the column and capped the detector and pumped back down. Still having ion gauge vacuum trouble but no air/water evident after the usual bakeout period. Foreline reaches high teens low 20s.
Any thoughts?