Chromatography Forum

Summary:

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?

If the system is clean and leak free and the multiplier still tunes at 2700 V then it is time to replace the multiplier. They are consumable and have a limited lifetime. How old is the multiplier?

Multiplier is relatively new. Few months at the oldest.

[quote="Balderquell"]Summary:

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?[/quote]


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Vacuumn is high check leak first... look for ion 14 should be less than 1000 counts.....
the quad could be give up after 17 years running... check with caltechscientific.com or call help line 650-799-4230 for more help... good luck
Henry

I think you use DFTTP tune to have after the DFTTP check, the main problem that I see is the high multiplier... I think is better change it.

Because of the design of the ion source on the Agilent GCMS systems it is possible to have a large leak without seeing high air and water in the MS leak check. I would vent the system, make sure the O-ring is clean and has not been pinched, replace the nut and ferrule at the interface, then pump down and try again.

I have seen a leak develop in the bellows section of the transfer line after several years in 1 or 2 5972s, that is another potential leak point.