Bad autotune/mass movemement/Agilent MSD 5975

[Svetlina75]

Dear all,

Could you please advise me for the following:

Two weeks ago I cleaned the Ion source (MSD 5975) and Autotune was ОК. After 40 samples on HSP, the calibration was perfect too.
But the problem has appeared:
Autotune goes bad, there is some moving of mass, mass 502 moved at 504. When the Autotune was repeated the error “Mass gain – out of range” occurred.

What are the possible reasons for the movement of big masses?
How to proceed for resolving the problem – put the masses in their range?
I can clean the Ion Source again, but it’s not normal so frequent and only after 40 samples to do this and it could not resolve the problem for a long time.
Please note that there is sufficient quantity of calibrating agent into “Calibration vial”.

The image applied here is from Tune evaluation records:


Looking forward to your comments.

[kubowicz.tomasz]

Hello

Could you paste autotune report? It'd be handy.
Regards

Tomasz Kubowicz

[Svetlina75]

Hope this helps:





Thank you!

[kubowicz.tomasz]

Hello

For second autotune report (I assume it is after ion source cleaning) repeller voltage is quite low - that is why ion 502 is so low. Check repeller insulation (white ceramic parts) and replace them if they are scratched or dirty (do not clean them).
I also noticed that you have different parameters for 2 autotunes (column flow, MSD interface temp). You should have them the same every time you run autotune.

Regards

Tomasz Kubowicz

[Bigbear]

Try another type of tune like bfb or dftt to check if autotune corrupt. I have a hard time believing there is 0 air and water!

[James_Ball]

I good test to see if the Repeller is dirty or if the insulators are bad is to look at the Repeller Ramp results. If it is a smooth curve then it is probably ok, if there are steps or a saw tooth pattern in the ramp then it is almost certainly a problem.

It also looks as if your Electron Multiplier has some age on it, since you are in the 1700-2000 volt range on those tunes and you only have about 300,000 counts on m/z 69. A new multiplier will have those counts with only about 1100 volts.

Shifting mass assignment can also be caused by dirty quadrupole or bad electrical connections between the quads and the side board, or even a problem with the side board. Use some dry nitrogen or some electronics dusting spray to blow through the quadrupole, I once had a tiny piece of lint on one of mine that caused very bad problems after a source cleaning.

Another odd setting I see is the EntLens(Entrance Lens Voltage). If that is not near zero it usually means there is some sort of contamination on the lens.

HiVac is reading Off,, do you know what the analyzer pressure is? It should be in the 10^-5 torr range if the vacuum system is in good condition and there are no leaks.

[Svetlina75]

Thank you, guys, for your suggestions!

Regards

[thohry]

Have you cleaned the ion source ?
If yes, there's possibly the quad or the quad driver problems.
Dipping coil may help.

[Svetlina75]

Have you cleaned the ion source ?
If yes, there's possibly the quad or the quad driver problems.
Dipping coil may help.

Thank you for your comment. Could you please explain what you mean with this "Dipping coil" as I don't have such an experience.

Regards

[kubowicz.tomasz]

Hello

In my opinion you should not play around with "dipping coil". It is service procedure (more electronics involved) and it is last thing I would suspect. I think your problem is linked with something else - ion source or dirty dynode.

Regards

Tomasz Kubowicz

[James_Ball]

Have you cleaned the ion source ?
If yes, there's possibly the quad or the quad driver problems.
Dipping coil may help.

Thank you for your comment. Could you please explain what you mean with this "Dipping coil" as I don't have such an experience.

Regards

It involves using the Set RFPA function in the tune menu and adjusting the large black screws in the middle of the side board. At Tom said though, if you don't have that much experience with it you probably should not try it, unless you just can't get a service technician out to see you.

If you watch the service tech do it, you will say "that was simple", but if you don't keep the adjustments even you can throw the RF way out of balance.

[Svetlina75]

Appreciate all your support, guys!

In addition, after ion source cleaning the following adjustments were checked:

10.00 amu -----> 7 mV
100.00 amu ------> 51 mV
650 amu -------> 306 mV

Regards

[kubowicz.tomasz]

Hello

Please paste autotune report (after ion source cleaning)
Regards

Tom

[Svetlina75]

Hi Tom,

Please see it above (posted on 31 Oct).

Thanks

[kubowicz.tomasz]

Hello

I still think your problem is with:
1.Ion source - dirty repeller/scratched insulators/wrong connections
2.Correct vacuum - leaking

Regards

Tomasz Kubowicz