Thermo LTQ iontrap MS tuning help

[manoj_dharaskar]

During calibration instruments fails saying multiplier voltage test fails. The mass 524 is also very low.
Tried to optimize the capillary position and ESI probe position but no luck.
Please guide

[leadazide]

Try with a new calibration solution. It could be your solution that has degraded.

What settings do you use?

I have ESI probe in B, Sheath 1-5, Aux 0, Sweep 0, Spray voltage 4.2 - 5 (with fused silica) or 3.5 - 4.2 (with metal needle)
and run the syringe pump between 1 and 5 ul/min.. Also make sure the probe is centered in the MAX Housing.

If using Fused Silica make sure it is cut nice and straigt and that it is about 1 mm inside the probe. If using metal needle the metal needle should stick out about 1-2 mm..

Also double check the tubing from the syringe to the probe.. It could be clogged.

Hope this helps.

[manoj_dharaskar]

Thanks for your reply

I have load the default tune and calibration. Before tuning the range of higher masses are in bet E to power 5 where as after tuning it optimizes the 195 but suppresses higher masses. When I go for calibration , it gives error low intensity during multiplier setting and stops.

The settings are Sheath 5- Aux 0, Sweep 0, Spray voltage 4.2 syringe pump flow 5 ul/min.
Using fused silica which is set 1mm inside probe.

Is there any steps to be carried out since I am starting with default factory tune and calibration file?

[leadazide]

The LTQ calmix is affected by the Tube lens voltage.. the higher the tube lens setting the more higher mass you get.. 110 V is a good compromise.

What I sometimes do is run a automatic tune on 524 and then manually set Tube lens to 110V. Running it on 195 and then setting tube lens to 110V is also an option..

This should give a 195 peak in the region of 1e6 in the IT and 524 apx. 20% of this. The ultramark peaks should start low and end low and top at 1422 or 1522 and they are usually around 30% to 50% of 195..

If the only problem is 524 is low you should consider your calmix solution.. 524 is MRFA and is the most unstable component in the Calmix. Try making a new solution or purchase the premade solution from Thermo/Pierce. P/N is 88322

Worst case contact your local Thermo service department and request assistence.. either physically onsite or maybe by remote. Many cases can be done via remote session.

[manoj_dharaskar]

Thanks. Ordering the new solution today

[manoj_dharaskar]

Thanks for your input. I am able to tune and calibrate as per your suggestion. I tune first 524 and all goes well with old standard.

[leadazide]

Good to hear that!