Chromatography Forum

I have cleaned source with aluminum oxide, ultersonic rinsed with DI, methanol, and hexane twice each. Replaced two new filaments. The vacuum is 5e-5 torr. Air and water check ok. The atune failed since it can't not obtain constant peak width. Recalibrate the #3widths, the atune is finally finished. But tuen evaluation saying position of isotope mass 503 is too low(479.61), ratio of 503 to 502 is high, and ratio of 219 to 69 is low (24.98). Also the 503 peak is wide and split at top. I also notice that EM Volts is high (2282) with a new cleaned source. Please advise.
Thank you,

dzhang1 wrote:
I have cleaned source with aluminum oxide, ultersonic rinsed with DI, methanol, and hexane twice each. Replaced two new filaments. The vacuum is 5e-5 torr. Air and water check ok. The atune failed since it can't not obtain constant peak width. Recalibrate the #3widths, the atune is finally finished. But tuen evaluation saying position of isotope mass 503 is too low(479.61), ratio of 503 to 502 is high, and ratio of 219 to 69 is low (24.98). Also the 503 peak is wide and split at top. I also notice that EM Volts is high (2282) with a new cleaned source. Please advise.
Thank you,

What happens is that your Electromultiplier is very close to reaching its limit. However, do the essay with Stune.u.

Do it and I await your response

If you use Manual tune and ramp the Repeller, the Ion Focus, and the Entrance Lens, do you get approximately Gaussian shaped curves or do you get noise on any of them?

If noise then it is possible the wires could be connected wrong, especially the blue and orange for the Entrance lens and the Ion focus.

Another thing to check is if the Repeller is grounding to the source body because either the ceramic insulator is cracked or is dirty.

The main problem I see that concerns me is that the 502/503 mass is apparently at 479m/z, or is that the abundance counts of 503?

Are your peak widths in the 0.50-0.70 range?

The electron multiplier is on the way.

The insulator for repeller is a newly replaced. The wire connections are correct. B is in back and y is in front. The peak widths are 0.48-0.65 and/or 0.5-0.7. 503 peak is ugly and wide, and also splitting on top. Haven't done the ramp yet. Waiting on the EM arriving. Thank you,

The 503 isotope peak has the smallest abundance so it is often not a nice clean peak. As long as it is separated from 502 that is the most important.

A normal tune for the 5973 would have 69 mass at 300,000 - 800,000 abundance depending on the sensitivity needed. Higher than that and you will normally encounter problems with low linear range on the analytes of interest. 219 can be anywhere from 35% to 100% of 69, again depending on what tune pattern you need to have, for EPA 8260/624 you need it in the 35-50% range to pass BFB tune check, it can be higher for 8270/625 to pass DFTPP tune check, if not using a regulated method tune to the max sensitivity of the mass range you are interested in.

If isotopic masses are too high, then you need wider peak widths, if they are too low then narrower peak widths. All the peaks should be within 0.2 of each other. Normally doing the "Peak width linearity" will bring them all in line automatically.

I have found over the years that too high pressure in the analyzer will reduce the higher mass abundances, but strangely if too much water is present there is a higher abundance of high mass peaks.

dzhang1 wrote:
The insulator for repeller is a newly replaced. The wire connections are correct. B is in back and y is in front. The peak widths are 0.48-0.65 and/or 0.5-0.7. 503 peak is ugly and wide, and also splitting on top. Haven't done the ramp yet. Waiting on the EM arriving. Thank you,

Tune in to Stune.u, Depending on the answer with that file I can tell you what to do. But Make it

Try restoring atune.u. the software file can go corrupt over time. There are backups of the file in a different Chemstation directory.