Chromatography Forum

Greetings,
I'm having trouble getting a DFTPP tune to pass on my Agilent 5973 GC/MS. The trouble is ion 198 is less than 50% of ion 442 and the relative abundance of 442 is much greater than it normally is (~210% of 198). Normally my 198 is greater than 442. Also, most of my voltages under "Dynamically Ramped Parameters" are very low as well (between 6-8, rather than 12+) Could this be a source issue?


B

I guess I would try and clean the source. That's usually the first thing I do if everything was working and now it's not. I'm not sure about the "dynamically ramped parameters." I don't remember what they were set at when I used to run 8270. I'm not sure but I don't think they are used unless you perform like a ramped tuning (please correct me if I'm wrong). I think the DFTPP tune just goes through it's standard ramps cycle with different target ion abundances of PFTBA (adjusted for higher masses) than the standard AutoTune. If you try a standard AutoTune it might bring the 198 back above the 50% range as a temporary fix. Also, which filament are you using (1 or 2) and how old is it? If this is going bad or in position 2 it may result in a poor tune. I have been told by some Agilent reps that the filament 2 position is more of a marketing deal than to be intended for everyday use. Kind of like their new combo CI/EI source for the 5975C. Not intended for everyday use between CI and EI.

Let me know your progress. I would definitely start at cleaning the source though.

Ty

I prefer using a manual tune. I run an At then cut the ion focus so that the 198/442 ratio is about 52-3%. I then add about 200v to the EM in my method.

i cannot auto tune im getting this message---Tune stopped: Gain and offset=0 and peaks are too narrow

i cannot auto tune im getting this message---Tune stopped: Gain and offset=0 and peaks are too narrow

I think you will have to use BigBear's advice and do a manual tune. Enter manual tune and view the peak profile. Look at an older tune file (assuming you have some printed out) and enter in these values manually. If you still don't see a peak in the profile window or it still looks really bad then start manually adjusting the parameters until you start to see an adequate peak shape. There is also kind of a semi-auto tune function (I don't remember what it's called right now) that will run a range of values for a selected parameter for all three masses. you can then manually set the parameter at the value that best suits your needs. This may be the quickest way to get a good peak back on the screen to allow the Autotune to function properly.

ty

i have alot of noise on the autotube screen then it just stops and gives the message mentioned

Julio:

You may have so much ions in the chamber, probably a massive leak, (Check transferline conections), a dirty ion source or a very bad eletron multiplier...

Julio can you post the tune values on your last good tune, and then open the manual tune window and also post your current values?

I'm mainly interested in your EM volts and repeller voltage. Also the N2, O2, H2O % near the bottom of the print out. If they're any higher than like 2% you have a leak. If the repeller voltage is like 30 you need to clean your source. If the EM volts are 2200+ you need to order a new electron multiplier.

Try another tune such as stune to see if the tune file is corrupt ( happens quite often if you keep over righting) . If the s tune passes call the 800 number for instructions to re set your tune file.

An eazy way to check for a leak is to go into manual tune, turn off the calibration valve, set the system to scan 28 ( N2) and scan. If you have < 28000 cts you do not have a leak. The most common place for a leak is at the transfer line nut in the oven.

these are air and water check

Rep=30.1 Entl=18.07 Entr=14 focus=83 EMV=1741

Relative abundances:
18/69=180.41 water%
28/69=153.24 nitrogen%
32/69=1.12 Oxygen%
44/69=54.06 Carbon Dioxide%
28/69=85.04 Nitrogen/Water%

I think Bigbear might be right about the corrupt tune file. I've had this happen a number of times. Try restoring a previous tune. I think these are the directions to follow: "File" - "restore previous tune" then there should be a bunch of tune files starting with the type of tune (I think) Atune_ then the date and time I think. Or maybe some other order. I'm not in the lab right now so I don't remember all the specifics. This is easy to try to see if it's a bad tune file. Load one from a point in the past where you know you were acquiring good data. Then try to autotune.

Also, regarding the rest of the info Bigbear asked about; did you try to turn the calibration (PFTBA) valve OFF and look at mass 28? As he said before, this should rule out a leak if it's low. Based on your ratios you listed it looks like you just might have poor ion transmission due to a corrupt tune file (i.e., there are no significant abundances for any ion especially 69 m/z thus the weird and wacky ratios). Let us know any other info you can provide. If none of this works, be sure and post abundances for relevant peaks in the PFTBA tune as well as the N2 peak.

Julio:
After I saw you water/air checks, I think there´s no doubt, you have a massive leak. Check your conections and once you have solved it, see if the repeler have the same value, I think you also is going to need to cleam the ion source.

Good Luck

Just cleaned the ion source thats the numbers i got after cleaning

Did you turn on the Aux. heater after pumpdown? When you go into vent this zone is cooled. Heating and cooling cycles can cause the transfer line nut to loosen.

I've got a 5973 that will not stay tight. Gotta get a 10/32 die and chase the threads!