Chromatography Forum

I have changed the source 3 times I just changed the horn everything looks great except the relative abundance of the 219 is less than 35% it used to run around 77% and now I hardly get 25%

This is on autotune mode
standard spectro autotune gets around 44%

any thoughts or ideas im willing to try anything

im using a .15 20m .15 film coulmn and tuning under 50psi head pressure

my foreline runs about 34torr with that setting

I also came across this pheonemon some time before. However, it didn't affect much on the analyses. Besides, there is no so-called acceptable % of 219 and 502 relative to 69 suggested in the 5973MSD hardware manual. Wondering if you have tried using this AUTOTUNE value on your routine analyses.
As you may know that vacuum (i.e. column flow rate) affects very much on the tune values. Did you record the conditions, say column flow rate, oven temp, ion source/quad temp., etc when tuning, vacuum pressure? Were they the same every time?
Also did you change the heat filament, the filament position in the ion source? Did you get the similar results?

All The Conditions are the same as when it was working

It almost seems like it is contribution to the 69 peak

it has had no affect on the chromotography

We have quality control criteria that we have to have >35 Rsd on 219

so im continuing to use the Standard spectra Autotune

Try target tune instead of standard spectra autotune. Set the target tune value for m/z 219 to 40. If it still doesn't work, gradually increase the target tune value.