Chromatography Forum

Can any one check if this tune report is ok.
We got some problems with sensitivity on our 5973 gcms

http://i54.tinypic.com/1r6a0h.jpg

tune report is ok for default values
however to maximize sensitivity you would probably need to tune manually ramping the repeller (above default 19.9V), emission current, electron energy, entrance lens and EM voltage
I usually tune my MSDs to have abundance of m/z 502 about 100,000

Tune looks like a "mid-mass" tune so you are optimized for the best response at the m/z 219 range. Usually if you are doing open characterization you would want a standard tune so that your mass spectral libraries could provide good matches. The m/z 502 is good (>> 1%) and the repeller is optimized below it's max value of 35.

You have no indication of air (m/z 28 and 32) so no major leaks and the autotune yields a multiplier voltage of 1200 volts (= good detector and effiecient ion production from the source).

The question now is...what sensitivity do you consider good? Because from the tune everything seems OK. If you ran a known amount of your substance, what on-column amount can the instrument detect? What mode of operation (S.I.M. or full scan mode)?

Roughly your instrument should be able to see 10 to 50 pg of a PAH, no matter how that substance is injected (split or splittless) but if you see it then that's just about all you are going to get for sensitivity. The tune doesn't really indicate sensitivity. Run your standard and let me know how much the instrument can detect with a 3:1 signal to noise. Timothy

I think the tune is OK. The sensitivity is influenced by GC parts as well. Inlet, column, flowrate etc... all can affect the sensitivity.