Chromatography Forum

This is a 100ppb standard that was run quite a while ago. It's my understanding from others in the industry that this should show me SOMEthing, at least.

Hello

In my opinion baseline level in SIM is very high... (you have just about 60 ions). I would check gas purity and column condition.

Regards

Tomasz Kubowicz

Hi Erika

The peaks between 18 and 26 minutes look as if they are concentration overloaded (front tailing) but the later peaks are sharp. The broadening from overloading should (obviously) not be a problem at lower concentrations, but there is clearly a difference in peak size between the early and late peaks, and that might point to inlet discrimination, which will make it more difficult to detect low levels of compounds that elute late.

Peak distortion can also be due to solvent effects - what solvent are you using and what is your injection volume ?

The 100 ppb standards have seriously noisy baselines that may be due to ghost peaks or general crud bleeding out of a dirty inlet. When last did you do inlet maintentance, and what kind of liner are you using ?

The column might also be deteriorated, what is its history ?

Peter

I am concerned looking at the autotune report. You have 2000+ on the Electron Multiplier Voltage but only 225K counts for m/z69. Those counts may be adequate but at that voltage you will be losing linear range. A new K&M multiplier should give you those counts at about 1100V, an ETP multiplier would give them at <1000V when new. Not sure how low the Triple Axis ones will tune when new in the 7500, but the one in my 7000MSMS is giving 10,000,000 counts for m/z 69 at 1100V. Some of the problem could come from increased noise from the high EMV setting.