Quantitative analysis with MS without chromatography

[Fabiano]

I know someone that use a Agilent 1100 MSD (VL) ESI and claim that Atual MSD don't need any LC separation before insertion even for quantitative analysis.

Someone know what kind of problems can appear besides ion suppresion in complex injections (infusion) without any chromatography?

What would be the pros and cons?

[Kostas Petritis]

One thing is for sure, the Agilent MS will have the same set of problems as any other companies ion traps. Maybe he things that the ion population control (somekind of automatic gain control but not exactly as this is Thermo's patent) of the Agilent ion trap will solve his problems, however it does not solve the ion suppression problems.

An additional problem on the top of ion suppression is sensitivity. If your compound is in the presence of something much more abundant, you'll probably won't see it, as the trap will almost immediatly reach the maximum ion population.

Example, your ion is in 1:10^6 in comparison with the sum of other compounds in the mixture. If 10^6 is the maximum population of your trap (and the VL is the entry level of Agilent's ion traps, so not that sensitive) then you'll have only 1 ion from your molecule for each scan. Good luck detecting it, not even mentioning to fragment it...

[Fabiano]

Thank you Kostas, I'm far from be an expert in Ion-Traps ....

I imagined that was possible to isolate the target ion in trap in the same time that you swept everything out with heliun (accumulation).... so the maximun ion population was from your target ion only....


Thank you again

[Kostas Petritis]

You can isolate your ion but still in my example would be 1 out of 10^6...

And as ion-traps have not a quadropole before to do the ion filtering, you need the ion filtering in the trap. The addition of a quadrupole before your trap (for filtering) would slow your cycle time dramatically...