Chromatography Forum

Hello All,
I have a method for phosphonates using an ion pairing agent (TEA or NNDHA) C18 column that is proven on a CAD. I need to adapt the method for use on a single quad MS.

My analyte masses are 204.5, 268.9 and 296.85 with NNDHA having a mass of 129.25.

Am I correct in thinking that I just need to program SIMS to look for the combined masses of the analytes and the ion pairing agent? (Plus a window to see to what degree these ionize.)

Is a better approach to start with a broad SIM and start to reduce the window to fine tune down to just the analytes of interest?

I'm using Xcaliber on a Thermo MSQ. Will the ion pairing likely survive electrospray ionization and a probe temp of 300C?

What about intentionally trying to break up the ion pair and just look for the raw analyte? Should higher needle kVs or higher temps do this?

As you can tell, I'm fairly new to MS.
Any guidance is greatly appreciated.
Thanks

if you have ion X+ you could have adducts of many such as X+.Na, X+.K, X+.(NaOAc)n, X+.ACN, X+.H2O, (X+)2(-H), (-H=one proton less).

Under different conditions one or a few of the adducts will dominate in the Mass spectrum.

Hope this helps.
YM

Thanks for the reply. I am seeing some unexpected adducts as you suggested-but nothing that is as large as the phosphonate paired with the NNDHA.

Someone suggested that a hotter probe temperature would be the best option for liberating the phosphonate for detection. Do you agree?

I'm seen only slight success with that and don't want to go too far down the wrong path if I can avoid it.

The question is why you need to get rid of the adducts.

Having said so, you can try to change nebulizer /sheath/Aux gas flow and temp to minimize or change mobile phase or sample preparation.

By the way, people here appreciate sharing. You can share your conditions, data, results, improvements and We can ours so that mutual benefits are achieved even though you have to agree the asking party will benefit much more than the asked one.

Good Luck
YM

Can you monitor in SIM mode and scan mode simultaneously? Then add all the adducts you can think of to the SIM chart. Then optimize spray chamber parameters to maximize production of your desired ion(s)?

Just a thought..