Chromatography Forum

What specs should water used in the mobile phase for an UPLC/MS/MS (QTOF) system have? I need to make sure we have teh right water system!

Thanks,
- Karen

Hi Karen,
We use HPLC grade water. I dont have any problem till now. Will warn you immediatly if we have some problem. Till then, go ahead with HPLC water.

Milli Q water is best

Milli Q works fine on our LC-MS/MS system (Shimadzu UFLC - 3200QTrap ABSciex)

Thanks all...

Milli-Q unfortunately is not an option.

We have a DI system (not an RODI system) that produces type II water and was wondering if i could get a not too expensive polisher that I could feed from that that which would give water good enough for LC/MS work.

Most polishers that produce ultrapure water want an RODI feed, so I wanted to know what specs were 'good enough' to figure out what I can get.

- Karen

Hi Karen,

HPLC grade water is fine ~ to be sure, run a blank or controlled samples prepared by the water quality that you have and check for yourself the background etc whether it's acceptable or not.

Usually, HPLC grade may not be as 'particles free' as UPW, so you may need to filter it ~

In anyway, I am with Juan ~ HPLC grade may be sufficient for you ~ just try it ^^

All the best ~

I have tested several vendors two times (2004 and 2008). I have never observed differences between HPLC-grade or LC/MS-grade solvents for my applications. During the installation of a Synapt G2 we have compared the solvents used for installation (ULC/MS-grade) with our usual HPLC-grade. Background ions with the ULC/MS solvent were clearly reduced. We have seen this with a Synapt G2 and an Orbitrap.

Ask the MS service engineer what brand is used for installing the instrument and try to get a testing sample for free from the vendor. After one short test-run of a known sample you will see, if the solvent makes a difference for your application and your instrument.

Be careful when using a DI water system. We had issues with the particulates from the DI canisters contaminating our LC/MS systems. We installed a Milli Q with our RO system feeding it and have had no issues since. If you don't use much water, then just go with the HPLC grade water as others have suggested.

I agree with Klaus. Using a QTOF you will have much more sensitivity in scan mode compared to triple quads. As a consequence you may detect more contaminants from the mobile phase. We have had a UHPLC-QTOFMS for a while and we have also tested milliQ water and several different LC-MS grade brands. FYI ULC-MS water from Biosolve gave the smallest background noise and if I remember well was the cheapest (at least in my country). If you use additives such as formic acid ou ammonium formate, take care to buy LC-MS grade additives as well.

Which QTOF do you have? It seems that the most recent or future QTOFs will be much more sensitive than the previous generation. This may become a problem in terms of background noise.