PS: I have already tried MeOH and acetonitrile, but both failed.

DMSO and DMF should not be used due to their high viscosity and interaction with the tubing of the Mass Spec at times a default methanol/ water 50:50 mixture is used and addition of acetic acid 0.1% at times helps in protonation

just try that mixture of water methanol and see what happens

Once I used AcOEt (Ethyl acetate) try it.

People in the ThoMSon Lab in the Chemistry Institute should be able to help you out. But I would also try to dissolve with minimum DMSO and them diluting with acetonitrile or methanol.

use Xylene or Toluene

I´ve tried the preparation of the stock solution in DMSO (use DMSO as little as possible) then further diluted in a mixed solvent like DMSO-MeOH, DMSO-ACN, DCM-MeOH, DCM-ACN, Chloroform-MeOH, or Chloroform-ACN, at v/v of 1:2, 1:3, etc., for ESI. As to the cleaning afterwards, I used to use ringe the ESI sample line and ion source first DMSO-MeOH/ACN, or DCM-MeOH/ACN, then MeOH/ACN, in the end MeOH/ACN-H2O, to get a decent background back.

Recommended organic solvents are methanol and acetonitrile. Nonpolar,nonprotic solvents do not make good ESI experiments. USe HPLC grade (or better) solvents. I do not have experience with DMSO solvent.

Thank you all for the responses, guys. I have worked it out by using MALDI-ITMS, very simple and straightforward sample preparation. I shall try using AcOEt next time, though, just to see if I can get anything on ESI.

Thanks!

Great solvent suggestions, also keep in mind that changing solvents can require significant "re-tuning" of the ESI optimal conditions (temp, volt, etc...) so it is important to be patient and search the "parameter space".

desove in DMSO and then dilute use acetonitrile

For LC-MS, DMSO causes very high back ground signal in both ESI and APCI. Then U are destroying your sensitive detector. Memory effect of DMSO is also found. If your sample can dissolve in DMSO, quite sure that it would dissolve in MeOH or ACN system or sometimes may require some added buffer.

Also learned by the question and answers. Based on my experience, better never use DMSO directly in the MS system.

As far as I know, not common to apply DMSO in a LC coupling with (ESI-) MS system. But it is not uncommon in studies of organometallics (metal complex or coordination compounds) in molecular materials field to use DMSO for identification and structural characterisation by ESI-MS, because there are many of these type of compounds are only dissolved in DMSO (I also came cross compounds dissolved in DMSO-MeOH system but not pure DMSO). The background problem and/or ionisation suppression issue can not be avoided, but the point is to try to work with DMOS as little as possible---definitely not 100% DMSO, in the solvent system mixed with ESI -friendly solvents, like some MeOH, or ACN to try to get some information. It´s case-specific, the instrument also need to be tuned to case by case. The cleaning of sampling line and ion source from time to time (as much as possible) is also crucial during playing around with these solvents and compounds. Good luck then!

DMSO causes some other problems aswell - PEEK connections might swell up and get clogged.

If your compound is almost insoluble in solvent systems suitable for ESI, I would think of testing APCI.

Mixing up different solvents like DCM & toluene might help quite a lot. And APCI has the wonders of his own, just like any other ionization method.

Try mixture of acetonitrile and isopropanol with any C18 column and APCI probe.

You can use ACN:MeOH mixture but can LC-MS grade. Try

:)

You can try to use ACN, MeOH, chloroform and dichloromethane

you can soluble your sample in 10 micro lt of TFA and then makeup it with meoh or acn.

ACN and methanol can definitely replace DMSO

Hi Diogo, we are analyzing the last 20 years samples by LC/MS which contain DMSO and we have no further problems. DMSO forms under ESI conditions a dimer. This dimer can be easily destroyed by increasing the cone voltage of your ESI source. If you start with a scan range e.g. from 120-2000 than the charged 'DMSO-monomer' is outside of your scan range and will not be detected.

Are you dealing with a pure compound or a crude mixture? You may dissolve your sample in pretty small volume of DMSO and mix it with MeOH or Water or Acetonitrile and use a direct infusion ESI-MS if it is a pure compound.

Dissolve your sample in DMSO to about 1mg/mL and then dilute to 1 or 2% in DCM/MeOH (50%). I do this regularly and it works fine. Samples do not need to be water soluble for ESI it's a big misconception - water can even prevent some samples from ionising.