Converting IEX mobile phase to MS compatible

[LWagner]

I would like to analyze fractions from an anion exchange separation by Maldi MS, however the samples are salty.

Mobile phase: 10mM Phosphate, pH6.5 with a 1M NaCl elution gradient. I need to either de-salt or change the MP to an MS compatible.

I have run pH studies on my protein and the best separation is approx. pH6.5 with all peaks eluting at <0.2M NaCl.

I could probably switch to Ammonium bicarb (pKa 6.3), but what can I use in place of the NaCl to elute from the An-IEX column that is MS compatible?

[Uwe Neue]

It appears as this is an off-line application. In this case, you can run the chromatography any way you want, if you are willing to follow it up with a suitable SPE method.

Assume for example a hydrophobic SPE, followed by extraction with an organic solvent. However, one would need to understand your sample better to give you good advice on the best SPE procedure.

Or, since your sample is a protein, you could do a size-exclusion SPE procedure to free the sample from the high concentration of salt.

Other options may be possible as well.