What can I do for Na aducct in LC-MS detection?

[karamiosboo]

In my extraction method I use sodium sulfate and sodium acetate, It make problems for mass detection, what I have to do?I use ammunium formate in eluent.

[orcicdejan]

Do you use Na2SO4/AcONa in extraction solvent (i.e. does it remain in the phase that you inject)? If so, due to a huge amount of Na+ ("huge" in MS sense, that is), I sincerely doubt you can do anything. Only to shift to some non-alkaline metal based additive. Using ammonium salts as additives may favor the formation of [M+NH4]+ adducts, but at least they fragment well.

If you are extracting the analyte *from* the sample with Na2SO4/AcONa as an additive, and some minute amounts of Na+ transfer to the extract, you may try desalting the extract afterwards (SPE, L/L extraction etc.). If working in positive mode, adding some acid (e.g. formic) might favor the formation of [M+H]+.

[karamiosboo]

Dear Dr orcic,
Yes I use Na2SO4/AcONa. I change salts to MgSO4 and I find the peaks, Tank you.
You wrote ' If working in positive mode, adding some acid (e.g. formic) might favor the formation of [M+H]+' you means at which step formic acid adding will help me?

[orcicdejan]

Apologies for being imprecise... you add HCOOH to your mobile phase. The optimal concentration should be determined by experiment, since pH influences both sensitivity (by favoring protonated/deprotonated species) and chromatography (if your compounds are weak acids/bases).

[karamiosboo]

Dr orcic, Tank you for information.