Hi,

Are you using positive, or negative, ion mode?

The 75 Da does that include a charge-bearing group, or is that on top of the charge (e.g. proton)?

And how accurate is your mass measurement? Is it really 75.00 Da, or not?

Dear Prof. D. Eef,

Thank you.

My compounds mass is 1080

I am geting around 1155.

I am doing MALDI-TOF (positive mode)

My molecules is organic salts.

As counter ion there is iodide.

Actually I am doing multistep reaction.

Last two step products Mass also found M+75 in maldi.

I will be really happy if you suggest me anything.

Thank you for your time.

Can you eliminate the DMF from the reaction medium or change the reagent for once to confirm if this is derived from the DMF complex formation? It is very likely an adduct formed by DMF additive...You indicated the step-by-step evaluation you followed. After which synthesis reaction step (meaning which new additives are in the reaction pot) may induce this adduct?

By the way, what is your sample matrix ? Do you use sodium or potassium and organic acid matrix additives to induce ionization but also suppress non-specific adduct variants...?

Lastly, for your target do you observe protonated or other main adducts simultaneously with +75 or only M+75 is the pseudomolecular parent ion?

Dear Prof. A. E. Islmail,

Thank you for your reply. I am using cyano 4 hydroxycinnamic acid as matrix.

I am only getting M+75 peak.

Thank you