Sodium is one of the most abundant contaminants in all commercially available solvents and most substance in the market contains 0,1 ppm (even HPLC grade solvents) of sodium ions or much more.

Sodium occurs in many places. The glassware used for solvent containers contains sodium that leaches out into solvent. Also many procedures use sodium. Reductions (sodium borohydride, sodium cyanoborohydride, etc). If you sale-out during an extraction, that adds more sodium. As Angel mentioned, you can control this through some extent by adjusting some of your ESI voltages, potentially at the loss of your parent ion.

Thanking you for better explanation...

The formation of sodium adduct can be reduced by adding organic acids such as formic acid, acetic acid, which would enhance 'protonation' and hence it is possible to observe intense signals due to protonated adduct ions in the mass spectrum. Ammonium acetate and ammonium formate also helps in enhancing the intensity of the signals of protonated adduct ions.

Sodium adduct are from the used glass during the sample preparation. On the other hand, from the used plastic, there is always contamination by ester phtalates.

Going along with the answer given by Trevor Alan Walmsley, I am herewith attaching one of my publications from the journal Rapid Commun. Mass Spectrom. (2006), wherein we utilized sodium adducts of neutral peptides for MS/MS experiments to understand their dissociation behaviour. In this investigation, it was noted that the fragmentation pattern of protonated adduct precursor ion drastically differed from the fragmentation pattern of sodium adduct precursor ion of these neutral peptides with modified N- and C- termini. Hope, this is interesting to you.

Hai Dr. Varatharajan Sabareesh and other respected researcher

Is there any possibility of sodium adduct, being attached more than one in a compound? for example compound such as glycerol trioleate or any other compound that have three same functional group in the compound.