G. Neubauer et Rj. Anderegg, IDENTIFYING CHARGE STATES OF PEPTIDES IN LIQUID-CHROMATOGRAPHY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY, Analytical chemistry, 66(7), 1994, pp. 1056-1061
The addition of submillimolar levels of sodium acetate to the mobile p
hase during an LC/ESI-MS experiment encourages the formation of sodium
replacement ions in addition to the normally observed protonated spec
ies. The spacing of these sodiated species allows unambiguous determin
ation of the charge state of the ions and, hence, their actual mass. S
uch information is very useful when unknown or modified peptides are b
eing analyzed. At the levels reported here (250 muM), the sodium salt
seems to cause no deterioration in chromatographic performance and doe
s not unduly foul the mass spectrometer.