Negative electrospray ionization mass spectrometry analysis of gangliosides, sulphatides and cholesterol 3‐sulphate

Negative electrospray ionization mass spectrometry (NESI‐MS) of a series of native gangliosides containing one, two or three sialic acid groups, sulphatide‐I and cholesterol 3‐sulphate was undertaken, using a magnetic sector instrument. The results show that NESI‐MS of gangliosides leads to the formation of multiple‐charged molecular ions of the type [M H] − , [M 2H] 2− and [M 3H] 3− . The number of charges appears to be correlated to the number of sialic acid groups present. NESI‐MS of sulphatide‐I predominantly gave ions of type [M H] − whilst cholesterol 3‐sulphate gave a more complex ionization pattern. The sensitivity of the NESI‐MS system was enhanced by using water+methanol, 9:1 (v/v) as solvent, containing 300 pmol/μL of NH 4 HCO 3 . The application of NESI‐MS to these compounds is discussed.