Determination of sialic acids by liquid chromatography-mass spectrometry

Sialic acids are widely found in nature as components of oligosaccharide un its in mucins, glycoproteins and other microbial polymers. Existing methods for determining these acids are long, tedious, and not specific. A simple, rapid, and sensitive method for determining the most commonly occurring ac ids, N-acetylneuraminic and N-glycolylneuraminic acid. using LC-MS is descr ibed. Standard solutions of the sialic acids with the internal standard, N- acetylneuraminic acid methyl ester, were quantitatively analyzed by positiv e ion electrospray ionization. Fetuin was used as a model glycoprotein and the hydrolysate was injected directly onto an ES Industries AquaSep 3 mum 1 50x4.6 mm column eluted with a 0.1% aqueous formic acid mobile phase at a h ow-rate of 0.5 ml/min. Detection was achieved using the Finnigan Navigator MS system in the selected ion monitoring mode for the protonated molecular ions at m/z 310, 324, and 326. The linearity over the dynamic range 10 to 1 000 ng of sialic acids on-column had a correlation coefficient greater than 0.999. The amount of sialic acids found in the fetuin hydrolysate was in a greement with values reported in the literature. (C) 2001 Elsevier Science B.V. All rights reserved.