Enumeration of carbohydrate hydroxyl groups by silylation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

A method for enumerating hydroxyl groups in analytes is described and applied to various carbohydrates. The analytes were derivatized in solution by using trimethylsilylimidazole (TMSI) and the products were analyzed without chromatography by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The mass spectra revealed consecutive product ion peaks that are separated by 72 m/z units. This 72 m/z unit separation is a result of displacement of a hydroxyl hydrogen atom by a trimethylsilyl group. The number of the observed ions was used to confirm the number of hydroxyl groups in each analyte. This method was utilized in the analysis of single and multi-component analytes.