Evaluation of Counterions for Electrospray Ionization Mass Spectral Analysis of A Highly Sulfated Carbohydrate, Sucrose Octasulfate

A systematic approach was used to evaluate the electrospray ionization mass spectral (ESI-MS) analysis of sucrose octasulfate (SOS), an important pharmaceutical agent. SOS represents a model for other sulfated carbohydrates, such as heparin and glycosaminoglycan-derived oligosaccharides that also are highly sulfated and pose difficult analytical problems. A survey of ammonium counterions showed that 1(degree), 2(degree), and 3(degree) ammonium salts of SOS gave substantial fragmentation as a result of sulfate loss. In contrast, quaternary ammonium and phosphonium salts gave excellent ESI spectra, particularly in the positive ion mode. This represents the first report of the ESI-MS analysis of sulfated carbohydrates in the positive ion mode.