Electrospray ionization in-source decay of N-glycans and the effects on N-glycan structural identification.

Large N-glycans are dissociated into small N-glycans in ESI in-source decay that may result in the interference of the structural identification of small N-glycans. Separation of large N-glycans from small N-glycans, for example, using HPLC, prior to ESI ionization is necessary to eliminate the interference. This is particularly important when N-glycans consist of sialic acid or large N-glycans have much higher concentration than that of small N-glycans in ESI solution.