Labeling of oligosaccharides and N-linked glycans by a rhodamine-based fluorescent tag for analysis by capillary electrophoresis with laser-induced fluorescence and mass spectrometry detection.

In this work, we present the synthesis and application of fluorescent rhodamine B hydrazide for the derivatization of simple oligosaccharides and complex glycans using a hydrazone formation chemistry approach. The labeling conditions and the experimental setup of CE/LIF were optimized by analyzing oligosaccharide standards. The CE/LIF separations were performed in polybrene-coated capillaries eliminating the need for the purification step after derivatization. The addition of methanol to the background electrolyte significantly increased the LIF detection sensitivity reaching the limits of detection in the attomole range. The resolution of carbohydrate samples was improved by using long (98 cm) capillaries and polymer additives (polybrene). The developed method was applied for CE/LIF and CE-MS analysis of N-linked glycans released from bovine ribonuclease B and the therapeutic monoclonal antibody of trastuzumab.