Oligosaccharide profiling: the facile detection of mono-, di- and oligosaccharides by electrospray orthogonal time-of-flight mass spectrometry using 3-aminophenylboronic acid derivatization

Monosaccharides, disaccharides and larger carbohydrates can be derivatized using 3-aminophenylboronic acid (3-APBA). This procedure is carried out at low pH (2.7-3.0) and allows the use of positive ion mode electrospray orthogonal time-of-flight mass spectrometry (ES-OTOFMS) to analyze the resulting boronate complexes. A carbohydrate profile map of a complex carbohydrate mixture, honey, was prepared which displayed superior sensitivity when compared with lithium ion cationization. Complexes formed using simple mono- and disaccharides show that facile in situ derivatization leads to an equilibrium mixture; which is reproducible for a specific set of electrospray conditions. D-Glucose could be detected at 5 microM concentration using the standard instrument spray interface. Lower detection levels of approximately 500 nM could be achieved using a nanospray device. The 3-APBA complexes are observed on instruments employing a low temperature interface (140-150 degrees C) which allows formation of the boronate species while still promoting efficient desolvation of the ions. The spectral identification of 3-APBA complexed carbohydrates in complex mixtures is facilitated by the easily observed 1 mass unit separated peak pair bearing the 1:4 ratio resulting from the natural isotopic abundance of (10)B and (11)B.