Abstract
The combination of harmine and ammonium chloride is a useful matrix in detecting the chloride ion adducts of neutral oligosaccharides in negative-ion MALDI-TOF mass spectra. Sandwich method is the best way to prepare the mixed crystals of matrix, analyte, and additive on the target. Changing the molar ratio of ammonium chloride additive from 0 to five times the amount of harmine matrix, the relative intensity of the chloride ion adducts of the analyte molecules to the deprotonated matrix molecular ion ( [Analyte+Cl]-/ [Matrix-H]-) increases logarithmically. A ratio of several times the amount of additive to matrix works most effectively in the formation and detection of the chloride ion adducts of the neutral oligosaccharides as opposed to an amount of additive that is on the same order as the analytes.
