MALDI-TOF MS analysis of food flavonol glycosides

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometr y (MALDI-TOF MS) is a new technique that is having a great impact on food a nalysis. This study is the first to demonstrate the use of MALDI-TOF MS to identify flavonol glycosides in food samples. 2',4',6'-Trihydroxyacetopheno ne was chosen as the best matrix because it worked for crude sample extract s and ionized flavonol glycosides in both positive and negative MALDI-TOF M S modes. In the positive mode, multiple ion forms were observed for flavono l glycosides, including [M + H](+), [M + Na](+), [M + K](+), and [M - H + N a + K](+), with further fragmentation through loss of glycosidic residues. The negative mode for all flavonol glycosides resulted in [M - H](-) ion fo rmation without detectable fragmentation. The multiple ions in the positive mode gave more information on individual flavonol glycoside structures tha n the negative mode. Flavonol glycosides showed similar intensities or resp onses in the positive mode, while kaempferol glycosides exhibited much less response than quercetin glycosides in negative mode.