High-performance liquid chromatography/continuous-flow liquid secondary ion mass spectrometry of flavonoid glycosides in leguminous plant extracts.

A method for the identification of flavonoid glycosides utilizing continuous-flow liquid secondary ion mass spectrometry (CF-LSIMS) is presented. Minimum detectable quantities (MDQs) were determined for three model flavonoid glycosides (rutin, naringin and esculin) by both positive ion direct insertion probe (DIP)-LSIMS (1.6 nmol, 1.7 nmol and 730 pmol, respectively) and positive ion CF-LSIMS (330 pmol, 340 pmol and 290 pmol, respectively). Optimization of CF-LSIMS instrumental parameters was performed using the model compound rutin. Parameters optimized included mobile phase composition, glycerol concentration, mobile phase flow rate, ion source temperature, acceleration lens potential (amplitude and polarity) and Cs+ primary ion energy. Final instrumental optimization yielded an MDQ of 1.0 ng (1.6 pmol) for rutin by flow-injection CF-LSIMS. The optimization parameters were utilized in the identification of flavonoid glucosides in alfalfa (Medicago sativa L) and chickpea (Cicer arietinum) extracts by high-performance liquid chromatogrphy/CF-LSIMS. The results support the controversial identification of a major extract component as formononetin-7-O-glucoside-6"-malonate as opposed to afrormosin-7-O-glucoside-6"-malonate.