Simultaneous determination of 49 amino acids, B vitamins, flavonoids, and phenolic acids in commonly consumed vegetables by ultra-performance liquid chromatography-tandem mass spectrometry.

A sensitive and reliable method was developed and validated for the simultaneous determination of 49 amino acids, B vitamins, flavonoids, and phenolic acids based on a rapid metabolomic extraction procedure combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in a single chromatographic run and applied in analysis of 26 commonly consumed vegetables. The chromatographic and sample preparation conditions were optimized, given the high diversity of the target analytes. Eight isotope-labeled standards were applied to validate the method in terms of recovery, linearity, matrix effects, precision, and sensitivity. Most recoveries in four vegetable matrices ranged from 65.0% to 105.3% with associated RSDs < 20%. Low LOQs ranged from 0.06 to 17 µg/kg. Linear calibration curves with different ranges were established with R > 0.993. Among the 26 vegetables, purple cabbage, broccoli, and red lettuce were found to contain the highest concentrations of free amino acids, B vitamins, and phenolic compounds.