A modified QuEChERS method as sample treatment before the determination of isoflavones in foods by ultra-performance liquid chromatography–triple quadrupole mass spectrometry

This paper reports the development of an analytical method for the determination of isoflavones in legumes using LC–MS/MS. A modified approach of the QuEChERS methodology was used to extract the analytes from the food samples. The proposed method includes a two-step extraction process and allows the determination of isoflavones in pulses without the need of a clean-up step. Use of this methodology for the extraction of natural occurring substances provides advantages such as simplicity and ease of use, especially taking into account the complexity of food matrices. The method was applied successfully for the determination of eight isoflavones, including aglycones and glucosides, in legumes of Spanish origin (chickpeas, lentils and beans from the region of Castilla y León). The target compounds were the glucosides daidzin, glycitin and genistin, and the aglycones daidzein, glycitein, genistein, formononetin, and biochanin A. The detection limits were in the 0.7 μg L−1 to 1.5 μg L−1 range for formononetin and glycitin respectively. Recoveries ranged from 72% to 119%, and standard deviations lower than 25% were obtained for the inter-day precision. The method described is precise, selective and not time-consuming.