SPE-UHPLC-DAD Method for the Simultaneous Determination of Three Flavonoids in Grape Juice by Using Bis(tetraoxacalix[2]arene[2]triazine)-Modified Silica as Sorbent

In this study, bis(tetraoxacalix[2]arene[2]triazine) modified silica gel was successfully prepared and used as an efficient sorbent for solid-phase extraction. Coupled with ultra-high pressure liquid chromatography (UHPLC), the extraction performance of the sorbent was evaluated by using three flavonoids as model analytes. Main parameters, which affecting extraction efficiency were carefully optimized. The results showed that multiple intermolecular interactions were involved in the sample pretreatment procedure, including π–π, hydrophobic and hydrogen bonding interactions. Under the optimal conditions, the proposed method was applied for the analysis of three flavonoids in grape juice. Satisfactory linear ranges for flavonoids were obtained in the range of 5–200 ng mL −1 for quercetin, 1–200 ng mL −1 for luteolin, and 2–200 ng mL −1 for kaempferol, with good correlation coefficients (>0.9996). Limits of detection (LODs) were in the range of 0.5–2 ng mL −1 , and the LOQs were between 1 and 5 ng mL −1 . The recovery values of spiked grape juice ranged from 97 to 106% with relative standard deviations (RSDs) less than 4.7% ( n  = 3). This method exhibited the advantages of simplicity, rapidity, and low solvent consumption, and was promising for the separation and determination of flavonoids in grape juice and other matrixes.