*Article* **Determination of Flavonoid Glycosides by UPLC-MS to Authenticate Commercial Lemonade**

**Ying Xue 1,2,3,**†**, Lin-Sen Qing 2,**†**, Li Yong 3, Xian-Shun Xu 3, Bin Hu 3, Ming-Qing Tang 1,2 and Jing Xie 1,\***


Academic Editors: Marcello Locatelli, Angela Tartaglia, Dora Melucci, Abuzar Kabir, Halil Ibrahim Ulusoy and Victoria Samanidou

Received: 31 July 2019; Accepted: 16 August 2019; Published: 20 August 2019

**Abstract:** So far, there is no report on the quality evaluation of lemonade available in the market. In this study, a sample preparation method was developed for the determination of flavonoid glycosides by ultra-performance liquid chromatography–mass spectrometry (UPLC-MS) based on vortex-assisted dispersive liquid-liquid microextraction. First, potential flavonoids in lemonade were scanned and identified by ultra-performance liquid chromatography–time of flight mass spectrometry (UPLC-TOF/MS). Five flavonoid glycosides were identified as eriocitrin, narirutin, hesperidin, rutin, and diosmin according to the molecular formula provided by TOF/MS and subsequent confirmation of the authentic standard. Then, an ultra-performance liquid chromatography–triple quadrupole mass spectrometry (UPLC-QqQ/MS) method was developed to determine these five flavonoid glycosides in lemonade. The results showed that the content of rutin in some lemonade was unreasonably high. We suspected that many illegal manufacturers achieved the goal of low-cost counterfeiting lemonade by adding rutin. This suggested that it was necessary for relevant departments of the state to make stricter regulations on the quality standards of lemonade beverages.

**Keywords:** vortex-assisted dispersive liquid-liquid microextraction; flavonoid glycoside; UPLC-MS; counterfeiting lemonade
