In the present study, an online liquid extraction coupled with high-performance liquid chromatography-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (HPLC-ABTS) system for rapid screening of antioxidants in tea samples was proposed. As an example, the tea samples were firstly extracted by online HPLC extractor with mobile phase at 70°C, then the hyphenated HPLC-ABTS was used for the chromatographic separation on a Poroshell EC C18 column by 0.3% aqueous formic acid and acetonitrile with a gradient elution at 1.5 mL·min⁻¹, and the UV and antioxidant chromatograms with detection wavelengths at 270 nm and 750 nm were recorded, respectively. The established system integrated the processes of online HPLC sample extraction, HPLC separation and online antioxidants detection, the total analysis time of which was <20 min. The developed method was successfully applied to samples of green tea, oolong tea and black tea. As a result, 11 antioxidants were found in tea samples, including gallocatechin, epigallocatechin, catechin, chlorogenic acid, epicatechin, epigallocatechingallate, epicatechingallate, rutin, 1,4,6-trigalloylglucose, quercetin-3-glycoside and kaempferol-3-glucoside. The combined online liquid microextraction and online HPLC-ABTS method is a rapid and green approach for the quality evaluation of tea.

中文翻译：

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在线液体微萃取结合HPLC-ABTS快速筛选天然抗氧化剂：三种不同茶的案例研究。

在本研究中，在线液体萃取结合高效液相色谱法-2,2'-叠氮基双（3-乙基苯并噻唑啉-6-磺酸）（HPLC-ABTS）系统用于快速筛选茶样品中的抗氧化剂。建议。例如，首先通过在线HPLC萃取器在70°C下用流动相萃取茶叶样品，然后将联用的HPLC-ABTS在Poroshell EC C18柱上进行色谱分离，用0.3％的甲酸水溶液和乙腈进行色谱分离。 1.5 mL·min ^-1的梯度洗脱分别记录了检测波长为270 nm和750 nm的UV和抗氧化剂色谱图。建立的系统集成了在线HPLC样品提取，HPLC分离和在线抗氧化剂检测过程，总分析时间小于20分钟。该方法成功应用于绿茶，乌龙茶和红茶样品中。结果，在茶样品中发现了11种抗氧化剂，其中包括没食子儿茶素，表没食子儿茶素，儿茶素，绿原酸，表儿茶素，表没食子儿茶素酸酯，表儿茶素酸酯，芦丁，1,4,6-三没糖基葡萄糖，槲皮素-3-糖苷和山茱fer醇-3-葡萄糖苷。在线液体微萃取和在线HPLC-ABTS相结合的方法是一种快速，绿色的茶叶质量评估方法。