A fast and innovative microextraction technique, μSPEed, followed by ultrahigh performance liquid chromatography for the analysis of phenolic compounds in teas

The objective of this study was to evaluate the efficiency of a promising solid phase microextraction technique, mu SPEed, in the analysis of selected phenolic compounds from teas by ultrahigh performance liquid chromatography with photodiode array detection (mu SPEed/UHPLC-PDA). The innovative mu SPEed configuration uses 3-mu m sorbent particles tightly packed in a disposable needle equipped with a pressure-driven valve to withdraw samples in a single direction. The system was operated by the electronic pipette eVol (R) and different parameters influencing the extraction efficiency, as the nature of sorbent, pH, loading and elution conditions, and solvents were optimized. The best extracting conditions were obtained by loading twice 100 mu L of tea samples through the PS/DVB-RP sorbent and eluting with 50 mu L of acidified MeOH 95%. The following chromatographic separation was carried out in an Acquity C-18 BEH capillary column using a gradient of 0.1% FA and acetonitrile. The optimized mu SPEed/UHPLC-PDA methodology is selective and specific and was properly validated for 8 phenolic compounds widely reported in different teas. Overall, an excellent analytical performance was obtained in the 0.2-20 mu g/L linear dynamic range (LDR), with very low limits of detection (LODs) and quantification (LOQs), ranging between 3.5-16.8 ng/mL and 10.6-50.6 ng/mL, respectively, high recoveries (89.3-103.3%), good precision (RSD < 5%) and negligible matrix effect. The methodology was used to assess the target polyphenols concentration in several tea samples. Rutin and quercetin-3-glucoside were the most abundant phenolics in all tea samples analysed and, with exception of naringenin and cinnamic acid, which are present in high amounts in the investigated citric teas, remain phenolic compounds are present in trace levels. (C) 2015 Elsevier B.V. All rights reserved.