Trace analysis of quercetin in tea samples by HPLC-DAD system by means of a new nanocomposite including magnetic core-shell.

A new magnetic core-shell multiwalled carbon nanotube@nanodiamond nanocomposite was synthesized, characterized and used as magnetic solid-phase extraction material. The usability of material was checked on the separation and pre-concentration of quercetin in tea samples by magnetic solid-phase extraction and high-performance liquid chromatography with diode array detector system. There was a linear relationship between chromatographic area and concentration of quercetin in the range of 5.0–600 ng mL⁻¹. The limit of detection and quantification limits were 1.46 and 4.91 ng mL⁻¹, respectively. The developed method has been applied to determine quercetin at trace levels in tea samples. [ABSTRACT FROM AUTHOR]