Abstract:

A novel method for the determination of α-tocopherol in Goji berries (Lycium barbarum) was developed using
dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography by UV detection
(HPLC-UV). The influence of DLLME experimental parameters including type and volume of extraction solvents and
dispersers, sample solution pH, ionic strength, extraction time and temperature on extraction efficiency were examined.
The method offered excellent linearity over a range of 100–50 000 μg/L with correlation coefficient (r) of 0.999 7. Under
the optimum conditions, intra-day and inter-day repeatability values, expressed as relative standard deviation (RSD), were
2.9% and 6.5%, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were 3.1 μg/L and 10.2 μg/L,
respectively. The developed method was successfully applied to the determination of α-tocopherol in 3 types of commercial
Goji berry products. Average recoveries varied from 85.7% to 106.3%, with RSD in the range of 0.68%–4.62%. In addition,
the DLLME technique had the advantages of simplicity, rapidity and low organic solvent consumption, excellent precision,
high sensitivity and good repeatability.

Key words: dispersive liquid-liquid microextraction, Lycium barbarum, α-tocopherol