Magnetic Solid-Phase Extraction Clean-Up Combined with Solidified Floating Organic Drop Microextraction for Determination of Trace Mercury (II) in Tea Samples

Magnetic solid-phase extraction (MSPE) clean-up combined with solidified floating organic drop microextraction (SFODME) has been developed as a new approach for extraction and determination of trace amounts of mercury (II) in tea samples. After purification of the samples by MSPE with the use of Fe3O4@SiO2/graphene as sorbents, SFODME technique was used to concentrate the target analytes. Various experimental parameters that could affect the extraction efficiencies were investigated. Under optimized experimental conditions a preconcentration factor of 23.0 was obtained using 15.0 mL sample solution. The calibration graph was linear from 0.05 mu g/L to 5.0 mu g/L with a detection limit of 4.0 ng/L. The relative standard deviation for 10 replicate measurements of 0.1 and 1.0 mu g/L of mercury (II) were 4.27% and 3.95%, respectively. The proposed method was applied in the analysis of four tea samples, and the accuracy of the method was assessed through the analysis of certified reference materials and recovery experiments.