Vortex-assisted dispersive liquid–liquid microextraction trace amounts of melatonin prior to HPLC determination in fruit juice samples

In the present study, a fast, simple and sensitive vortex-assisted dispersive liquid–liquid microextraction method was developed for extraction and preconcentration of trace amounts of melatonin in fruit juice samples. The extraction conditions were optimized as extraction solvent, chloroform; volume of extracting, 200.0 μL; and vortex time, 120 s. The HPLC determinations were done using ODS Waters C18 column under gradient elution. The calibration curve was linear in the range of 1.0–1000.0 ng mL–1 and detection limit was 0.23 ng mL–1. The validated method was applied for separation and determination of melatonin in different fruit juice samples (cherry, tomato and grape).