A horizontally oriented setup for liquid–liquid–liquid microextraction of estrogens

Abstract

A horizontally oriented liquid–liquid–liquid microextraction (HOLLLME) setup was developed and applied for the isolation of two major estrogens from aquatic media. In contrast to the conventional procedure, in this setup the extracting microdrop was suspended from a horizontally positioned needle in order to provide much higher stability to the extracting phase. The developed HOLLLME approach was applied to isolate two major selected estrogens from aquatic media followed by high performance liquid chromatography-ultraviolet (HPLC-UV) determination. Estrogens were, initially, extracted from water samples into hexane and subsequently, the back extraction stage was performed with 6 μL of sodium hydroxide solution suspended from a horizontally fixed GC microsyringe tip. Important parameters influencing the extraction process were optimized and an extraction time of 25 min, back extraction time of 5 min, temperature of 35 °C, pH of 6 for a donor phase, dropsize of 6 μL and organic phase volume of 300 μL were achieved as optimum values. The enrichment factors of 111 for estrone and 80 for estriol were obtained at 1 mg L⁻¹ concentration. The calibration curves showed linearity in the range of 10–500 μg L⁻¹ with coefficients of determination higher than 0.99. The limits of detection and quantification were 3 and 10 μg L⁻¹, respectively. Under optimized conditions, the relative standard deviation percent (RSD%) values were found to be from 6.8 to 13.0. Two typical surface water samples were used to assay the validation of the developed method.