Determination of chlorophenols in environmental water samples using directly suspended droplet liquid-liquid-liquid phase microextraction prior to high-performance liquid chromatography

Abstract

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5 mL acidic donor phase, (pH 2, P1) into an organic phase, 350 µL of benzene/1-octanol (90 : 10 v/v, P2) and then were back-extracted into a 7 µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe and neutralised by adding of 7 µL HCl 0.1 M. The total amount was eventually injected into the HPLC system with UV detection at 225 nm for further analysis. Parameters such as the organic solvent, phases volumes, extraction and back-extraction times, stirring rate and pH values were optimised. The calibration graphs are linear in the range of 10–2000 µg L−1 with r ≥ 0.9973. The enrichment factors were ranged from 115 to 170, and the limit of detection (LOD, n = 7) varied from 5 to 10 µg L−1. The relative standard deviations (RSDs, n = 5) were found 6.8 to 7.4 at S/N = 3. All experiments were carried out at room temperature, (22 ± 0.5°C).