In-situ derivatisation, extraction, and preconcentration of some phenolic compounds from water and wastewater samples through cold-induced homogenous liquid-liquid extraction followed by dispersive liquid-liquid microextraction

Abstract

ABSTRACT In this study, an efficient sample preparation method for the extraction and preconcentration of some phenolic compounds was developed before their analysis with gas chromatography equipped with a flame ionisation detector. Initially, cold-induced homogeneous liquid-liquid extraction was performed for the extraction of polar target compounds from petrochemical, pharmaceutical, well water, and city sewage samples. In the following for more preconcentration, dispersive liquid-liquid microextraction was carried out to enhance enrichment factors. For this purpose, in a glass test tube, a mixture of acetonitrile and acetic anhydride (derivatisation agent) was added to the sample solution in which sodium chloride and sodium carbonate were dissolved. A homogeneous solution was obtained. The solution was frozen by immersion of the tube in liquid nitrogen for a few seconds. The frozen solution was removed from the bath and let stand for a few minutes at room temperature. The organic phase (acetonitrile) was melted and collected on the solidified aqueous solution. The organic phase containing the derivatised phenols was removed and mixed with µL-level of 1,2-dibromoethane and injected into an aqueous solution of sodium chloride. The created cloudy solution was centrifuged and 1 μL of the sedimented phase was injected into the separation system. The effective parameters including the type and amount of base, amount of derivatisation agent, ionic strength of solutions, type and volume of solvents, and vortexing time were investigated. High extraction recoveries (80–92%) and enrichment factors (412–478), wide linear ranges, and satisfactory limits of detection (4.82–9.27 μg L−1) and quantification (14.25–30.86 μg L−1) were obtained.