A novel salt-controlled homogenous ionic liquid phase microextraction based on the salting out effect and optimization of the procedure using the experimental design methodology

Abstract

A novel salt-controlled homogenous ionic liquid phase microextraction based on the salting out effect, combined with high performance liquid chromatography-diode array detection (HPLC-DAD), was proposed for simultaneous preconcentration and separation of azole compounds from wastewater samples. According to this procedure, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and methanol were used as the extraction and consolute solvents; the homogenous solution was also broken by the addition of sodium chloride. Optimization of the conditions for high extraction efficiency was studied simultaneously using experimental designs. A Plackett–Burman design (PBD) was applied to screen the significant factors on the extraction efficiency. A Box–Behnken design (BBD) was then used for the optimization of significant factors and the response surface equations were obtained. Under the best conditions, the detection limits (in the range of 1.25–5 μg L⁻¹), relative standard deviation (RSD% < 11.1) and error percent (between 7.2% and −11.8%) were obtained. Preconcentration factors were obtained in the range of 75–111. Finally, the performance of the proposed method was tested to determine trace amounts of azole compounds in wastewater and satisfactory results were obtained.