Centrifuge-free dispersive liquid–liquid microextraction based on the salting-out effect followed by high performance liquid chromatography for simple and sensitive determination of polycyclic aromatic hydrocarbons in water samples

Abstract

A simple approach is described for the elimination of the centrifugation step in dispersive liquid–liquid microextraction (DLLME). For this purpose, in the absence of a disperser solvent, a solidifiable organic solvent (1-dodecanol) was dispersed into the sample solution (10.0 mL), and the resulting mixture was passed through a small column that was filled with 5 g of sodium chloride. Under these conditions, phase separation was achieved through the salting-out phenomenon, and the extraction solvent was suspended on top of the sample solution. By immersing the column into an ice bath, the extraction solvent was solidified, and this solvent was then transferred into a conical vial. Finally, after melting the extraction solvent, 20 μL of it was injected into a high performance liquid chromatography column for analysis. By performing this convenient method, a minimum amount of toxic solvent was consumed, the overall extraction time was 6 min, and an efficient extraction was achieved. The optimal conditions obtained for the major experimental parameters affecting the microextraction efficiency of some polycyclic aromatic hydrocarbons (PAHs) as the model compounds through the proposed method consisted of 50 μL of 1-dodecanol as the organic extraction solvent, a flow rate of 3 mL min⁻¹ for the sample solution, and 13 air-agitation cycles for the extraction number. Under the optimized experimental conditions, the method provided a good linearity in the range of 0.3–800 ng mL⁻¹, low limits of detection (0.04–0.6 ng mL⁻¹), good extraction repeatabilities (RSDs below 8.7%, n = 5), and enrichment factors (EFs) of 114–156. Finally, the developed method was successfully used for the determination of the mentioned analytes in some environmental samples.