Determination of polycyclic aromatic hydrocarbons in soil samples using flotation-assisted homogeneous liquid–liquid microextraction

In this study, flotation-assisted homogeneous liquid–liquid microextraction (FA-HLLME) was developed as a fast, simple, and efficient method for extraction of four polycyclic aromatic hydrocarbons (PAHs) in soil samples followed by gas chromatography-flame ionization detector (GC-FID) analysis. A special home-made extraction cell was designed to facilitate collection of the low-density extraction solvent without a need for centrifugation. In this method, PAHs were extracted from soil samples into methanol and water (1:1, v/v) using ultrasound in two steps followed by filtration as a clean-up step. The filtrate was added into the home-made extraction cell contained mixture of 1.0 mL methanol (homogenous solvent) and 150.0 μL toluene (extraction solvent). Using N2 flotation, the dispersed extraction solvent was transferred to the surface of the mixture and was collected by means of a micro-syringe. Then, 2 μL of the collected organic solvent was injected into the GC-FID for subsequent analysis. Under optimal conditions, linearity of the method was in the range of 40–1000 μg kg−1 soil (dry weight). The relative standard deviations in real samples varied from 5.9 to 15.2% (n = 4). The proposed method was successfully applied to analyze the target PAHs in soil samples, and satisfactory results were obtained.