A novel switchable solvent liquid-phase microextraction technique based on the solidification of floating organic droplets: HPLC-FLD analysis of polycyclic aromatic hydrocarbon monohydroxy metabolites in urine samples

A novel switchable solvent liquid-phase microextraction technique, based on the solidification of floating organic droplets (SS-LPME-SFO), was developed for the pretreatment of aqueous samples. In this process, octanoic acid was selected as the extractant due to its low density, moderate melting point, and ability to switch between hydrophilic and hydrophobic characteristics. This technique has been successfully applied in the enrichment of five polycyclic aromatic hydrocarbon monohydroxy metabolites (OH-PAHs) in urine samples. Furthermore, a HPLC-FLD detection procedure was established to analyze the samples. A series of parameters affecting the extraction were systematically studied. Under the optimal conditions, all analytes showed good linearity within the studied range, and the values of the correlation coefficient (R-2) were higher than 0.99. The limits of detection (LODs) and the limits of quantitation (LOQs) were within the range of 0.018-0.076 mu g L-1 and 0.059-0.25 mu g L-1, respectively. The method also achieved good recoveries, ranging between 88.5% and 102.5%. Overall, the method is highly cost-effective, environmentally-friendly, fast and efficient. This study proposes an efficient extraction method for the analysis of most organic pollutants in complex environmental aqueous phases.