Determination of nitrated and oxygenated polycyclic aromatic hydrocarbons in water samples by a liquid–liquid phase microextraction procedure based on the solidification of a floating organic drop followed by solvent assisted back-extraction and liquid chromatography–tandem mass spectrometry

Abstract

A methodology was optimized for the determination of nitrated-PAHs (nitro-PAHs) and oxygenated-PAHs (oxy-PAHs) in natural waters. The extraction/preconcentration procedure was performed by liquid–liquid phase microextraction based on the solidification of a floating organic drop followed by a novel solvent assisted back-extraction (DLLME-SFO-SBE) combined with liquid chromatography-tandem mass spectrometry. The solvent assisted back extraction into a suitable solvent enabled the direct injection of nitro and oxy-PAHs into the UHPLC-(+)APCI-MS/MS system. Parameters affecting the efficiency of the back-extraction procedure were evaluated and optimized, including the nature of the back-extractant volume, temperature and agitation effect. Additionally, various strategies related to the emulsion formation process were assayed. Detection and quantification limits were in the range of 0.02–0.85 ng mL−1 and 0.15–1.10 ng mL−1. Acceptable extraction recoveries between 95.1 and 100% and enrichment factors between 192 and 200-fold, with relative standard deviations <7.6%, were obtained. The method was successfully applied to the analysis of different types of water samples. In addition, concentration levels of nitro-PAHs and oxy-PAHs ranging from 0.97 to 7.16 ng mL−1 and from 0.69 to 2.36 ng mL−1; respectively, were detected in lake water. The proposed methodology is an easy, sensitive, and accurate analytical approach for determining nitrated and oxygenated PAHs of environmental concern in water samples.