Monitoring polycyclic aromatic hydrocarbons in seawaters and wastewaters using a dispersive liquid–liquid microextraction method

Abstract

An evaluation has been made of a dispersive liquid–liquid microextraction (DLLME) procedure for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in different environmental waters including seawaters and wastewaters, using gas-chromatography (GC) with flame-ionization detection (FID). The optimized method requires 18 μL of the extractant solvent tetrachloroethylene (C₂Cl₄), 1 mL of acetonitrile as dispersive solvent, and 5 mL of aqueous sample. After centrifugation (5 min), 2 μL of the obtained micro-droplet containing the extracted PAHs, which varied from ∼15 μL for seawaters to ∼9 μL for wastewaters, is directly injected in the GC-FID. The performance of the method is characterized for average extraction efficiencies of 99.0% and 98.1% when analysing real seawaters and wastewaters, respectively, at low spiked levels (3 ng · mL⁻¹); and average precision values of 8.4% as relative standard deviation. The performance of the method was also compared with conventional liquid–liquid extraction. The DLLME calibrations have been obtained in different aqueous matrices to thoroughly evaluate the matrix effect. The application of the joint-confidence ellipse F-test showed that seawaters can be simply analysed using DLLME calibrations obtained in the laboratory using deionized water. However, important caution must be taken into account when dealing with wastewater, because of matrix effects.

Keywords:

• polycyclic aromatic hydrocarbons
• environmental waters
• dispersive liquid–liquid microextraction
• matrix effects
• gas-chromatography

Acknowledgements

A.M.A. acknowledges funding from the Spanish Ministry of Innovation and Science (MICINN) project ref. CTQ2008-06253/BQU. V.P. thanks the MICINN for the Ramón y Cajal contract with the University of La Laguna (ULL). C.V.R.-D. thanks the Environmental Service of ULL (SEMALL) for financial support. The SEMALL is also acknowledged for kindly providing the sampled real seawaters and wastewaters.