Determination of PAHs in soil leachates by magnetic solid-phase extraction using nanoparticles and gas chromatography-tandem mass spectrometry

Abstract

A magnetic solid-phase extraction (mSPE) method, using palmitate coated magnetite nanoparticles, coupled with gas chromatography-tandem mass spectrometry was developed for the extraction of 16 PAHs from soil leachates. Fourier transform infrared spectroscopy analysis showed CH₂ peaks in the region about 2900 cm⁻¹ and CO peaks in the region about 1500 cm⁻¹ which confirmed that palmitate was successfully attached to the surface of Fe₃O₄ particles. The optimal extraction conditions for these particles were: 200 mg of modified magnetite nanoparticles, 50 mL of soil leachate containing 2.5% of acetone, 45 min of mSPE and elution of the analytes with ethyl acetate. The efficiency of the nanoparticles for the extraction of PAHs from soil leachates was evaluated. Recoveries of these contaminants from soil leachates spiked at three different fortification levels, from 0.2 to 1 ng mL⁻¹, were low for the four PAHs with lower molecular weights but satisfactory recoveries were obtained for the rest. The developed method provided a pre-concentration factor of, at least, 50 and the limits of detection ranged from 0.8 to 5.1 ng L⁻¹. Finally, the developed method was successfully applied to examine soil leachates obtained from soils with different physico-chemical characteristics, the soil organic matter content being one important parameter that may explain, together with other factors, the amount of PAHs present in these leachates. The present work demonstrates the applicability of the developed method for the determination of PAHs in soil leachates, which is of interest for the mobility and bioavailability studies of these pollutants in soil.