Zeolite/iron oxide composite as sorbent for magnetic solid-phase extraction of benzene, toluene, ethylbenzene and xylenes from water samples prior to gas chromatography-mass spectrometry

This study reports a new composite based on ZSM-5 zeolite decorated with iron oxide magnetic nanoparticles as a valuable sorbent for magnetic solid-phase extraction (MSPE). A proposal is made to determine benzene, toluene, ethylbenzene and xylenes (BTEX) as model analytes in water samples using gas chromatography-mass spectrometry. A two-step multivariate optimization strategy, using Plackett-Burman and circumscribed central composite designs, was employed to optimize experimental parameters affecting MSPE. The method was evaluated under optimized extraction conditions (i.e., amount of sorbent, 138 mg; extraction time, 11 min; sample pH, pH of water (i.e., 5.5-6.5); eluent solvent volume, 0.5 mL; and elution time, 5 min), obtaining a linear response from 1 to 100 mu g L-1 for benzene; from 10 to 100 mu g L-1 for toluene, ethylbenzene and o-xylene; and from 10 to 75 mu g L-1 for m,p-xylene. The repeatability of the proposed method was evaluated at a 40 mu g L-1 spiking level and coefficients of variation ranged between 8 and 11% (n = 5). Limits of detection were found to be 0.3 mu g L-1 for benzene and 3 mu g L-1 for the other analytes. These values satisfy the current normative of the Environmental Protection Agency and European Union for BTEX content in waters for human consumption. Finally, drinking water, wastewater and river water were selected as real water samples to assess the applicability of the method. Relative recoveries varied between 85% and 114% showing negligible matrix effects. (C) 2016 Elsevier B.V. All rights reserved.