Barium alginate caged Fe3O4@C18 magnetic nanoparticles for the pre-concentration of polycyclic aromatic hydrocarbons and phthalate esters from environmental water samples

The hydrophobic octadecyl (C₁₈) functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄@C₁₈) were caged into hydrophilic barium alginate (Ba²⁺-ALG) polymers to obtain a novel type of solid-phase extraction (SPE) sorbents, and the sorbents were applied to the pre-concentration of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) pollutants from environmental water samples. The hydrophilicity of the Ba²⁺-ALG cage enhances the dispersibility of sorbents in water samples, and the superparamagnetism of the Fe₃O₄ core facilitates magnetic separation. With the magnetic SPE technique based on the Fe₃O₄@C₁₈@Ba²⁺-ALG sorbents, it requires only 30 min to extract trace levels of analytes from 500 mL water samples. After the eluate is condensed to 0.5 mL, concentration factors for both phenanthrene and di-n-propyl-phthalate are over 500, while for other analytes are about 1000. The recoveries of target compounds are independent of salinity and solution pH under testing conditions. Under optimized conditions, the detection limits for phenanthrene, pyrene, benzoa]anthracene, and benzoa]pyrene are 5, 5, 3, and 2 ng L⁻¹, and for di-n-propyl-phthalate, di-n-butyl-phthalate, di-cyclohexyl-phthalate, and di-n-octyl-phthalate are 36, 59, 19, and 36 ng L⁻¹, respectively. The spiked recoveries of several real water samples for PAHs and PAEs are in the range of 72-108% with relative standard deviations varying from 1% to 9%, showing good accuracy of the method. The advantages of the new SPE method include high extraction efficiency, short analysis time and convenient extraction procedure. To the best of our knowledge, it is unprecedented that hydrophilic Ba²⁺-ALG polymer caged Fe₃O₄@C₁₈ magnetic nanomaterial is used to extract organic pollutants from large volumes of water samples.