Alginate-Polymer-Caged, C18-Functionalized Magnetic Titanate Nanotubes for Fast and Efficient Extraction of Phthalate Esters from Water Samples with Complex Matrix

The magnetic titanate nanotube (Fe3O4-TN composite) was prepared and functionalized with C-18 groups and then coated by a hydrophilic alginate polymer cage. This material (ALG@C-18-Fe3O4-TN) exhibited the properties of large surface area, superparamagnetism, high adsorption ability, and good dispersibility in water. ALG@C-18-Fe3O4-TNs possessed high extraction efficiency to phthalate esters di-n-propyl-phthalate (DPP), di-n-butyl-phthalate (DBP), dicyclohexyl-phthalate (DCP), and di-n-octyl-phthalate (DOP). The dispersed adsorbents in solution could be collected with an external magnetic field within 10 min. The extraction could be conducted under some extreme conditions such as high salinity, acid or alkali solution or humic acid-rich samples without the decrease in extraction efficiency. In the presence of 100 mg L-1 humic acid (11 As), the recoveries of analytes were not affected at pH >6, and decreased recoveries of DPP and DCP were observed only in acid solution. Potential analysis and comparison study with the biphthalate acid or n-decanoic acid-rich matrix indicated that the anti-interference ability of adsorbents to HAs mainly resulted from the repulsion interaction and size exclusion provided by alginate cage to HAS. Under the optimized conditions, ALG@C-18-Fe3O4-TNs were used to analyze several environmental water samples, a concentration factor of 1000 and detection limits of phthalate esters ranging in 11-46 ng L-1 were achieved, and the recoveries of analytes were in the range of 84-109% for all samples.