Hemimicelles/admicelles supported on magnetic graphene sheets for enhanced magnetic solid-phase extraction.

In this work, superparamagnetic nanoparticle-decorated graphene (MG) sheets were synthesized and used as support for hemimicelles/admicelles for solid-phase extraction (SPE) of different compounds from environmental water samples for the first time. The MG sheets were facilely synthesized by a one-step, one-pot redox reaction between graphene oxide and Fe(II). Due to the large surface area and unique nanosheet morphology, MG served as an excellent nano-scaled support material for hemimicelles and admicelles, exhibiting higher loading capacity than conventional materials and pure Fe₃O₄ nanoparticles. The MG sheets could be negatively or positively charged depending on solution pH, allowing the extraction to be conducted in different modes. In cationic mode, cetyltrimethylammonium bromide (CTAB) was used as micelle-forming reagent, and perfluoroalkyl and polyfluoroalkyl substances (PFASs) and alkylphenols were used as model analytes. In anionic mode, sodium dodecyl sulfate (SDS) was used as micelle-forming reagent and alkyltrimethylammonium salts were selected as analytes. In both modes, the formation processes of hemimicelles/admicelles on MG sheets were studied and the extraction conditions were optimized. For PFASs, the analytical sensitivity was enhanced by 50-113-fold by the extraction, and the method detection limits (MDLs) ranged from 0.15 to 0.50 ng/L. For alkyltrimethylammonium salts, the MDLs were in the range of 1.4-8.0 ng/L. In both modes, good recoveries (56.3-93.9%) and reproducibility (run-to-run RSDs<9.3%) were obtained. The results from this work show a potential new role of graphene in analytical sample preparation.