Facile preparation of nanomaterial/polymer composite porous membranes for solid phase extraction of aflatoxins in peanuts.

In order to facilitate the application of nanomaterials in sample preparation, a scratching membrane method was proposed to prepare nanomaterial/polymer composite porous membranes, in which the type of nanomaterial and its loading amount could be tuned easily. The membranes were then ground and packed into cartridges for solid phase extraction (SPE) applications. In this work, multi-walled carbon nanotubes (MWCNT), nano carbon powder (NC), mesoporous silica (SBA-15), zeolitic imidazolate framework-8 (ZIF-8), Cu, and ZnO nanoparticles were chosen to prepare the corresponding composite porous membranes with polyacrylonitrile (PAN). The color and surface morphology of composite membranes were changed with the type and amount of incorporated nanoparticles. Large specific surface areas of 74.6-88.2 m2 g-1, along with abundant mesopores of ∼30 nm, enable rapid mass transfer for efficient extraction and elution. Among them, the 0.5 % MWCNT-5 % PAN membrane was chosen and used to extract aflatoxins (AFs) from water and peanut samples. Coupled with ultra-high performance liquid chromatography-fluorescence detection (UHPLC-FLD), some important SPE parameters were optimized, including sample solvents, sample pH, elution solvents and volume. Under optimal conditions, the method achieved a linear range of 0.05-10.0 μg l-1, recoveries of 86.91-104.57 %, LODs of 0.0016-0.0095 μg l-1 in water samples, and a linear range of 2.5-50.0 μg l-1, recoveries of 86.5-111.1 %, LODs of 0.029-0.56 μg l-1 in peanut samples. These results highlighted that nanomaterial/polymer composites could be prepared in a simple and cost-effective way, and employed as high-efficient SPE adsorbents.