Organic aerogels embedded in triple-shelled hollow MIL-101 as fiber coating for optimizing the solid-phase microextraction performances of tetracyclines in egg and milk samples

A multi-step growing and etching method was used to synthesize metal–organic framework materials (MIL-101) with a hollow structure of distinct shell layers. The resorcinol–formaldehyde organic aerogel (RFOA) was embedded in-situ into the triple-shelled hollow MIL-101 (TSHM) to form a novel RFOA@TSHM spherical multilayer shell composite, which was used as a fiber coating material of solid-phase microextraction for the enrichment and determination of six tetracyclines (TCs) by coupling with HPLC-UV–vis detector in aqueous solutions. Due to the embedding of the RFOA and the multilayer shell structure, the RFOA@TSHM composite is characterized by a stable structure with a larger pore size and specific surface area compared with the TSHM alone. Under optimal conditions, limits of detection of 0.13–1.16 μg L−1 and limits of quantification of 0.43–3.83 μg L−1 were obtained for TCs detection. Moreover, the RFOA@TSHM coating fiber was successfully applied to detect TCs in egg and milk real samples.