Tailorable yolk-shell FeO@graphitic carbon submicroboxes as efficient extraction materials for highly sensitive determination of trace sulfonamides in food samples.

A well-designed yolk-shell FeO@graphitic carbon (YS-FeO@GC) submicroboxes with a tunable internal cavity were constructed by one-step pyrolysis strategy followed by partially etching, in which the FeO magnetic core was well confined in compartment of GC submicroboxes. The suitable internal cavity, graphitic carbon shell and large specific surface area, play great roles in improving mass transfer of analytes. Compared to its core-shell structure, the YS-FeO@GC submicroboxes as dispersive magnetic solid-phase extraction (d-MSPE) materials exhibited superior enrichment performance for sulfonamides (SAs). Thus, it was applied to sensitive/simultaneous detection of trace SAs in milk and meat samples, combing with high performance liquid chromatography (HPLC). Under optimized conditions, limits of detection (LODs, 0.11-0.25 μg L for milk and 0.46-2.24 μg kg for meat) and recoveries (77.2-118.0%) were obtained. This work not only offers a facile strategy for the tunable fabrication of yolk-shell architecture, but also successfully affords its exploration as d-MSPE materials.