Ciprofloxacin (CIP), a typical fluoroquinolone antibiotic, is extensively employed in the treatment of bacterial infections and diseases due to its broad-spectrum and highly potent antimicrobial activity [1,2]. Excessive use of CIP hinders its complete metabolism by animals, causing the residues in animal-derived foods such as egg [3]. Long-term consumption of animal-derived foods containing CIP residues can disrupt the balance of intestinal flora and increase bacterial resistance, posing serious threats to human health [4]. Therefore, developing sensitive methods for detecting CIP is an urgent task to ensure food safety and public health.

High performance liquid chromatography (HPLC) method, known for its high sensitivity and excellent separation efficiency, has been widely used for the quantitative analysis of trace compounds such as CIP in foods. The detection of CIP in complex food matrices using HPLC requires effective sample pretreatment to eliminate matrix interference. Traditional pretreatment techniques include liquid-liquid extraction [5], protein precipitation [6], and solid-phase extraction (SPE) [7]. SPE offers superior recovery rates and significantly lower organic solvent consumption, making it the preferred method for complex matrices [8]. However, conventional SPE adsorbents fail to achieve highly selective enrichment of CIP in complex matrices, it is urgent to develop advanced SPE adsorbents for efficient enrichment and sensitive detection of CIP [9].

Metal-organic frameworks (MOFs), a class of porous crystalline materials constructed from metal ions/clusters and organic linkers with precisely tunable pore geometries, ultra-high specific surface areas, and customizable functional groups, exhibit promising application potential in solid-phase extraction as adsorbents [10]. Zeolitic imidazolate framework-8 (ZIF-8), a typical MOF, has emerged as a potential adsorbent for CIP due to its high surface area (typically>1000 m2/g), low density (∼0.35 g/cm3), and abundant surface functional groups [11]. However, the unsaturated specific surface area and pore size of ZIF-8 limit its adsorption capacity [12]. Tannic acid is a natural polyphenolic compound with abundant phenolic hydroxyl groups and acidic groups [13], which induces defects or vacancies on the surface and inside of the ZIF-8 crystalline framework [14]. The formation of hollow ZIF-8 (H-ZIF-8) particles effectively increases the reactive sites, promoting the diffusion of adsorbent into the interior of the material, and accelerating the adsorption rate [15]. However, H-ZIF-8 typically exists as a micro/nano-powder, and its inherent powdered nature makes it difficult to separate and recover during handling [16,17]. Loading H-ZIF-8 onto aerogels is an effective way to solve the agglomeration and moldability problem [18]. Reduced graphene oxide (rGO) aerogel has a good three-dimensional self-supporting structure, providing a powerful material carrier for H-ZIF-8. Additionally, rGO aerogels with abundant oxygen-containing functional groups (e.g., hydroxyl, carboxyl, and epoxy groups) can interact with H-ZIF-8 particles through hydrogen bonding and π-π stacking, improving the dispersibility of H-ZIF-8 in solution and enhancing the recyclability of the adsorbent. Moreover, decorating H-ZIF-8 onto rGO to form hierarchical structure may increase the mass transfer effect and improve the adsorption efficiency for CIP [19]. The three-dimensional H-ZIF-8/rGO aerogel (HRA) SPE columns are expected to efficient adsorption and extraction of CIP residues in food matrix for enhancing detection sensitivity.

Based on the above theoretical considerations, the three-dimensional HRA is successfully synthesized by loading acid-etched hollow H-ZIF-8 onto rGO aerogels, which serves as an SPE column coupled with HPLC for the efficient and sensitive detection of trace CIP in egg (Fig. 1). The adsorption performance of HRA is investigated through adsorption kinetic models and isotherm experiments. The optimal conditions for adsorbing CIP are analyzed. The adsorption mechanism is further explored using experimental and theoretical simulations. The standard curve of CIP is established. The practical application of HRA as SPE columns coupled with HPLC for determining CIP in actual egg samples is implemented. The reusability of HRA is conducted. This study designed a novel aerogel-based SPE column and provides a potential pretreatment technique for the efficient extraction of antibiotics from egg.