Monodispersed CaCO₃@hydroxyapatite/magnetite microspheres for efficient and selective extraction of benzoylurea...

A novel monodispersed CaCO₃@hydroxyapatite/magnetite microsphere (CaCO₃ @HAP/Fe₃O₄) was prepared via an in-situ growth strategy, and applied as an adsorbent for efficient and selective adsorption of benzoylurea insecticides (BUs) in various tea beverages samples. The sorbent exhibited uniformity in particle size, good mono-dispersibility and excellent solvent stability. The adsorption equilibrium of BUs (100 ng/mL) in 10 mL of tea beverages samples was achieved on 20 mg of CaCO₃ @HAP/Fe₃O₄ within 10 min. The adsorption followed pseudo-second-order kinetics and Langmuir models and the maximum adsorption capacities of 131.9-161.3 mg/g were accomplished via hydrophobic interactions, hydrogen bonding, and the affinity of F atom and Ca²⁺. Coupled with high performance liquid chromatography, the method offered wide linear ranges of 0.8-1000 ng/mL with correlation coefficients (r) ≥ 0.9995, low limits of detection of 0.2-0.3 ng/mL and large enrichment factors of 75.7-102. The recoveries ranged from 75.7%- 102% with intra- and inter-day precisions of 1.9%- 9.3% and 1.6%- 11.8%, respectively. In addition, CaCO₃ @HAP/Fe₃O₄ could be easily regenerated and reused at least 10 times with no significant loss of recovery. These results revealed an alternative strategy for fast and convenient determination of BUs in tea beverages samples and proved the great feasibility of CaCO₃ @HAP/Fe₃O₄ in the application for the selective adsorption of BUs.