A novel magnetic C₃N₅ framework material (Fe₃O₄/C₃N₅) was developed as a high selectivity extractant for La(III) determination in food samples. The Fe₃O₄/C₃N₅ material was synthesized by thermal deammoniation method and has larger surface area (100.3 m²⋅g^-1) and more effective adsorption sites compared with that of individual C₃N₅ material (19.4 m²⋅g^-1). It was proved that Fe₃O₄/C₃N₅ material displayed excellent selectivity and adsorption capacity for La(III). In addition, adsorption isotherm and kinetic data indicated that La(III) adsorption based on Fe₃O₄/C₃N₅ material is a monolayer adsorption which is compatible with Langmuir model and follows a pseudo-second-order kinetic equation. By using Fe₃O₄/C₃N₅ material as extractant, an analytical method was established with low limits of detection (3σ, n=6) of 10.4 μg⋅L^-1, reasonable recoveries ranged from 86% to 106% and good precision with the RSD less than 10.7%. The analytical method was further applied to the determination of trace La(III) in food sample. It evinced that the concentration of La(III) in sea fish is 13.2 μg⋅kg^-1 and the content of ¹³⁸La is 0.138 μg⋅kg^-1, which is 1.03% of total La(III).

开发了一种新型的磁性C ₃ N ₅骨架材料（Fe ₃ O ₄ / C ₃ N ₅）作为食品中La（III）测定的高选择性萃取剂。中的Fe ₃ ö ₄ / C ₃ Ñ ₅物质通过热去氨的方法合成，并具有较大的表面积（100.3米² ⋅g ^-1与该个体的C相比），更有效的吸附位点₃ Ñ ₅材料（19.4米² ⋅g ^-1）。证明了Fe ₃ O ₄/ C ₃ N ₅材料对La（III）表现出出色的选择性和吸附能力。此外，吸附等温线和动力学数据表明，基于Fe ₃ O ₄ / C ₃ N ₅材料的La（III）吸附是单层吸附，与Langmuir模型兼容，并遵循伪二级动力学方程。通过使用Fe ₃ O ₄ / C ₃ N ₅材料作为萃取剂，建立了一种分析方法，其检出限低（3σ，n = 6）为10.4μg⋅L ^-1，合理的回收率在86％至106％之间，且RSD小于10.7％时具有良好的精密度。该分析方法进一步应用于食品样品中痕量La（III）的测定。它明证与La（III）的在海鱼类的浓度为13.2μg⋅kg ^-1和内容¹³⁸ La的0.138μg⋅kg ^-1，这是总的La（III）的1.03％。