pH-responsive aMIL-68(In)-NH₂-TiO₂ composite for selective dispersive micro solid-phase extraction and sensitive...

Lead (Pb²⁺) is a persistent and non-degradable pollutant that poses serious threats to human health and food safety. However, conventional methods are often limited by matrix interferences, sensitivity, and selectivity pose significant challenges for the direct quantification of trace metal ions in complex samples. Therefore, the development of efficient sample pretreatment techniques is necessary to address these limitations and enable reliable quantification of trace Pb²⁺ in food and environmental samples.

A novel method for the separation and enrichment of trace Pb²⁺ in Angelica sinensis (Oliv.) Diels (AS) and water samples was developed, using a newly synthesized pH-responsive amorphous MIL-68(In)-NH₂-TiO₂ (aMIL-68(In)-NH₂-TiO₂) composite prepared with green deep eutectic solvents as a dispersive micro solid-phase extraction (DMSPE) adsorbent. At pH = 3, the composite showed excellent selectivity for Pb²⁺ adsorption in multi-metal ion systems and achieves adsorption equilibrium within 3 min, providing a practical improvement over conventional extraction process and enhancing overall experimental efficiency. Under the optimized conditions, the method showed efficient extraction of Pb²⁺ with an enrichment factor of 31, a limit of detection (LOD) of 0.1 μg L^-1, and a wide linear range (1-6000 μg L^-1).

In this work, aMIL-68(In)-NH₂-TiO₂ was prepared as a DMSPE adsorbent for the environmentally friendly, highly sensitive, and highly selective monitoring of trace Pb²⁺ in AS and water samples, providing a novel strategy for the sensitive detection of metal ions, offering a promising approach for food and environmental monitoring.