Sustainable Waste-Derived Mineral-Carbon Composites as Reusable Sorbents for Solid-Phase Extraction of Selected...

Organophosphorus pesticides (OPs) are persistent environmental contaminants requiring monitoring in aquatic ecosystems. In this study, four novel mineral-carbon composites (K-HNT, K-C-HNT, D-HNT, and D-C-HNT) were synthesized via thermal treatment at 800 °C from halloysite nanotubes, casein, dextrin, and pyrolyzed sawdust. Moreover, these materials were characterized (BET, FT-IR, Raman, SEM/EDS), revealing high specific surface areas (up to 218.3 m²/g for the D-C-HNT composite), and evaluated as solid-phase extraction (SPE) sorbents for the determination of six OPs from water. The eluates were analyzed using GC-MS/MS in MRM mode. This study examined the effect of eluent, sorbent mass, and multiple extractions on SPE efficiency. Ethyl acetate-n-hexane (1:1, v/v) was confirmed to be the most effective eluent, achieving high pesticide recoveries (>80%) at optimal sorbent masses of 50 and 75 mg. The method demonstrated satisfactory sensitivity, with limits of detection (LODs) ranging from 1.6 to 3.3 μgL^-1. Notably, the synthesized composites outperformed pure precursors and demonstrated extraction efficiency comparable to commercial sorbents (C-18, Florisil, active carbon). Furthermore, reusability tests confirmed that second and third extraction repetitions reduced the efficiency of the SPE process only slightly, indicating that these waste-derived composites can be reused multiple times without cartridge replacement.