Assembly of a Fe–pamoate porous complex on magnetic microspheres for extraction of sulfonamide antibiotics from environmental water samples

Abstract

Unique ternary single core–double shell structured magnetic microspheres of Fe₃O₄@SiO₂@Fe–pamoate were successfully fabricated via a step-by-step assembly strategy. The procedures involved initial pre-treatment of silica-coated magnetic cores with carboxyl groups to functionalize the magnetic microspheres, and subsequent alternating treatments with Fe³⁺ and pamoic acid solutions for the growth of Fe–pamoate complexes on the microsphere surface to form Fe₃O₄@SiO₂@Fe–pamoate magnetic microspheres. Characterization using various techniques demonstrated that the microspheres were porous, thermally stable, and possessed a single core–double shell sandwich structure. The as-synthesized materials possessed a bifunctional character derived from the magnetic properties of Fe₃O₄ nanoparticles and the high porosity of Fe–pamoate, making them excellent candidates as adsorbents for the magnetic enrichment of trace analytes. The potential applicability of the microspheres was demonstrated by preconcentrating sulfonamide antibiotics from environmental water samples prior to high-performance liquid chromatography analysis. The method combining enrichment with high-performance liquid chromatography had higher precision (relative standard deviations 1.4–12.3%), lower detection limits (0.08–0.12 ng mL⁻¹), and good linearity (correlation coefficients higher than 0.9947) for five sulfonamide antibiotics investigated. Average recoveries at three spiked levels were in the range of 86.3 to 99.7% with relative standard deviations below 12.3%.