Development, synthesis, and application of magnetic layered double hydroxides (Fe3O4@SiO-LDH/DS−) as an efficient adsorbent for the removal of tetracyclines from milk samples

Abstract

This work presents the development, synthesis, and application of a layered double hydroxide (LDH) coupled to magnetic particles for the removal of antibiotics as tetracyclines (TC´s): tetracycline (TC), chlortetracycline (CT), oxytetracycline (OT), and doxycycline (DT) from milk samples. The LDH synthesis conditions, reaction time (30–90 min), molar ratios Mg2+/Al3+ (7:1–1:7), interlayer anion (NO3−, Cl−, CO32−, and dodecyl sulphate (DS−)) were evaluated. Under synthesis conditions (reaction time of 30 min, Mg2+/Al3+ molar ratio of 7:1, and DS− as interlayer anion), the LDH was coupled in a magnetic solid phase microextraction (MSPμE) methodology. At the optimal extraction conditions (pH 6, 5 min of contact time, 10 mg of adsorbent), a removal percentage of 99.0 % was obtained for each tetracycline. FTIR, TGA, SEM, and adsorption isotherms were employed to characterize the optimal adsorbent. Each experiment was corroborated by large-volume sample stacking capillary electrophoresis (LVSS-CE). The adsorbent was applied directly to positive milk samples (previously tested) for TC´s removal.