Azadirachta indica assisted green synthesis of magnetic Ag/GO-Fe3O4 nanocomposites for the solid-phase extraction of tetracyclines from milk

Antibiotics are frequently used as growth boosters in animal husbandry. Tetracyclines (TCNs) are among the most widely used antibiotics compared to others, leaving traces in animal-based foodstuffs like milk and meat. Thus, monitoring of TCNs is paramount, especially in the feedstuff. In the present study, a green method is developed to synthesize magnetic Ag/GO-Fe₃O₄ nanocomposites using Azadirachta indica leaf extract. The synthesized adsorbent (Ag/GO-Fe₃O₄) was analyzed for the residual extraction of oxytetracycline (OTC) and chlortetracycline (CTC) from the fresh milk samples through the magnetic solid-phase extraction principle. The extraction procedure involved the deproteinization of milk, spiking with antibiotics, followed by magnetic solid-phase extraction and quantification of TCNs by HPLC with a UV detector. Different factors that affected the adsorption capacity of the adsorbent for the TCNs like pH, temperature, amount of nanocomposite, and time were studied. The inter-day and intra-day precision were calculated for OTC (4% and 6%) and CTC (3% and 4%), respectively. The limit of detection and quantification for OTC was 0.5 and 1.5 μgL⁻¹ and for CTC was 0.2 and 0.6 μgL⁻¹ respectively while the percentage extraction was 94%–96%.