Abstract
Food safety problems caused by tetracycline antibiotics residues are a significant concern due to their great risk to human health even at trace levels. In the current work, a highly sensitive and selective determination of similar chemical composition tetracycline (TC) and doxycycline (DC) antibiotics in milk samples was developed by offline solid phase extraction using beta-cyclodextrin functionalized magnetic graphene oxide nanoparticles (beta-CD-MGONPs) followed by differential pulse voltammetric determination with a beta-cyclodextrin modified carbon paste (beta-CD-MCP) sensor. beta-CD-MGONPs was prepared, characterized by XRD, FTIR, TEM, and TGA and applied for the removal of TC/DC using batch adsorption experiments. The effects of medium acidity, equilibration time, adsorbent dose, initial antibiotic concentration, and ionic strength were extensively investigated using UV-Vis spectrophotometry at optimal adsorption conditions. The experimental data are well described by the Langmuir isotherm and pseudo-second-order kinetic model. The maximum adsorption capacity was found to be 666.7 mg g(-1) for TC and 769.2 mg g(-1) for DC. Furthermore, loss in the removal efficiency was 3.5-5.6% after three adsorptiondesorption cycles. Then, the electrochemical response of the beta-CD-MCP sensor following beta-CDMGONPs extraction was investigated by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Under optimal electrochemical parameters, anodic differential pulse voltammetry (ADPV) at +320.0 mV and cathodic differential pulse voltammetry (CDPV) at -800.0 mV were selectively used to detect TC and DC, respectively. The response currents of the beta-CD-MCP sensor exhibited a linear relationship towards TC/DC concentrations ranging from 0.5-90.0 ng L-1. The limit of detection (LOD) of TC or DC was calculated as 0.18 ng L-1. Other validation parameters confirmed the adequate applicability of the proposed system to detect TC/DC in milk samples. The proposed platform showed advantages of simplicity, rapidity, reliability, and low cost compared to other previously published reports.