Electrochemical Immunosensorbased On The Niobiumpentoxide For Detection Of Tetracycline In Milk

In this paper, a simple, low cost and high sensitive electrochemical immunosens was successfully fabricated for the detection of tetracycline using a conventional three electrode system （Nb₂O₅ chip and a gold electrode（GCE） as the working electrode, a platinumwire as the auxiliary electrode, and a saturated calomel electrode as the refere-nce electrode）,Which are based on work electrode surface modified with chitosan （CS） and Fe₃O₄ magnetic nanoparticles （MNPs）.ELISA analysis was also conducted to detect tetracycline in the same milk samples and underpinned the applicability of the electroc-hemical immunosensor. The results show that immunesensor can be fabricated using the Nb₂O₅ semiconductor materials as working electrode to detect veterinary drug resi-due in food. The main results as follows:（1） The Ab-MNPs-CS/Nb₂O₅ immunosensor for the determination of tetracycline was structured. The Nb₂O₅ was calcined at 650 ℃ in vacuum, which was cut into 1 cm in diameter. The CS and MNPs was modified on Nb22O5 surface.The assembly process of the immunosensor was characterized using of cyclic voltammograms, electrochemical impedance spectroscopy and scanning electron microscopy respectively. The detection of tetracycline residues in milk was performed using the immunosensor. Under the optimum operating conditions, the fabricated immunosensor showed a linear current response to the tetracycline concentration in the range from 0.04 to 1 ng/mL with a lower detection limit of 0.0224 ng/mL （S/N=3）. Moreover, the fabricated immunosensor has the good specificity, reproducibility and acceptable stability.The relative good recovery form 95.4 to 110% for tetracycline were obtained. The Nb₂O₅ semiconductor materials can be used as working electrode. Which provides a theoretical basis for the development of new electrode materials.（2） The Ab-MNPs-CS/GCE immunosensor for the determination of tetracycline was structured.The CS and MNPs was modified on GCE surface. The Ab was immobilized on the modified GCE surface, and the binding of tetracycline to Ab was analyzed by differential pulse voltammetry.The stepwise assembly process of the electrochemical immunosensor was characterized by cyclic voltammetry and electrochemical impedance and canning electron microscopy. In order to verify the feasibility of the modified materials, the Ab/GCE electrochemical immunosensor was build,Under the optimum operating conditions, the Ab/GCE immunosensor showed a linear currentresponse to the target concentrationin the range from 0.1 to 1 ng/mL with the correlation coefficients of 0.9839 and with a lower detection limit of 0.082 ng/mL （S/N=3）.The relative good recovery is form 75.8% to 83.5%. The Ab-MNPs-CS/GCE immunosensor showed a linear current response to the target concentration in the range from 0.08 to 1 ng/mL with a lower detection limit of 0.0321 ng/mL （S/N=3）. The sensitivity of the Ab-MNPs-CS/GCE immunosensor is 2.5 times than that of Ab/GCE electrochemical immunosensor. It was successfully applied to the detection of tetracycline residues in milk. The Ab-MNPs-CS/GCE has the good specificity, reproducibility and acceptable stability.The relative good recovery is form 95.9 to 108%.（3）The ELISA method was used to detect tetracycline. The tetracycline in same milk samples were detected using ELISA.The ELISA showed a linear response range to tetracycline in the 0.0 μg/L～0.45 μg/L with the correlation coefficients of 0.9920. The linear regression equation is y= 2.389 to 3.57 x. The relative standard deviation is from 1.46% to 7.77%. The recovery is from 97.1 to 104%. The results indicate that the Ab-MNPs-CS/Nb₂O₅ and the Ab-MNPs-CS/GCE immunsensor for detecting tetracycline is reliable, and had a better sensitivity than the ELISA.