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Abstract: A highly sensitive and selective label-free impedimetric immunosensor based on silver (Ag) wire electrode for the detection aflatoxin M1 (AFM1) in milk is presented. The sensor was constructed by functionalizing Ag wire coupled with selective monoclonal antibodies of AFM1 through self assembled monolayers. The antigen–antibody interaction was quantified by measuring impedance in the frequency range (1–100Hz) at 10mV applied ac potential. A linear working range (6.25–100pgmL−1) for AFM1 was obtained with 20min analysis time. The sensor sensitivity was found to be about 2.1% impedance change per decade with limit of quantitation 6.25pgmL−1 and limit of detection 1pgmL−1. Good recoveries were obtained with SD=1.13 and R 2 =0.982 in spiked milk samples. The proposed method is useful for sensitive analysis of AFM1 in milk. [Copyright &y& Elsevier]