A label-free impedimetric immunosensor for direct determination of the textile dye Disperse Orange 1

Abstract A strategy for a label-free impedimetric immunosensor is described for detection of the textile dye Disperse Orange 1 (DO1). The compounds 1,12-diaminododecane (DADD) and then 1,7-diaminoheptane (DAH) were firstly successively grafted onto a glassy carbon electrode (GCE) surface by electro-oxidation of one amino group, while the other terminal amino group was modified with the antibody anti-DO1. The construction process of the immunosensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and capacitance measurements. The electron transfer resistance ( R ct ) exhibited an effective response to the affinity between the immobilized antibody and the antigen in solution. The linear range for the target compound was from 5.0 nmol L −1 to 0.5 μmol L −1 ( R =0.9980), and the limit of detection (LOD) was 7.56 nmol L −1 . The proposed impedimetric immunosensor has the advantages of simplicity, cost-effectiveness, and sensitivity.