Determination of 3,3′,4,4′-Polychlorinated Biphenyls by an Electrochemical Sensor Based on a Methylene Blue Probe

In this paper, a thiol-β-cyclodextrin—graphene/gold nanoparticles/glassy carbon electrode (β-CD-SH-GR/AuNPs/GCE) electrochemical sensor was prepared by electrochemical deposition and electrode reduction. A new method for the indirect determination of 3,3',4,4'-polychlorinated biphenyls (PCB77) with methylene blue (MB) as an electrochemical probe based on its competitive inclusion of thiol-β-cyclodextrin (β-CD-SH) was established. The electrochemical behavior of MB was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which proved that MB shows good performance for detecting PCB77. Experimental results show a good linear relationship between the concentration of PCB77 and changes in the peak current of MB when the concentration of PCB77 is 0.05–10.0 μmol/L. The detection limit was 0.028 μmol/L (S/N = 3), and the correlation coefficient was 0.9939. The proposed method is suitable for coplanar polychlorinated biphenyl detection with relatively good selectivity and stability, as well as high sensitivity, and was successfully applied to real samples with good recoveries of 94.0%–106.0%.