A new electrochemical sensor for ultrasensitive determination the polychlorinated biphenyls (PCBs) is presented here, exploiting the electrochemical route of sensing which has a distinct advantage over other conventional analysis. Chemically converted reduced graphene oxide modified with beta-cyclodextrin polymer (beta-CDP), being more soluble in water and the formation constants of target molecules with beta-CDP are generally stronger and larger than that of beta-CD, provides a platform for the electrochemical detection of PCBs using ferrocene as redox indicator. Ferrocene can form a host-guest complex with beta-CDP. PCBs will replace the ferrocene in the cavity due to its higher affinity towards beta-CDP, offering wide linear range and higher detection sensitivity via selective host-guest interaction. As ferrocene is a well known redox probe and hence can be easily detected using differential pulse voltammetery (DPV) technique. The new method exhibited excellent analytical performance toward PCBs with a low detection limit of 5.0 x 10(-13) M (S/N = 3). More importantly, the developed method was applied to the quantitative determination of PCBs level in sediment core collected from Lake Nansihu and displayed satisfactory results. These results indicate that the method offers considerable potential for trace PCBs monitoring. We believe that the method has a profound impact on the design of a convenient platform for rapid screening and determination of PCBs in environment. (C) 2016 Elsevier Ltd. All rights reserved.