Polychlorinated biphenyls (PCBs) detection in milk samples by an electrochemical magneto-immunosensor (EMI) coupled to solid-phase extraction (SPE) and disposable low-density arrays

An electrochemical immunosensor for polychlorinated biphenyl (PCB) detection based on graphite screen-printed low-density arrays and on magnetic beads is reported. The immunological reaction for the detection of PCBs is based on a direct competitive assay using alkaline phosphatase (AP) as enzymatic label. After the immunochemical recognition, the modified magnetic beads are captured by a magnet on the surface of the graphite working electrode. The electrochemical detection is thus achieved through the addition of the AP substrate (alpha-naphthyl-phosphate). Two different antibodies (sIgG anti-PCB28 and rIgG anti-PCB77) were tested and compared in terms of sensitivity and ability to recognise different congeners. The developed electrochemical magneto-immunosensor (EMI) was successfully combined with solid-phase extraction (SPE) for the analysis of PCBs in milk samples. In spiked samples a recovery of 80% was obtained. The proposed strategy offers great promise for rapid, simple, cost-effective, and on-site analysis of clinical, food and environmental samples, considering also that low-density arrays allow the simultaneous analysis of different processed samples. (c) 2007 Elsevier B.V. All rights reserved.