Ανάπτυξη και αξιολόγηση μεθόδων προσδιορισμού PCBs στα τρόφιμα

Abstract

Polychlorinated biphenyls (PCBs) are industrial compounds which are known to be among the most persistent and widely distributed pollutants in the global ecosystem. Since they are lipophilic, they tend to bioaccumulate in the fatty tissues of living organisms, including humans. Owing to the chemical and physical properties of PCBs, the analysis by conventional methods is difficult and expensive. Therefore simple methods for the detection of PCBs in environmental, industrial and food samples are required. The Ph.D. thesis involved the study, design and construction of electrochemical bilayer lipid membrane-based biosensors for rapid detection of compounds of biomedical, environmental and industrial interest such as PCBs. This work describes a novel electrochemical biosensor based on a supported polymerized lipid film with incorporated Sheep anti-PCB antibody for the rapid detection of aroclor 1242, at the levels of 10-9 M concentrations, in flowing solution streams. The antibody was incorporated into the lipid film during polymerization. Injections of Aroclor 1242 antigen solutions were made into flowing streams of a carrier electrolyte solution. Experiments were done in a stopped-flow mode using lipid mixtures containing 15% (w/w) dipalmitoylphosphatidic acid (DPPA) to provide only a single transient current signal with a magnitude related to the antigen concentration. An immunosensor based on the BLM transduction scheme should be regenerable and capable of multiple analyses. Thus, lipid films containing 35% DPPA were used to examine regeneration of the active sites of antibody after complex formation by washing with the carrier electrolyte solution. Repetitive cycles of injection of antigen have shown that the maximum number of cycles is about 5. The mechanism of signal generation was investigated by physicochemical methods of IR, Raman spectrometry and Scanning Electron Microscopy. The device was tested/ evaluated in real samples of vegetables. The investigation of the effect of potent interferences included a wide range of compounds usually found in foods. The results showed no interferences from these compounds in concentration levels usually found in real samples. The analyses that have been concluded in order to define the PCBs in the foods as well as the comparison of these results against the results of other established methods have proved that the biosensor used provides reliable results and it can therefore constitute a valuable tool for future applications in the field of Environmental Chemistry.