AGENT ORANGE HERBICIDES, ORGANOPHOSPHATES AND TRIAZINIC PESTICIDES ANALYSIS USING NEW ORGANIC PHASE IMMUNOSENSORS

The determination of traces of pesticides in edible oils is an important problem. In fact several kind of pesticides are scarcely soluble in aqueous solutions, in addition also the oily matrix is practically insoluble in aqueous solvent, therefore the quantitative determination of these species in oily matrices has always posed a serious problem only partially solved by such techniques as gas chromatography, which are more suitable when employed in a laboratory than in situ. A substantial contribution to solving this problem was the development of Organic Phase Enzyme Electrodes (OPEEs), i.e. enzymatic electrodes capable of operating in organic solvents [1] and that can also act in situ. One classical example is that of inhibition OPEEs [2] to analyse different types of pesticides that are relatively insoluble in aqueous solution, in the development of which also our team was recently involved [3]. The drawback consists in the fact that it is often complained that inhibitio

The determination of traces of pesticides in edible oils is an important problem. In fact several kind of pesticides are scarcely soluble in aqueous solutions, in addition also the oily matrix is practically insoluble in aqueous solvent, therefore the quantitative determination of these species in oily matrices has always posed a serious problem only partially solved by such techniques as gas chromatography, which are more suitable when employed in a laboratory than in situ. A substantial contribution to solving this problem was the development of Organic Phase Enzyme Electrodes (OPEEs), i.e. enzymatic electrodes capable of operating in organic solvents [1] and that can also act in situ. One classical example is that of inhibition OPEEs [2] to analyse different types of pesticides that are relatively insoluble in aqueous solution, in the development of which also our team was recently involved [3]. The drawback consists in the fact that it is often complained that inhibition biosensors are relatively unselective also versus pesticides belonging to different phytopharmaceutical classes. Immunosensors, on the contrary, are the most selective biosensors. However, in the last year we developed a new organic phase Immuno Electrode (OPIE) [4]. Using this new device, applications were developed first of all to detect triazinic pesticides in extra virgin olive oil, obtaining good results [4]. Therefore new applications were recently developed using the novel OPIEs to detect other herbicides and pesticides such as 2,4-D and 2,4,5-T (i.e. agent orange herbicides), atrazine and simazine (triazinic pesticides) and parathion (organophosphate pesticide) both in olive and in sunflower oil. The working conditions were studied and optimized for new OPIE in the first previous research on the triazinic analysis containing in extra virgin olive oil [4]. For the analysis of the same pesticides in sunflowers oil, the only condition changed was the use of 75% V/V n-hexane/chloroform mixture, which replaced the 50% V/V mixture of the same solvents used in the previous research [4] and employed in the competition step of the immunological method. This was because of the better solubility of sunflower oil in the first mixture than in the latter. For all the pesticides studied also the values of the affinity constant were estimated on the basis of the value of the concentration at which half of the maximum response was obtained. kaff were found to be of the order of 106 M-1 in all cases. [1] J. Wang, Y. Lin, Q. Chen, Analyst, 1993, 118, 277-283. [2] J. Wang, E. Demsey, A. Eremenko, and M. R. Smyth, Anal. Chim. Acta., 1993, 279, 203-208. [3] L. Campanella, S. Eremin, D. Lelo. E. Martini, M. Tomassetti, Sens. Act. B, Chem., 2011, 156, 501-515. [4] M. Tomassetti, E. Martini, L. Campanella, Electroanalysis , 2012, 24(4), 842-856