Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA) are the most extensively investigated perfluoroalkyl and polyfluoroalkyl substances (PFASs), because human exposition can occur through different pathways, even if the dietary intake seems to be their main route of exposure [1]. They are widely distributed in the environment and should be detected in various kinds of micro-polluted water, such as river water, lake water and seawater. Also due to their remarkable chemical stability, they are inert and refractory to different chemical and microbiological treatments. Consequently, they are persistent, bio-accumulative and toxic to mammalian species. In fact, the immune-toxic effects of PFASs in cellular systems and animals is largely demonstrated [2], and different epidemiologic research have demonstrated possible effects of these chemical compounds on various immune related diseases in humans.
In this work we show a new approach for the selective detection of the PFOA in water solution. The low-cost chemical sensor system is based on a new Molecular Imprinted Polymer (MIP) receptor deposited on a D-shaped POF platform. We have realized the optical sensing D-shaped POF platform using polishing papers [3]. The modification of the surface roughness of the POF’s sensing region allowed to increase the optical sensor’s sensitivity. In the D-shaped POF region, on the exposed core POF, we have deposited by spin coater the MIP's pre-polymeric mixture and we have obtained the polymerization process by oven at 70°C overnight. Finally, we have used a washing step by ethanol to remove the template (PFOA).
The MIP-POF sensor has been characterized using a simple and low-cost experimental setup based on a LED (627 nm), an optical coupler (50:50) and two photodetectors (see Figure 1a).
When the binding between the MIP receptor and the analyte (PFOA) is present the signal output changes. The response of the sensor (k) is defined as the sensor optical power normalized on the reference optical power. The response variation (Δk), respect to 0ppb PFOA (blank), versus the PFOA concentration [ppb], in semi-logarithmic axes, is shown in Figure 1b and the Hill Fitting of the experimental values is also shown.