Room temperature phosphorescence optosensing of benzo[a] pyrene in water using halogenated molecularly imprinted polymers

A selective optosensor for benzo[ a] pyrene (BaP) determination in water samples, using a molecularly imprinted polymer (MIP) for the recognition of the analyte, has been developed. Detection was based on measurements of the native strong room temperature phosphorescence (RTP) emission from the BaP recognized by the MIP The non-covalent MIP was synthesized using BaP as a molecular template. Different halogenated-bisphenol A compounds were compared as precursors in the polymerization ( thus ensuring the presence of a heavy atom, required to induce RTP emission from the analyte). In the developed optosensor, samples are injected in a flow system and the analyte is on-line retained onto the polymeric material. In the absence of oxygen ( using sodium sulfite as the oxygen scavenger) the heavy atom present in the MIP structure induced analytically useful RTP emission from the recognized BaP. After measurement of the luminescent emission, the sensing material can be easily regenerated by passing 2 mL of methanol over the MIP. The optosensor demonstrated a very high selectivity for BaP determination in water even in the presence of other luminophores that could be non-specifically adsorbed onto the MIP surface. Under optimal experimental conditions, a benzo[ a] pyrene detection limit of 10 ng L-1 (20 mL sample injection volume) was achieved with good reproducibility ( a RSD of 3% was obtained for 1 mu g L-1 BaP). Finally, the proposed optosensor was successfully applied to the analysis of spiked natural water with BaP.