Sensing pollutants with iodinated polymers

Molecularly imprinted polymers (MIPs) containing iodine have been used to trap polycyclic aromatic hydrocarbons (PAHs) from river water for optical sensing.

Chemical sensors based on room-temperature phosphorescence (RTP) have been synthesised by Alfredo Sanz-Medel and colleagues from the universities of Oviedo and Granada, Spain, for the selective determination of trace amounts of PAHs in water. The sensors consist of polyurethane MIPs that were prepared using methylene bisphenylisocyanate and tetraiodobisphenol A, in the presence of fluoranthene as the PAH template.

The cavities in the MIP selectively trap fluoranthene in the presence of other PAHs of various sizes that are commonly found in environmental water. Under excitation at 365nm, strong RTP emission was observed at 550nm due to an external heavy atom effect induced by the iodine atoms. An efficient oxygen scavenger such as sodium sulfite was added to prevent quenching of the emission, especially at low fluoranthene concentrations.

RTP is highly selective for the molecules retained in the MIP cavities. Potential interferences from the polymer itself or other non-specifically bound molecules were eliminated, giving a detection limit of 35 mg/L for fluoranthene.

The polymer was easily regenerated with a solvent wash and was reusable for up to 450 cycles without loss of sensitivity.

’The approach opens new perspectives for further research on the preparation of highly selective iodinated MIPs for phosphorescent molecules (eg PAHs, antibiotics, pesticides) in aqueous media,’ said Sanz-Medel. Steve Down