Molecularly imprinted polymer thin-film as a micro-extraction adsorbent for selective determination of trace concentrations of polycyclic aromatic sulfur heterocycles in seawater.

A tailor-made porous molecularly imprinted polymer (MIP) thin-film was prepared by in situ photo-radical polymerization on a glass slide and used as a microextraction adsorbent. Detection was carried out using gas chromatography-mass spectrometry (GC-MS) to afford a method suitable for the selective determination of trace concentrations of polycyclic aromatic sulfur heterocycles (PASHs) in seawater. PASHs are one of the most problematic aromatic organic pollutants, as they are considered more persistent and toxic compared to other analogous aromatic compounds in the environment. The optimized thin-film consisted of a 2-thiophenecarboxaldehyde pseudo-template with 1-vinylimidazole (1-Vim) as the functional monomer, bisphenol A dimethacrylate (BPADMA) as the cross-linker, acetonitrile as the porogen, and polyethylene glycol to boost porosity through formation of interpenetrating polymer networks. The adsorption behaviours of the thin-film, including adsorption kinetics, binding isotherms, and selectivity of MIP thin-film were investigated in detail. The highest imprinting factors (2.3-3.0) and adsorption capacity for targeted PASHs were achieved at a template:monomer:cross-linker ratio of 1:4:8. The method with no sample or film pretreatment showed very good reproducibility for the extraction of PASHs from spiked seawater samples (RSDs ≤ 6.0%, n = 3), was linear (R2 > 0.9960) over a range of 0.5-40 µg L-1, and gave limits of detection n the range of 0.029-0.166 µg L-1.