Novel molecularly imprinted polymer thin-films as micro-extraction adsorbents combined with various chromatographic and mass spectrometry systems for selective determination of trace concentrations of thiophene compounds in water

Hijazi, Hassan Yasin (2017) Novel molecularly imprinted polymer thin-films as micro-extraction adsorbents combined with various chromatographic and mass spectrometry systems for selective determination of trace concentrations of thiophene compounds in water. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Thiophene compounds are polycyclic aromatic sulfur heterocycles (PASHs) present in petroleum in concentrations up to 7%, depending on the source. They are considered as the most relevant and problematic components in petroleum products due to their mutagenicity, carcinogenicity, and acute toxicity. These compounds can be used as organic markers for monitoring of oil pollution, which can come into marine waters through regulated oil discharges, accidental oil spills and shipping related inputs. Current analytical methods for thiophenes usually combine solid-phase extraction (SPE) with gas chromatography (GC) or high performance liquid chromatography (HPLC). However, matrix complexity, low analyte concentrations, and the low selectivity of SPE can limit the efficiency of separation and detection. To overcome these problems, selective sorbent materials, such as molecularly imprinted polymers (MIPs) can be used for analysis. MIPs are synthetic polymers that contain artificial recognition sites formed by polymerization in the presence of a template molecule. The molecular recognition mechanism in MIPs is simple. They have a high mechanical and thermal stability, and can be prepared easily at low cost. In our work, MIPs are prepared as thin-films on glass substrates, simplifying fabrication and allowing for flexibility in deployment and use with a variety of detection systems. A pseudo-template is used in the imprinting process to avoid positive bias associated with template-bleeding, which can be problematic when working at low (μg L⁻¹) analyte concentrations. Ours is the first reported MIP for uptake of thiophene compounds from aqueous matrices. Binding affinity, heterogeneity, uptake behaviour of thiophene compounds over a range of concentrations from 0.5-100 μg L⁻¹, and imprinting factors (IFs) for this MIP thin-film have been determined. Coupling of MIP thin-film with different detection systems such GC-MS, head-space GC with sulfur chemiluminescence detection (GC-SCD), and desorption electrospray ionization mass spectrometry (DESI-MS) has been accomplished. Linear calibration curves and reproducible results with low limit of detection values were achieved for the extraction of thiophene compounds from spiked seawater samples using these techniques. The results showed that the MIP films can be used effectively as a selective sorbent for thiophene compounds from water samples.

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