Optimization and evaluation of the performance of thin-film molecularly imprinted polymers for the analysis of cotinine in fluids from human subjects

Beaton, Adam G. (2019) Optimization and evaluation of the performance of thin-film molecularly imprinted polymers for the analysis of cotinine in fluids from human subjects. Masters thesis, Memorial University of Newfoundland.

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Abstract

Molecularly imprinted polymers (MIPs) are cross-linked synthetic polymers that can selectively take up target analytes from a solution. They are often used in bulk format for solid phase extraction and HPLC. In this work, the main goal was to develop MIPs in a thin-film format for direct analysis of analyte species by desorption electrospray ionization-mass spectrometry (DESI-MS). A cotinine template was used with methacrylic acid (MAA) monomer and ethyleneglycol dimethacrylate (EDGMA) cross-linker to synthesize these MIPs. Cotinine is the primary metabolite of nicotine and was chosen as the template due to its high concentration in biological fluids from smokers and non-smokers. Optimization of the ratios of polymer components (template:monomer:cross-linker) and porogen was completed using a modified Box-Behnken experimental design. Each composition tested was assessed for polymer robustness, imprinting factor and sorption capacity. The optimal molar ratio was 1:2:22.5 (template:monomer:cross-linker), with 239 μL porogen added for each 0.02 mol of template. Template removal from the MIP was studied and reduced from 2 h to 100 min. For optimal analyte uptake, MIPs were placed for 90 min in samples buffered at pH 7.0. Cotinine was quantified in extracts using GC-MS. Myosmine, B-nicotyrine, 1-phenyl-3-pyrazolidinone and nicotine-N-oxide were used as pseudo-templates to overcome template bleed were studied but with little success due to the lack of uptake by these pseudo-templates. Scanning electron microscopy showed that the MIPs were porous and up to approximately 0.05 μm in diameter. Cotinine calibration curves for human urine spiked with cotinine gave results of R²=0.6 with n=2. Testing with saliva samples did not produce any promising results. Proof of principle was demonstrated for detection of cotinine using MIPs with DESI-MS.

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