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Niacinamide analysis using molecularly imprinted polymers Mistry, Reena

Abstract

The objectives of this research were to use molecularly imprinted polymers (MIP) and microfluidic chips as an approach to a rapid and low cost analytical method for niacinamide analysis. Lab-on-a-chip (microfluidics) devices are becoming increasingly popular due to their relatively low cost, sensitivity, and speed. MIPs may be able to serve as solid-phase extraction packing material in microfluidic chips. To reach the objectives, it was necessary to identify the mechanisms by which binding of analyte to polymer occur, determine the optimal functional monomer to cross-linker ratio, and gain an understanding of the polymeric structure and characteristic bonds. An MIP was created using niacinamide (NAM) as the template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, azobisisobutyronitrile (AIBN) as the free-radical initiator, and chloroform as the porogen. It was hypothesized that rebinding occurs via hydrogen-bonding of the carbonyl and amide groups of NAM to the oxygen atoms in the carboxyl group of MAA. Rebinding studies were conducted using compounds with similar functional groups to NAM to determine binding mechanism to the polymer. Both the pyridyl nitrogen and the amide group were found to be important in hydrogen bonding interactions with the polymer. Polymers were optimized for rebinding by using different ratios of functional monomer:cross-linker (MAA:EGDMA) and determining imprint factor of NAM to each polymer. The 1:4 polymer yielded the highest imprinting factor, indicating that the polymer is most selective for NAM. FTIR was conducted to determine the structure of polymers created and whether NAM detection and quantification was possible. There was a peak at 1725 cm⁻¹, which was a shift of the C=O stretching band from 1694 cm⁻¹ in MAA and 1717 cm⁻¹ in EGDMA, indicating a chemical interaction between the two compounds. The disappearance of a peak at 1633 cm⁻¹ showed a loss of conjugation in the carboxylic acid in the polymeric structure. Through this research, knowledge was gained about the polymer optimization and structure. However, more studies need to be conducted to determine the feasibility of an MIP application for a lab-on-a-chip device.

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