Rational design of polymer-based absorbents: application to the fermentation inhibitor furfural

BACKGROUND: Reducing the amount of water-soluble fermentation inhibitors like furfural is critical for downstream bio-processing steps to biofuels. A theoretical approach for tailoring absorption polymers to reduce these pretreatment contaminants would be useful for optimal bioprocess design. RESULTS: Experiments were performed to measure aqueous furfural partitioning into polymer resins of 5 bisphenol A diglycidyl ether (epoxy) and polydimethylsiloxane (PDMS). Experimentally measured partitioning of furfural between water and PDMS, the more hydrophobic polymer, showed poor performance, with the logarithm of PDMS-to-water partition coefficient falling between −0.62 and −0.24 (95% confidence). In contrast, the fast setting epoxy was found to effectively partition furfural with the logarithm of the epoxy-to-water partition coefficient falling between 0.41 and 0.81 (95% confidence). Flory-Huggins theory is used to predict the partitioning of furfural into diverse polymer absorbents and is useful for predicting these results. CONCLUSION: We show that Flory-Huggins theory can be adapted to guide the selection of polymer adsorbents for the separation of low molecular weight organic species from aqueous solutions. This work lays the groundwork for the general design of polymers for the separation of a wide range of inhibitory compounds in biomass pretreatment streams

Tailoring Polymer Micro-extraction Phases to Enhance the Sensitivity and Selectivity of Raman Spectroscopy

Thesis (Ph.D.)--University of Washington, 2013Raman Spectroscopy (RS) systems are evolving toward portable, affordable, and highly versatile analytical chemistry platforms, though sensitivity, selectivity, and fluorescence in many complex multi-component real-world samples remains challenging. We investigated the combination of solid phase micro-extraction (SPME) with Raman spectroscopy as a strategy to address some of these limitations. SPME is best known as a technique in chromatography that uses hydrophobic polymer phases like polydimethylsiloxane (PDMS) to extract and preconcentrate non-polar target analyte in headspace analysis. SPME not only enhances detection by pre-concentration of analytes, but when combined with Raman spectroscopy, offers an opportunity to reduce interference from the background by tailoring the polymer phase to specific classes of analytes in complex mixtures. Here we establish SPME/Raman as a quantitative technique that is capable of enhancing the measurement of organic contaminates in water, anesthetic compounds in serum, and inhibitory molecules in the multi-phase and multi-component broths produced by pretreatment of biomass. Flory-Huggins theory is used to describe the predicted trends in the thermodynamic partitioning of dilute analytes into polymer phases. We show experimentally and theoretically that the equilibrium partitioning, denoted by the partition coefficient K, can enhance the Raman signal by 2 orders of magnitude or more when the analyte is detected in the polymer phase rather than the solvent phase. Specifically, we find that SPME/Raman measurements of aqueous benzene and toluene partitioning into PDMS phases have log (K) values of 2.35 and 1.90, respectively, matching literature values determined with other methods. We also examine the use of SPME/Raman for enhanced detection of general anesthetics (halothane, isofluorane, propofol), quinoline, and fermentation inhibitors (furfural, HMF) into either PDMS or epoxy polymer phases. We then demonstrate the utility of Flory-Huggins theory in understanding and optimizing the selection of polymer-analyte pairs to enhance the sensitivity and selectivity of SPME/RS