Response Factors Enable Rapid Quantitative 2D NMR Analysis in Catalytic Biomass Conversion to Renewable Chemicals

Abstract

Carbohydrate conversion offers access to a variety of chemicals with diverse functionalities. An accurate analysis of the multiple products in post-reaction material is indispensable for enabling good atom economy in biorefining. A certain need for reconsidering current analytical approaches to chemocatalytic biomass conversion is witnessed by the often poor carbon balances that are reported for carbohydrate conversion processes. Carbohydrate conversion usually includes isomerization and/or dehydration, therefore analytical approaches that are suitable for the distinction and concurrent quantification of isomers are desirable for developing sustainable processes towards known and new chemicals. Quantitative 1D NMR spectroscopy can be used to determine absolute concentrations in the absence of purified reference compounds and can thereafter be used to obtain response factors in other analytical methods resolving the compounds of interest. Here, we show that this approach is applicable for obtaining response factors relative to an internal standard for rapid, highly resolved 2D NMR spectra at natural isotopic abundance. Following calibration, this approach provides a limit of quantification in the order of 0.8 mM within an experiment time of a few minutes. The approach is particularly beneficial for the quantification of compounds at low concentrations, for instance in initial rate experiments, and for the quantification of low populated reaction intermediates.