Analysis of lignins using ³¹P benchtop NMR spectroscopy: quantitative assessment of substructures and comparison to high-field NMR

Lignin is quickly emerging as a biomass-derived source for the production of some crucial organic chemistry building blocks, typically obtained from unsustainable and non-renewable petroleum feedstocks. As a complex polymer, lignin characterization is often challenging due to its random structure and multitudes of different repeating substructures. Over the last 20 years, advances in our understanding and processing of lignin, as well as important work on its characterization using ³¹P NMR, have led to numerous publications highlighting the many potential uses of this material. With the emergence of high-resolution benchtop NMR instruments, these types of analyses can now be accessed by many laboratories and industries that have historically not been able to take advantage of NMR due to cost or size constraints. Herein, we demonstrate that benchtop NMR is a viable technique for the ³¹P NMR analysis of lignin and compare our results to those obtained on a traditional high-field instrument.