Uniformly 13C Labeled Lignin Internal Standards for Quantitative Pyrolysis−GC−MS Analysis of Grass and Wood

Abstract

With the ever-advancing lignocellulose valorization strategies, lignin analyses need to advance as well. However, lignin quantification still heavily relies on unspecific, time- and sample-consuming gravimetric, and spectrophotometric analyses. Here, we demonstrate that lignin isolates from uniformly 13C-labeled wheat straw, willow, and douglas fir serve as “ideal” internal standards for pyrolysis gas chromatography high-resolution mass spectrometry (py–GC–HR-MS) analyses of plant biomass, allowing the accurate and precise quantification and structural characterization of lignin in grasses, hardwoods, and softwoods. The 13C lignin internal standards were comprehensively structurally characterized by HSQC NMR and py–GC–HR-MS analyses, and their application for lignin quantification was validated in biomass model systems and in actual plant biomass. For all botanical origins and species, the lignin content was determined within 5% relative deviation of the Klason benchmark. These results establish the capab...