Owing to the complex relationship between fermentability and molecular composition, it has become increasingly important to fully characterize biomass pretreatment hydrolysates.  Recent advances have enabled identification of most major components observed in pretreatment samples; however, numerous components remain unidentified.  Moreover, the composition of pretreatment hydrolysates can vary substantially depending on the feedstock type or pretreatment scheme employed, leading to the occurrence of additional compounds that have not been encountered previously.  Considering also that compound abundance is not necessarily correlated with toxicity (i.e., molecules present at low levels may have a greater impact on downstream fermentability than molecules in greater abundance), it is necessary to employ technologies that are capable of rapidly and accurately assessing the composition of pretreatment hydrolysates.
In this work, ultra performance liquid chromatography – ion mobility – high resolution mass spectrometry (UPLC-IM-HRMS) is utilized to screen several biomass hydrolysates resulting from dilute acid, ammonia, and liquid-hot-water pretreatments of a switchgrass feedstock.  Profiling biomass hydrolysates via UPLC-IM-HRMS provides an information-rich, high-throughput technique that is more suitable to the complexity of biomass samples than traditional LC-ultraviolet and LC-MS approaches.  Briefly, the incorporation of an ion mobility spectrometer provides a rapid post-ionization separation technique capable of distributing sample complexity into two dimensions (i.e., mass and size) which has been shown to greatly reduce the complexity of spectra from proteomic and metabolic samples.   In addition, the use of HRMS to identify molecular formulas and ion mobility spectrometry (IMS) to evaluate analyte class enables a discovery-based approach to compositional assessments.