Resolution-enhanced Kendrick mass defect plots for the data processing of mass spectra from wood and coal hydrothermal extracts

Abstract

The Kendrick mass defect (KMD) analysis conveniently turns a complex high-resolution mass spectrum into a compositional map with informative clustering of points depending on the elemental composition of the associated ions. It has nevertheless been left unchanged for thirty years with the use of chemical moieties such as methylene as base units for the computation of “regular” mass defects displayed in condensed plots regardless of the samples. The concept of “resolution-enhanced” KMD analysis using the mass of the repeating unit divided by an integer as the new fractional base unit has been recently introduced for the computation of expanded plots from polymeric mass spectral data with a dramatically improved separation of ion series. This user-friendly data processing is extended to the case of carbonaceous samples for the first time with the analysis of water-insoluble organic microspheres recovered from the hydrothermal extraction of wood and coals. In a didactic discussion with illustrative examples, the direct resolution-enhanced KMD analysis, the consecutive resolution-enhanced analysis of a part of a regular KMD plot or the systematic slicing of plots in a multistep procedure are shown to produce simple resolution-enhanced KMD plots or resolution-enhanced zooming from complex mass spectra. The combination of these techniques in a unique “advanced KMD analysis” toolkit is expected to revolutionize the data processing of high-resolution mass spectra with unprecedented separating and unraveling capabilities.