Direct analysis of cellulose in poplar stem by matrix-assisted laser desorption/ionization imaging mass spectrometry

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) was applied to the analysis of the spatial distribution of cellulose on a cross-section of juvenile poplar (Populus deltoids) stems. Microcrystalline cellulose (MCC) was used to optimize matrix (2,5-dihydroxybenzoic acid) application and instrument parameters for the detection of low hexose oligomers, which originated from cellulose in the solid phase. A section of poplar cellulose isolated from juvenile poplar stem which consisted primarily of glucose (∼95%) and minor components such as xylose and lignin was used for the MALDI-IMS studies. The mass spectrum of poplar cellulose consisted of a series of evenly spaced signals having a difference of 162  m/z units, which was similar to that of MCC in linear and reflectron positive ion modes. MS images of cellulose compounds with sodium ion adducts were generated and illustrated the distribution of cellulose on the surface of the poplar stem.