Matrix‐Assisted Laser Desorption Mass Spectrometry of Lignins^**

Abstract

tically quantitative yields in all cases. By far the highest asymmetric induction is obtained with the B-methyl and B-n-butyl derivatives 4b and 4c, independent of the lactone used.Discrete eight-coordinate complexes of the actinides, lanthanides, and early transition metals are fairly common. However, only two high-symmetry, idealized, polyhedrons are generally observed; the dodecahedron (DD, D,, point group) and the square antiprism (SAP, D4,)." -31 Various calculations based on interligand repulsion[3' 41 or Hiickel methods['] obtain higher energy surfaces for other geometries, such as the hexagonal bipyramid (HB, D,,), bicapped trigonal antiprism (BTAP, D,,), end-bicapped trig-

Characterization of the water-insoluble fraction from fast pyrolysis liquids (pyrolytic lignin)

“…Reale et al [6] reviewed comprehensively the application of MALDI in lignin chemistry over the last 13 years. In 1992, Metzger et al [7] published a MALDI mass spectrum of birch lignin, which reflected well the molar mass distribution determined by SEC. In that mass spectrum it was also possible to distinguish a fine structure, which has been assigned to oligomeric lignin molecules.…”

Structural elucidation of the wheat straw lignin polymer by atmospheric pressure chemical ionization tandem mass spectrometry and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

“…MALDI-MS of birch lignin indicates that the structure of this polymer is composed of repetitive units, with a molecular mass in the range 600-1800 Da. 8 In our hands, ESI-MS, ESI-MS/MS and MALDI-TOFMS of pine lignin polymer, isolated by the AVIDEL process, indicated the presence of a series of regular homopolymers with varying molecular masses.…”

“…The wheat straw lignin was extracted using the novel AVIDEL procedure, which selectively separates the cellulose, hemicellulose and lignin, and this allows the destructuring of the vegetable matter at atmospheric pressure by a catalyst-solvent system of formic acid-acetic acid. 13,14 Recently, a study on the structural elucidation by MALDI-TOFMS of lignins, 8 chestnut elligitannins and polyflavonoid tannins has been reported. 15,16 The APCI-mass spectra of the lignin extracted from wheat straw in a mixture of formic acid, acetic acid and water were recorded in the negative and positive ion modes and are presented in Fig.…”

Genesis of structural features of humic acids from the sediments of a high productive coastal zone

“…31, 69.46, 91.88, 103.74, 178.12, 236.09, 319.46, 497.13, 531.48, 562.78, 650.20, 666.54, 720.37, 732.17, 840.81, 857.90, 894.42, 945.91, 970.49, 1067.35, 1156.05, 1398.76 1572.40 and 1819.57. Presence of mass fragments m/z 400-1000 is common observation for HAs of diverse origin (Gajdosova et al, 2001;Metzger et al, 1992). MALDI-TOF-MS spectral area between m/z 100-600 confirms the presence of various degraded lignin oligomers in the HAs.…”