Optimization of sample preparation conditions in the study of lignin by MALDI mass spectrometry

Abstract

In this study we compared the efficiencies of six crystalline matrices and their mixtures for the MALDI of lignin and studied the effect of sample application technique and matrix to analyte ratio on the quality of the mass spectrum. It was found that the best results can be obtained when α cyano 4 hydroxycin namic and 2,5 dihydroxybenzoic acids, and also 2,4,6 trihydroxyacetophenone are used as matrices, taken in 10 to 100 fold excesses with respect to lignin and sequentially applied onto the target in the order analytematrix-analyte. The use of ionic liquids as martices for obtaining lignin MALDI mass spectra was proposed for the first time. It was shown that the N tert butyl N isopropyl N methylammonium α cyano 4 hydroxy cinnamate ionic liquid, which forms a homogeneous solution with lignin, gives substantially better results compared to crystalline matrices in the intensity and reproducibility of the mass spectra obtained. The struc ture of MALDI mass spectra of spruce dioxane lignin related to the predominance of units derived from α guaiacylpropanone in the macromolecule is analyzed.

Negative ion mode atmospheric pressure ionization methods in lignin mass spectrometry: A comparative study

“…To study this phenomenon, we selected a number of intense peaks of oligomers in the mass spectra of the DL preparation, containing from two to eight guaiacylpropane structural units and that differed in mass by 196.0736 Da. This value corresponds to a guaiacylglycerol unit, the most common for softwood lignin, with the gross formula of C 10 H 12 O 4 , observed previously in the MALDI‐TOF mass spectra of spruce dioxane lignin . The [C 20 H 19 O 6 ] − ion with m / z 355.1184 which is the base peak in all the mass spectra obtained (excluding the peaks of impurities in ESI spectra) was selected for study.…”

“…Methods such as matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry and atmospheric pressure ionization mass spectrometry, including those in combination with preliminary chromatographic separation, have been used in various studies. Despite the undoubted advantages of MALDI, this method is not currently favored in structural studies of lignin for several reasons, the most important of which is a low ionization efficiency of the biopolymer achieved using conventional matrices …”

Reductive deconstruction of organosolv lignin catalyzed by zeolite supported nickel nanoparticles

“…37,38 The α-cyclodextrin/α-cyano-4-hydroxycinnamic acid (α-CD/CHCA) matrix was prepared by mixing 2.4 ml of a 10 mM aqueous α-CD solution with 75 mM CHCA in 0.4 ml acetonitrile/H 2 O (7/3 v/v) containing 0.1 vol% trifluoroacetic acid. 37,38 The α-cyclodextrin/α-cyano-4-hydroxycinnamic acid (α-CD/CHCA) matrix was prepared by mixing 2.4 ml of a 10 mM aqueous α-CD solution with 75 mM CHCA in 0.4 ml acetonitrile/H 2 O (7/3 v/v) containing 0.1 vol% trifluoroacetic acid.…”

Top‐down lignomic matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry analysis of lignin oligomers extracted from date palm wood

“…Matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry has been used in various lignin structural investigations . Notwithstanding its unquestionable advantages, this method is not widely used for the structural analyses of lignin because of the poor ionization efficiency of the lignin biopolymer using conventional matrices …”

“…11 Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been used in various lignin structural investigations. [16][17][18][19] Notwithstanding its unquestionable advantages, this method is not widely used for the structural analyses of lignin because of the poor ionization efficiency of the lignin biopolymer using conventional matrices. [16][17][18][19] We have performed the direct analysis of the mixture of lignin oligomers without any chromatographic pre-separation and the determination of the ion formulae was accomplished with the aid of some basic rules in MS and MS/MS.…”