Pyrolysis-desorptiodchemical-ionisation mass spectrometry (PyD/CIMS), using ammonia as ionization gas, was employed to investigate the influence of potassium hydroxide on the pyrolytic behaviour of glucans. The mass spectrum of native amylose, a 1+4 linked a-D-glucan, revealed an ion series pointing to desorption of intact 1,6-anhydro-oligosaccharides. Ions indicating oligomers up to the nonamer were observed. Addition of trace amounts of potassium hydroxide to amylose resulted in reduction in the size of the 1,,6-anhydro-oligosaccharide ions and a simultaneous increase of ions resulting from ring rearrangements. Larger amounts of potassium hydroxide led to a complete loss of mass spectral information at the oligomer level.Similar mass spectrometric distributions in the PyD/CIMS data of a potassium hydroxide extracted tobacco fraction clearly reveal that alkali remnants must be present in this sample, which severly reduce the mass spectrometric information from polysaccharide oligomers. It is important to evaluate the role of inorganics on the thermal activation and subsequent fragmentation of biopolymers in PyD/CIMS experiments.In the course of the pyrolysis/mass spectrometric analysis under chemical ionization (CI) conditions of KOH extracted plant polymer fractions, an effect of residual potassium hydroxide on the quality of the mass spectral data was noted. In order to study this effect, amylose spiked with increasing amounts of potassium hydroxide was studied by pyrolysis-desorptiodchemicalionization mass spectrometry (PyD/CIMS), using ammonia as a reagent gas. The effect of salts, organic solvents, acids, and bases on the pyrolytic behaviour of amylose has been investigated by van der Kaaden et d 3 using Curie-point pyrolysis/mass spectrometry (CuPy/MS). It was shown that the matrix plays a prominent role in the thermal activation and subsequent fragmentation of this polymer. However, the investigations were limited to the (sub)-monomer level. PyD/CIMS has several advantages compared to CuPy/MS. In CuPy/MS, fragments generated upon pyrolysis of biopolymer material enter an expansion chamber before ionization occurs in the ion source. Mass fragments heavier than 250 mass numbers are not detected in this mode due to low transmission of these fragments to the ion source. Mass spectral information up to the hexamer is contained in PyD/CIMS data of cellulose, when this incorporates soft ionization by using ammonia as a reagent gas in the chemical ionization.' Although the heating rate of the platinum wire (approx. 10 K/s) used by in-source pyrolysis techniques is much lower than the heating rate used in the CuPy/MS mode (approx. SO00 K/s), previous experiments2 have shown that the mass spectral data obtained by both methods are comparable.The present PyD/CIMS study was undertaken to investigate the effect(s) of potassium hydroxide on the fragmentation pattern of amylose, especially at the oligomer level.
SUMMARYThis paper presents an evaluation of a fractionation procedure for use with tobacco. Correlation coefficients calculated from the weights of the polymer fractions obtained and data obtained with classical wetchemical methods show that these parameters have a low resolving power, which precludes any detailed distinction between tobaccos and tobacco-derived fractions. Pyrolysis mass spectrometry combined with multivariate analysis is presented as a promising approach for investigating the variability in the chemical composition of tobacco. Multivariate analysis performed on the pyrolysis mass-spectrometric fingerprints of all tobacco fractions indicates that the differences between the individual tobaccos are smaller than the differences induced by the fractionation procedure. Multivariate analysis of subfdes of the pyrolysis mass-spectrometric fingerprints of separate polymer fractions is an excel- lent method for classifying tobaccos. Leaf and stem material can easily be distinguished. A further differentiation is made between the flue-cured and Burley-type tobaccos. The strong clustering of tobacco samples after treatment with potassium hydroxide points to a uniform cell-wall skdeton. The greater variability in the ethanolized tobacco samples, and samples subjected to hot-water extractia:n or amylase digestion, is related to the cytosol characteristics. These fractions appear to reflect both the dissimilarities between the distinct tobacco types and phenotypic variations due to differences in cultural management. Pyrolysis mass spectrometry of the K.lason lignin residues points to a large variety of chemical constituents unrelated to lignin. Pyrolysis gas-chromatography mass-spectrometric data on the K.lason lignin residues of a Burley tobacco showed that the correlation made between the organic-nitrogen content and the protein content of this fraction might be misleading. As a consequence the maximum value for the lignin content of this tobacco is estimated incorrectly. sieurs variables (multivariance) se rC:vele une approche prometteuse pour !'etude des differences de composition chimique des tabacs. L'analyse des spectres de masse (fingerprints) obtenus aprh pyrolyse de toutes les fractions de tabac montre que les differences existant entre les divers types de tabac soot plus faibles que celles qui soot induites par la mC:tbode de fractionnement. L'analyse (multivariance) realisee separement sur les spectres de masse des differentes fractions polymeres est une excellente methode pour la classification des tabacs. Les cOtes et les feuilles se distinguent facilement; le tabac Hurley et le tabac «flue-cured• soot aussi nettement differencies. La formation marquee de grappes (cluster) parmi les ecbantillons apres traitement par l'hydroxyde de potassium indique que la structure de la paroi cellulaire semble etre la meme chez tous les tabacs. Apres extraction par l'Ctbanol suivie d'une extraction par I' eau chaude ou d'un traitement par !'amylase, on obtient dans chaque cas des residus presentant une varia...
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