Analysis of complex materials using thermal and chemical degradation methods with laser mass spectrometry.

摘要

The structures of macromolecular compounds were determined by degradation by thermal or chemical methods and analysis by laser mass spectrometry. Pyrolysis-photoionization mass spectrometry was used to analyze synthetic polymers. Pyrolyzates were photoionized with coherent vacuum ultraviolet radiation (10.49 ev) and mass analyzed with a reflectron time-of-flight mass spectrometer. The compositions of acrylonitrile-butadiene copolymers with acrylonitrile contents from 21–51 wt % were determined within ±1 wt % using pyrolysis- photoionization mass spectrometry. The number average sequence lengths of monomers were determined by statistical modeling (first-order Markovian) of the oligomer distributions. A wide variety of polyolefin samples were classified using a principal components analysis. The comonomer content for ethylene-octene and ethylene-butene copolymers in the range of 2–12 wt % α-olefin by partial least-squares analyses. Pyrolysis-photoionization mass spectrometry was also used to determine the deuteration levels for several partially deuterated polybutadienes (23–41 %D). The distribution of deuterium atoms within the polymer chain was estimated by statistical modeling of the C₄ distributions.; Styrene-butadiene and acrylonitrile-butadiene copolymers were partially degraded with ozone and analyzed by MALDI mass spectrometry. Random and block styrene-butadiene copolymers were distinguished by their ozonolysis products. A random ozonolysis model confirmed that the difference between the acrylonitrile contents obtained by ozonolysis/MALDI-MS and those obtained by FT-IR were due, in part, to the ozonolysis process.; The sequestration of hydrocarbons in soils as a function of organic matter, clay and aging time was determined by thermal desorption mass spectrometry. The extent of sequestration for each compound was determined from its temperature of maximum desorption.; Volatile matter evolved during pyrolysis of 20 different rank coals was studied by thermogravimetry-photoionization mass spectrometry (TG-PI-MS). The relative intensities of peaks due to compounds containing oxygen such as C_nH_2nO ( n = 2, 3 or 4), phenols and dihydroxybenzenes decreased with increasing coal rank. The relative intensities of peaks due to aromatic compounds such as naphthalenes, phenanthrenes and pyrenes increased with increasing coal rank. The majority of the compounds observed by TG-PI-MS were products of thermal cleavage of bonds within the coal structure.