Low-voltage mass

Seven Argonne Premium coal samples ranging from lignite to low volatile bituminous in rank were analyzed by Pyrolysis-Field Ionization Mass Spectrometry (Py-FIMS) in order to determine the existence and structural nature of a thermally extractable "mobile phase". In addition, Curie-point Pyrolysis-Low Voltage Mass Spectrometry (Py-LVMS) was employed to demonstrate the importance of mild oxidation on the thermally extractable mobile phase components. 

The rate of formation of oxidation intermediates was followed by withdrawing aliquots during oxidation runs and determining intensities of the parent peaks in low voltage mass spectra as measures of the relative concentrations of starting hydrocarbon and products. Although sensitivity—i.e., the proportionality factor between parent-peak intensity and concentration—differs from one compound to another, peak heights for any one compound in the spectra of samples of equal size (0.6ft) are... 

During the workup of the o-xylene oxidation run, a strong lachrymator made its presence felt. This was probably a-bromo-o-xylene, although it was not detected in the low voltage mass spectrum. We suspected that a strong peak at mass 104, undoubtedly caused chiefly by a fragment ion derived from o-methylbenzyl alcohol by loss of H20 (I), might also contain a contribution from benzocyclobutene from the interaction of a-bromo-o-xylene with the indium tube used to introduce samples into the spectrometer. To test this possibility, benzyl bromide and a-bromo-o-xylene were run separately under the same conditions. 

Mass spectrometer analyses of the fractions taken at regular intervals indicate the optimum conversions of aromatic hydrocarbons directly to aldehydes and alcohols by oxidation, as shown in Table III. Semiquanti-tative yields derived from low voltage mass spectral intensities and values found by gas chromatography were generally in good agreement—for example, oxidations of toluene and p-xylene, worked up after 2 hours, gave the results shown in Table IV. 

Minor oxidation products are shown in Table V the numbers are relative intensities in the low-voltage mass spectra. The trimeric products... 

Toluene Analysis by Gas Chromatography Estimate from Low-voltage Mass Spectrum... 

By adjusting catalyst concentration from the higher value of Hay and Blanchard to that used in this study, we can direct the oxidation of aromatic hydrocarbons to increase the yields of alcohols and aldehydes. The oxidation period for optimum conversion can readily be determined by low voltage mass spectrometry. 

In many studies precise quantitative data are not needed to clarify the chemistry under study. Especially in a series of related samples, low voltage mass spectrometry can quickly and easily furnish data that parallel changes in concentration and are entirely adequate for the purpose of the study. This analytical tool has enabled us to follow readily the formation and disappearance of products, instead of being limited to observing the rate of oxygen absorption we expect it to be at least equally useful in determining rates and analyzing products of co-oxidations now under way. 

From low voltage mass data. Will not dissolve in benzene. 

Low-voltage mass spectrometry has been used to identify ferrocene and its derivatives, for by using an ionizing voltage of 8 eV only the molecular ion peaks are observed (44,189). Reed and Tabrizi studied the mass spectra... 

To test this prediction, phthalic anhydride was pyrolyzed in admixture with chlorobenzene at 690° (Fields and Meyerson, 1966b). The major products and their relative parent-peak intensities in a low-voltage mass... 

The questions raised by these products led to a study of the pyrolysis products of thiophene itself. Thiophene, 0-4 mole, pyrolyzed alone under the identical conditions as with phthalic anhydride, gave 0-76 g of product (thiophene-free) that analyzed (relative intensities in the low-voltage mass spectrum) ... 

To test this hypothesis, phthalic anhydride, acetylene, and acetylene-d2 were separately reacted with hexafluorobenzene at 690° under the same conditions as those used with acetylene alone. Phthalic anhydride gave tetrafluoronaphthalene, by 1,4-addition, and hexafluorobiphenyl, by insertion of benzyne, in a 1 5 ratio as estimated from the low-voltage mass spectrum and directly-coupled gas chromatography-mass spectrometry ... 

The extracting liquor containing the oily low molecular weight extractable fraction and some antioxidant (2,6-di-tcrt-butyl-p-cresol) was concentrated by evaporation of the volatile solvents and dried in vacuum at 50 °C. for further analysis by GLC, NMR, and low voltage mass spectrometry, or used in other experiments as previously described. 

Low Voltage Mass Spectrometry of Macrocyclic Extractables. Nominal parent mass analyses of the macrocyclic extractables, obtained from typical polymerization products of cyclooctene and 1,5-cyclooctadiene, were performed on a Model MS-9 double focusing mass spectrometer (Associated Electrical Industries, England) at a resolution of 1/1000 and an emission of 7.0 e.v. Samples were introduced directly into the source chamber by the direct-probe technique. The temperature range during the experiment was 125°-200°C., and the source pressure was maintained in the 0.1-3 X 10-6 torr range. In addition, a high resolution measurement was carried out on the mass number 220 to identify the two components present at that mass number. 

Low Voltage Mass Spectrometry. The nominal parent mass numbers of the various components in the low molecular weight extractable fractions obtained from polyoctenamer and poly-1,5-octadienamer are listed in Table I. Quantitative estimation of the relative amounts of individual components were not carried out owing to experimental difficulties. The large variation in the volatilities of the various oligomers limits this procedure to the determination of molecular weights of the oligomers. 

Combining the results of NMR, low voltage mass spectrometry, (Table I), and gas chromatography (Figures 3-7) with the undisputed fact that the low molecular weight extractable fractions can be polymer-... 

The authors acknowledge the assistance of J. K. Phillips for the low voltage mass spectra analyses. 

The pyrolysis methods applied in this study are used as a tool for a general characterization of the organic matter from the sediments. We describe here the results from screening of estuarine and open sea sediment samples by automated pyrolysis low voltage mass spectrometry combined with factor-discriminant analysis. Characteristic mass peaks resulting from this procedure were investigated in more detail by pyrolysis-tandem mass spectrometry and pyrolysis-photoionization GCMS. 

The hydrocarbon ("oil") fraction of a coal pyrolysis tar prepared by open column liquid chromatography (LC) was separated into 16 subfractions by a second LC procedure. Low voltage mass spectrometry (MS), infrared spectroscopy (IR), and proton (PMR) as well as carbon-13 nuclear magnetic resonance spectrometry (CMR) were performed on the first 13 subfractions. Computerized multivariate analysis procedures such as factor analysis followed by canonical correlation techniques were used to extract the overlapping information from the analytical data. Subsequent evaluation of the integrated analytical data revealed chemical information which could not have been obtained readily from the individual spectroscopic techniques. The approach described is generally applicable to multisource analytical data on pyrolysis oils and other complex mixtures. 

Low voltage mass spectra of subfractions 1-15 were obtained on an Extranuclear 5000-1 quadrupole mass spectrometer with Curie-point heating inlet using 1/4 jiil glass capillary probe tips as described by McClennen et al. (4). The inlet was heated to 200 C, electron energy was set at 12 eV. Samples were scanned from m/z 20 to m/z 300. All spectra were recorded with an IBM 9000 computer. 

Figure 2. Low voltage mass spectra of (a) subfraction 1 and (b) subfraction 12.

---