GC/MS experiments

Infrared (in) spectrometers are gaining popularity as detectors for gas chromatographic systems, particularly because the Fourier transform iafrared (ftir) spectrometer allows spectra of the eluting stream to be gathered quickly. Gc/k data are valuable alone and as an adjunct to gc/ms experiments. Gc/k is a definitive tool for identification of isomers (see Infrared and raman spectroscopy). 

Pyrolysis GC/MS experiments were performed on packing materials recovered from retired columns that had been washed thoroughly. Packing materials near the entrance and exit of the retired column were discarded and not included in the pyrolysis GC experiment. GC/MS used in this study is EIP and the conditions are ... 

GC-MS Experiments. GC-MS pyrolyses were carried out using a Porapak Q column 6-ft (flow rate 35 mL/min) attached to a Finnigan 4000 quadrupole GC-MS. The sample was placed in a stainless steel tube 10 cm long connected to a 4 way valve. One of the outlets was attached to a Porapak Q column interfaced with the M.S. The stainless steel tube containing a portion of Au colloid film was placed in a furnace connected to a Variac provided with a digitial quartz pyrometer to measure the temperature. Three pyrolyses were performed at 100, 200 and 350°C with the Au-acetone film. 

The authors wish to thank the following individuals for performing the experiments Mr. David A. Bulpett of AMTL (PY-GC-MS experiments), Ms. Claudette LeCroy of AMTL (Oxygen Index experiments) and Mr. Stephen D. Ogden of FMRC (experiments in the FMRC s Small-Scale Flammability Apparatus). 

Not all ionization methods are available for use in GC-MS experiments. Because the GC experiment is a gas-phase experiment, only... 

The gas phase limitation imposed by the very nature of the GC-MS experiment limits its applicability to chemical space. The Venn diagram in Fig. 19.4 illustrates an approximate mapping of applicability of the combined chromatography-mass spectrometry techniques discussed here. Using only relative molecular mass and polarity as two dimensions that can map chemical space, the figure indicates that the applicability of GC-MS is limited to those relatively small, thermally stable, nonpolar compounds that can be readily volatized (or made to volatilize by derivatization [26]) to pass through a gas chromatographic column. 

Most optically active polysilanes owe their optical activity to induced main-chain chirality, as outlined above. However, backbone silicon atoms with two different side-chain substituents are chiral. Long-chain catenates, however, are effectively internally racemized by the random stereochemistry at silicon, and inherent main-chain chirality is not observed. For oligosilanes, however, inherent main-chain chirality has been demonstrated. A series of 2,3-disubstituted tetrasilanes, H3Si[Si(H)X]2SiH3 (where X = Ph, Cl, or Br), were obtained from octaphenylcyclote-trasilane and contain two chiral main-chain silicon atoms, 6.16 These give rise to four diastereoisomers the optically active S,S and R,R forms, the activity of which is equal but opposite, resulting in a racemic (and consequently optically inactive) mixture and the two meso-forms, S,R and R,S, which are optically inactive by internal compensation. It is reported that the diastereoisomers could be distinguished in NMR and GC/MS experiments. For the case of 2-phenyltetrasilane, a racemic mixture of (R)- and (A)-enantiomers was obtained. 

In order to gain some information about the fundamentals of the hydrothermal carbonization process, the hydrothermal carbonization of different carbohydrates and carbohydrate products was examined [12, 13]. For instance, hydrothermal carbons synthesized from diverse biomass (glucose, xylose, maltose, sucrose, amylopectin, starch) and biomass derivatives (HMF and furfural) were treated under hydrothermal conditions at 180 °C and were analyzed with respect to their chemical and morphological structures by SEM,13 C solid-state NMR and elemental analysis. This was combined with GC-MS experiments on residual liquor solutions to analyze side products... 

We wish to thank Dr. Y. Y. Lin for assistance with the GC-MS experiments. We are also indebted to Drs. L. W. Jelinski, J. B. Wooten, and G. Odian for helpful discussions during the course of this work. Partial support for this research was provided by grants (to R.E.S.) from the National Science Foundation (DMR-8617595), the Professional Staff Congress-City University of New York, and the College of Staten Island. 

Figure 14. Variation in the carbon number distribution of the bicyclic terpenoid sulfides as a function of depth as shown by the m/z =183 fragmentograms from the SIR-GC/MS experiment. All traces are normalized to the most abundant peak. The oils vary from a heavy Cretaceous oil (Lloydminster) to a light Devonian oil (Leduc). Increasing thermal maturity results in the gradual loss of the isoprenoid side chain until in the Leduc the C13 compound dominates the distribution. Note the intensity distribution of the peaks. Minima occur at C12, C17, and C23. (Reproduced from Ref. 10 with permission. Copyright 1986, Pergamon Journals Ltd.)...

We wish to thank Unilever, Vlaardingen for supplying samples of macrocyclic ketones and Dr. P.E.J. Verwiel and Ing. A. Lakwijk for carrying out GC/MS experiments. The work was supported by a grant from the Dutch Departments of Wildlife Management and Public Works. We also thank Dr. W.J. Doude van Troostwijk and his collaborators of the Committee for Muskrat Control for their valuable help and advices. 

It was fonnd that the pyrolysis of the ATH-filled PMMA yielded only 58% MMA monomer instead of 97% fonnd with a pure PMMA feed. Hydrolysis products from MMA such as methacrylic acid, methanol and isobutyric acid were found to be the other main by-prodncts from the thermal decomposition of this composite material. Pyrolysis-GC-MS experiments showed that the yield of the monomer MMA can be increased to 65 wt% by lowering the process temperature to 400°C. Water released during pyrolysis of ATH and the chemical starter/stabilizer in the composite material were found to be responsible for the low monomer yield. The high amount of the alnmininm components in this material has almost no catalytic influence on the hydrolysis reaction because the same result was found if steam was used as fluidizing medinm instead of nitrogen. 

Table 4.2.2. Typical parameters for Py-GC/MS experiments described in this book.

The differences between low and high-density polyethylene in a Py-GC/MS experiment without hydrogenation is exemplified in Figure 6.1.5. 

The Py-GC/MS experiment for poly(4-vinylpyridine) uses a sample with M = 60,000. The pyrolysis was done in the same conditions as for poly(2-vinylpyridine). The pyrogram for poly(4-vinylpyridine) is shown in Figure 6.5.13 with the peak identification in Table 6.5.12. 

Another Py-GC/MS experiment was performed on polyacrylic /nfer-net-polysiloxane, a copolymer used as impact properties modifier. This is a polymer of butyl acrylate with low levels of allyl, methyl, and 3-(dimethoxymethylsilyl)propyl methacrylates interpenetrated with cyclic dimethylsiloxane. The copolymer has CAS 143106-82-5. The pyrolysis was done at 600 C in He similar to other experiments previously discussed. The pyrogram is shown in Figure 6.7.14 and peak identification is given in Table 6.7.10. 

One more example of pyrolysis results is given for poly(ethylene oxide) with M = 300,000 and is shown in Figure 9.1.5. The Py-GC/MS experiment was done in similar conditions as for other examples (see Table 4.2.2) and peak identification is given in Table 9.1.3. 

Pyrolysis studies on PEEK by thermogravimetry/MS and Py-GC/MS were reported in literature [7], The compounds described to be generated in the Py-GC/MS experiment, which was performed at 971° C, are shown in Table 9.3.2. 

Another polyester with aromatic groups in its structure is poly(diallyl isophthalate), CAS 25035-78-3. This polymer has a crosslinked structure and its pyrolysis products were discussed in Section 3.1. The polymer used for the Py-GC/MS experiment described in Section 3.1 had M = 500,000, and the experimental conditions were similar to those for other examples described in this book (600° C pyrolysis in He and Carbowax column separation). The main pyrolysis product was found to be 1,4-benzendicarboxylic acid di-2-propenyl ester. This compound is the homolog of terephthalic acid dibutylene ester formed in the pyrolysis of PBT. 

The mass spectrum of the GC/MS experiment with an empty reactor provided us with the fragmentation pattern of i3C-labelled 1-butene. Subsequently, isomerization experiments were carried out using fresh and spent HS-FER catalysts. The MS spectra corrected for the fragmentation pattern of the butene in question provided us with the label distribution in butenes. In Fig. 4 the results of the label distribution for isobutene, as obtained from isomerization at 350°C over the catalysts, are displayed. The scrambling of 13C over isobutene as observed with the fresh HS-FER after correction for natural abundance of 3C, is close to the values expected from complete (statistical) scrambling. Clearly, with the spent Ferrierite catalyst, which is still active for butene isomerization, scrambling has not taken place either in isobutene, or in the other butenes. Very similar results were obtained using i3C-labelled isobutene instead of 1-butene. 

Pilotti et al. carried out studies on the identification of tobacco alkaloids, their mammalian metabolites and related compounds by gas chromatography-mass spectrometry using packed columns (SE-30, SE-52 and Carbowax 20 M + KOH) and capillary columns (33 m - Emulphor 0 and 9.6 m - 0V-101). Various pyridine compounds, either identified or implied as intermediates in the manmalian metabolism of nicotine present in tobacco or tobacco smoke, were studied by GC-MS. Preliminary GC-MS experiments on the determination of nicotine using capillary columns in combination with multiple ion detection (MID) employing deuterated nicotine as internal standard were reported. The gas chromatographic data of the compounds investigated... 

We secured about 250 mg of the crystalline and naturally occurring enantiomer (—)-79, and examined its pyrolysis. GC-MS analysis of (—)-79 at the column temperature of 180 °C gave a product with a mass spectrum identical to that reported for Persoons periplanone-A. Having been encouraged by the preliminary GC-MS experiment, about 80 mg of (—)-79 was subjected to thermal decomposition at 220 °C on a 3% OV-17 column, which had been employed by Persoons for his purification experiment. After TLC purification of the thermolysis product, we obtained an oil in 71% yield based on (—)-79, whose IR and H-NMR spectra were identical with those reported for Persoons periplanone-A. It was therefore the pyrolysis product of (—)-79, although its structure was still unknown. 

Recent developments in spectroscopy and in analytical separation science, in the hyphenation of those methods as well as in multidimensional separations, have led to a dramatic increase in the amount of data emerging from a single analytical measurement. For example, a gas chromatography-mass spectrometry (GC-MS) experiment with a capillary column and a... 

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