Mass spectrometry and GLC

Mass spectrometry and glc, 12 (1975) 1 Mast cells, calcium and histamine secretion, 19 (1982) 59... 

Many of the resulting complexes can be chromatographed, distilled, or crystallized, and standard methods such as thin layer (tic) and gas-liquid (glc) chromatography are frequently applicable. Mass spectrometry and nmr spectra are very useful for defining structures. For key references to the characterization of organometallic compounds by ir, nmr, mass spectrometry, and glc, see Tsutsui (1971), Maddox et al. (1965), Bruce (1968), Lewis and Johnson (1968), and Guiochon and Pommier (1973). 

Mizutani and coworkers57a confirmed the presence of polychloro(methylsulfonyl)biphenyls (159-170) as sulfur-containing metabolites of chlorobiphenyls (Cl-BP) in the feces of mice based on both GLC-mass spectrometry and chemical derivatization. In some cases comparison with authentic samples (161 and 162) was also made. When preparing 161 and 162,2,5-dichloro-3-(methylsulfonyl)aniline, 2,5-dichloro-l-iodo-3-(methylsulfonyl)benzene and 2,2, 5,5 -tetrachloro-3,3 -bis(methyl-sulfonyl)biphenyl were also obtained and their four peak El mass spectra reported572. Similar data were given for the corresponding 4-substituted intermediates, which were involved in the preparation of 162. Also 2,4, 5-trichloro-2 -(methylsulfonyl)-biphenyl was prepared and its four peak mass spectra given. Metabolites 163 and 164 were also identified by comparison with the authentic standards. 

Dichlorodibenzo- -dioxin. 2-Bromo-4-chlorophenol (31 grams, 0.15 mole) and solid potassium hydroxide (8.4 grams, 0.13 mole) were dissolved in methanol and evaporated to dryness under reduced pressure. The residue was mixed with 50 ml of bEEE, 0.5 ml of ethylene diacetate, and 200 mg of copper catalyst. The turbid mixture was stirred and heated at 200°C for 15 hours. Cooling produced a thick slurry which was transferred into the 500-ml reservoir of a liquid chromatographic column (1.5 X 25 cm) packed with acetate ion exchange resin (Bio-Rad, AG1-X2, 200-400 mesh). The product was eluted from the column with 3 liters of chloroform. After evaporation, the residue was heated at 170°C/2 mm for 14 hours in a 300-cc Nestor-Faust sublimer. The identity of the sublimed product (14 grams, 74% yield) was confirmed by mass spectrometry and x-ray diffraction. Product purity was estimated at 99- -% by GLC (electron capture detector). 

The use of modern physical methods (NMR, UV, and IR spectroscopy, mass spectrometry, and gas-liquid (GLC) and thin-layer (TLC) chromatography is becoming increasingly noticeable. By 19522 few systematic studies of the preparation of derivatives of benzo [6]thiophene had been undertaken, no attempt had been made to alkylate benzo[6]thiophene by means of the Friedel-Crafts reaction, and Friedel-Crafts acylation had been little studied. Halogenation of benzo[6]thiophene had only been superficially investigated and... 

Widely used techniques are GLC, HPLC, and TLC for general identification and quantitation, with mass spectrometry and infrared spectroscopy for specific identification. 

Off-gas analyses were done by mass spectrometry and reactor effluent samples were analyzed by glc. Most of the glc work was done with an 8-foot 1/4-inch OD column containing 10% SE-30 on acid washed Chromsorb W. However, the separation of n-propyl-benzene from cumene had to be done with a dual 3/16-inch copper column consisting of a 12-foot section having 10% Bentone 34 and 10% Dow Corning silicone gum 550 on 60-80 mesh acid washed Chromsorb W and a 6-foot section containing 20% Apiezon L on 60-80 mesh acid washed Chromsorb P. 

The pyrolysis products were separated by trapping in various low temperature baths and the residual noncondensable gases were pumped into a known volume, where the pressure was measured and samples were taken for mass spectro-metric analysis. Samples of the liquid products could be taken for analysis by both mass spectrometry and gas liquid chromatography (GLC). Samples of materials for identification of products were obtained as follows ... 

An early indication that a widely used agricultural chemical might be metabolized to a nonpolar conjugate in plants came from an in vitro enzyme study with C-labeled surfactants of the Triton family. A crude particulate enzyme preparation from com shoots catalyzed the formation of fatty acid ester conjugates from the two 1"c-labeled polyethoxylated surfactants indicated below (Equation 32). The ester conjugates were formed primarily from palmitic and linoleic acids 0851). They were identified by mass spectrometry and by GLC analysis of hydrolysis products (J48). In vljro, rice and... 

The isotopic composition of the reaction product, purified by preparative GLC, was determined by high-resolution mass spectrometry and corresponded to 10.5 it 1.0 mol% C-C4H7T, 12.8 mo % c-C4HeT2, 26.6 mol% C-C4H6T3, 28.9 mol% C-C4H4T4, 16.2 mol% C-C4H3T6, and <5 mol% of more heavily tritiated cyclobutanes. 

Products from oxidative and non-oxidative alkaline treatment of D-galacturonic acid were analysed using glc-mass spectrometry and found to contain 13 hydroxymonocarboxyllc acids and 26 dicarboxylic acids. In the absence of oxygen the main products were 3-deoxy-... 

In summary, the most useful standard procedures for determining the structure of fatty acids are a combination of TLC and GLC separations with mass spectrometry and chemical degradation. Unfortunately, many research workers publish results on inadequately characterized fatty acids and it cannot be over-emphasized that relative retention times on GLC are insufficient to conclusively identify a given compound. 

Poly(dimethyl/methylphenyl siloxane)s and poly(dimethyl/diphenyl siloxane)s have been prepared with a range of phenyl contents and their thermal degradations studied. The products of degradation are shown to be benzene and a complex mixture of cyclic oligomers, the latter being analysed by GLC, mass spectrometry, and n.m.r. spectrometry. The mechanism of degradation is discussed in relation to the degradation reactions previously described for (PDMS) and poly(methylphenyl siloxane)s. A study of soluble and insoluble heat stability additives for (PDMS) has been reported and a mechanism of stabilization proposed. ... 

The preparative reactions were conducted in sealed tubes in which — 1-3 g of the reagents had been placed. After the vessels had been maintained at the indicated temperatures for the designated times, the contents were removed, to be separated by fractional condensation and GLC. In addition to the (trifluoromethyl)Group 4A halides reported next, each sample contained unreacted (CFalaHg, the expected (tri-fluoromethyDmercuric halide, and the mercuric halide, identified by fluorine-NMR spectroscopy and mass spectrometry. 

The chemical purity and identity of the unlabeled and labeled chemicals were determined by infrared spectroscopy, mass spectrometry, GLC, and TLC. 

The synthetic preparation of 2,8-dichlorodibenzo-p-dioxin was facilitated in that the chemical precursor, 2,4,4 -trichloro-2 -hydroxydiphenyl ether, was available as a pure material. Condensation was induced by heating the potassium salt at 200 °C for 15 hours in bis (2-ethoxyethyl) ether. Product analysis by GLC and mass spectrometry revealed an unexpected dichlorophenol and a monochlorodibenzo-p-dioxin. Further, the product initially isolated by crystallization from the reaction mixture was 2,7-dichlorodibenzo-p-dioxin, rather than the expected 2,8-isomer. Cooling of the mother liquor yielded crystalline plates which were shown to be 2,8-dichlorodibenzo-p-dioxin by x-ray diffraction (Reaction 2). 

The o-dichlorobenzene extracts were combined and analyzed by GLC. Four peaks were observed under standard GLC conditions in the 10 to 15 min retention time range which is characteristic of hexachloro-dibenzo-p-dioxins (sample 1 in Table IV). The mixture was fractionally sublimed (120° to 175°G/1 mm). The major crop was harvested at 175 °G and recrystallized from anisole. Analysis of this material by GLG indicated that two isomeric hexachlorodibenzo-p-dioxins were present (sample 2). Overall yield (1.5 grams) of the product was 1-3% at 99+% purity, as determined by GLG and mass spectrometry. 

Spiroaziridinium compounds have also been synthesized under photochemical conditions. For example, the photolysis of piperidine 83 in acetonitrile resulted in 3-azoniaspirooctane 85 (Equation 19) <1997JOC6903>. Its presence was detected by H NMR spectroscopy and mass spectrometry. This azoniaspiro species was thought to be transient and went on to form N-substituted piperidines which were qualitatively identified by gas liquid chromatography (GLC). 

Many sophisticated analytical techniques have been used to deal with these complex mixtures.5,45,46 A detailed description is not possible here, but it can be noted that GLC, often coupled with mass spectrometry (MS), is a major workhorse. Several other GLC detectors are available for use with sulfur compounds including flame photometer detector (FPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED).47 Multidimensional GLC (MDGC) with SCD detection has been used48 as has HPLC.49 In some cases, sniffer ports are provided for the human nose on GLC equipment. 

J. N. Damico and R. P. Barron. Application of Field Ionization to Gas-Liquid Chromatography-Mass Spectrometry (GLC-MS) Studies. Anal. Chem., 43(1971) 17-21. 

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