GC/mass spectroscopy

This analytical methodology deduces the four photooxidative processes. The data on the total CO2 evolved from the samples were measured by gas chromatography and the isotopic C02 ( 6C02 and 4°C02) data by GC/mass spectroscopy. The rate constants of the two major photooxidative degradation processes at 25°C were deduced from h 18o2 per -(C H NO)- (i.e., to produce C02 product, t = 42 hr) at 196°C and the other from 02 per -(C H NO)- (i.e., to 2produce C02 product, t = 8 min) at 196°C. The rate constants of the former process was estimated as 1.10 x 10- 1 mole sec-- - and the latter as 1.03 x lO-- - 1 mole-- - sec-- -. The activation energies of these two processes were deduced as 10.8 kcal/mole for the former and 15.7 kcal/mole for the latter. 

An initial experiment involved determination of Arapahoe Smoke Chamber results for samples with and without the zinc coating present. Data are presented in Table II. Depending upon orientation of the sample, an increase in char occurred for some samples with zinc present, while no change in smoke formation was seen. Initial pyrolysis GC/mass spectroscopy results at 90CPC in helium showed no difference in volatiles formed with or without zinc. These results suggested enhanced char formation as the origin of the Radiant Panel results for zinc on modified-polyphenylene oxide (m-PPO). Zinc oxide is a known, effective thermal stabilizer in the alloy. The next work then focused on DSC/TGA studies. 

A large number of chemicals, which are used for communication, attack or defense, are secreted by ants. In general, these substances are small molecules, and their availability in minute amounts (50 p,g per ant) does not allow the use of the traditional isolation and characterization procedures. Thus all of the structural work on ant substances rests on gas chromatography (GC), mass spectroscopy, and chemical synthesis. Two review articles have been published on the chemicals from the glands of ants (128, 128a) and we shall mention here only the work relevant to the pyrrolidine field. 

In addition, a total of 146 sheep urine and 87 chicken muscle samples from birds sold in local markets and originating from Brazil, Denmark, France, and Turkey were tested for residues of diethylstilbestrol and ethinylestradiol (41). Although some of the samples were positive to both analytes by an immunochemical screening assay, confirmatory analysis by GC-mass spectroscopy (MS) showed that none of the samples contained residues of the examined steroids. 

The photocatalytic oxidation of alkylbenzenes and alkenylbenzenes has been widely reported. The data concerning alkylbenzenes have shown that the reactivity of toluenes is low when compared to other monosubstituted benzenes (Somarani et al., 1995). The effect of adding a zeolite, which is an acid solid catalyst, by Ti02/UV on various 4-substituted toluenes was studied by Somarani et al. (1995). The compounds of interest were prepared at 0.03 M in solutions containing TiOz. The effect of a zeolite was also studied by adding HY-type zeolites with various Si/Al ratios. The solutions were irradiated with a 125-W mercury lamp emitting light at 330 nm. Samples were taken at 48 hours and analyzed by GC/mass spectroscopy (MS) to determine percent conversions of the toluenes to the desired products. 

Triethylarsine pyrolysis under MOCVD-type conditions was investigated by Speckman and Wendt using GC-mass spectroscopy. In studies of this type it is essential to be mindful of the apparatus employed. Accordingly the appratus is shown schematically in Figures 3 and 4. Their results are summarized in Figures 5 and 6. 

One of the main purposes of derivatization is the transformation of nonvolatile compounds into volatile derivatives. However, it is not the sole purpose of this treatment of analytes. Each chromatographic method [gas chromatography (GC), GC-mass spectroscopy (MS), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), etc.] being... 

To a l l-mol ratio solution of indole and enone in EtOH is added NaAuCl4-2 H2O (5 mol%). The resulting mixture is allowed to react with stirring at RT or at 30 °C while being monitored by TLC or GC-mass spectroscopy (MS). After completion, the solvent is removed by evaporation under reduced pressure. To the residue, acetone (few mL) is added to precipitate the catalyst, which is separated by filtration. The filtrate is concentrated and the crude products are purified by chromatography on silica gel (230-400 mesh) eluting with -hexane/EtOAc mixtures. ... 

Gas chromatography (GC) and GC-mass spectroscopy (GC-MS) methods often rely on the quantitative cleavage of folate to para-amino benzoic acid (pABA), in which molar concentration of HCl is used to hydrolyse folates to pABA, which is subsequently assayed by GC or GC-MS after derivatization (Dueker et al. 2000 Gregory et al. 2006 Lin et al. 2003) with an appropriate reagent. 

One of the limitations of gas chromatography (GC) and conseqnently of GC - mass spectroscopy (MS) is that in many cases polymer additives are insnfficiently volatile to he separated on GC columns operating an even the maximum of their temperature range. As a consequence of this, there is a growing interest in applying high-performance liquid chromatography (HPLC), which is not subject to this temperature limitation, to the analysis of polymer extracts. 

Garteiz, D.A., and Walle,T. (1972) Electron impact fragmentation studies of b-blocking drugs and their metabolites by GC-mass spectroscopy. Journal of Pharmaceutical Sciences, 61,1728-1731. 

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