GC/MS analysis

For GC analysis of a sample by a GC system equipped with a capillary column and flame ionization detector (FID) (Note 7), the minimum amount of a constituent that can be detected by a FID is, on the average, approximately 1 ng. Conservatively, the solute concentration of a GC sample should be approximately 50 ng/1 solvent [=0.05mg/ml] per major constituent. Thus, for a sample with ten major constituents, the sample concentration would be approximately 1 mg/ml solvent (=10mg/10ml) after taking into account the presence of minor constituents. The sample solution thus prepared is usually divided into two equal parts. One part is used for determination of the optimum conditions for GC analysis of the sample, i.e., optimum conditions for GC-MS analysis. After the identity of the major constituents of the sample has been established, the remaining half of the solution is used for the quantitative determination of the major constituents. 

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The iaterpretation of forensic toxicology (18) results is often challenging. Courts frequently ask if an amount of dmg detected ia a specimen could cause a specific type of behavior, ie, would someone be under the influence of a dmg at a specific concentration, would a particular dmg concentration cause diminished capacity, or was the dmg the cause of death In a random employee dmg testing case, a worker screened positive for opiates by EMIT and gc/ms analysis of the urine specimen showed low levels of morphine. Although one possibiUty was that the iadividual was a heroia user, a review of foods eaten ia the prior 24 hours suggested a more innocent cause a poppy-seed bagel. 

Isotope peaks can be very informative in GC/MS analysis. Generally for interpretation, one focuses on the monoisotopic peak. The monoisotopic... 

By treating groups of mice with 2,4, 5-trichIorobiphenyI and [35S]cysteine or [35S]methionine the formation of 4-[35S]methylsulfonyl-2,4, 5-trichlorobiphenyl (194) was indicated and shown to deposit in the lungs. GC-MS analysis confirmed the presence of 194 as the minor component60. 

Gardner impact, 243 Gas chromatography/mass spectrometry (GC/MS) analysis, 304 Gaymans, Reinoud J., 135 Gel coats, 30... 

GC-MS analysis showed the crude material to be 95% pure. The title compound is the only detectable species in the NMR-spectrum. The submitters obtained 61.8 g (99%)of the product which was 99.5% pure by GC-MS analysis. 

While the molecular masses of expanded [n]pericyclines 82,83,122 can easily be determined by GC-MS analysis, higher dehydrocyclooligomers fail to vaporize sufficiently [7]. Fast atom bombardment mass spectometry (FAB-MS) had to be applied for the characterization of the acetal-protected expanded pericyclinones 123-126 and 176 [39]. Attempts to determine the molecular masses of the... 

Figure 18. Gas chromatogram from the full-scan GC/MS analysis of a high-temperature distillation fraction (343 °C) containing diamondoids. Taken from Ref. [11] with permission.

APT, GC and GC-MS Analysis ofNIGOGA Reference Samples (NSO-1 andJR-Ij, 2 May 2003, Applied Petroleum Technology AS, Kjeller, Norway. 

Twenty populations were sampled with plants from Hailuoto, at 65°00 N, representing the northernmost site and material from Hanko, at 59°49 N, representing the southernmost collection site (and, incidentally, the southernmost point of land in the country). Five samples represented central Finland with the remainder originating from the southern part. Fifty-five compounds were detected by GC-MS analysis, 53 of which were identified. The data obtained were subjected to complete linkage analysis, which differentiated several clusters that corresponded moderately well with geography. Genetic distance values derived from the RAPD data correlated well with chemical distance values determined from the terpene data (r=0.41, P<0.0001). 

Headspace analysis has also been used to determine trichloroethylene in water samples. High accuracy and excellent precision were reported when GC/ECD was used to analyze headspace gases over water (Dietz and Singley 1979). Direct injection of water into a portable GC suitable for field use employed an ultraviolet detector (Motwani et al. 1986). While detection was comparable to the more common methods (low ppb), recovery was very low. Solid waste leachates from sanitary landfills have been analyzed for trichloroethylene and other volatile organic compounds (Schultz and Kjeldsen 1986). Detection limits for the procedure, which involves extraction with pentane followed by GC/MS analysis, are in the low-ppb and low-ppm ranges for concentrated and unconcentrated samples, respectively. Accuracy and precision data were not reported. 

Oligosaccharides were isolated from PMII by weak acid hydrolysis and separation by SEC and HPAEC-PAD. The isolated oligosaccharides were desalted, reduced and methylated. GC-MS analysis of the partially methylated alditol acetates has been used to reveal the structure of the oligosaccharides. 

In a typical run, bis(l,2-diphenylphosphino)ethane (DPPE) (0.022 g, 0.05 mmol) and 1,3 diene (32.5 mmol) are added to a portion of the co-condensate, containing 5.2 mg of rhodium (0.05 mg. atom) in 10 ml of mesitylene. The solution is introduced by suction into an evacuated, 80 ml stainless steel autoclave. Carbon monoxide is introduced to the desired pressure and the autoclave is rocked and heated at 80 °C. Hydrogen is rapidly charged to give 1 1 gas composition. When the pressure reaches the theoretical value corresponding to the desired conversion, the autoclave is cooled, depressurised, and the reaction mixture analyzed by GLC. The crude product is distilled. The aldehydes are obtained as pure samples by preparative GLC and characterized by H NMR spectroscopy and GC-MS analysis. 

The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

Bentivenga, G., D Auria, M., Fedeli, P., MaurieUo, G., and Racioppi, R. (2004). SPME-GC-MS analysis of volatile organic compounds in honey from Basilicata. Evidence or the presence of pollutants from anthropogenic activities. Int. J. Food Sci. Technol. 39,1079-1086. 

Radovic, B. S., Careri, M., Manglia, A., Musci, M., Gerboles, M., and Anklam, E. (2001a). Contribution of djmamic headspace GC-MS analysis of aroma compormds to authenticity testing of honey. Food Chem. 72,511-520. 

Table 1 Effect of Iron Stress on Chemical Composition of Root Exudates Collected from Barley Plants, as Determined by Combined NMR and GC-MS Analysis (Fan et al., 1997)...

Inspect the culture tubes in the manifold to determine if there is water in the organic eluent for any sample. If a water layer is present, quantitatively transfer the organic phase into a clean culture tube using a small amount of additional solvent as necessary. Return the culture tube containing the organic extract to its proper location in the manifold rack. Remove the Cig and sodium sulfate mbes, and reinstall the silica tubes on the manifold. With the sample remaining in the culture tube, continue to apply vacuum to the manifold to remove excess solvent. When the solvent volume is < 1 mL, discontinue vacuum, and allow the sample to return to room temperature. Adjust the sample volume in the culture mbe to 1 mL with isooctane-ethyl acetate (9 1, v/v). Transfer the entire sample into an autosampler vial for GC/MS analysis. Sample extracts may be stored for up to 1 month in a refrigerator (< 10 °C) before analysis. 

The products were identified by comparing the retention times of the reaction products with commercial compounds, and by GC-MS analysis in a Hewlett-Packard 5973/6890 GC equipped with an electron impact ionization at 70 eV detector and a cross-linked 5% PH ME siloxane (0.25 mm coating) capillary column. The reaction products were separated from the catalyst with filter syringes and analyzed in an Agilent 4890D and a Varian 3400 GC equipped with a flame ionization detector, and CP-Sil 8CB (30 m x 0.53 mm x 1.5 pm) and DB-1 (50 m x 0.52 mm x 1.2 pm) columns, respectively. Decane was used as an internal standard. The catalyst was thoroughly washed after reaction with acetonitrile, acetone and water, and dried overnight under vacuum at 40°C. 

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