Product analysis by gas chromatography

To address whether O2 is involved in f-BuOOH epoxidation by a radical pathway, the corresponding labeling experiments were conducted. The product analysis by gas chromatography-mass spectrometry shows substantial incorporation of from O2 into norbomylene oxide (74.6 2% incorporation vs... 

The symposium upon which this volume is based was organized at a turning point in nitrosamine research. Almost all types of commercial products have been tested for volatile nitrosamines, and there have been a number of outstanding accomplishments of combined university-gov-emment-private industry actions to lower or eliminate volatile nitrosamines in those products found to be contaminated. However, there is still a major gap of knowledge with regard to compounds that are not amenable to analysis by gas chromatography, and this is clearly a frontier of current research. There are also many important questions regarding chemistry, mechanism of action, and relation to human disease whose answers lie in the future of research in this field. 

Stirring was initiated, and the autoclave was heated to 400°C which required 90 minutes for E10 and 100 minutes for El9. The temperature was maintained at 400°C for 1 hour, then lowered to room temperature. The cooling duration to 300°C was 5 minutes for E10 and 40 minutes for El9. Stirring was terminated at room temperature. Gaseous products were removed for analysis by gas chromatography coupled with mass spectrometry (GC-MS). The reaction products were distilled at reduced pressure to remove the spent donor solvent mixture, and the remaining coal products were solvent fractionated. 

Fig. 6 By-product concentration distribution for 1.3% DMTC + 20% O2 at T = 893 K (downstream effluent analysis by gas chromatography) and predicted concentration at two positions along the flow direction [31]...

A sample (ca. 1 g) of K-crotonate was placed in a Pyrex tube (6 mm i.d. (x200 mm) and heated in a metal bath maintained at a constant temperature. The tube was evacuated through the reaction. After a given time the reaction tube was taken out of the bath and allowed to cool to room temperature. The heat-treated salt was weighed and dissolved in aqueous hydrochloric acid solution and extracted with ether. The ether extract was treated with diazomethane. The methyl ester derivatives of the products were subjected to analysis by gas chromatography using diethyl maleate as internal standard. 

Solutions of triethylamine (Et3N) 14 (1.0M), premixed carboxylic acid/alkyl chloroformate (1.0 M respectively), and 4-dimethylaminopyri-dine 15 (0.5 M) in MeCN were introduced into the reactor from separate inlets and the reaction products collected at the outlet in MeCN, prior to analysis by gas chromatography-mass spectrometry (GC-MS). Under optimized reaction conditions, the authors were able to synthesize the methyl 16, ethyl 17, and benzyl 18 esters in quantitative conversion, with no anhydride or deprotection by-products detected (as observed in conventional batch reactions). In addition to the Boc-glycine derivatives illustrated in Scheme 4, the authors also esterified a series of aromatic carboxylic acids with yields ranging from 91 to 100%, depending on the additional functional groups present. 

In a typical experiment, a solution of 1-48 g (0-01 mole) of phthalic anhydride in 8-05 ml (0-1 mole) of pyridine was pyrolyzed at 690° in dry, high-purity nitrogen flowing at the rate of 2-7 1/hr. Contact time was 20-2 sec. The products were distilled to recover 6-34 ml of pyridine. The distillation residue weighed 2-12 g, of which 0-06 g was removed for analysis by mass spectrometry. The remainder was dissolved in ether and separated into nitrogen bases (1-44 g) and hydrocarbons (0-62 g) by extraction with dilute hydrochloric acid. Analysis by gas chromatography, by comparison of retention times with authentic samples, gave the results shown in Table 9. 

Vetter, W. Krock, B. Klobes, U. Luckas, B., Enantioselective analysis of a heptachlorobomane isolated from the technical product Malipax by gas chromatography/mass spectrometry J. Agric. Food Chem. 1997, 45, 4866-4870. 

In some cases, a given step can be coupled on-line with USAL but off-line development provides better results. Such is the case with a method for the determination of the frans-fatty acid content in bakery products [32] following isolation of total fat, the fatty acids must be derivatized to methyl esters, which are volatile, for subsequent analysis by gas chromatography separation with mass spectrometry as detection system. The derivatization reaction must be complete, selective and sensitive enough, which is difficult to accomplish in a continuous manner as the procedure involves ... 

For splitting, 100 g of 1,1-dimethoxy diphenyl propane from the condensation stage (a) were heated to 200° C. in a distillation apparatus fitted with a Claisen attachment, followed by the addition of 0.5 g of concentrated phosphoric acid. The products formed during the splitting reaction distilled off over a period of 15 minutes at about 5 to 30 Torn According to analysis by gas chromatography, the distillate (95.5 g) contained 32.7 g of unsplit 1,1-dimethoxy diphenyl propane, 24.1 g of ira .9-p-anethole, 9.1 g of trans-o- and cns-p-anethole and 1.2 g of p-propyl anisole, corresponding to a yield of 91.4% of anetholes, based on reacted condensate. 

In a round-bottom flask one gives to 469 g of 98% formic acid anti 130 g /i-butanol under agitating successively 20 g concentrated sulphuri acid and 264 g 2-methyl-l-phenyl-propene-2, the temperature of the mixture does not exceed 30°C. After completion of the addition, one agitates for another 2 hours at 30°C. Subsequently, the raw product is mixed with 1600 g 30% caustic soda and warmed up briefly to 80°(h After analysis by gas chromatography the organic phase contains ... 

In this paper, we have compared two commonly used permethylation methods [4, 5] and have applied them to a model carbohydrate compound. The completeness of the methylation steps was established by matrix-assisted laser desorption/ionization tlme-of-flight mass spectrometry (MALDI-TOF MS). The methylated carbohydrate products were acid-hydrolyzed and converted to methylated partially acelylated aldononitrile derivatives (Me PAANs) for linkage analysis by gas chromatography-mass spectrometry (GC-MS) [11]. 

The product gas was separated from the quench water, passed through a filter, and then passed through a gas meter. Samples of filtered gas were withdrawn for analysis by gas chromatography. The char was filtered from the quench water, dried, and analyzed for ash content to verify material balance calculations. 

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