Ethyl phenol analysis

Brett flavor in wine The question still remains what is "Brett" flavor Results from our initial work indicates that "Brett" aroma in wine is a complex mixture of odor-active compounds, including acids, alcohols, aldehydes, ketones, esters, and phenolics. Analysis by gas chromatography-olfactometry revealed two predominate odor-active compounds responsible for the Brett flavor in the wines studied isovaleric acid and a second unknown compound other identified odor-active compounds included 2-phenyl ethanol, isoamyl alcohol, cis-2-nonenal, trans-2-nonenal, B-damascenone, ethyl decanoate, guaiacol, 4-ethyl guaiacol, 4-ethyl phenol. Our findings are a snapshot into the much larger picture know as Brett flavor. Ultimately this preliminary investigation requires the descriptive analyses of many more wines to know what odor active compounds describe the flavor know as "Brett". 

R. A. Friedel and L. Pierce, Infrared Analysis of Phenol, Cresols, Xylenols, and Ethyl Phenols, Anal. Chem. 22, 418, 1950. 

Repeat this analysis for the reaction of phenyl methyl ether with HI leading to phenol and methyl iodide or methanol and phenyl iodide and involving protonated phenyl methyl ether as an intermediate. (Note In this case, the appropriate empty molecular orbital is LUMO+2 the LUMO is concentrated primarily on the CO bond.) Which reaction, with ethyl propyl ether or phenyl methyl ether, appears to be more likely to give selective ether cleavage ... 

One of the earlier tests [58] contains as hydrophobic samples toluene and ethyl benzene, as a weakly acidic component phenol, and weakly basic analytes like aniline and the isomeric toluid-ines. Chemometric analysis showed the proper selection of the analytes for characterization, with the surprising result that /V,/V-dimethyl aniline is not a signihcant analyte in characterization for silanophilic interactions [59]. As the mobile phase, a mixture of 49 Vol.% methanol with 51 Vol.% water has been used. In the beginning, an unbuffered mobile phase has been used because silanophilic interactions can be blocked by buffer constituents. For better reproducibility and transfer-ability, a 10 mM phosphate buffer of pH 7 is recommended. The comparison of RP columns for hydrophobic interaction by this test procedure is shown in Figure 2.8. The k value of toluene... 

In a polyphenolic extract, anthocyanins can interfere with other polyphenolics such as pro-cyanidins during HPLC analysis and hence should be removed prior to analysis. Anthocyanins from crude polyphenolic extracts can be removed as described in Basic Protocol 2. The ethyl acetate used for elution of phenolic compounds other than anthocyanins is removed using a rotary evaporator at 20°C. The non-anthocyanin polyphenolics are dissolved in deionized distilled water and the pH is adjusted to 7.0 with NaOH as described in Alternate Protocol 2 or the method developed by Oszmianski and Lee (1990a). In the latter method, polyphenolics were fractionated into three groups neutral fraction A (flavanols and other polar phenolics), neutral fraction B (flavonols), and acidic phenolics. Polyphenolic extracts were adjusted to pH 7.0 with NaOH... 

Although the GC separation of methyl ethers [16] of phenols has been described, these derivatives are nowadays mainly employed only in special instances, e.g., for increasing the sensitivity of the analysis. The determination of chlorinated phenols in spent bleach liquors from paper mills was reported by Lindstrom and Nordin [17]. A water sample was extracted stepwise with diethyl ether at various pH values, after preliminary purification by means of HPLC, phenols were converted into ethyl ethers by reaction with diazoethane in isooctane—ethanol (9 1) and good reproducibility was achieved. 

A solution containing 1 mg of a free base in 1 ml of ethyl acetate was shaken with 0.5 ml of carbon disulphide for 30 min. Under reduced pressure the solution was evaporated to dryness and the residue dissolved in 1 ml of ethyl acetate. Aliquots of 1 pi were taken for analysis. For phenolic and indolic amines 100-pg aliquots of isothiocyanate derivatives are subjected to reaction with a mixture of BSTFA and TMCS (99 1) at 90°C for 15 min. 

Phenolic and acidic pesticides and herbicides were chromatographed as chloromethyl and bromomethyldimethylsilyl derivatives [502] and the entire procedure was applied to the analysis of these substances in soil, as follows. A 1-ml volume of n-hexane, 0.075 ml of dimethylamine and 0.09 ml of halomethyldimethylchlorosilane were mixed in a 5-ml vial, which was then closed and shaken vigorously. The mixture was centrifuged and 0.4 ml of the supernatant was transferred into an 8-ml test tube and 0.1 ml of ethyl acetate containing 100 jug of the substrate was added. The contents were refluxed for 30 min at 65°C, cooled and the reflux condenser was rinsed with 0.5 ml of n-hexane. 

Esterases. Acetyl esterase (EC 3.1.1.6) removes acetyl esters from acetylated xylose and short-chain xylo-oligomers. It s polymeracting counterpart, acetyl xylan esterase (EC 3.1.1.72), has a similar activity, but prefers polymeric xylan.244 In addition to acetate-specific enzyme detection kits, HPLC or GC analysis of acetate release from native extracted xylan and chemically acetylated xylan, colorimetric substrates, such as p-nitrophenol acetate and /3-napthyl acetate, or the fluorometric substrate, 4-methylumbelliferyl acetate are also used to assay acetyl esterases.244,253 The third esterase, ferulic acid esterase (EC 3.1.1.73), hydrolyzes the ester bond between ferulic acid or coumaric acid and the arabinose side chain of arabinoxylan. Assays for this activity are usually carried out using starch-free wheat bran or cellulase-treated gramineous biomass as a substrate and monitoring ferulic or coumaric acid released by HPLC or TLC. When preparing enzyme-treated substrates, care must be taken to employ phenolic-acid-esterase-free cellulases.244 Other substrates include methyl and ethyl esters of the phenolic acids, as well as finely ground plant biomass.240,254,255... 

SBSE can be successfully used in the analysis of environmental samples [93-97] and for food analysis [98, 99]. PDMS is the most commonly used polymer, primarily because of its thermal stability and durability. SBSE has been modified by application of derivatization with different reagents (acetic anhydride, BSTFA, etc) [100-104]. This approach is suitable for the extraction of compounds requiring derivatization. The use of multistep derivatization with several extraction elements (each reaction is performed on a different stir bar) allows efficient extraction, desorption, and chromatographic analysis of compounds with different functional groups (e.g., phenols, steroids, amines, thiazoles, ketones). Acetic anhydride (ester formation), ethyl chloroformate (reaction of acids and amines), tetraethyloborane, and sodium bis-trimethylotrifluoroacetamide have been used for extraction and simultaneous derivatization [105]. 

Thin layer chromatographic analysis is also highly applicable to the determination of aromatic organic acids.In human organisms, aromatic acids are synthesized as metabolites in intoxication by toluene, xylene, and ethyl benzene. These compounds are easily absorbed through the skin or respiratory system, and are oxidized to aromatic acids. The separation, identification, and quantitative analyses of aromatic acids are also necessary because they appear as semiproducts of the biosynthesis of aromatic amino acids in plants (phenolic acids), and metabolites of numerous toxic substances, drugs, and catecholamines. Polar adsorbents and polar-... 

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