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Muconic Acid (muconic + acid)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Oxidation and chemiluminescence of catechol by hydrogen peroxide in the presence of Co(II) ions and CTAB micelles

LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007
Jan Lasovsky
Abstract The oxidation of catechol in neutral and slightly alkaline aqueous solutions (pH 7,9.6) by excess hydrogen peroxide (0.002,0.09 mol/L) in the presence of Co(II) (2.10,7,2.10,5 mol/L) is accompanied by abrupt formation of red purple colouration, which is subsequently decolourized within 1 h. The electron spectra of the reaction mixture are characterized by a broad band covering the whole visible range (400,700 nm), with maximum at 485 nm. The reaction is initiated by catechol oxidation to its semiquinone radical and further to 1,2-benzoquinone. By nucleophilic addition of hydrogen peroxide into the p -position of benzoquinone C=O groups, hydroperoxide intermediates are formed, which decompose to hydroxylated 1,4-benzoquinones. It was confirmed by MS spectroscopy that monohydroxy-, dihydroxy- and tetrahydroxy-1,4-benzoquinone are formed as intermediate products. As final products of catechol decomposition, muconic acid, its hydroxy- and dihydroxy-derivatives and crotonic acid were identified. In the micellar environment of hexadecyltrimethylammonium bromide the decomposition rate of catechol is three times faster, due to micellar catalysis, and is accompanied by chemiluminescence (CL) emission, with maxima at 500 and 640 nm and a quantum yield of 1 × 10,4. The CL of catechol can be further sensitized by a factor of 8 (maximum) with the aid of intramicellar energy transfer to fluorescein. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Simultaneous determination of t,t -muconic, S -phenylmercapturic and S -benzylmercapturic acids in urine by a rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry method

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2004
Anna Barbieri
We describe a rapid and sensitive high-performance liquid chromatography/electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) method for simultaneous determination of the most relevant metabolites of benzene and toluene, t,t- muconic acid (t,t -MA), S -phenylmercapturic acid (S-PMA), and S -benzylmercapturic acid (S-BMA). Urine samples were purified before analysis by solid-phase microextraction (SPE) on SAX cartridges with 50,mg sorbent mass. The developed method fulfils all the standard requirements of precision and accuracy. Calibration curves were linear within the concentration range of the standards (0,80,,g/Lurine for t,t -MA, and 0,25,,g/Lurine for S-PMA and S-BMA), and had correlation coefficients ,0.997. Limits of detection were 6.0,,g/L for t,t -MA, 0.3,,g/L for S-PMA, and 0.4,,g/L for S-BMA. The method was used to determine t,t -MA, S-PMA and S-BMA levels in urine of 31 gasoline-station workers, with personal monitoring data obtained from radial symmetry passive diffusive samplers. In the context of mean work-shift exposures of 75.9,,g/m3 (range 9.4,220.2) for benzene and 331.9,,g/m3 (78.2,932.1) for toluene, metabolite concentrations in end-of-shift urine samples ranged from 23.5,275.3,,g/gcreatinine for t,t -MA, non-detectable to 0.9,,g/gcreatinine for S-PMA, and 3.8,74.8,,g/gcreatinine for S-BMA. No significant correlation was found between the environmental concentrations and urinary metabolites (p,>,0.05 for all cases); the ratios of benzene metabolites could be influenced by exposure levels and co-exposure to xylenes and toluene. The high throughput of this procedure should facilitate exploration of the metabolic effects of benzene-related co-exposure to toluene and alkylbenzenes in large populations of subjects exposed to gasoline. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Determination of organic acids in urine by solid-phase microextraction and gas chromatography,ion trap tandem mass spectrometry previous ,in sample' derivatization with trimethyloxonium tetrafluoroborate

BIOMEDICAL CHROMATOGRAPHY, Issue 10 2008
Marco Pacenti
Abstract A method for the determination of the organic acids directly in the urine employing derivatization with trimethyloxonium tetrafluoroborate as a methylating agent and sequential extraction by head space and direct immersion/solid phase microextraction is reported. Furoic acid, hippuric acid, methylhippuric acid, mandelic acid, phenylglyoxylic acid and trans, trans muconic acid contained in urine and proposed by the American Conference of Governmental Industrial Hygienists as biological exposure indices were determined after a fast and economically convenient preparation step and sensitive gas chromatography,ion trap,mass spectrometry/tandem mass spectrometry analysis. Urine is rather a complex sample and hence the acquisition method required specific GC-MS instrumentation capable of supporting the changeover, fully automated during a single chromatographic separation, from mass to tandem mass spectrometry and both chemical and electron ionization modes. The automation of the analytical method provides a number of advantages, including reduced analysis time for both routine analysis and method development, and greater reproducibility. The equilibrium and kinetics of this substances vs head space/direct immersion-solid phase microextraction were investigated and evaluated theoretically. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Orientational Control of Guest Molecules in an Organic Intercalation System by Host Polymer Tacticity

CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006
Shinya Oshita
Abstract Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n -alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals. [source]