5401. Identification of sweet cherry anthocyanins and hydroxycinnamic acids using HPLC coupled with DAD and MS detectorPolonca Trebše, Branka Mozetič Vodopivec, 2004, izvirni znanstveni članek Opis: In absence of standards, HPLC coupled with DAD offers identification of polyphenols by scanning UV-Vis spectra of individual components, which spectral characteristics are unique, but not selective. At the same time HPLC-DAD determination methods of polyphenols differ in mobile phase solutions resulting in DAD scanned spectra deviation between different studies, aggravating the precise identification based on agreement to UV-Vis data from literature. Mass spectrometry (MS) detection with molar weight determination of the individual components in the sample enables more precise identification of compounds eluted from the column. Sweet cherry Petrovka polyphenols were separated on C18 Hypersil PEP 300 column (250 x 4.6 mm, 5 [mu]m) using gradient solvent mixture consisting of methanol, water and formic acid. MS and UV-Vis spectra of eluted anthocyanins and hydroxycinnamic acid were recorded. HPLC-MS analyses were performed using a LCQ [sup]TM ion trap, Finnigan, MAT mass spectrometer by atmospheric pressure chemical ionisation (ACPI). Molecular and fragmented ion masses of sweet cherry hydroxycinnamic acids and anthocyanins were determined and with UV-Vis spectra, in the range of 190-600 nm, used for identification of compounds. Electro spray mass spectrum of two hydroxycinnamic acids produced ions with m/z ratios of 353.0 and 337.0, which corresponded to molecular weights of neochlorogenic acid and 3'-p-coumarylquinic acid. The molecular weights of 5 anthocyanins corresponded to cyanidin-3-glucoside (449.0), cyanidin-3-rutinoside (595.1), peonidin-3-glucoside (463.1), pelargonidin-3-rutinoside (579.1) and peonidin-3-rlltinoside (609.2).
Ključne besede: češnje, antociani, hidroksicimetne kisline, HPLC-DAD/MS
Objavljeno v RUNG: 10.07.2015; Ogledov: 5880; Prenosov: 23
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5402. High-resolution X-ray absorption spectrometry of atomic vaporsIztok Arčon, Jana Padežnik Gomilšek, Alojz Kodre, Andrej Mihelič, 2004, izvirni znanstveni članek Opis: A measurement of an x-ray absorption spectrum of a monatomic sample yields pure atomic absorption essential for the EXAFS (Extended X-ray Absorption FineStructure) analysis in cases of a weak structural signal. A construction of an absorption cell to contain vapor sample takes into account specific properties of the investigated element. Metal-vapor absorption cells for the elements K, zn, Rb, Cd, Cs, and Hg are presented and comments are made on the use of materials and the operating mechanisms of the cells.
Ključne besede: X-žarki, absorpcija, EXAFS, absorpcijske celice
Objavljeno v RUNG: 10.07.2015; Ogledov: 5027; Prenosov: 27
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5403. X-ray absorption spectroscopy and related techniquesIztok Arčon, Alojz Kodre, Jana Padežnik Gomilšek, 2004, izvirni znanstveni članek Opis: In the extensive field of X-ray diagnostic techniques, nowadays mostly implemented on synchrotron X-ray sources, the X-ray absorption methods offer a relatively simple tool for structural analysis of materials. The advantage of the methods is the sensitivity to chemical species and the insensitivity to the long-range order. An overview of various detection techniques is given together with the discussion of accuracy of the method with regard to the spatial resolution and the possible contamination by intra-atomic contributions, the multielectron photoexcitations.
Ključne besede: X-žarki, absorpcija, EXAFS, XANES
Objavljeno v RUNG: 10.07.2015; Ogledov: 4764; Prenosov: 26
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