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Chiara Lavarello Sebastiano Barco Martina Bartolucci Isabella Panfoli Emanuele Magi Gino Tripodi Andrea Petretto Giuliana Cangemi 《Molecules (Basel, Switzerland)》2021,26(14)
Liquid-chromatography coupled to high resolution mass spectrometry (LC-HRMS) is currently the method of choice for untargeted metabolomic analysis. The availability of established protocols to achieve a high confidence identification of metabolites is crucial. The aim of this work is to describe the workflow that we have applied to build an Accurate Mass Retention Time (AMRT) database using a commercial metabolite library of standards. LC-HRMS analysis was carried out using a Vanquish Horizon UHPLC system coupled to a Q-Exactive Plus Hybrid Quadrupole-Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Milan, Italy). The fragmentation spectra, obtained with 12 collision energies, were acquired for each metabolite, in both polarities, through flow injection analysis. Several chromatographic conditions were tested to obtain a protocol that yielded stable retention times. The adopted chromatographic protocol included a gradient separation using a reversed phase (Waters Acquity BEH C18) and a HILIC (Waters Acquity BEH Amide) column. An AMRT database of 518 compounds was obtained and tested on real plasma and urine samples analyzed in data-dependent acquisition mode. Our AMRT library allowed a level 1 identification, according to the Metabolomics Standards Initiative, of 132 and 124 metabolites in human pediatric plasma and urine samples, respectively. This library represents a starting point for future metabolomic studies in pediatric settings. 相似文献
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Crystal Structure of non‐aqueous Melaminium Chloride Melaminium chloride was obtained as colorless, needle‐shaped, single crystalline material from solid state reactions between melamin and ammonium chloride. The structure of [C3N6H7]Cl was refined by single crystal X‐ray diffraction: I2/m, Z = 8, a = 852.87(4), b = 1704.4(1) c = 918.44(4) pm and β = 92.165(6)°. The crystal structure contains melaminium ions stacked to columns along [100] and linked via N‐H···N bridges to form bands along [001]. Both of the two distinct chloride ions are stabilized by six hydrogen bonds through distorted trigonal prismatic arrangements of hydrogen atoms to yield a supramolecular structure. 相似文献
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Oriňák Andrej Arlinghaus Heinrich Frank Vering Guido Justinová Martina Oriňáková Renáta Turčániová L’udmila Halama Maroš 《平面色谱法杂志一现代薄层色谱法》2003,16(1):23-27
JPC – Journal of Planar Chromatography – Modern TLC - Two interfaces have been tested for coupling thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry... 相似文献
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A search for suitable reaction conditions in Mukaiyama-type aldol condensations activated by CeCl(3) and InCl(3) revealed that the reaction proceeds best in i-PrOH/H(2)O (95:5). Contrary to literature precedent, no reaction was observed in pure water, and the encountered destruction of the starting silyl enol ether can be ascribed to initial hydrolysis of the Lewis acid. As anticipated from the dual parameter (pK(h), WERC value) characteristics of CeCl(3) and InCl(3), the former proved more efficient as Lewis acid-promoter, in terms of reaction speed and yield. Nevertheless, InCl(3) was a superior catalyst during evaluation of the diastereoselectivity of the process. In this regard, determination of diastereoselectivity as a function of time showed that the InCl(3)-catalyzed reaction is irreversible, whereas the CeCl(3)-catalyzed reaction is a reversible process. In both cases, formation of the syn product is kinetically preferred, although DeltaDeltaG(++)273K(InCl(3)) = 1.50 kcal/mol versus DeltaDeltaG(++)273K (CeCl(3)) = 0.38 kcal/mol. Molecular modeling (semiempirical PM3, ab initio HF/3-21G*, hybrid B3LYP/3-21G*, and B3LYP/LANL2DZ) of the diastereoselective aldol reaction promoted by InCl(3) supports a "closed", Zimmermann-Traxler transition state. 相似文献
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Martina Havlikova Radomir Cabala Vera Pacakova Miroslava Bursova Zuzana Bosakova 《Journal of separation science》2019,42(1):273-284
Sample pretreatment techniques or preconcentration constitute a very important step before the analysis of environmental, clinical, pharmaceutical, and other complex samples. Thanks to extraction techniques it is possible to achieve higher method sensitivities and selectivities. Miniaturization microextraction methods make them more environmentally friendly and only small amounts of samples are required. In the past 30 years, a number of microextraction methods have been developed and used and are documented in thousands of articles. Many reviews have been written focusing on their use in specified professional fields or on the latest trends. Unfortunately, no uniform nomenclature has been introduced for these methods. Therefore, this review attempts to classify all the essential microextraction techniques and describes their advantages, disadvantages, and the latest innovations. The methods are divided into two main groups: single drop and sorbent‐based techniques according to the type of extraction phase. 相似文献
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Six 4-substituted quinolones 6-8, which bear an ω-iodoalkyl chain, were prepared and subjected to reductive radical cyclisation conditions employing BEt(3)/O(2) as the initiator and either Bu(3)SnH or TMS(3)SiH as hydride source. 4-(4-Iodobutyl)-quinolone (6a) and 4-(3-iodopropylthio)-quinolone (8a) gave the respective 6-endo-cyclisation products in good yields. 4-(3,3-Dimethyl-4-iodobutyl)-quinolone (6b) cyclised in a 5-exo-fashion, while the other substrates delivered only reduction products. The cyclisation reactions could be conducted in the presence of a chiral template (1) with high enantiomeric excess (94-99% ee). The association behaviour of substrate 6a to 1 was studied by NMR titration experiments. In the enantioselective cyclisation of 6b a significant nonlinearity was observed when comparing the product ee with the ee of the template. 相似文献