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Analysis of Pesticide Residues by Chromatographic Techniques Coupled with Mass Spectrometry
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Wan Jing, Jin Maojun, Jae-Han Shim, A.M. Abd El-Aty
Argon gas produces argon ions through the discharge in the ionization chamber. The high-energy argon ions get a high-energy argon atom stream by charge exchange. The argon atom hits the sample placed on a target surface coated with a substrate (such as glycerin), and the sample molecules are ionized. Sample ions enter a vacuum chamber and then enter the analyzer under the action of the electric field. It is not necessary to vaporize them during ionization, so FAB is suitable for the analysis of samples with large molecular weight, difficult gasification, and poor thermal stability, such as peptides, oligosaccharides, natural antibiotics, and organometallic complexes. The mass spectrum obtained by the FAB source not only has strong excimer ion peaks, but also has abundant structural information. However, it is very different from the mass spectrum obtained by the EI source. First, its information of molecular weight is not obtained from the molecular ion peak M, but often from the quasi-molecular ion peak, such as (M+H)+ or (M+Na)+. Second, there are fewer fragmentation peaks than in the EI spectrum. The FAB source is mainly used for magnetic double-focus mass spectrometers. Due to the appearance of electrospray source and laser desorption ionization source, the importance of the FAB source has been greatly reduced.
Synthesis, physicochemical, thermal, and XRD/HSA interactions of mixed [Cu(Bipy)(Dipn)](X)2 complexes: DNA binding and molecular docking evaluation
Published in Journal of Coordination Chemistry, 2020
Nabil Al-Zaqri, Kifah S. M. Salih, Firas F. Awwadi, Ali Alsalme, Fahad A. Alharthi, Amjad Alsyahi, Anas Al Ali, Abdelkader Zarrouk, Meshari Aljohani, Ahmed Chetouni, Ismail Warad
All fine chemicals and solvents were of analytical grade and utilized as delivered. Elemental analyses were verified employing an Elementar Vario EL analyzer. Fourier-transformation infrared spectra were obtained from 4000–400 cm−1 in solid state from KBr disks using a Perkin–Elmer 621 spectrophotometer. Thermogravimetric and differential thermal analyses (TG/DTA) were carried out using a TA Instruments SDT-Q600 in air ambience. Electronic spectra were obtained in water at room temperature using a Pharmacia LKB-Biochrom 4060 spectrophotometer. Fast atom bombardment mass spectrometry (FAB-MS) data were obtained employing a Finnigan 711 A (8 kV), modified by AMD and described as m/z values. The cyclic voltammograms for 1 titrated with DNA different concentrations were measured using a BAS 100 B/W electrochemical workstation in connection with a glassy carbon working electrode and a saturated calomel reference electrode. Hirshfeld surfaces and the attached two-dimensional fingerprint plots were simulated using CrystalExplorer17 [29]. Molecular docking was performed with AutoDock 4.2 using available DNA fragment (PDB ID: 1BNA) [30, 31].
Effect of fluorination on the partitioning of alcohols
Published in Molecular Physics, 2019
Mohammad Soroush Barhaghi, Chloe Luyet, Jeffrey J. Potoff
Concerns about the environmental impact of PFAS led to the phase-out of the two most common surfactants, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS); however, the development of new fluorinated surfactants, some with reduced potential for bioaccumulation, is on-going [12,13]. Analysis of fire sites where aqueous film forming foams (AFFF) had been used in Ontario, Canada, identified 103 different PFAS [14]. Fast atom bombardment and high resolution quadrupole-time-of-flight mass spectrometry performed on seven AFFF formulations used by the United States Military identified 10 unique classes of compounds, with perfluoroalkyl chain lengths ranging from 4 to 12 carbon atoms [15]. The physicochemical properties, environmental fate, and toxicity of these compounds are largely unknown [15].
Extraction of Non-Ferrous Metals and Iron with Systems based on Bis(2,4,4-Trimethylpentyl)Dithiophosphinic Acid (CYANEX 301), A Review
Published in Solvent Extraction and Ion Exchange, 2018
I. Yu. Fleitlikh, N. A. Grigorieva, O. A. Logutenko
CYANEX 301 is a very selective extractant for copper. Complete extraction of copper takes place in the range of hydrochloric acid concentrations of 0.0–12 mol/L and in the range of sulfuric acid concentrations of 0.0–8.0 mol/L.[4] Solvent extraction of copper by CYANEX 301 in xylene from sulfate media was studied by Sole and Hiskey.[20] Since a study of the extraction chemistry by conventional slope analysis or Job’s method is not possible under these conditions, the extracted complex stoichiometries and geometries were determined from analysis of the electronic, phosphorus-31 nuclear magnetic resonance (31P-NMR), and fast-atom bombardment mass spectrometry (FAB-MS) spectra of the complexed species. Copper extraction was shown to be accompanied by a redox reaction in the organic phase, wherein copper(II) is reduced to copper(I) while the extractant itself is oxidized to the disulfide (R–R). CuR is further polymerized in the organic phase, which accounts for its high stability (Eqs. 1 and 2):