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acid base strong ion

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https://www.readbyqxmd.com/read/28209350/n-decyl-s-trityl-r-cysteine-a-new-chiral-selector-for-green-ligand-exchange-chromatography-applications
#1
Andrea Carotti, Federica Ianni, Emidio Camaioni, Lucia Pucciarini, Maura Marinozzi, Roccaldo Sardella, Benedetto Natalini
In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C10-(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for ligand-exchange chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C10-(R)-STC-based CSP, with resolution factor (RS) values up to 8...
February 5, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28208256/effects-of-drift-gas-selection-on-the-ambient-temperature-ion-mobility-mass-spectrometry-analysis-of-amino-acids
#2
Kimberly L Davidson, Matthew F Bush
Ion mobility (IM) separates ions based on their response to an electric field in the presence of a drift gas. Because of its speed and sensitivity, the integration of IM and mass spectrometry (MS) offers many potential advantages for the analysis of small molecules. To determine the effects that drift gas selection has on the information content of IM separations, absolute collision cross sections (Ω) with He, N2, Ar, CO2, and N2O were measured for the 20 common amino acids using low-pressure, ambient-temperature ion mobility experiments performed in a radio frequency-confining drift cell...
February 7, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28193054/conductometric-gradient-ion-exclusion-chromatography-for-volatile-fatty-acids
#3
C Phillip Shelor, Purnendu K Dasgupta, Hongzhu Liao
We describe a fatty acid vapor extractor (FAVE) as a postcolumn device for sensitive detection following ion exclusion chromatographic (ICE) separation of weak acids. The device consists of a single length of a permselective membrane tube surrounded by a jacket that consists of two isolated sections. The separation column effluent flows through the lumen. A suitable strong acid is put in the upstream, short section of the jacket and permeates in, rendering the lumenal flow strongly acidic (pH ≤ 2) that suppresses eluite weak acid dissociation...
December 20, 2016: Analytical Chemistry
https://www.readbyqxmd.com/read/28163341/complexation-of-nickel-ions-by-boric-acid-or-poly-borates
#4
REVIEW
Anais Graff, Etienne Barrez, Philippe Baranek, Martin Bachet, Pascale Bénézeth
An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel-boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C...
2017: Journal of Solution Chemistry
https://www.readbyqxmd.com/read/28156116/structural-and-transport-properties-of-tertiary-ammonium-triflate-ionic-liquids-a-molecular-dynamics-study
#5
Amir Taghavi Nasrabadi, Lev D Gelb
Ammonium-based protic ionic liquids (PILs) have shown promising physicochemical properties as proton conductors in polymer membrane fuel cells. In this work, molecular dynamics simulations are used to study the structural, dynamic, and transport properties of a series of tertiary ammonium triflate PILs. Nonpolarizable all-atom force fields were used, including two different models for the triflate anion. Previous simulation studies of these PILs have yielded poor results for transport properties due to unrealistically slow dynamics...
February 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28121142/stable-covalent-organic-frameworks-for-exceptional-mercury-removal-from-aqueous-solutions
#6
Ning Huang, Lipeng Zhai, Hong Xu, Donglin Jiang
The pre-designable porous structures found in covalent organic frameworks (COFs) render them attractive as a molecular platform for addressing environmental issues such as removal of toxic heavy metal ions from water. However, a rational structural design of COFs in this aspect has not been explored. Here we report the rational design of stable COFs for Hg(II) removal through elaborate structural design and control over skeleton, pore size, and pore walls. The resulting framework is stable under strong acid and base conditions, possesses high surface area, has large mesopores, and contains dense sulfide functional termini on the pore walls...
February 7, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28102930/modulation-of-the-thermodynamic-signatures-of-an-rna-thermometer-by-osmolytes-and-salts
#7
Mimi Gao, Loana Arns, Roland Winter
Folding of ribonucleic acids (RNAs) is driven by several factors, such as base pairing and stacking, chain entropy, and ion-mediated electrostatics, which have been studied in great detail. However, the power of background molecules in the cellular milieu is often neglected. Herein, we study the effect of common osmolytes on the folding equilibrium of a hairpin-structured RNA and, using pressure perturbation, provide novel thermodynamic and volumetric insights into the modulation mechanism. The presence of TMAO causes an increased thermal stability and a more positive volume change for the helix-to-coil transition, whereas urea destabilizes the hairpin and leads to an increased expansibility of the unfolded state...
January 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28099805/the-importance-of-cannizzaro-type-reactions-during-electrocatalytic-reduction-of-carbon-dioxide
#8
Yuvraj Y Birdja, Marc T M Koper
A seemingly catalytically inactive electrode, boron-doped diamond (BDD), is found to be active for CO2 and CO reduction to formaldehyde and even methane. At very cathodic potentials, formic acid and methanol are formed as well. However, these products are the result of base-catalyzed Cannizzaro-type disproportionation reactions. A local alkaline environment near the electrode surface, caused by the hydrogen evolution reaction, initiates aldehyde disproportionation promoted by hydroxide ions, which leads to the formation of the corresponding carboxylic acid and alcohol...
January 30, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28099170/exploring-the-ability-of-the-nalidixate-to-sensitize-visible-and-near-infrared-emitting-lanthanide-iii-cations
#9
Svetlana V Eliseeva, Valerii S Liasotkyi, Iurii P Golovach, Pavel G Doga, Valery P Antonovich, Stéphane Petoud, Svetlana B Meshkova
Recently, a strong interest has been directed towards near-infrared (NIR) emitting lanthanide(III) compounds as they do possess complementary advantages in respect to organic molecules and semi-conductor nanocrystals, especially in the fields of biological analysis and imaging. To benefit from their emission, a key requirement to fulfill is the sensitization of lanthanide(III) cations with an appropriate chromophore. This condition is especially challenging to address for the lanthanide(III) cations emitting in the NIR...
January 18, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/28070588/a-silica-based-sers-chip-for-rapid-and-ultrasensitive-detection-of-fluoride-ions-triggered-by-a-cyclic-boronate-ester-cleavage-reaction
#10
Jian Zhang, Lifang He, Peirong Chen, Chao Tian, Jianping Wang, Bianhua Liu, Changlong Jiang, Zhongping Zhang
Chemical sensing for the convenient detection of trace aqueous fluoride ions (F(-)) has been widely explored with the use of various sensing materials and techniques. It still remains a challenge to achieve ultrasensitive but simple, rapid, and inexpensive detection of F(-) for environmental monitoring and protection. Here we reported a novel surface-enhanced Raman scattering (SERS) nanosensor, fluorescein phenylboronic acid covalently linked to 1,4-dimercapto-2,3-butanediol modified Au@Ag NPs by a cyclic boronate ester (Flu-PBA-Diol-Au@Ag NPs), for the rapid and ultrasensitive detection of F(-)...
January 10, 2017: Nanoscale
https://www.readbyqxmd.com/read/28063295/role-of-calcium-ions-on-the-removal-of-haloacetic-acids-from-swimming-pool-water-by-nanofiltration-mechanisms-and-implications
#11
Linyan Yang, Jin Zhou, Qianhong She, Man Pun Wan, Rong Wang, Victor W-C Chang, Chuyang Y Tang
We investigated the removal of haloacetic acids (HAAs) from swimming pool waters (SPWs) by two nanofiltration membranes NF270 and NF90. The strong matrix effect (particularly by Ca(2+)) on membrane rejection prompts us to systematically investigate the mechanistic role of Ca(2+) in HAA rejection. At typical SPW pH of 7.5, NF90 maintained consistently high rejection of HAAs (>95%) with little influence by Ca(2+), thanks to the dominance of size exclusion effect for this tight membrane (pore radius ∼ 0...
November 14, 2016: Water Research
https://www.readbyqxmd.com/read/28034959/counting-the-ions-surrounding-nucleic-acids
#12
David R Jacobson, Omar A Saleh
Nucleic acids are strongly negatively charged, and thus electrostatic interactions-screened by ions in solution-play an important role in governing their ability to fold and participate in biomolecular interactions. The negative charge creates a region, known as the ion atmosphere, in which cation and anion concentrations are perturbed from their bulk values. Ion counting experiments quantify the ion atmosphere by measuring the preferential ion interaction coefficient: the net total number of excess ions above, or below, the number expected due to the bulk concentration...
December 29, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/28034505/high-performance-thin-layer-chromatography-mass-spectrometry-of-japanese-knotweed-flavan-3-ols-and-proanthocyanidins-on-silica-gel-plates
#13
Vesna Glavnik, Irena Vovk, Alen Albreht
On-line elution based TLC-MS is now a well-established technique, but the quality of the data obtained can sometimes be hampered by a severe spectral background or by strong ion suppression, especially when silica gel plates are used in combination with an acidic modifier in the developing solvent. We solved this issue simply and efficiently using two pre-developments of the plates, firstly with methanol-formic acid (10:1, v/v) and secondly with acetonitrile-methanol (2:1, v/v). This solution resulted in significant improvement in the sensitivity of HPTLC-MS methods...
January 27, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28033575/multi-wavelength-spectrophotometric-determination-of-cr-vi-in-water-with-abts
#14
Wenjuan Fan, Junlian Qiao, Xiaohong Guan
A new method for Cr(VI) (0.025-8.00 mg/L) determination based on the reaction of Cr(VI) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solutions was developed. The colorless ABTS reacted with Cr(VI) under strong acidic conditions ([H(+)] = 3.0 or 6.0 M) producing a stable colored radical ABTS(+), which could be measured spectrophotometrically at 415, 649 or 732 nm. The absorbance increase at these three wavelengths for ABTS(+) generation were all linear (less than 1.0% deviation) with respect to the amount of added Cr(VI) and the sensitivity were 1...
December 1, 2016: Chemosphere
https://www.readbyqxmd.com/read/28028530/acid-base-and-hemodynamic-status-of-patients-with-intraoperative-hemorrhage-using-two-solution-types-crystalloid-ringer-lactate-and-1-3-sodium-bicarbonate-in-half-normal-saline-solution
#15
Sayed Jalal Hashemi, Sayed Morteza Heidari, Ahmad Yaraghi, Reza Seirafi
BACKGROUND: Intraoperative hemorrhage is one of the problems during surgery and, if it happens in a high volume without an immediate action to control, it can be fatal. Nowadays, various injectable solutions are used. The aim of this study was to compare the acid-base and hemodynamic status of the patient using two solutions, Ringer lactate and 1.3% sodium bicarbonate, in half saline solution. MATERIALS AND METHODS: This clinical trial was performed at the Al-Zahra Hospital in 2013 on 66 patients who were randomly selected and put in two studied groups at the onset of hemorrhage...
2016: Advanced Biomedical Research
https://www.readbyqxmd.com/read/27990831/-clinical-evaluation-of-acid-base-status-henderson-hasselbalch-or-stewart-fencl-approach
#16
Karel Matoušovic, Jan Havlín, Otto Schück
Two approaches have been used in clinical evaluation the acid-base status: traditional (bicarbonate-centered) is based on the Henderson-Hasselbalch equation complemented by calculation of the anion gap, and more recent quantitative approach proposed by Stewart and Fencl. The latter method defines the three independent variables, which regulate pH. These include: the difference between the sum of charges carried by strong plasma cations and anions termed the strong ion difference - SID (decrease causes acidosis, and vice versa); the total concentration of the weak non-volatile acids [Atot] (inorganic phosphate and albumin, decrease causes alkalosis and vice versa), and pCO2...
2016: Casopís Lékar̆ů C̆eských
https://www.readbyqxmd.com/read/27990824/surface-tension-of-acid-solutions-fluctuations-beyond-the-nonlinear-poisson-boltzmann-theory
#17
Tomer Markovich, David Andelman, Rudi Podgornik
We extend our previous study of surface tension of ionic solutions and apply it to acids (and salts) with strong ion-surface interactions, as described by a single adhesivity parameter for the ionic species interacting with the interface. We derive the appropriate nonlinear boundary condition with an effective surface charge due to the adsorption of ions from the bulk onto the interface. The calculation is done using the loop-expansion technique, where the zero loop (mean field) corresponds of the full nonlinear Poisson-Boltzmann equation...
December 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/27987757/in-situ-production-of-silver-nanoparticles-for-high-sensitive-detection-of-ascorbic-acid-via-inner-filter-effect
#18
B Rezaei, M Shahshahanipour, Ali A Ensafi
In the present research, a sensitive biosensing method was proposed for the detection of trace amounts of ascorbic acid (AA). Herein, colloidal silver nanoparticles (SNPs) were successfully in-situ produced by chemical reduction of silver ion in the presence of AA, as a reducing agent. The one-pot in-situ produced silver nanoparticles were characterized by UV-vis, dynamic light scattering (DLS), zeta potential and transmission electron microscopic (TEM). SNPs act as a strong fluorescence quencher for the CdTe quantum dots via an inner filter effect (IFE)...
February 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/27979313/high-resolution-of-racemic-phenylalanine-with-dication-imidazolium-based-chiral-ionic-liquids-in-a-solid-liquid-two-phase-system
#19
Xiaoxia Huang, Haoran Wu, Zhixia Wang, Yingjie Luo, Hang Song
A novel solid-liquid two-phase system was developed for the chiral separation of racemic phenylalanine with new dication imidazolium-based chiral ionic liquids. Preliminary experiments showed distinct enantioselectivity in amino acid extraction with the novel solid-liquid two-phase system, more L-enantiomer of amino acid cooperatively interacted with ionic liquids and copper ions to be the solid phase. Various factors, including the alkyl chain length of cations of ionic liquids, the amount of copper acetate, the ratio of n(ILs)/n(Cu(2+)), the amount of water and racemic phenylalanine, the resolution time together with the resolution temperature, were systematically investigated for their influence on resolution efficiency...
January 6, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27976871/metabolism-of-the-tobacco-carcinogen-2-amino-9h-pyrido-2-3-b-indole-a%C3%AE-c-in-primary-human-hepatocytes
#20
Medjda Bellamri, Ludovic Le Hegarat, Robert J Turesky, Sophie Langouët
2-Amino-9H-pyrido[2,3-b]indole (AαC) is the most abundant carcinogenic heterocyclic aromatic amine (HAA) formed in mainstream tobacco smoke. AαC is a liver carcinogen in rodents, but its carcinogenic potential in humans is not known. To obtain a better understanding of the genotoxicity of AαC in humans, we have investigated its metabolism and its ability to form DNA adducts in human hepatocytes. Primary human hepatocytes were treated with AαC at doses ranging from 0.1-50 μM, and the metabolites were characterized by ultra-performance LC/ion trap multistage mass spectrometry (UPLC/MS(n))...
December 15, 2016: Chemical Research in Toxicology
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