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Chromatographia

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https://www.readbyqxmd.com/read/28860670/specific-refractive-index-increment-%C3%A2-n-%C3%A2-c-of-polymers-at-660-nm-and-690-nm
#1
André M Striegel
The specific refractive index increment (∂n/∂c) is an essential datum for the accurate quantitation of molar mass averages and distributions (inter alia) of macromolecules when refractometry, static light scattering, and/or viscometry detection are coupled on-line to size-based separation techniques. The latter include methods such as size-exclusion and hydrodynamic chromatography, and asymmetric and hollow-fiber flow field-flow fractionation. The ∂n/∂c is also needed for accurate determination of the weight-average molar mass of polymers by off-line, batch-mode multi-angle static light scattering...
June 2017: Chromatographia
https://www.readbyqxmd.com/read/28725084/development-of-a-single-drop-microextraction-with-derivatization-procedure-for-analysis-of-volatile-fatty-acids-in-water-samples
#2
Grażyna Wejnerowska
A single-drop microextraction (SDME) was developed for the analysis of volatile fatty acids (VFAs) (C2-C7) in water by gas chromatography (GC) with flame ionization detection. The significant parameters affecting the SDME performance such as selection of microextraction solvent, extraction time, stirring rate, sample pH and temperature, and ionic strength were studied and optimized. To lower limits of detection, derivatization of VFAs by N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) was performed...
2017: Chromatographia
https://www.readbyqxmd.com/read/28725083/estimation-of-nonlinear-adsorption-isotherms-in-gradient-elution-rp-lc-of-peptides-in-the-presence-of-an-adsorbing-additive
#3
Dennis Åsberg, Marek Leśko, Tomas Leek, Jörgen Samuelsson, Krzysztof Kaczmarski, Torgny Fornstedt
ABSTRACT: In electrostatic repulsive interaction chromatography, using a charged surface hybrid sorbent carrying positive charges can improve the peak shape of peptides in reversed-phase liquid chromatography (RP-LC), especially in overloaded conditions, compared with standard C18 sorbents. However, the positive surface charges can interact with anionic additives commonly used in peptide separations, e.g., trifluoroacetic acid (TFA), complicating adsorption isotherm estimation. We investigated how the competition for available adsorption sites between TFA and two peptides influenced the adsorption isotherm in gradient elution...
2017: Chromatographia
https://www.readbyqxmd.com/read/28725082/retention-and-separation-changes-of-ternary-and-quaternary-alkaloids-from-chelidonium-majus-l-by-tlc-under-the-influence-of-external-magnetic-field
#4
Irena Malinowska, Marek Studziński, Henryk Malinowski, Maria Gadzikowska
Thin layer techniques proved their usefulness in the analysis of plant extract material. Thanks to their low operation costs, high sample throughput and possibility to gather chromatographic data for the whole sample in a single act, they allowed to find, and in some cases identify, active ingredients often hidden in sophisticated plant extract matrices. It was also proved that the presence of a magnetic field changes the retention of some substances, and moreover changes the separation efficiency of chromatographic systems...
2017: Chromatographia
https://www.readbyqxmd.com/read/28529348/different-stationary-phase-selectivities-and-morphologies-for-intact-protein-separations
#5
REVIEW
A Astefanei, I Dapic, M Camenzuli
The central dogma of biology proposed that one gene encodes for one protein. We now know that this does not reflect reality. The human body has approximately 20,000 protein-encoding genes; each of these genes can encode more than one protein. Proteins expressed from a single gene can vary in terms of their post-translational modifications, which often regulate their function within the body. Understanding the proteins within our bodies is a key step in understanding the cause, and perhaps the solution, to disease...
2017: Chromatographia
https://www.readbyqxmd.com/read/28216694/analytical-methods-for-determining-third-and-fourth-generation-fluoroquinolones-a-review
#6
REVIEW
Andrzej Czyrski
ABSTRACT: Fluoroquinolones of the third and fourth generation posses wide bactericidal activity. Monitoring concentrations of antibacterial agents provides effective therapy and prevents the increase of bacterial resistance to antibiotics. The pharmacodynamic parameters that best describe fluoroquinalone activity are AUC/MIC and Cmax/MIC. Determining the level of this type of drug is essential to reach the effective concentration that inhibits the growth of bacteria. Determining the pharmaceutical formulation confirms the purity of a substance...
2017: Chromatographia
https://www.readbyqxmd.com/read/27885300/rebooting-the-franchise-the-2015-international-symposium-on-gpc-sec-and-related-techniques
#7
André M Striegel
No abstract text is available yet for this article.
August 2016: Chromatographia
https://www.readbyqxmd.com/read/27932849/report-from-the-18th-international-symposium-on-advances-in-extraction-technologies-extech-2016-and-the-22nd-international-symposium-on-separation-science-isss-2016-toru%C3%A5-3-6-july-2016
#8
EDITORIAL
https://www.readbyqxmd.com/read/27867207/purification-of-bioactive-lipopeptides-produced-by-bacillus-subtilis-strain-bia
#9
Muaaz Alajlani, Abid Shiekh, Shahida Hasnain, Adelheid Brantner
Bacillus subtilis strain BIA was used for the production of bioactive lipopeptides. Different extraction and purification methods were assayed as liquid-liquid extraction, and acid and ammonium sulfate precipitation followed by TLC, SPE, and gel filtration. Active fractions were further purified using RP-HPLC. The molecular mass of the purified product from HPLC was determined through Tris-Tricine SDS-PAGE and MALDI-TOF-MS. The results revealed that Bacillus subtilis strain BIA produced surfactin and iturin like compounds...
2016: Chromatographia
https://www.readbyqxmd.com/read/27738352/combining-chemometric-models-with-adsorption-isotherm-measurements-to-study-omeprazole-in-rp-lc
#10
Dennis Åsberg, Marek Leśko, Jörgen Samuelsson, Anders Karlsson, Krzysztof Kaczmarski, Torgny Fornstedt
The adsorption of the proton-pump inhibitor omeprazole was investigated using RP-LC with chemometric models combined with adsorption isotherm modelling to study the effect of pH and type of organic modifier (i.e., acetonitrile or methanol). The chemometric approach revealed that omeprazole was tailing with methanol and fronting with acetonitrile along with increased fronting at higher pH. The increased fronting with higher pH for acetonitrile was explored using a pH-dependent adsorption isotherm model that was determined using the inverse method and it agreed well with the experimental data...
2016: Chromatographia
https://www.readbyqxmd.com/read/27738351/liquid-crystals-as-stationary-phases-in-chromatography
#11
REVIEW
H Grajek, Z Witkiewicz, M Purchała, W Drzewiński
The most correct analysis of the compositions of diverse analytes mixtures is significant for analytical studies in different fields; however, many prevalent analytes cannot be identified employing traditional partition gas chromatographic methods. Thus, the increasing requirements on analytes of isomeric compounds and the problems encountered in their separation demand a study of more diverse analytical systems which are characterised by higher selectivity. Therefore, the selectivity and polarities of various liquid crystals (rod-like, banana-shape, biforked, oxygen, sulphur, nitrogen, and metal containing molecules, Schiff-base, and polymeric dendrimers) employed as liquid crystalline stationary phases (LCSPs) have been discussed from both points of views, namely, their analytical applications and thermodynamic characteristics of infinitely diluted probes with different acceptor-donor properties...
2016: Chromatographia
https://www.readbyqxmd.com/read/27616782/development-and-validation-of-a-uhplc-uv-method-for-the-in-process-control-of-bosentan-monohydrate-synthesis
#12
Marta Jatczak, Katarzyna Sidoryk, Magdalena Kossykowska, Wojciech Łuniewski, Joanna Zagrodzka, Elżbieta Lipiec-Abramska
Bosentan monohydrate (4-tert-butyl-N-[6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl) pyrimidin-4-yl]benzene-1-sulfonamide monohydrate) is a dual endothelin receptor antagonist (ERA) applied in the treatment of pulmonary arterial hypertension. To achieve effective process control of the bosentan monohydrate synthesis, it was necessary to develop a selective and not highly time-consuming method for ultra-high performance liquid chromatography (UHPLC). The method is characterized by adequate sensitivity, reproducibility and selectivity for the determination of bosentan monohydrate and related compounds from all synthetic stages...
2016: Chromatographia
https://www.readbyqxmd.com/read/27616781/automated-mini-column-solid-phase-extraction-cleanup-for-high-throughput-analysis-of-chemical-contaminants-in-foods-by-low-pressure-gas-chromatography-tandem-mass-spectrometry
#13
Steven J Lehotay, Lijun Han, Yelena Sapozhnikova
This study demonstrated the application of an automated high-throughput mini-cartridge solid-phase extraction (mini-SPE) cleanup for the rapid low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS) analysis of pesticides and environmental contaminants in QuEChERS extracts of foods. Cleanup efficiencies and breakthrough volumes using different mini-SPE sorbents were compared using avocado, salmon, pork loin, and kale as representative matrices. Optimum extract load volume was 300 µL for the 45 mg mini-cartridges containing 20/12/12/1 (w/w/w/w) anh...
2016: Chromatographia
https://www.readbyqxmd.com/read/27512157/comparison-of-the-multiple-reaction-monitoring-and-enhanced-product-ion-scan-modes-for-confirmation-of-stilbenes-in-bovine-urine-samples-using-lc-ms-ms-qtrap-%C3%A2-system
#14
Iwona Matraszek-Zuchowska, Barbara Wozniak, Andrzej Posyniak
In accordance with Commission Decision 2002/657/EC, confirmatory methods for the detection of prohibited substances should comply with specific requirements, including the criteria for confirmation. Two strategies: multiple reaction monitoring (MRM) and enhanced product ion (EPI) scanning functions were compared for confirming the anabolic compounds from synthetic stilbenes group in bovine urine samples. In the research, twenty samples fortified at the Recommended Concentration (RC) of 1 µg L(-1) with diethylstilbestrol, dienestrol and hexestrol were analyzed by liquid chromatography-tandem mass spectrometry on a QTRAP 5500 instrument...
2016: Chromatographia
https://www.readbyqxmd.com/read/27429473/determination-of-bendamustine-in-human-plasma-and-urine-by-lc-fl-methods-application-in-a-drug-monitoring
#15
Alina Plenis, Agnieszka Frolow, Natalia Rekowska, Ilona Olędzka, Piotr Kowalski, Ewa Bień, Małgorzata Anna Krawczyk, Elżbieta Adamkiewicz-Drożynska, Tomasz Bączek
Simple and sensitive liquid chromatography (LC) methods with fluorescence (FL) detection for the determination of bendamustine (BM) in human plasma and urine were developed and validated. The procedure of BM extraction from a plasma sample involved solid-phase extraction with a C18 SPE column, while liquid-liquid extraction with dichloromethane was applied for a urine sample. In both methods, cinoxacin was used as the internal standard. Chromatographic separations were performed on a Synergi Max-RP column, while FL detector was set at the excitation wavelength of 328 nm and the emission wavelength of 420 nm...
2016: Chromatographia
https://www.readbyqxmd.com/read/27069275/application-of-inverse-liquid-chromatography-for-surface-characterization-of-biomaterials
#16
Katarzyna Adamska, Karol Kadlec, Adam Voelkel
In the present study, a novel approach for surface characterization of ceramic biomaterials is proposed. Two ceramic biomaterials-hydroxyapatite and β-tricalcium phosphate-were examined by means of inverse liquid chromatography. The Abraham LFER model was applied for physicochemical characteristics of the surface. Different compounds, characterized by different polarity and different donor-acceptor properties of functional group, were used as test solutes. The chromatographic experiments were carried out with two compositions of the mobile phase: pure acetonitrile (MeCN) and the mixture of acetonitrile and water in 80:20 ratio (MeCN/H2O)...
2016: Chromatographia
https://www.readbyqxmd.com/read/25892741/applications-of-multiple-reaction-monitoring-to-clinical-glycomics
#17
L Renee Ruhaak, Carlito B Lebrilla
Multiple reaction monitoring or MRM is widely acknowledged for its accuracy of quantitation. The applications have mostly been in the analysis of small molecules and proteins, but its utility is expanding. Protein glycosylation was recently identified as a new paradigm in biomarker discovery for health and disease. A number of recent studies have now identified differential glycosylation patterns associated with health and disease states, including aging, pregnancy, rheumatoid arthritis and different types of cancer...
March 1, 2015: Chromatographia
https://www.readbyqxmd.com/read/26435545/choice-of-model-for-estimation-of-adsorption-isotherm-parameters-in-gradient-elution-preparative-liquid-chromatography
#18
Marek Leśko, Dennis Åsberg, Martin Enmark, Jörgen Samuelsson, Torgny Fornstedt, Krzysztof Kaczmarski
The inverse method is a numerical method for fast estimation of adsorption isotherm parameters directly from a few overloaded elution profiles and it was recently extended to adsorption isotherm acquisition in gradient elution conditions. However, the inverse method in gradient elution is cumbersome due to the complex adsorption isotherm models found in gradient elution. In this case, physicochemically correct adsorption models have very long calculation times. The aim of this study is to investigate the possibility of using a less complex adsorption isotherm model, with fewer adjustable parameters, but with preserved/acceptable predictive abilities...
2015: Chromatographia
https://www.readbyqxmd.com/read/25814696/high-throughput-analysis-and-automation-for-glycomics-studies
#19
Archana Shubhakar, Karli R Reiding, Richard A Gardner, Daniel I R Spencer, Daryl L Fernandes, Manfred Wuhrer
This review covers advances in analytical technologies for high-throughput (HTP) glycomics. Our focus is on structural studies of glycoprotein glycosylation to support biopharmaceutical realization and the discovery of glycan biomarkers for human disease. For biopharmaceuticals, there is increasing use of glycomics in Quality by Design studies to help optimize glycan profiles of drugs with a view to improving their clinical performance. Glycomics is also used in comparability studies to ensure consistency of glycosylation both throughout product development and between biosimilars and innovator drugs...
2015: Chromatographia
https://www.readbyqxmd.com/read/25750457/lipid-analysis-of-airway-epithelial-cells-for-studying-respiratory-diseases
#20
Nicole Zehethofer, Saskia Bermbach, Stefanie Hagner, Holger Garn, Julia Müller, Torsten Goldmann, Buko Lindner, Dominik Schwudke, Peter König
Airway epithelial cells play an important role in the pathogenesis of inflammatory lung diseases such as asthma, cystic fibrosis and COPD. Studies concerning the function of the lipid metabolism of the airway epithelium are so far based only on the detection of lipids by immunohistochemistry but quantitative analyses have not been performed. Although recent advances in mass spectrometry have allowed to identify a variety of lipid classes simultaneously in isolated tissue samples, up until now, these methods were not suitable to analyze lipids in the airway epithelium...
2015: Chromatographia
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