Search results for "Ion chromatography"

showing 10 items of 314 documents

Partial purification and characterization of an NAD-dependent 3 beta-hydroxysteroid dehydrogenase from Clostridium innocuum

1989

In nine strains of Clostridium innocuum, 3 beta-hydroxysteroid-dehydrogenating activities were detected. 3 beta, 7 alpha, 12 alpha-Trihydroxy- and 3 beta-hydroxy-12-keto-5 beta-cholanoic acids were identified as reduction products of the respective 3-keto bile acids by gas-liquid chromatography and gas-liquid chromatography-mass spectrometry. One strain was shown to contain a NAD-dependent 3 beta-hydroxysteroid dehydrogenase. Enzyme production was constitutive in the absence of added bile acids. The specific enzyme activity was significantly reduced by growth medium supplementation with 3-keto bile acids, with trisubstituted acids being more effective than disubstituted ones. A pH optimum o…

3-Hydroxysteroid DehydrogenasesIon chromatographyDehydrogenaseApplied Microbiology and BiotechnologySubstrate SpecificityBile Acids and SaltsFeceschemistry.chemical_compoundHumansNucleotideClostridiumchemistry.chemical_classificationGrowth mediumChromatographyClostridium innocuumEcologybiologyHydrogen-Ion Concentrationbiology.organism_classificationMolecular WeightKineticsEnzymechemistryBiochemistryNAD+ kinaseBacteriaResearch ArticleFood ScienceBiotechnologyApplied and Environmental Microbiology
researchProduct

Thermomineral waters of Greece: geochemical characterization

2020

75 °C). In terms of pH most results vary from 5.5 to 823 °C) ii) warm (23 40 °C) iii) thermal (40 75 °C) and iv) hyperthermal (&gtfew springs show either very low pH (&lt10) proposing serpentinization processes. Regarding TDS concentrations collected waters can be subdivided into low salinity (up to 1.5 g/L) brackish (up to 20 g/L) and saline (up to 43 g/L). The medium high salinities can be justified by mixing with sea water and/or strong waterrock interaction processes. Isotope composition of O and H ranges from 12.7 to +2.7 ‰ SMOW and from 91 to +12 ‰ SMOW respectively and is generally comprised between the Global Meteoric Water Line and the East Mediterranean Meteoric Water Line. Only few water samples show a positive shift for δ18O possibly related to high temperature waterrock interaction processes. Carbon dioxide (18 997000 μmol/mol) or N2 (1100 989000 μmol/mol) or CH4 (&ltMany geothermal areas of Greece are located in regions affected by Miocene or Quaternary volcanism and in continental basins characterised by elevated heat flow. Moreover the majority of them is found along the coast as well as in islands of the Aegean Sea and thus thermal water is often brackish to saline due to marine intrusion into costal aquifer. In the present study almost 300 thermal and cold mineral water samples were collected along the Hellenic territory with their physicochemical parameters (temperature pH electrical conductivity and Eh) and the amount of bicarbonates (titration with 0.1N HCl) being determined in situ. Additionally gases found either in free or dissolved phase were sampled. Both water and gas samples were analysed at the INGVPa laboratories for major ions (Ion Chromatography) silica (Inductively Coupled Plasma Optical Emission Spectrometry) chemical composition of free and dissolved gases (Gas Chromatography) water isotopes (O and H) and carbon and helium isotopes of free and dissolved gases (Mass Spectrometry). The temperature of the investigated waters ranges from 6.5 to 98°C pH from 1.96 to 11.98 whilst Total Dissolved Solids (TDS) from 0.06 to 43 g/L. Based on the temperature parameter waters can be divided into four groups: i) cold (&lt0.5 913000 μmol/mol) are the prevailing gas species found in the studied sites. The δ13CCO2 values ranged from 20.1 to +8.5 ‰ whilst the isotope ratio of He from 0.21 to 6.71 R/RA.4) suggesting interaction with H2Srich gases or very high pH values (&gtSettore GEO/08 - Geochimica E Vulcanologia
researchProduct

Sample Preparation Improvement in Polycyclic Aromatic Hydrocarbons Determination in Olive Oils by Gel Permeation Chromatography and Liquid Chromatogr…

2005

Abstract The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid–liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile–water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15°C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluor…

AcetonitrilesTime FactorsFluoreneChemistry Techniques AnalyticalAnalytical ChemistryGel permeation chromatographychemistry.chemical_compoundPlant OilsEnvironmental ChemistryFluorometryUltrasonicsSample preparationPolycyclic Aromatic HydrocarbonsOlive OilChromatography High Pressure LiquidPharmacologychemistry.chemical_classificationDetection limitFluorantheneFluorenesMethylene ChlorideChromatographyChemistryExtraction (chemistry)TemperatureSilicon DioxideSpectrometry FluorescenceHydrocarbonChromatography GelPyreneAgronomy and Crop ScienceChromatography LiquidFood ScienceJournal of AOAC INTERNATIONAL
researchProduct

Renewable polyol obtained by microwave-assisted alcoholysis of epoxidized soybean oil: Preparation, thermal properties and relaxation process

2019

[EN] The soybean oil polyol (SOP) use as feedstock in the polyurethane industry has been recently emphasized due to its excellent resistance to hydrolysis, which is also applicable in coatings and thermal insulation. In this article, the SOP was obtained by a very fast microwave-assisted alcoholysis of epoxidized soybean oil (ESO). The preparation method, thermal properties, and relaxation process were evaluated. High yields as opening and consumption epoxy group and selectivity of 99.8 mol%, 985 mol%, and 71.2 mol% were obtained. Through titrations, nuclear magnetic resonance and gel permeation chromatography were identified parameters as 0.32 mg KOH.g(-1) acid number, 190 mg KOH.g(-1) hyd…

Acid valuefood.ingredientMaterials scienceThermal properties02 engineering and technologyDielectric relaxation spectroscopy010402 general chemistry01 natural sciencesSoybean oilGel permeation chromatographychemistry.chemical_compoundfoodMaterials Chemistry13.- Tomar medidas urgentes para combatir el cambio climático y sus efectosPhysical and Theoretical ChemistrySoybean oil polyolSpectroscopyPolyurethane021001 nanoscience & nanotechnologyCondensed Matter PhysicsAtomic and Molecular Physics and Optics0104 chemical sciencesElectronic Optical and Magnetic Materials02.- Poner fin al hambre conseguir la seguridad alimentaria y una mejor nutrición y promover la agricultura sostenibleEpoxidized soybean oil08.- Fomentar el crecimiento económico sostenido inclusivo y sostenible el empleo pleno y productivo y el trabajo decente para todos12.- Garantizar las pautas de consumo y de producción sostenibles07.- Asegurar el acceso a energías asequibles fiables sostenibles y modernas para todosChemical engineeringchemistryHydroxyl valueMAQUINAS Y MOTORES TERMICOS0210 nano-technologyGlass transitionMicrowave-assisted alcoholysisSaponification
researchProduct

F1-ATPase from Micrococcus sp. ATCC 398. Purification by Ion-Exchange Chromatography and Further Characterization. (Auto)proteolysis and Dissociative…

1977

The preparation of highly purified F1-ATPase from Micrococcus sp. ATCC 398 by application of DEAE-Sepharose CL-6B chromatography as final step is described. This enzyme consists of five subunits of different molecular weight: alpha (65000), beta (55000),gamma (35000), delta (20000), and epsilon (17000). Disc electrophoresis on 5% polyacrylamide gels removes the epsilon-polypeptide yielding an active ATPase complex with four different subunits: alpha, beta, gamma, delta. Additionally, by variation of the ionic strength delta can (partly) removed allowing the isolation by disc electrophoresis of an active ATPase complex which consists only of three different subunits alpha, beta, and gamma. I…

Adenosine Triphosphataseschemistry.chemical_classificationChromatographymedicine.diagnostic_testbiologyMacromolecular SubstancesStereochemistryProteolysisATPaseIon chromatographyPolyacrylamideATPase complexBiochemistryMicrococcusMolecular Weightchemistry.chemical_compoundEnzymechemistryIonic strengthMolemedicinebiology.proteinAmino AcidsEuropean Journal of Biochemistry
researchProduct

Towards comprehensive non-target screening using heart-cut two-dimensional liquid chromatography for the analysis of organic atmospheric tracers in i…

2021

Abstract Non-target screening of secondary organic aerosol compounds in ice cores is used to reconstruct atmospheric conditions and sources and is a valuable tool to elucidate the chemical profiles of samples with the aim to obtain as much information as possible from one mass spectrometric measurement. The coupling of mass spectrometry to chromatography limits the results of a non-target screening to signals of compounds within a certain polarity range based on the utilized stationary phases of the columns. Comprehensive two-dimensional liquid chromatography (LCxLC) introduces a second column of different functionality to enable the analysis of a broader range of analytes. Conventional LCx…

AerosolsDetection limitChromatography Reverse-PhaseAnalyteChromatographyChemistryHydrophilic interaction chromatographyOrganic ChemistryGeneral MedicineRepeatabilityMass spectrometrySnowBiochemistryMass SpectrometryAnalytical ChemistryAerosolVolume (thermodynamics)Hydrophobic and Hydrophilic InteractionsChromatography LiquidJournal of Chromatography A
researchProduct

A Quantitative Estimate of Ascorbic and Isoascorbic Acid by High Performance Liquid Chromatography: Application to Citric Juices

1993

Abstract The present report deals with the optimization and verification of a simple HPLC isocratic method useful for determining ascorbic and isoascorbic acids in standard solutions and fruit juices. Sample preparation is minimal and docs not require derivatization. The method uses an octadecyl reversed phase, a mobile phase which contains cetyltrimethyl ammonium bromide 0.05M as the ionic pair and potassium dihydrogen phosphate as a buffer, at pH=4.5, and 4-hydro-xyacetanilide as internal standard. The proposed method makes it possible to quantify ascorbic and isoascorbic acid in less than 13 minutes, with precision (C. V. 3.5%) and accuracy (recover' of 98%).

Ammonium bromidechemistry.chemical_compoundChromatographychemistryPotassiumIon chromatographyMolecular Medicinechemistry.chemical_elementSample preparationStandard solutionDerivatizationAscorbic acidHigh-performance liquid chromatographyJournal of Liquid Chromatography
researchProduct

Zu den Ursachen der unterschiedlichen pH-Empfindlichkeit vonGammarus pulex L., G.fossarum KOCH (Amphipoda) undAselus aquaticus L. (Isopoda)

1992

By means of ion chromatography the extensive and significantly higher loss of ions of G. pulex and G. fossarum in acid water (pH 3.0) as compared to neutral water is proved. While cations are being accumulated in the water, some ions (Na+, Cl−) leave the hemolymph in important percentage, others increase highly after being set free from the cells (K+ and Ca2+). The loss of cations with Asellus aquaticus in acid water (pH 3) is clearly lower than with Gammarus, and it is not significantly higher than when the animals are put into neutral water.

AmphipodabiologyEcologyIon chromatographyEnvironmental factorAquatic Sciencebiology.organism_classificationmedicine.disease_causeIsopodaGammarus pulexPulexGammarusEnvironmental chemistrymedicineAsellus aquaticusGeneral Agricultural and Biological SciencesEcology Evolution Behavior and SystematicsInternationale Revue der gesamten Hydrobiologie und Hydrographie
researchProduct

N-Terminal amino acid sequence analysis indicates that isolated atrial amyloid is derived from atrial natriuretic peptide

1988

Isolated atrial amyloid, the most frequent senile cardiac amyloid type, was chemically analysed. Amyloid fibrils obtained from a patient (NIP) were extracted and the predominant low-molecular-weight polypeptide (approximately 3.5 kDa, designated ASc2 NIP) was isolated by size exclusion high performance liquid chromatography in 60% formic acid. N-Terminal amino acid sequence analysis of this polypeptide was identical to that of the atrial natriuretic peptide alpha-hANP for the first 12 residues determined.

AmyloidAmyloidFormic acidMolecular Sequence DataSize-exclusion chromatographyIsolated atrial amyloidHigh-performance liquid chromatographyPathology and Forensic Medicinechemistry.chemical_compoundAtrial natriuretic peptidechemistryBiochemistrymental disordersHumansNIPFemaleAmino Acid SequencePeptide sequenceAtrial Natriuretic FactorAgedVirchows Archiv B Cell Pathology
researchProduct

Comparison of Three Techniques for Lipid Removal from Seal Blubber: Gel Permeation, Acid Treatment, and Dialysis with Semipermeable Membrane

2000

Abstract Harbor seal blubber samples were analyzed for PCDD/Fs and PCBs by splitting the initial extract into three aliquots and applying three different techniques for lipid removal (the first step of sample cleanup methodology for GC-HRMS analysis): gel permeation chromatography (GPC), sulfuric acid treatment, and dialysis through semipermeable membrane. Correlation coefficients of analyte concentrations obtained from three sets of replicate samples ranged from 0.965 to 0.994. In addition, a number of seal blubber samples were processed without pre-extraction using only the dialysis technique. The analyte concentrations in these samples correlated well with the analyte concentrations obta…

AnalyteChromatographyChemistryHealth Toxicology and MutagenesisPublic Health Environmental and Occupational HealthSoil ScienceSulfuric acidPermeationPollutionSeal (mechanical)Analytical ChemistryGel permeation chromatographychemistry.chemical_compoundBlubberEnvironmental ChemistrySemipermeable membraneDialysis (biochemistry)Waste Management and DisposalWater Science and TechnologyInternational Journal of Environmental Analytical Chemistry
researchProduct