Search results for "Liquid Chromatography"
showing 10 items of 942 documents
Distribution of Δ5-olefinic acids in the triacylglycerols fromPinus koraiensisandPinus pinasterseed oils
1996
Purified triacylglycerols (TAG) fromPinus koraiensis andP. pinaster seed oils, which are interesting and commercially available sources of Δ5-olefinic acids (i.e.,cis-5,cis-9,cis-12 18:3 andcis-5,cis-11,cis-14 20:3 acids) were fractionated by reversed-phase high-performance liquid chromatography, and each fraction was examined by capillary gas-liquid chromatography for its fatty acid composition. A structure could be assigned to more than 92% of TAG from both oils. In both instances, ca. 48% of the TAG were shown to contain at least one δ5-olefinic acid. In the great majority of TAG, our data showed that there is only one molecule of δ5-olefinic acid per molecule of TAG. This is compatible …
Prediction of the retention in reversed-phase liquid chromatography using solute-mobile phase-stationary phase polarity parameters.
2002
Abstract A previously reported algorithm, based on the equation: log k=( log k) 0 +p(P N m −P N s ) , that relates the retention in reversed-phase liquid chromatography with solute (p), mobile phase (PmN) and stationary phase (PsN) relative polarity parameters, is improved. The retention data reported by several authors for different sets of compounds, eluted with acetonitrile–water and methanol–water mixtures, are used to test the algorithm and elaborate a database of p values. The methodology is successfully applied to predict the retention using PmN values calculated as PmN=1.00−(2.13ϕ)/(1+1.42ϕ) for acetonitrile–water and PmN=1.00−(1.33ϕ)/(1+0.47ϕ) for methanol–water, ϕ being the organi…
Separation of Proteic Primary Amino Acids under Several Reversed‐Phase Liquid Chromatographic Conditions
2006
Abstract The reversed‐phase liquid chromatographic (RPLC) analysis of proteic primary amino acids with acetonitrile‐water, using pre‐column derivatisation with o‐phthalaldehyde (OPA) and N‐acetylcysteine (NAC), was compared with RPLC modes using trifluoroacetic acid or pentadecafluorooctanoic acid and evaporative light‐scattering detection, or sodium dodecyl sulphate micelles with pre‐ and post‐column derivatisation. The importance of column lifetime, risk of potential damages in the instrumentation, retention and resolution, was considered. Among the assayed approaches, the best is still aqueous‐organic RPLC with pre‐column derivatisation. It not only yields the most reliable results, but …
Polymer-coated reversed-phase packings in high-performance liquid chromatography
1993
The synthesis and properties of polymer-coated RP stationary phases are reviewed. The sorbents are classified according to the method of synthesis. More flexibility in the tailoring of polymer-coated packings is noted. The impact of the polymer coating on the porosity of the oxides to be modified and their chromatographic properties is discussed.
Characterisation of Diarylheptanoid- and Flavonoid-type Phenolics in Corylus avellana L. Leaves and Bark by HPLC/DAD-ESI/MS
2013
Introduction The leaves of Corylus avellana L. (common hazel, Betulaceae), a plant with a wide distribution in Europe, have been used in folk medicine for various diseases, but phytochemical exploration of C. avellana is still incomplete. To the best of our knowledge there is no previous report concerning diarylheptanoids in C. avellana, although these compounds show a frequent occurrence among Betulaceae plants. Objective To improve existing online chromatographic methods for the investigation of the phenolic compounds in C. avellana leaves and bark, focusing on diarylheptanoid-type molecules. Methods Dried and powdered leaves and bark of C. avellana were extracted with increasing polarity…
Analysis of kynurenine transaminase activity in Drosophila by high performance liquid chromatography
1991
Abstract A sensitive assay for kynurenine transaminase activity (E.C. 2.6.1.7) based on rapid separation of the reaction product by high performance liquid chromatography (HPLC) has been developed. Drosophila sordidula extracts have been assayed by this new method and this is the first time that kynurenine transaminase activity has been demonstrated in Drosophila . The method of assay developed can be extended to any other organism. Kynurenine and 3-hydroxykynurenine were both used as substrates, and they were transaminated to kynurenic acid and xanthruenic acid, respectively. HPLC is used to separate and quantitate these reaction products from all other components in the reaction mixture. …
Enzyme class identification in cleaning products by hydrolysis followed by derivatization with o-phthaldialdehyde, HPLC and linear discriminant analy…
2008
The enzymes present in raw materials of the cleaning industry (enzyme industrial concentrates) and in household cleaners were isolated by precipitation with acetone and hydrolyzed with HCl. The resulting amino acids were derivatized with o-phthaldialdehyde, and the derivatives were separated by HPLC. The peaks of 14 amino acids were observed using a C18 column and a multi-segmented gradient of acetonitrile-water in the presence of a 5 mM citric/citrate buffer of pH 6.5. Using either normalized peak areas (divided by the sum of the peak areas of the chromatogram) or ratios of pairs of peak areas as predictor variables, linear discriminant analysis models, capable of predicting the enzyme cla…
CHROMATOGRAPHIC DETECTION OF SESQUITERPENE LACTONES IN PARTHENIUM PLANTS FROM NORTHWEST ARGENTINA
1999
Several chloroformic extracts containing some sesquiterpene lactones from autochtonous plants of Parthenium hysterophorus, collected in the province of Salta (Argentina), were separated and identified by high performance reversed-phase liquid chromatography with C18 column and propanol-water mobile phases, using gradient elution and concentrations of propanol larger than 10% (v/v). Lactones previously purified and characterized by H1 RMN, C13 RMN, IR, and mass spectrometry, were used as standards. The objective of the study was to check if the nature of the lactones was modified according to the altitude of the region where the plants were grown. Among the lactones, five were already descri…
Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography
1987
Abstract The reversed-phase chromatography of proteins by gradient elution with acidic, low-ionic-strength aqueous—organic eluents is often associated with losses of the biological activity of the protein. In this study, the enzymatic activities of catalase, horseradish peroxidase and pepsin were examined under static and dynamic column conditions on non-porous, monodisperse 1.5-μm reversed-phase silicas with various n -alkyl ligands. Catalase readily lost its enzymatic activity under the influence of the acidic aqueous—organic eluents in the absence of the reversed-phase packing, whereas peroxidase was partially deactivated as a result of combined mobile phase and stationary phase effects …
Determination of polycyclic aromatic hydrocarbons in atmospheric particulate matter of Valencia city
1991
Polycyclic aromatic hydrocarbons (PAHs) were determined in atmospheric particulate matter in 11 sites of the Valencia area and at several times during the year. Sample analysis was carried out by ultrasonic acetonitrile extraction followed by reverse phase HPLC separation and fluorescence detection. The maximum concentration of total PAH developed in winter and spring. Mean values per sampling site varied from 0.193 to 1.668 μg/m3 of filtered air. Environmental noise and temperature were determined at those same 11 sites and correlated with PAH levels.