Search results for "liquid chromatography"
showing 10 items of 942 documents
Determination of soyasaponins I and βg in raw and cooked legumes by solid phase extraction (SPE) coupled to liquid chromatography (LC)-mass spectrome…
2013
Legumes contain a rich variety of phytochemicals as soyasaponins, triterpenoidal glycosides that possess multiple health-promoting properties, such as lowering of cholesterol. In this work, the quantification of soyasaponins I and βg in 60 raw and cooked legumes by using a solid phase extraction (SPE) coupled to a liquid chromatography (LC)-mass spectrometry (MS) method was carried out. Results showed that lentils are a good source of soyasaponins, with a content of soyasaponin I that ranged from 636 to 735 mg kg(-1) and of soyasaponin βg from 672 to 1807 mg kg(-1). The cooking process produced a small loss of soyasaponins in water, that is, 4.8-8.7%, and partially converted soyasaponin βg …
On the determination of underivatised fatty alcohol ethoxylates by electrospray ionisation–mass spectrometry
2006
Abstract The oligomers of fatty alcohol ethoxylates (FAEs) exhibit large sensitivity differences in mass spectrometry with electrospray ionisation (ESI–MS) and atmospheric pressure chemical ionization (APCI). Standards of the oligomers from m = 1 to 7 ethylene oxide units (EOs) and linear alkyl chains from n = 10 to 18 carbon atoms were infused to examine the relative sensitivities or response factors in several media. The response factors of the [M + H]+ and [M + Na]+ peaks in 9:1 acetonitrile/water and methanol/water media containing acid buffers increased following irregular patterns when n and m increased. In methanol/water the response factors depended on the parity of m, being larger …
Racemic and Optically Pure Heptahelicene-2-carboxylic Acid: Its Synthesis and Self-Assembly into Nanowire-Like Aggregates
2010
Heptahelicene-2-carboxylic acid was effectively synthesised from suitably functionalised naphthalene building blocks. Methoxy-substituted 1,1'-ethyne-1,2-diylbis(2-but-3-yn-1-ylnaphthalene) was cyclised in the presence of CpCo(CO)(2)/PPh(3) to 2-methoxy-7,8,11,12-tetrahydroheptahelicene, which was converted into heptahelicen-2-yl trifluoromethanesulfonate. This reactive intermediate underwent Pd(OAc)(2)/dppp-catalysed methoxycarbonylation reaction to provide, after hydrolysis, heptahelicene-2-carboxylic acid. The racemate was resolved into enantiomers by semipreparative HPLC on a chiral column. The helicity of (+)-(P)-heptahelicene-2-carboxylic acid was assigned by correlating its CD spectr…
ChemInform Abstract: Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.
2010
A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.
Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.
1998
A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.
Determination of albendazole and ivermectin residues in cattle and poultry-derived samples from India by micellar liquid chromatography
2021
We have developed a method, based on micellar liquid chromatography, to determine albendazole and ivermectin in dairy products and biological waste from bovine, as well as edible tissues from poultry. Anthelmitics were resolved in less than 10 min using a C18 column and a mobile phase of 0.15 mol/L sodium dodecyl sulfate – 6% 1-pentanol at buffered at pH 7 with a 0.01 M phosphate salt, running under isocratic mode at 1 mL/min. Detection was by absorbance at 292 nm. Method was successfully validated following official validation guidelines, in terms of: selectivity, sensitivity, calibration range (0.0125−0.5 mg/kg to 25−50 mg/kg), linearity (r2 > 9990), trueness (86.3–105.6%), precision (<12…
Carbohydrates from Chemical Pulps: Characterization by Capillary Zone Electrophoresis
2006
Capillary zone electrophoresis (CZE) is one of the novel separation techniques, being applicable, for example, to virtually all important biomass-derived monosaccharides. However, in spite of this fact the utilization of this technique in the pulp and paper industry is currently rather limited. In this chapter practical guidance and some application examples are given to show how carbohydrate material (polysaccharides, oligosaccharides, and neutral and acidic monosaccharides) in pulps and spent liquors can be analyzed by CZE. Emphasis is placed on sample preparation and separation conditions including comparison with other separation methods, such as gas chromatography (GC) and high-perform…
Simultaneous Automated Determination of Catecholamines, Serotonin, and Their Metabolites in Brain Tissue by HPLC and Electrochemical Detection
1993
Abstract A robust procedure with minimal tissue sample pretreatment, based on reversed-phase, ion-pair high performance liquid chromatography (HPLC) combined with electrochemical detection has been developed for the automated and simultaneous determination of the biogenic amines norepinephrine (NE), epinephrine (E), dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), 3,4-dihydroxyacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (H I A A) in as little as 0.5 mg brain tissue. The chromatographic conditions remain stable for at least 8 weeks. In particular small amounts of samples which do not allow reexamina…
Sensitive and selective determination of metabolically formed trans -dihydrodiols and phenols of benzo[ a ]pyrene in water and urine samples by HPLC …
1998
A method has been developed to separate hydroxylated metabolites of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene, i. e. trans-4,5-, 7,8-, 9,10-dihydrodiol and 1-, 3-, 7-, and 9-phenol, by HPLC with amperometric detection employing an isocratic methanol/water eluent (70:30, v/v) containing 0.5 g/L sulfuric acid and 1 g/L lithium perchlorate. Compared with the usually applied fluorescence (λex = 265 nm, λem = 460 nm) and ultraviolet (λ = 265 nm) detection, the amperometric technique is about 2–12 times more sensitive for the determination of all metabolites investigated. The method was applied to the determination of the seven metabolites of benzo[a]pyrene in different wate…
Reliable and simple analytical methods for determination of citrulline and metabolically related amino acids by liquid chromatography after derivatiz…
2014
We describe the development of a high-performance liquid chromatography (HPLC) method for the determination of citrulline and other amino acids relevant to intestinal diseases. The amino acids were derivatized with 9-fluorenylmethylchloroformate (FMOC-Cl) and their derivatives were separated on two different columns, a core-shell column (Halo C18) and a silica-based monolith (Chromolith Performance RP-18). The derivatization reaction was optimized with respect to pH, buffer concentration and reproducibility. The optimal derivatization conditions were achieved with 0.4 M borate buffer at pH 9.20, a constant ratio of FMOC-Cl/total amino acids (10 : 1) and 75 mM tyramine after 1 min (quenching…