Search results for "Chromatographic separation"

Gas—liquid chromatographic analyses

1985

Abstract The gas chromatographic retention behaviour of methylethyl, 1-methylpropyl, 2-methylpropyl, 1,2-dimethylpropyl, 1-methylbutyl and 3-methylbutyl esters of benzoic and o-, m- and p-chlorobenzoic acids on low-polarity (SE-30) and polar (OV-351) capillary columns under several temperature-programmed and isothermal conditions is reported. The retention data and the Kovats retention indices for all 24 components are given and the separation of a complex mixture is discussed. The retention index increments have been used to examine the effects of chain branching and chlorine substitution. The results are compared with those for n-alkyl benzoates and monochlorobenzoates.

Chlorinated acetic and propionic acids in pine needles from industrial areas

1998

Abstract Concentrations of chlorinated acetic and propionic acids in pine needles from the surroundings of a pulp and paper mill and a metal reclamation plant were measured. Different ways of extraction and chromatographic separation were tried. Ultrasonic extraction with water of the powdered needles was found to be efficient. The acids were analysed as their pentafluorobenzyl esters with GC-ECD. The ECD sensitivity of the pentafluorobenzyl derivatives was good. The detection limit was below 1 ng/g for the chlorinated acetic and propionic acids. The concentrations of dichloroacetic acid and 2,2-dichloropropionic acid in fresh needles were on the 0–4 ng/g level. Monochloroacetic acid, 2-chl…

Occurrence of glyphosate in beer from the Latvian market.

2018

A sensitive LC-MS/MS method for the determination of glyphosate in beer has been developed, validated, and applied to analyse 100 beer samples from 24 different producers and distributors in Latvia. The selected samples represented most beer brands and varieties sold in local supermarkets. Different procedures for sample preparation and chromatographic separation were compared. The final version of the method consisted of solid phase extraction, chromatographic separation on aminopropyl stationary phase, and detection using tandem mass spectrometry. The concentration of glyphosate in beer varied from below the LOD of 0.2 μg kg-1 up to 150 μg kg-1, higher than previously reported. Significan…

Fast preparation and gas-chromatographic separation of lanthanide and actinide hexafluoroacetylacetonates

1986

A fast method for the separation of lanthanide elements by gas chromatography of their hexafluoroacetylacetonates is described. Individual lanthanides can be isolated within a few minutes, and the whole group can be separated in less than 10 min. The hexafluoroacetylacetonates are applied in form of mixed complexes with tri-n-butyl phosphate or trioctylphosphine oxide prepared by fast extraction into quasi-solid solvents. The applicability of this method for the separation of trivalent actinide elements is shown, including the fast preparation of thin counting samples.

Simultaneous Determination of Thiamin and Riboflavin in Mushrooms by Liquid Chromatography

2001

A simple, fast, inexpensive, and reliable method useful for the simultaneous, routine determination of thiamin and riboflavin in mushrooms is examined. It uses the extraction procedure, with slight modifications, proposed by the AOAC for the extraction of thiamin and riboflavin, followed by a liquid chromatographic separation on a reversed-phase Spherisorb ODS column with methanol/water as mobile phase gradient. Fluorometric detection is used at the following excitation and emission wavelengths, respectively, 360 and 425 nm in the case of thiamin and 422 and 515 nm for riboflavin. The analytical parameters of linearity, the precision of the method (RSD = 2.45 and 2.51% for thiamin and ribof…

2017

A new isoflavone, 8-prenylmilldrone (1), and four new rotenoids, oblarotenoids A–D (2–5), along with nine known compounds (6–14), were isolated from the CH2Cl2/CH3OH (1:1) extract of the leaves of Millettia oblata ssp. teitensis by chromatographic separation. The purified compounds were identified by NMR spectroscopic and mass spectrometric analyses, whereas the absolute configurations of the rotenoids were established on the basis of chiroptical data and in some cases by single-crystal X-ray crystallography. Maximaisoflavone J (11) and oblarotenoid C (4) showed weak activity against the human breast cancer cell line MDA-MB-231 with IC50 values of 33.3 and 93.8 μM, respectively.

Rotenoids, Flavonoids, and Chalcones from the Root Bark of Millettia usaramensis.

2015

Five new compounds, 4-O-geranylisoliquiritigenin (1), 12-dihydrousararotenoid B (2), 12-dihydrousararotenoid C (3), 4'-O-geranyl-7-hydroxyflavanone (4), and 4'-O-geranyl-7-hydroxydihydroflavanol (5), along with 12 known natural products (6-17) were isolated from the CH2Cl2/MeOH (1:1) extract of the root bark of Millettia usaramensis ssp. usaramensis by chromatographic separation. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas their absolute configurations were established on the basis of chiroptical data and in some cases also by X-ray crystallography. The crude extract was moderately active (IC50 = 11.63 μg/mL) against the ER-negative…

A germacrane derivative from Pallenis spinosa

1991

Abstract Extraction of aerial parts of Pallenis spinosa and chromatographic separation have yielded a new germacrane derivative and the known sesquiterpenes shiromool and α-cadinol.

Germacrane esters from roots of Ligularia persica

1991

Abstract Extraction of roots of Ligularia persica and chromatographic separation yielded one new derivative of tovarol, four new derivatives of shiromodiol, α- and β-eudesmol, bakkenolide A and four known eremophilane derivatives.

Chemical degradation products of lignin and humic substances part I Synthesis, structure verification and gas chromatographic separation of chlorinat…

1993

Abstract Chlorinated vanillins (4-hydroxy-3-methoxybenzaldehydes) and syringaldehydes (3,5-dimethoxy-4-hydroxy-benzaldehydes) were synthesized and their purities and structures were examined by quartz capillary gas chromatography and mass spectrometry. The detailed procedures for the synthesis, gas chromatographic separation and mass spectroscopic features are presented.