Search results for "cyclic"
showing 10 items of 2439 documents
Refined carotenoid analysis of the major light-harvesting complex of Mantoniella squamata
1997
The major light-harvesting complex (LHC) of the prasinophycean alga Mantoniella squamata is unique compared to other chlorophyll (Chl) a/b-binding LHC with respect to the primary protein structure and the pigmentation. Although the presence of Chl a, Chl b, a Chl c-type pigment and the xanthophylls neoxanthin, violaxanthin and prasinoxanthin was clearly determined, several carotenoids remained unidentified or were described controversially. We re-analysed the carotenoid composition and identified a new set of xanthophylls present in the LHC: uriolide, micromonol, micromonal and dihydrolutein. Additionally, one hydrophobic component was detected, presumably a xanthophyll. The pigment analysi…
Comparison of extraction methods for polycyclic aromatic hydrocarbon determination in sediments
1990
Different sample preparation methods for the determination of polycyclic aromatic hydrocarbons (PAHs) in lake and river sediments were compared and evaluated. Freeze‐dried sediment materials were e...
Environmental analysis of chlorinated aromatic thioethers, sulphoxides and sulphones
1993
Abstract Chlorinated aromatic thioethers discussed here are polychlorinated dibenzothiophenes, thianthrenes and diphenylsulphides. Relatively little is known about their occurrence, behaviour and fate in the environment. Polychlorinated dibenzothiophenes and diphenylsulphides have recently been found to be formed in waste combustion and analysed in pulp mill effluents. Chlorinated sulphoxides and sulphones are usually metabolites or oxidation products of different chlorinated aromatic compounds. Different gas chromatographic-mass spectrometric techniques are used in the analysis of the chlorinated thioethers. The sulphoxides and sulphones, because of their higher polarity, can be isolated f…
Reversed-phase liquid chromatography without organic solvent for determination of tricyclic antidepressants
2012
The chromatographic behavior of seven tricyclic antidepressants (amitryptiline, clomipramine, doxepin, imipramine, maprotiline, nortryptiline, and trimipramine) was examined with micellar mobile phases containing the nonionic surfactant Brij-35. Acetonitrile-water mixtures were also used for comparison purposes. Tricyclic antidepressants are moderately polar basic drugs, which are positively charged in the usual working pH. This gives rise to a strong association with the alkyl chains and residual ionized silanols in silica-based stationary phases, which is translated in a high consumption of organic solvent to get appropriate retention times. Brij-35 modifies the surface of the stationary …
A micellar liquid chromatographic method for quality control of pharmaceutical preparations containing tricyclic antidepressants
2002
Micellar liquid chromatography methods for quality control of pharmaceutical preparations (capsules, pills, tablets, injections) containing the tricyclic antidepressants amineptine, amitriptiline, clomipramine, doxepin, imipramine, melitracen and nortriptyline alone or together with other CNS drugs like diazepam, medazepam and perphenazine are described. The methods using micellar solutions of cetyltrimethylammonium bromide as mobile phases and UV detection are rapid and reproducible. Due to the versatility of interactions in micellar liquid chromatography, it is possible determine highly hydrophobic compounds such as TCAs in a short time using mobile phases containing low organic solvent c…
Determination of sterols, oxysterols, and fatty acids of phospholipids in cells and lipoproteins: A one-sample method
1998
In addition to fatty acids, especially polyunsaturated species, cholesterol oxidizes and leads to various oxygenated derivatives, named oxysterols. They display a wide range of adverse biological properties. Monitoring oxysterols is important in the evaluation of the potential risks associated with lipid oxidation. In the present study, a quick and reliable method was developed for analysis of oxysterols, sterols, and fatty acid composition of phospholipids in the same biological sample. Total lipid extraction was determined after addition of several internal standards (epicoprostanol for sterols, 19-hydroxy-cholesterol for oxysterol and di-heptadecanoyl-phosphatidylcholine for phospholipid…
Gas chromatography of homologous esters
1985
Abstract The retention behaviour of C 1 C 18 n -alkyl esters of butanoic 2-, 3- and 4-chlorobutanoic acids was examined isothermally at several temperatures on SE-30 and OV-351 capillary columns. Retention increments showing the effects of each position of chlorine substitution are presented. The considerable enhancement of terminal chlorine substitution is discussed together with the corresponding behaviour of the monochloropropanoate esters.
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.
Über die Verbreitung von Flavonoiden bei pleurokarpen Laubmoosen II. Apigenin and Apigenin-7-rhamnoglucosid bei Pleurozium schreberi (Willd.) Mitt.
1980
Summary 12 species of pleurocarpous mosses have been investigated as to their content of flavonoids. Flavonoid tests on 11 species have given negative results. Only one species, Pleurozium schreberi , contains three flavonoids. They were purified by means of paper chromatography. Two of them are by chromatography, acid hydrolysis and absorption spectrum identical with apigenin and apigenin-7-rhamnoglucoside. The third flavonoid is as yet unidentified. Qualitative hydrolysis yields apigenin. The chemotaxonomic importance of the results is briefly discussed.
Complex Metabolic Activation Pathways of Polycyclic Aromatic Hydrocarbons: 3-Hydroxy-trans-7,8-Dihydroxy-7,8-Dihydrobenzo[a]Pyrene as a Proximate Mut…
1988
3-Hydroxybenzo[a]pyrene (3-OH-BP) is a major metabolite of benzo[a]pyrene (BP) in various systems. Metabolites of 3-OH-BP, formed by liver enzymes, bind to DNA1,2 and are mutagenic3,4. However, the active species have not yet been identified. Administration of 3-OH-BP to rats results in the excretion of sulfate and glucuronic acid conjugates of 3-hydroxy-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (3-OH-BP-7,8-diol) (Fig. 1) as major metabolites in the bile5. The hydroxyl groups of this triol are structurally superimposable to those of 9-hydroxy-trans-1,2-dihydroxy-1,2-dihydrochrysene (9-hydroxychrysene-1,2-diol, Fig. 1), which is a metabolite of chrysene6,7 and a potent promutagen8,9. 9-…