Search results for "gas chromatography."
showing 10 items of 725 documents
Identification of indigoid compounds present in archaeological Maya blue by pyrolysis-silylation-gas chromatography–mass spectrometry
2014
Abstract A study based on the use of pyrolysis-silylation-gas chromatograpy–mass spectrometry (Py-GC–MS), which aimed to identify indigoid compounds and to clarify the multicomponent composition of Maya blue (MB) pigment, has been carried out. A series of reference compounds and synthetic MB specimens prepared in the laboratory have been analysed by this technique. An analysis of archaeological MB samples from 14 Maya archaeological sites from Mexico and Guatemala has also been performed. The obtained results demonstrate that, in addition to indigo, oxidised species such as dehydroindigo, which is formed as a result of redox processes taking place while preparing the pigment, are present in…
Chemical composition of the essential oil of Salvia multicaulis Vahl. var. simplicifolia Boiss. growing wild in Lebanon
2004
The essential oil of aerial parts of Salvia multicaulis Vahl. var. simplicifolia Boiss. (Lamiaceae) growing wild in Lebanon was obtained by hydrodistillation and was analysed by GC and GC-MS. 67 compounds constituting 95.2% of the oil were identified, the major components being alpha-copaene (8.0%), alpha-pinene (6.6%), myrtenol (5.7%), trans-sabinyl acetate (5.3%).
GC and GC-–MS Analysis of Volatile Compounds From Ballota nigra subsp. uncinata Collected in Aeolian Islands, Sicily (Southern Italy)
2020
In the present study, the chemical composition of the essential oils from aerial parts of Ballota nigra subsp. uncinata (Bég.) Patzak collected in Sicily was evaluated by gas chromatography (GC) and GC-mass spectrometry. The main components of the oil were ( E)-phytol (20.0%), α-pinene (9.0%), hexahydrofarnesyl acetone (5.7%), and α-selinene (5.1%). Cluster analysis of the essential oil compositions of all the taxa belonging to B. nigra s.l. group was performed.
Contribution to a Taxonomic Revision of the Sicilian Helichrysum Taxa by PCA Analysis of Their Essential-Oil Compositions
2016
The chemical profile of the essential oils in ten populations of the genus Helichrysum Mill. (Asteraceae), collected in the loci classici of the nomenclatural types of the taxa endemic to Sicily, were analyzed. Our results confirm that the analysis of secondary metabolites can be used to fingerprint wild populations of Helichrysum, the chemical profiles being coherent with the systematic arrangement of the investigated populations in three main clusters, referring to the aggregates of H. stoechas, H. rupestre, and H. italicum, all belonging to the section Stoechadina. The correct nomenclatural designation of the investigated populations is discussed and the following two new combinations ar…
Gas—liquid chromatographic analyses
1989
Abstract The retention (I), dispersion (IM) and selectivity (I*) indices of sixteen polychlorinated dibenzo-p-dioxins and fourteen polychlorinated dibenzofurans were determined on a low-polarity HP-5 capillary column using a gas chromatograph connected with an ion-selective detector. IM and I* values were also calculated for all 73 dibenzo-p-dioxins from the di- to the octachloro isomer and for all possible 135 chlorinated dibenzofurans based on the predicted retention index data reported earlier. The effect of the position of chlorination is shown and the results are compared with those for several series of chlorinated aromatics.
Efficiency of the microwave-assisted extraction of hydrocarbons and pesticides from sediments
1997
Abstract A mixture of toluene and water is proposed for the microwave-assisted extraction of organic pollutants, hydrocarbons and pesticides, from marine sediments. The effect of experimental conditions, such as microwave power and irradiation time, on the extraction of linear, unresolved and polycyclic aromatic hydrocarbons as well as PCBs and DDTs has been evaluated using real marine sediment samples. Values found by Soxhlet and ultrasonic extraction were employed to evaluate the efficiency of the microwave-assisted extraction. Analytical determinations were carried out by gas chromatography using FID, ECD and MS detectors. For 2 g of a dry sediment, an extraction time of 6 min with 10 ml…
A new proposal for the determination of polychlorinated biphenyls in environmental water by using host-guest adsorption
2020
Abstract Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants whose wide industrial use has been banned over the years in most countries due to their persistence and bioaccumulation. In fact, the International Agency for Research on Cancer defined them in 2016 as carcinogenic to humans based on sufficient evidence of an increased risk of cancer, being children and pregnant or lactating women the most vulnerable population subgroups. In this work, a new alternative for the determination of polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB138, PCB153, and PCB180) in water samples has been developed by using a cyclodextrin-containing silica microparticulated material as …
Evaluation of the Soil Contamination of Tangier (Morocco) by the Determination of BTEX, PCBs, and PAHs
2009
Benzene, toluene, ethylbenzene, and xylenes (BTEX), twelve polycyclic aromatic hydrocarbons (PAHs) and seven polychlorinated biphenyls (PCBs), were selected as pollutants to evaluate the contamination of soils in the urban and industrial areas of Tangier (Morocco). PAHs and PCBs were determined by gas chromatography-mass spectrometry (GC-MS) after a microwave-assisted extraction (MAE) and gel permeation chromatography (GPC) clean-up. BTEX were directly determined by head-space GC-MS. Results obtained in this study show the presence of high levels of BTEX and PAHs in the soil near the urban waste deposit. However, the analysis of pollutants in the other sampling sites provided comprehensive …
The Seasonality Impact of the BTEX Pollution on the Atmosphere of Arad City, Romania
2021
Benzene, toluene, and total BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations registered for one year (2016) have been determined every month for one high-density traffic area. The assessment was performed in Arad City, Romania, to evaluate these pollutants and their influence on the inhabitants’ health. The contaminants were sampled using a static sampling method and analyzed by gas chromatography coupled with mass spectrometry. Benzene was the most dominant among the BTEX compounds—the average concentrations ranged from 18.00 ± 1.32 µg m−3 in December to 2.47 ± 0.74 µg m−3 in August. The average toluene concentration over the year was 4.36 ± 2.42 µg m−3 (with a maximum of 9…
Polycyclic aromatic hydrocarbons (PAHs) in indoor dust matter of Palermo (Italy) area: Extraction, GC–MS analysis,distribution and sources
2008
Abstract Studies on indoor pollution are important since people spend more than 80% of their time indoor environments. In this work the method for PAHs analysis in indoor dust (used as passive sampler) and the results relative to samples collected in the area of Palermo are reported. Dust samples for analysis were collected from 45 indoor environments. Total PAHs concentrations in indoor dusts ranged from 36 to 34 453 μg kg −1 d.w. To correlate indoor and outdoor pollution we analyze, also, the particulate matter and PAHs levels samples collected in four stations. The percentage measured in indoor dusts results more low than that found outside. The values of isomeric ratios for the differe…