Search results for "Gas Chromatography"
showing 10 items of 750 documents
Optimization of large-volume injection for the determination of polychlorinated biphenyls in children's fast-food menus by low-resolution mass spectr…
2008
International audience; This study includes the determination of five indicator polychlorinated biphenyls (PCBs) (52, 101, 153, 138, and 180), six non-ortho PCBs (35, 80, 81, 77, 126, and 169), and two mono-ortho PCBs (28 and 118) in fast food for children. A freeze-dried sample of 10 g is extracted by using pressurized n-hexane in two 5 min cycles at 120 degrees C and 100 mbar. Fatty extracts were cleaned up by means of acetonitrile/n-hexane partitioning and gel-permeation chromatography. The fractionation of non-ortho, mono-ortho, and indicator PCBs was made on graphitized carbon solid-phase extraction cartridges by using n-hexane, n-hexane/toluene (99:1, v/v), and toluene as elution solv…
Effects of Plant Density on the Number of Glandular Trichomes and on Yield and Quality of Essential Oils from Oregano.
2016
Plants yields are influenced by agronomic techniques. Plant density is a complex issue and extremely important when maximizing both crop quality, and biomass and essential oil yields. Plants belonging to the Origanum vulgare subspecies hirtum (Link) Ietswaart were grown adopting four types of plant density and were characterized in biometric and chemical terms. The samples were analyzed using the ANOVA (Principal Component Analysis) statistical method regarding biometric aspects, EO yield and peltate hair density. Essential oil (EO) was extracted by hydrodistillation and analyzed using GC-FID and GC-MS. GC-FID and GC-MS analysis led to the identification of 45 compounds from the EO. Plant …
Aqueous enzymatic process assisted by microwave extraction of oil from yellow horn (Xanthoceras sorbifolia Bunge.) seed kernels and its quality evalu…
2013
Abstract In this study, aqueous enzymatic process (AEP) assisted by microwave extraction (ME) of oil from yellow horn ( Xanthoceras sorbifolia Bunge.) seed kernel was investigated. Central composite design (CCD) and response surface methodology (RSM) were used to optimise an enzyme cocktail (cellulase, hemicellulase, pectinase) for AEP. The main factors of ME were also studied. A maximal oil extraction yield of 55.8% was achieved under optimal conditions. Moreover, scanning electron microscope (SEM) was applied to characterise the extraction process. Analysing chemical composition of the extracted oil by GC–MS showed that the content of unsaturated fatty acids by this emerging method (91.18…
Lipid-containing semipermeable membrane devices (SPMDs) as concentrators of toxic chemicals in the lower Fraser River, Vancouver, British Columbia.
1998
Abstract Semipermeable membrane devices (SPMDs) were deployed in the water column and in the sediments of the Lower Fraser River (B.C., Canada) to compare the levels and the congener profiles of polychlorinated dibenzo- p -dioxins (PCDDs), dibenzofurans (PCDFs) and non- ortho -chlorinated biphenyls (N-o,o′-PCBs) against those sampled by an Infiltrex resin column water sampler. Also the relationship between what was present in the ecosystem as sampled by SPMDs and what was accumulated in the tissue of resident benthic-feeding fish was explored. Only the lipid portion of the SPMDs was prepared for analysis, due to some technical difficulties in cleaning the polyethene tubing. The calculated w…
Assessment of polycyclic aromatic hydrocarbons (PAHs) in soil of a Natural Reserve (Isola delle Femmine) (Italy) located in front of a plant for the …
2009
Isola delle Femmine Natural Reserve is a very little isle about 15 km from the centre of Palermo, in front of a plant for the production of cement and about 600 m from coast. In the present research, profiles soil PAHs were obtained for 16 sites within the reserve and for 8 stations on the rural soil taken as reference. summation Sigma PAHs, in the soil of investigated area, ranged from 35 to 545 microg/kg. With the aim to find the origin of PAHs in the soil of Isola delle Femmine, we compare the distribution of single analytes in the investigated area with those of the reference rural area (Monte Raffo Rosso), with those of atmospheric urban particulate collected at Palermo along with repo…
Pollutant concentrations in placenta.
2011
Unborn children are exposed to environmental pollutants via the placenta, and there is a causal relationship between maternal intake of pollutants and fetal exposure. Placental examination is an effective way for acquiring data for estimating fetal exposure. We analyzed the concentrations of 104 congeners of persistent organic pollutants, seven organotin compounds, five heavy metals, and methylmercury in 130 randomly selected placentas. Additionally, we examined similarities between pollutant concentrations by analyzing correlations between their placental concentrations. Our results yield new information for conducting contaminant risk assessments for the prenatal period. Out of the 117 in…
Detection of lactobacillic acid in low erucic rapeseed oil--A note of caution when quantifying cyclic fatty acid monomers in vegetable oils.
2010
International audience; The purpose of this work was to identify an unknown component which has been detected during the analysis of cyclic fatty acid monomers (CFAMs) in low erucic acid rapeseed oils (LEAR). A sample of crude LEAR was transformed into fatty acid methyl esters (FAMEs) and hydrogenated using PtO2. The hydrogenated sample was fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and the fraction containing the CFAMs transformed into picolinyl esters. Analysing these picolinyl derivatives by gas-liquid chromatography coupled to mass spectrometry (GC-MS) showed that the unknown product observed in LEAR is the 11,12-methylene-octadecanoic acid. This cyc…
Reaktionen an Aluminiumoxiden. 1. Mitt.: Umsetzungen von Aceton an Aluminiumoxiden
1972
Die Umsetzungsraten von Aceton (1) an verschiedenen Aluminiumoxiden wurden bei unterschiedlichen Bedingungen untersucht. Die auftretenden Stoffe wurden durch Vergleichssubstanzen identifiziert und durch Dunnschicht- und Gas-Flussig-Chromatographie nachgewiesen. Reactions on Aluminium Oxides The reaction rates of 1 on various aluminium oxides were investigated under different conditions. The resulting products were identified comparing with synthesized compounds and by thin layer and gas liquid chromatography.
Reflux reactions for chromatography
1976
Reactions under pressure are mainly used to prepare derivatives before chromatographic analysis because of the lack of microequipment. A ml-refluxer has been designed to allow reactions under atmospheric pressure for volumes from 0.2 to 5 cm3. The reaction temperature is determined by the boiling point of the solvent thus derivatives of heat sensitive compounds can be made in the micro scale. With the aid of the ml-refluxer large series of derivatisations can be carried out and hence the reaction parameters can be optimized. This is shown at the example of the alkylation of barbituric acids for gas chromatography, where thus only N,N′-derivatives were obtained. The reliability of the appara…
Ein unabh�ngiges Verfahren zur Messung der Zusammensetzung von Gasgemischen mit Hilfe der Gaschromatographie
1977
The volume fraction of gas mixtures may be measured gas chromatographically by application of the 100% method, provided they can be separated. In case of gases it is not necessary to calibrate with another method. The specific character of the detector signals can be eliminated by measurements with pure components. The procedure is compared with the Scholander method. In case of O2/N2 mixtures the results agree within reproducibility, but in case of O2/CO2/N2 mixtures a systematic deviation of the CO2 fractions to smaller values is found as concerns the Scholander method. A gas mixture with 5.6 Vol% CO2 shows a difference of approximately 0.3 Vol%. The gas chromatographic method is almost 1…