Search results for "gas chromatography."

Comparative assessment of solid-phase extraction clean-up procedures, GC columns and perfluoroacylation reagents for determination of type B trichoth…

2005

Abstract Various solid-phase extraction (SPE) procedures for clean-up, two perfluoroacylation reagents (pentafluoropropionic anhydride (PFPA) and heptafluorobutyric anhydride (HFBA)) and two chromatographic columns (HP-1701 and HP-5) have been assessed comparatively to achieve the determination of type B trichothecenes (deoxynivalenol (DON), nivalenol (NIV), 3- and 15-acetyldeoxynivalenol (3- and 15-ADON)) in wheat grain by gas chromatography (GC)–electron-capture detection (ECD). Spiked wheat samples were extracted with acetonitrile–water (84:16, v/v). Tested SPE procedures were MycoSep 225 column, Florisil and different cartridges prepared in the laboratory with mixtures of various sorben…

Biogenic volatile organoiodine and organobromine hydrocarbons in the Atlantic Ocean from 42°N to 72°S

1997

During the cruise ANT X/1 and 2 of the research vessel Polarstern from November 1991 to March 1992, 39 surface water samples of the Atlantic Ocean from 42°N to 72.5°S were collected and analysed for their concentration of volatile iodinated and brominated hydrocarbons. The concentration of chlorophyll-a was used as an indicator for phytoplankton, which is one of the main producers of iodinated and brominated compounds in the ocean. For determination of chlorophyll-a, fluorescence spectroscopy was applied, whereas the measurement of halogenated volatile hydrocarbons was carried out by a purge and trap system with subsequent gas chromatographic separation and detection by an electron capture …

New developments in immunochemical water analysis down to 30 mul sample volume.

1999

Abstract The determination of trace levels of pesticides like atrazine in water samples of small, restricted volumes is one of the future demands of environmental analysis. In a brief review existing chromatographic and immunochemical methods for atrazine are critically discussed. Then a simple rapid enzyme-linked immunosorbent assay (ELISA) using the tip of an inoculation needle as a solid surface is presented. The sample volume could be reduced to 30 μl. The assay had a centre of the test IC50 of 0.12 μg l−1 and permitted the characterisation of atrazine at levels of 0.022–2.90 μg l−1. A first outlook for automatisation is given. The new method was compared with an ELISA using 96 well mic…

1984

By means of data from critical demixing and vapour pressure measurements and by inverse gas chromatography, including the results of published light scattering measurments, a consistent picture is obtained for the entire dependence of the Flory-Huggins parameter χ on the weight fraction w2 of the polymer and on the temperature T for the system tert-butyl acetate/polystyrene. Within the entire T-range (ca. 0°C – 140°C), χ increases stronger than exponentially with w2, the rise being the larger the larger χH (the enthalpy contribution to χ) becomes in the limit of infinite dilution. At sufficiently high temperatures (≳ 50°C), χH changes its sign from negative to positive as w2 is raised. This…

Volatile Constituents ofTeucrium poliumL. from Turkey

1998

Abstract The volatile constituents obtained from the aerial parts of Teucrium polium were analyzed by GC and GC/MS. The oil was found to contain 37 components, of which 30 were identified. The major constituents were β-pinene (18.0%), β-caryophyllene (17.8%), α-pinene (12.0%), caryophyllene oxide (10.0%), myrcene (6.8%) and germacrene-D (5.3%)

Determination of fatty acids and lipid classes in salmon oil by near infrared spectroscopy

2017

International audience; Near-infrared (NIR) spectroscopy was evaluated as a rapid method for the determination of oleic, palmitic, linoleic and linolenic acids as well as omega-3, omega-6, and to predict polyunsaturated, monounsaturated and saturated fatty acids, together with triacylglycerides, diglycerides, free fatty acids and ergosterol in salmon oil. To do it, Partial Least Squares (PLS) regression models were applied to correlate NIR spectra with aforementioned fatty acids and lipid classes. Results obtained were validated in front of reference procedures based on high performance thin layer and gas chromatography. PLS-NIR has a good predictive capability with relative root mean squar…

Evidence of oxidative stress in very long chain fatty acid--treated oligodendrocytes and potentialization of ROS production using RNA interference-di…

2011

X-linked adrenoleukodystrophy (X-ALD) and pseudo neonatal adrenoleukodystrophy (P-NALD) are neurodegenerative demyelinating diseases resulting from the functional loss of the peroxisomal ATP-binding cassette transporter D (ABCD1) and from single peroxisomal enzyme deficiency (Acyl-CoA oxidase1: ACOX1), respectively. As these proteins are involved in the catabolism of very long chain fatty acids (VLCFA: C24:0, C26:0), X-ALD and P-NALD patients are characterized by the accumulation of VLCFA in plasma and tissues. Since peroxisomes are involved in the metabolism of reactive oxygen species (ROS) and nitrogen species (RNS), we examined the impact of VLCFA on the oxidative status of 158N murine o…

The gas chromatography/mass spectrometry can be used for dose estimation in irradiated pork

2009

Abstract Food safety can be improved using ionizing radiation to reduce food spoilage and to extend its shelf life. The gas chromatography/mass spectrometry (GC/MS) has been validated by the European Community as a powerful method to identify irradiated food containing fat. The preliminary goals of our research were: (i) to set up this method, based on the detection of radiation induced 2-dodecylcyclobutanones (2-DCB) in pork muscle samples and (ii) to check the microbiological efficacy of the treatment. The main objective was to render the GC/MS a quantitative technique for dose estimation, through the measurement of the 2-DCB concentration in the irradiated sample. Our results show that t…

Presence of mycotoxins in Tunisian infant foods samples and subsequent risk assessment

2018

Abstract A study on a set of cereal and cereal-based products (n = 117) intended for infant consumption was performed to determine the natural presence of twenty different mycotoxins by both liquid chromatography and gas chromatography coupled to tandem mass spectrometry (MS/MS). Analytical data showed that 67% of analyzed samples were contaminated by at least one mycotoxin at variable levels. Deoxynivalenol presented the highest incidence (38%) and reached a maximum level of 240 ng/g in a bsissa sample (oat product), higher than the maximum level set for DON in cereal products (200 ng/g). While, enniatin B was found in 25 samples with a maximum level of 316 ng/g found also in a bsissa samp…

Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical study

2009

Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features d…