Search results for "Gas Chromatography"
showing 10 items of 750 documents
Fast pyrolysis of hot-water-extracted and soda-AQ-delignified okra (Abelmoschus esculentus) and miscanthus (miscanthus x giganteus) stalks by Py-GC/MS
2018
Abstract The thermochemical behavior of various samples of okra ( Abelmoschus esculentus ) and miscanthus ( Miscanthus x giganteus ) stalks (initial, hot-water-extracted, and those from sulfur-free delignification) were studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). In all cases, major GC-amenable condensable products were measured semi-quantitatively and classified into several product groups. The formation of these product groups from different feedstock samples with varying mass portions of their structural constituents (carbohydrates and lignin) was investigated at 500 °C and 700 °C with a residence time of 5 s and 20 s. The main product groups were aliphatic comp…
Effect of Seasonal Storage on Single-Stem Bark Extractives of Norway Spruce (Picea abies)
2021
Increasing the net value of forestry side-streams has both ecological as well as economic benefits for emerging biorefining industries. Spruce bark represents one of the nature’s abundant sources of valuable extractives. In this study, the impact of storage on the quality and quantity of Norway spruce (Picea abies) extractives was examined as a function of storage time, environmental conditions and season (i.e., winter or summer). The bark from stored spruce saw logs was extracted with an accelerated solvent extractor (ASE) at 120 °C with hexane and water. The produced extracts were analysed qualitatively and quantitatively by gas chromatography with a flame ionisation detector (GC-FID) and…
Fast pyrolysis of hot-water-extracted and delignified silver birch (Betula pendula) sawdust by Py-GC/MS
2017
The thermochemical behavior of birch (Betula pendula) sawdust both untreated and after various chemical treatments (hot-water extraction, delignification, and hot-water extraction followed by delignification) was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). In each case, major GC-amenable condensable products were classified into several compound groups, and the formation of these monomer-related fragments from feedstock samples with varying mass portions of the structural constituents (cellulose, hemicelluloses, and lignin) were determined at 500 °C and 700 °C at hold times of 5 s and 20 s. The formation of pyrolysis products was shown to be characteristically…
Cholesterol Content in Human Milk during Lactation: A Comparative Study of Enzymatic and Chromatographic Methods.
2018
This study validates a gas chromatography (GC) method for determining the sterol profile of human milk (HM) and compares it with an enzymatic-spectrophotometric (E-S) method. Good linearity ( r > 0.97) and low limits of detection and quantification were obtained with the GC method (<1.8 and <6 μg/100 g of HM, respectively). Suitable intra- and interassay precisions (all <18%) and satisfactory recovery percentages (80-109%) were obtained for both methods. In addition, both methodologies were used to assess cholesterol evolution in HM during lactation, showing a 50% decrease at 6 months versus colostrum. The E-S method overestimated cholesterol content by <20% versus the GC method. The result…
Sterols in infant formulas: validation of a gas chromatographic method.
2017
AbstractSterols are components present in the fat fraction of infant formulas (IFs). Their characterization is therefore of interest, though there are no official reference methods for their analysis in these matrices.Aim: To validate a gas chromatographic method with flame ionization detection for the determination of animal (cholesterol and desmosterol) and plant sterols (brassicasterol, campesterol, stigmasterol, β-sitosterol and sitostanol) found in IFs.All correlation coefficients obtained for the calibration curves of sterols studied were >0.99. Limits of detection (<1 μg/100 mL) and quantification (<4 μg/100 mL) are suitable for sterols determination in IFs. The within-assay precisio…
Highly effective, regiospecific reduction of chalcone by cyanobacteria leads to the formation of dihydrochalcone: two steps towards natural sweetness
2017
Abstract Background Chalcones are the biogenetic precursors of all known flavonoids, which play an essential role in various metabolic processes in photosynthesizing organisms. The use of whole cyanobacteria cells in a two-step, light-catalysed regioselective bio-reduction of chalcone, leading to the formation of the corresponding dihydrochalcone, is reported. The prokaryotic microalgae cyanobacteria are known to produce phenolic compounds, including flavonoids, as natural components of cells. It seems logical that organisms producing such compounds possess a suitable “enzymatic apparatus” to carry out their biotransformation. Therefore, determination of the ability of whole cells of select…
First international descriptive and interventional survey for cholesterol and non-cholesterol sterol determination by gas- and liquid-chromatography–…
2019
International audience; Serum concentrations of lathosterol, the plant sterols campesterol and sitosterol and the cholesterol metabolite 5alpha-cholestanol are widely used as surrogate markers of cholesterol synthesis and absorption, respectively. Increasing numbers of laboratories utilize a broad spectrum of well-established and recently developed methods for the determination of cholesterol and non-cholesterol sterols (NCS). In order to evaluate the quality of these measurements and to identify possible sources of analytical errors our group initiated the first international survey for cholesterol and NCS. The cholesterol and NCS survey was structured as a two-part survey which took place…
International descriptive and interventional survey for oxycholesterol determination by gas- and liquid-chromatographic methods
2018
International audience; Increasing numbers of laboratories develop new methods based on gas-liquid and high-performance liquid chromatography to determine serum concentrations of oxygenated cholesterol metabolites such as 7alpha-, 24(S)-, and 27-hydroxycholesterol. We initiated a first international descriptive oxycholesterol (OCS) survey in 2013 and a second interventional survey 2014 in order to compare levels of OCS reported by different laboratories and to define possible sources of analytical errors. In 2013 a set of two lyophilized serum pools (A and B) was sent to nine laboratories in different countries for OCS measurement utilizing their own standard stock solutions. In 2014 eleven…
Diversity of Sterol Composition in Tunisian Pistacia lentiscus Seed Oil
2016
International audience; Pistacia lentiscus L. seed oil is used in some Mediterranean forest area for culinary and medicinal purposes. In this study, we aim to examine, for the first time, the effect of growing area on sterol content of Pistacia lentiscus seed oil. Fruits were harvested from 13 different sites located in northern and central Tunisia. Gas chromatography-flame-ionization detection (GC-FID) was used to quantify sterols and gas chromatography/mass spectrometry (GC/MS) was used to identify them. The major sterol identified was b-sitosterol with a value ranging from 854.12 to 1224.09 mg/kg of oil, thus making up more than 54% of the total sterols. The other two main sterols were c…
Bioactive triterpenes of protium heptaphyllum gum resin extract display cholesterol-lowering potential
2021
Hypercholesterolemia is one of the major causes of cardiovascular disease, the risk of which is further increased if other forms of dyslipidemia occur. Current therapeutic strategies include changes in lifestyle coupled with drug administration. Statins represent the most common therapeutic approach, but they may be insufficient due to the onset of resistance mechanisms and side effects. Consequently, patients with mild hypercholesterolemia prefer the use of food supplements since these are perceived to be safer. Here, we investigate the phytochemical profile and cholesterol-lowering potential of Protium heptaphyllum gum resin extract (PHE). Chemical characterization via HPLC-APCI-HRMS2 and…