Search results for "flame"
showing 10 items of 108 documents
Gel combustion synthesis and magnetic properties of CoFe2O4, ZnFe2O4, and MgFe2O4 using 6-aminohexanoic acid as a new fuel
2020
Abstract For the first time, 6-aminohexanoic acid is used as an alternative fuel in the synthesis of the spinel ferrites with compositions CoFe2O4, ZnFe2O4 and MgFe2O4 using gel combustion synthesis with different oxidizer-to-fuel (O/F) ratios. The gel precursors were studied by differential thermal analysis and thermogravimetry (DTA/TG), which showed that the ignition temperature depends on the gel precursor, being around 230 °C, 130 °C and 275 °C for CoFe2O4, ZnFe2O4, and MgFe2O4, respectively. These results showed than the 6-aminohexanoic acid has an ignition temperature lower than the urea and the citric acid when were used in the synthesis of the spinel ferrites by gel combustion. More…
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…
Tetrabromobisphenol A (TBBPA)-stimulated reactive oxygen species (ROS) production in cell-free model using the 2′,7′-dichlorodihydrofluorescein diace…
2016
t Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant, applied in a variety of commercial and household products, mainly electronic ones. Since the production of reactive oxygen species (ROS) is considered one of the principal cytotoxicity mechanisms, numerous studies undertake that aspect of TBBPA’s mechanism of action. The present study verifies if the fluorogenic substrate 2′,7′- dichlorodihydrofluorescein diacetate (H2DCFDA) should be used to detect ROS production induced by TBBPA. To determine the ability of TBBPA alone to stimulate the conversion of H2DCFDA to its fluorescent product 2’, 7’- dichlorofluorescein (DCF), we used a cell-free model. In the experiments…
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…
Chemical characterization of a variety of cold-pressed gourmet oils available on the Brazilian market
2018
Different specialty extra virgin oils, produced by cold-pressing fruits/nuts (olive, pequi, palm, avocado, coconut, macadamia and Brazil nut) and seeds (grapeseed and canola), and retailed in the Brazilian region of Minas Gerais, were chemically characterized. Specifically, for each type of oil, the fatty acid composition was elucidated by GC-FID, the contents of selected polyphenols and squalene were determined respectively by UHPLC-MS and UHPLC-PDA, whereas minerals were explored by means of ICP-MS. Olive oil was confirmed to have the highest MUFA content due to a valuable level of oleic acid, while oils from grapeseed, Brazil nut and canola were marked by nutritionally important PUFA lev…
Determination of 21 perfluoroalkyl substances and organophosphorus compounds in breast milk by liquid chromatography coupled to orbitrap high-resolut…
2018
Abstract The human exposure to perfluoroalkyl (PFASs) and organophosphorus (OPs) compounds is a cause of concern and its determination in biological matrices, including human milk, is an emergent approach for evaluate their exposure. A comprehensive strategy for the quantitative determination of 21 PFASs and OPs compounds in breast milk was developed. The proposed method includes an extraction and clean-up procedure based on the QuEChERs methodology followed by an ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) determination. The full-scan mass data were acquired with a resolution of 50000 FWHM and a mass accuracy better than 5 ppm. Met…
Risk assessment of benzene in food samples of Iran's market
2018
Abstract The concentration of benzene in ninety-eight collected food and drink samples (carbonated beverage, fruit juice, pickle, lime juice, mayonnaise and salad dressing, 16 samples from each) from Iran local markets were investigated using gas chromatography equipped with flame ionization detector (GC-FID). Moreover, the correlation of benzene concentration with sodium benzoate and ascorbic acid concentrations was assessed. Benzene concentration in carbonated beverages, fruit juices, pickle, lime juices, mayonnaise and salad dressing were 3.57 ± 1.70, 5.17 ± 3.63, 4.37 ± 2.24, 4.99 ± 0.54, 1.38 ± 0.87 and 1.47 ± 0.83 μg/L, respectively, being in all cases below the acceptable limit (10 μ…
Effects on Heat Stress of a Flame-Retardant Ensemble for Aluminum Smelters
2000
A common belief is that a flame-retardant clothing ensemble will increase the level of heat stress over ordinary cotton work clothes. This is supported by bench tests on fabrics that indicate higher insulation and vapor resistance values for flame-retardant clothing. This research compared a flame-retardant clothing ensemble for an aluminum smelter (Zirpo wool shirt and FR8 denim pants) with typical cotton work clothing. Four young men walked on a treadmill at two work levels inside a climatic chamber under controlled conditions of heat stress. During each test, heart rate, core temperature, and skin temperatures were continuously monitored and recorded every 5 min. After a physiological st…
Prenatal Exposure to Polybrominated Flame Retardants and Fetal Growth in the INMA Cohort (Spain)
2015
Our aim was to investigate the relation between PBDEs and fetal growth or newborn anthropometry in a Spanish cohort (2003-2008). PBDE congeners (BDE-47, -99, -153, -154, and -209) were determined in serum of 670 mothers at gestational week 12 and in 534 umbilical cord samples. Abdominal circumference (AC), estimated fetal weight (EFW), femur length (FL), and biparietal diameter (BPD) during gestation were measured by ultrasounds. At birth, weight (BW), head circumference (HC), and length (BL) were also measured. We assessed growth in the intervals between 12-20 and 20-34 weeks of gestation and size at birth by standard deviation (SD)-scores adjusted for constitutional characteristics. We co…
Determination of alcohols in essential oils by liquid chromatography with ultraviolet detection after chromogenic derivatization
2013
Abstract An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. The sample is diluted with 1,4-dioxane and the analytes are derivatized with phthalic anhydride. The derivatives (phthalates hemiesters) are separated on a C8 column using an acetonitrile (ACN)/water gradient. Separation conditions were optimized using the DryLab® method development software. For the alcohols and phenols present in mint and rose essential oils, optimization led to a ca. 40 min gradient time and a column temperature of 8 °C. The alcohol and its derivatives were identified using HPLC with mass spectrometry (MS) detection. A large sensitivity enhancement w…