Search results for "Boiling"
showing 10 items of 50 documents
Genesis of chlorine and sulphur in fumarolic emissions at Vulcano Island (Italy): assessment of pH and redox conditions in the hydrothermal system
2002
Chlorine- and sulphur-bearing compounds in fumarole discharges of the La Fossa crater at Vulcano Island (Italy) can be modelled by a mixing process between magmatic gases and vapour from a boiling hydrothermal system. This allows estimating the compounds in both endmembers. Magma degassing cannot explain the time variation of sulphur and HCl concentrations in the deep endmember, which are more probably linked to reactions of solid phases at depth, before mixing with the hydrothermal vapours. Based on the P–T conditions and speciation of the boiling hydrothermal system below La Fossa, the HCl and Stot contents in the hydrothermal vapours were used to compute the redox conditions and pH of th…
Gas—liquid chromatographic analyses
1984
Abstract The gas chromatography (GC) of n -alkyl acetates (CH 3 COOR), chloroacetates (CH 2 ClCOOR), dichloroacetates (CHCl 2 COOR) and trichloroacetates (CCl 3 COOR), where the alcohol chain length (R) varied between 1 and 8, and certain of their monochlorinated derivatives, 176 compounds altogether, has been studied on SE-30 and OV-351 glass capillary columns under the same operating conditions. The isomeric monochlorinated esters are eluted in direct order from the 1- chloro to the ω-chloro isomer, the separation of the isomers being complete on OV- 351. On SE-30, however, the peaks of the 6- and 7-chlorooctyl esters are partly overlapped. The separation of the mixtures of odd- and e…
Effects of Cooking Method upon Flavor of Carrots and Peas
1987
Two modalities of pressure (atmospheric pressure and high-pressure of 5.5.104 Pa) and two modalities of immersion (boiling and cooking in steam) were combined factorially to produce four ways of cooking. These different cooking methods were studied on two vegetables: carrots and peas. Sensory attributes of samples were assessed on an unstructured scale. Steam-cooked vegetables have higher sensory attributes (odor and flavor intensities, typical odor and flavor notes, sweetness). Larger losses of soluble solids and volatiles are believed to account for these differences between vegetables cooked in water and cooked in steam.
Glass capillary gas chromatography of chlorinated methyl acetates, propanoates and butanoates on Carbowax 20M and SE-30 columns
1982
The gas chromatography of all chlorinated methyl acetates, methyl propanoates and methyl mono- and dichlorobutanoates has been studied on Carbowax 20M and SE-30 glass capillary columns under various running conditions. The order of elution on a non-polar column was largely determined by the boiling point of esters, whereas on a polar column it was much influenced by the structure of compounds. Complete separation of the combined mixture of all 27 compounds could not be achieved, however, methyl 3,3-dichlorobutanoate was the only ester overlapped on both columns in spite of the various column temperatures used. The best separation of the mixture was on Carbowax 20M with a temperature program…
High-performance liquid chromatographic determination of furfural compounds in infant formulas during full shelf-life
2005
Abstract In order to evaluate the extent of the Maillard reaction in adapted and follow-up infant formulas (IF), a study was made of the evolution of furfural compound (2-furaldehyde, 5-hydroxymethyl-2-furfuraldehyde, 2-furylmethylketone and 5-methyl-2-furaldehyde) in these products, along with their relation to available lysine during the shelf-life period (two years at 20 and 37 °C). Total and free furfural contents were measured by RP-HPLC and UV detection, heating or not the sample in boiling water to free the furfurals bound to proteins and the furfurals formed from precursors. Only 2-furylmethylketone and 5-hydroxymethyl-2-furfuraldehyde were detected. Adapted and follow-up IF showed …
Glass-capillary gas chromatography of chlorobenzenes on SE-30 and Carbowax 20M columns. Simultaneous determination of chlorobenzenes and chlorophenols
1983
Gas chromatography of benzene and all chlorobenzenes has been studied on SE-30 and Carbowax 20M glasscapillary columns under various operating conditions. The benzene isomers are eluted on both columns according to their boiling points. Separation of all components in a mixture is achieved on Carbowax 20M, whereas on SE-30 the peaks of closely related isomers overlapped. Also one partial overlapping is observed on a non-polar phase. The relative retention times for compounds are given and the retention order is discussed. The retention behaviour of chlorobenzenes and chlorophenols is compared. By using an SE-30 quartz-capillary column a mixture of 33 individual components gives 29 resolved …
Development a mitigation strategy of enniatins in pasta under home-cooking conditions
2016
The effect of pasta cooking on the enniatins (ENs) contents was evaluated in white and whole-grain pasta. The cooking of pasta was performed for 10 min in boiling water. ENs were extracted from raw and cooked pasta by Solid-Liquid extraction with acetonitrile, and from cooking water by Dispersive Liquid–Liquid Micro-Extraction (DLLME) with a mixture of acetonitrile and carbone tetrachloride. Mycotoxin analysis was performed by Liquid Chromatography coupled to Tandem Mass Spectrometry. The effect of pasta cooking has a marked influence on the reduction of ENs levels. Reductions of 98–100% for ENA, 94–95% for ENA1, 14–49% for ENB and 53–65% for ENB1 were achieved after the process. ENs were d…
Thermal degradation of novolac resins by pyrolysis-gas chromatography with a movable reaction zone
1999
Abstract A previously described, a pyrolysis device with a movable reaction zone was used in the present work for thermal degradation of novolac resins. The products of thermal reactions were analysed by pyrolysis–GC. Owing to the heating of reaction zone to the maximal temperature of the chromatographic column, the high boiling pyrolysis products could be analysed. Bisphenols and trisphenols with aromatic rings coupled by methylene bridges and its methyl derivatives have been found among the compounds. The structure of the heavy pyrolysis products has been confirmed using GC–MS.
Recent advances on ionic liquid uses in separation techniques
2018
International audience; The molten organic salts with melting point below 100°C, commonly called ionic liquids (ILs) have found numerous uses in separation sciences due to their exceptional properties as non molecular solvents, namely, a negligible vapor pressure, a high thermal stability, and unique solvating properties due to polarity and their ionic character of molten salts. Other properties, such as viscosity, boiling point, water solubility, and electrochemical window, are adjustable playing with which anion is associated with which cation. This review focuses on recent development of the uses of ILs in separation techniques actualizing our 2008 article (same authors, J. Chromatogr. A…
Phase equilibria and multiple azeotropy in the associating system methanol + diethylamine
1997
Vapor−liquid equilibrium has been measured for the binary system of methanol (1) + diethylamine (2) at 101.3 and 300 kPa. Both equilibrium isobars show strong deviations from ideal behavior and a single maximum boiling point azeotrope of practically constant composition x1 ≈ 0.76, corresponding to a temperature of 339.8 K at 101.3 kPa and 370.0 K at 300 kPa. The trend of the high-pressure isobar data is consistent with the formation of a second minimum boiling azeotrope, confirming the multiple azeotropic behavior found by others at a higher temperature (398.58 K). Furthermore, the excess Gibbs energy is negative and inflects markedly with composition with increased pressure. The equilibriu…