Search results for " Phase"
showing 10 items of 1862 documents
Efficiency of QuEChERS approach for determining 52 pesticide residues in honey and honey bees
2016
A comparison between QuEChERS and other pesticide extraction procedures for honey and honey bee matrices is discussed. Honey bee matrix was extracted by solvent based procedure whereas solid phase extraction was the protocol for the honey matrix. The citrate buffered QuEChERS method was used for both matrices. The methods were evaluated regarding cost (equipment and reagents), time, accuracy, precision, sensitivity and versatility. The results proved that the QuEChERS protocol was the most efficient method for the extraction of the selected pesticides in both matrices. QuEChERS is the most economical and less time-consuming procedure.SPE and solvent-based extraction procedures show equivale…
Analysis of furan in coffee of different provenance by head-space solid phase microextraction gas chromatography-mass spectrometry: effect of brewing…
2009
A simple, sensitive and accurate method for the analysis of furan in roasted coffee has been used based on headspace-solid-phase micro-extraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The extraction was performed using 75-microm carboxen/polydimethylsiloxane fiber. Ionic strength, extraction time and temperature, and desorption time were assessed as the most important parameters affecting the HS-SPME procedure and d(4)-furan was used as the internal standard. The linearity range was in the range 0.0075-0.486 ng g(-1); the LOD and LOQ calculated using the signal-to-noise ratio approach were 0.002 and 0.006 ng g(-1), respectively. The inter- and intra-day precisio…
Quasi-Lie Brackets and the Breaking of Time-Translation Symmetry for Quantum Systems Embedded in Classical Baths
2018
Many open quantum systems encountered in both natural and synthetic situations are embedded in classical-like baths. Often, the bath degrees of freedom may be represented in terms of canonically conjugate coordinates, but in some cases they may require a non-canonical or non-Hamiltonian representation. Herein, we review an approach to the dynamics and statistical mechanics of quantum subsystems embedded in either non-canonical or non-Hamiltonian classical-like baths which is based on operator-valued quasi-probability functions. These functions typically evolve through the action of quasi-Lie brackets and their associated Quantum-Classical Liouville Equations, or through quasi-Lie brackets a…
Valorization of alginate for the production of hydrogen via catalytic aqueous phase reforming
2018
Abstract Alginate, a carbohydrate abundant in the outer cell wall of macroalgae, was subjected to catalytic aqueous phase reforming (APR) to produce hydrogen using a 3% Pt/C commercial catalyst. The performance of the process was evaluated according to the conversion of the carbon to gas, the hydrogen yield and the hydrogen selectivity. The catalyst and feed amount, temperature, reaction time, pH and the presence of H2 were modified to understand the dependence of the outcome of the process on these parameters. The presence of the catalyst was fundamental in order to increase the hydrogen yield compared to the uncatalyzed reaction, and it can be reused without activity loss. In addition, it…
Monitoring pH and ORP in a SHARON reactor
2011
This paper analyses the valuable information provided by the on-line measurements of pH and oxidation reduction potential (ORP) in a continuous single high ammonia removal over nitrite (SHARON) reactor. A laboratory-scale SHARON reactor equipped with pH, ORP, electric conductivity and dissolved oxygen (DO) probes has been operated for more than one year. Nitrogen removal over nitrite has been achieved by adding methanol at the beginning of anoxic stages. Time evolution of pH and ORP along each cycle allows identifying the decrease in nitritation rate when ammonia is consumed during the aerobic phase and the end of the denitrification process during the anoxic phase. Therefore, monitoring pH…
Micropollutants removal in an anaerobic membrane bioreactor and in an aerobic conventional treatment plant
2012
The paper expresses an attempt to tackle the problem due to the presence of micropollutants in wastewater which may be able to disrupt the endocrine system of some organisms. These kinds of compounds are ubiquitously present in municipal wastewater treatment plant (WWTP) effluents. The aim of this paper is to compare the fate of the alkylphenols-APs (4-(tert-octyl)) phenol, t-nonylphenol and 4-p-nonylphenol and the hormones (estrone, 17ß-estradiol and 17¿-ethinylestradiol) in a submerged anaerobic membrane bioreactor (SAMBR) pilot plant and in a conventional activated sludge wastewater treatment plant (CTP). The obtained results are also compared with the results obtained in a previous stud…
Understanding fat, proteins and saliva impact on aroma release from flavoured ice-creams
2017
Publication également référencée sous le numéro WOS:000437803400018; The release profile of fourteen aroma compounds was studied in ice cream samples varying in fat and protein, both in level and type. In vitro aroma release was monitored by solid phase micro-extraction gas chromatography using an innovative saliva reactor, which imitated human chewing under temperature control. The results showed that the effect of the fat type on aroma release was smaller than that of fat level. Ice creams with low fat level released more hydrophobic aroma compounds than ice creams with high fat level. At low fat level more aroma compounds were released from ice creams with lower protein content. At high …
Nonazeotropy in the System Methyl Ethanoate + 1,2-Epoxybutane
1997
New vapor−liquid equilibrium data for the binary system methyl ethanoate + 1,2-epoxybutane are reported at 35 and 101.3 kPa and at 298.15 K. It is shown that no azeotropes are present in the system, in disagreement with data reported by others who claim that two azeotropes are present at 298.15 K. We claim that previously reported data are in error because of impurities in the reagents and experimental errors. According to our results, the system methyl ethanoate + 1,2-epoxybutane behaves like a regular solution and its vapor phase can be considered practically ideal so that it cannot fulfill the necessary conditions for multiple azeotropy. The data were satisfactorily correlated using the …
Multi‐residue extraction to determine organic pollutants in mussel hemolymph
2021
This study assesses the extraction of eleven pharmaceuticals, five pesticides, five perfluoroalkyl substances, and two illicit drugs in hemolymph from (Mytilus Galloprovincialis). Four extraction procedures using Phree™ Phospholipid Removal cartridges were tested using different volumes of methanol (400 and 600 μL) and acetonitrile (300 and 450 μL). The pollutants were determined by high-performance liquid chromatography–tandem mass spectrometry. The use of methanol gave several problems during the extraction procedure, such as longer times and sample loss. Three methods (acetonitrile 300 and 450 μL; and methanol 600 μL) were validated. Recoveries at three concentration levels (5, 50, and 1…
Determination of pesticide residues in fruit and vegetables.
1996
A review concerning the determination of pesticide residues in fruit and vegetables is presented. The basic principles and recent developments in the extraction and quantitation of pesticides are discussed. Consideration is given to solid phase and supercritical extraction techniques, automation and robotic systems, and immunoassay procedures.