Search results for "CHROMATOGRAPHY"
showing 10 items of 5037 documents
Structure and properties ofn-alkyldimethylsilyl bonded silica reversed-phase packings
1978
Summary The effects of the modifier functionality and the chain length ofn-alkylchlorosilanes on the surface structure of packings and on their retention behaviour in reversed-phase chromatography were investigated. Comparative retention studies on three silica packings that had been treated to maximum conversion withn-octyltrichlorosilane (I),n-octylmethyldichlorosilane (II) andn-octyldimethylmonochlorosilane (III) showed that the most pronounced reversed-phase character is obtained by using III as the modifying reagent. A series ofn-alkyldimethylsilyl bonded silica packings were prepared with widely differingn-alkyl chain lengths. Although the packings are very hydrophobic, the maximum su…
Calcium efflux from human erythrocyte ghosts
1970
The passive Ca efflux from human red cell ghosts was studied in media of differing ion compositions and compared to the ATP-dependent Ca efflux. Cells were loaded with(45)Ca during reversible hemolysis, and the loss of radioactivity into the non-radioactive incubation medium was measured, usually for 3 hr at 37°C. Analysis of the efflux curves revealed that(45)Ca efflux followed the kinetics of a simple two-compartment system. In the concentration range between 0 and 1MM Ca in the external solution ([Ca(++)] o ), the rate constant of passive Ca efflux (k min(-1), fraction of(45)Ca lost per minute into the medium) increased from 0.00732 to 0.0150 min(-1). There was no further increase at hig…
Biological nutrient removal in membrane bioreactors: denitrification and phosphorus removal kinetics.
2007
The impact of including membranes for solid liquid separation on the kinetics of nitrogen and phosphorus removal was investigated. To achieve this, a membrane bioreactor (MBR) biological nutrient removal (BNR) activated sludge system was operated. From batch tests on mixed liquor drawn from the MBR BNR system, denitrification and phosphorus removal rates were delineated. Additionally the influence of the high total suspended solids concentrations present in the MBR BNR system and of the limitation of substrate concentrations on the kinetics was investigated. Moreover the ability of activated sludge in this kind of system to denitrify under anoxic conditions with simultaneous phosphate uptak…
Engineered membranes for residual cell trapping on microfluidic blood plasma separation systems. A comparison between porous and nanofibrous membranes
2020
AbstractBlood-based clinical diagnostics require challenging limit-of-detection for low abundance, circulating molecules in plasma. Micro-scale blood plasma separation (BPS) has achieved remarkable results in terms of plasma yield or purity, but rarely achieving both at the same time. Here, we proposed the first use of electrospun polylactic-acid (PLA) membranes as filters to remove residual cell population from continuous hydrodynamic-BPS devices. The membranes hydrophilicity was improved by adopting a wet chemistry approach via surface aminolysis as demonstrated through Fourier Transform Infrared Spectroscopy and Water Contact Angle analysis. The usability of PLA-membranes was assessed th…
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…
Cultivation ofZymomonas mobilis 113 S at Different Mixing Regimes and their Influence on the Levan Formation
2001
The Zymomonas mobilis I 13 S strain was cultivated in a bioreactor with a working volume of 1.4 I at different stirring regimes in a 15% initial sucrose medium The levan obtained in the fermentation process was analyzed by gel filtration. Because the sucrose/biomass ratio in the fermentation broth decreased to below 300 g/g, the insufficient concentration of sucrose might have decreased the concentration of levan. Besides the growth characteristics of the population, the mixing intensity and flow structure were also found to influence the molecular mass of levan. At 600 rpm, the microorganisms produced levan with a molecular mass lower than at 300 rpm. The stirring of a fermentation broth w…
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…
Universal method to determine acidic licit and illicit drugs and personal care products in water by liquid chromatography quadrupole time-of-flight
2016
Graphical abstract
Caffeine analysis and extraction from a topical cream intended for UV-skin protection
2020
Made available in DSpace on 2021-06-25T10:16:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 This study aimed to develop and validate a method for the analysis of caffeine in complex cosmetic samples, such as sunscreens. Besides, an extraction method of caffeine from coffee oil and from creams, which contains both lipophilic and hydrophilic components, has been developed. The method to analyze caffeine was developed using an isocratic pump, Waters 1515 and an automatic injector Perkin-Elmer Series 200 and an UV detector Perkin-Elmer. As stationary phase, Kromasil C-18 (150 × 4.6 mm ID with particle size of 5 µm) column was used and a mixture of water (pH 4.00)/acetonitrile (…