Search results for "Aqueous solution"
showing 10 items of 1610 documents
Fluorimetric determination of captopril by flow injection analysis
1991
A flow injection analysis procedure is proposed for the determination of captopril. The sample solution was directly injected into the carrier-reagent stream which was prepared by a solution of ceric ions in 0.25 M sulfuric acid. The procedure is based on the fluorimetric monitoring of the formed Ce(III). Chemical, FIA, and instrumental parameters were optimized and the procedure is applied to the captopril determination in pharmaceutical formulations with competitive precision and adequate accuracy.
Flow injection spectrophotometric determination of lead using 1,5-diphenylthiocarbazone in aqueous micellar
2009
A simple flow injection colorimetric procedure for determining lead was established. It is based on the reaction of lead in sulfuric acid with 1,5-diphenylthiocarbazone and sodium dodecyl sulfate, resulting in an intense red-blue complex with a suitable absorption at 500 nm. A standard or sample solution was injected into the sulfuric acid stream (flow rate of 2.0 ml min(-1)), which was then merged with sodium dodecyl sulfate stream (flow rate of 2.0 ml min(-1)) and 1,5-diphenylthiocarbazone stream (flow rate of 1.5 ml min(-1)). Optimum conditions for determining lead were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range…
Fluorometric determination of diphenhydramine by flow-injection analysis
1992
A sensitive, rapid and simple flow injection procedure for the determination of diphenhydramine has been designed based on a fluorometric approach. An aqueous solution of diphenhydramine is injected into a carrierreagent stream containing Ce(IV) in dilute sulphuric acid and the fluorescence intensity of the Ce(III) produced is monitored. Chemical, FIA and instrumental variables were optimized. Analytical features of the method are: linear range 0.2–2 ppm, precision 0.7%, sample throughput 80/h. The influence of some foreign substances which can be found in typical pharmaceutical samples containing diphenhydramine was also investigated. The diphenhydramine content of a pharmaceutical prepara…
Urea as a PCDD/F inhibitor in municipal waste incineration.
2001
Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from municipal waste incineration have been widely studied because of their extensive toxicity, and many efforts have been made to restrict their emissions. Although a number of chemical compounds have been shown in laboratory-scale tests to inhibit the formation of PCDD/Fs, few have been tested in pilot- or full-scale plants. This work evaluates the effect of urea as a PCDD/F inhibitor in a pilot-scale incinerator that uses refuse-derived fuel (RDF). The decomposition of urea under the test conditions was also studied using detailed kinetic modeling. An aqueous solution of urea was injected into the flue gas stream …
A wind tunnel study on the drop-to-particle conversion
1992
Abstract An experimental study was carried out to investigate the processes which occur during drop-to-particle conversion in atmospheric clouds whose drops are evaporating. The experiment was carried out in the Mainz vertical wind tunnel and in a 4-m high fall shaft. Drops consisting of aqueous solutions of NaCl, (NH 4 ) 2 SO 4 , and salts of artificial and natural ocean water, containing various kinds of solid, water-insoluble particles such as clays, were studied. The aerosol particles produced by the evaporation of drops had diameters in the range 0.1–1 μm, 5–20 μm, 40–80 μm and 100–300 μm. The shape and fall mode of these particles are discussed. It was found that the aerosol particles…
18F-labeling of peptides by means of an organosilicon-based fluoride acceptor.
2006
Fluorine-18 is among the most commonly used radionuclides for positron emission tomography (PET). This non-invasive imaging technique is capable of providing in vivo information about the distribution of radiolabeled biomolecules by 1808 coincidence detection of two simultaneously emitted photons from positron–electron annihilation. Although a number of different radiotracers have been successfully employed in PET, only a few, such as 2-[F]fluoro-2-deoxy-d-glucose (FDG) and [F]fluorodopa, have gained widespread application in nuclear medicine. The reason for this is that the regioselective introduction of F into tracer molecules is often non-specific and radiochemical yields (RCY) of the Fl…
Hyaluronan-Based Graft Copolymers Bearing Aggregation-Induced Emission Flurogens
2017
In order to develop a technology platform based on two natural compounds from biorenewable resources, a short series of hyaluronan (HA) copolymers grafted with propargylated ferulic acid (HA-FA-Pg) were designed and synthesized to show different grafting degree values and their optical properties were characterized in comparison with reference compounds containing the same ferulate fluorophore. Interestingly, these studies revealed that the ferulate fluorophore was quite sensitive to the restriction of intramolecular motion and its introduction into the rigid HA backbone, as in HA-FA-Pg graft copolymers, led to higher photoluminescence quantum yield values than those obtained with the isola…
Simultaneous Separation of Antioxidants and Carbohydrates From Food Wastes Using Aqueous Biphasic Systems Formed by Cholinium-Derived Ionic Liquids
2019
project CICECO-Aveiro Institute of Materials, UID/CTM/50011/2019. Associate Laboratory for Green Chemistry-LAQV, FCT Ref. UID/QUI/50006/2019. POCI-01-0145-FEDER-016403. Investigator FCT project IF/00621/2015. Programa Mais Centro under project CENTRO-07-ST24-FEDER-002008. COMPETE: PEst-C/SAU/UI0709/2011. The food industry produces significant amounts of waste, many of them rich in valuable compounds that could be recovered and reused in the framework of circular economy. The development of sustainable and cost-effective technologies to recover these value added compounds will contribute to a significant decrease of the environmental footprint and economic burden of this industry sector. Acc…
Isolation and Characterization of a New Less-Toxic Derivative of the Fusarium Mycotoxin Diacetoxyscirpenol after Thermal Treatment
2011
Trichothecenes are an important class of mycotoxins that act as potent protein synthesis inhibitors in eukaryotic organisms. The compound 4,15-diacetoxyscirpenol is highly toxic for plants and animals. Potatoes are especially prone to be contaminated with 4,15-diacetoxyscirpenol after infection with Fusarium sambucinum. In the current study, the reduction of 4,15-diacetoxyscirpenol during thermal treatment in aqueous solution was monitored. A new derivative was detected and named DAS-M1. After isolation, DAS-M1 was characterized with LC-HR-MS and LC-MS/MS and structurally elucidated with (1)H, (13)C, and 2D NMR. Potatoes were inoculated with F. sambucinum, and the infected potatoes were coo…
Solution properties of polyelectrolytes. III. Effect of sodium polystyrene sulfonate concentration on viscometric and size exclusion chromatographic …
1988
The effect of sodium polystyrene sulfonate concentration on the shape of its molecules in aqueous solution at different NaNO3 ionic strengths has been analyzed by viscometry and size-exclusion chromatography (s.e.c). An equation has been developed which predicts the intrinsic viscosity, [η] p.cp.cs, at finite concentration of both polyion (cp) and electrolyte (cs). The experimental results obtained by both techniques can be accounted for in terms of the theory. Several factors involved in the elution mechanism have been considered and the variation of the slopes of s.e.c. calibration curves with cp and cs has been discussed in terms of polyion conformation changes.