Search results for "Matrix"
showing 10 items of 3205 documents
Determination of Boron in Fertilizers by Inductively Coupled Plasma-Atomic Emission Spectrometry: Studies of Some Spectral Interferences at Different…
1995
Abstract The most sensitive analytical wavelengths of boron cannot be used in the determination of boron in fertilizers by inductively coupled plasma-atomic emission spectrometry because of spectral interference by potassium, phosphorus, and iron. For the 4 wavelengths of boron investigated, it was noticed that, at the same wavelength, the pattern of spectral interference changes according to fertilizer composition. The spectral interference patterns at the 4 analytical boron wavelengths were studied by adding matrix elements typically found in fertilizers to real fertilizer samples. When levels of added matrix elements correlate less than 0.2 to each other, the effect of added matrix eleme…
Determination of fluoxetine enantiomers in pharmaceutical formulations by electrokinetic chromatography-counter current technique
2012
In this work, an electrokinetic chromatography–counter current procedure for the separation of fluoxetine enantiomers using highly sulfated β-cyclodextrin was optimized and applied to the determination of the enantiomers in three pharmaceutical formulations according to the matrix features. Quality criteria were applied to facilitate its transferability to testing laboratories. Fluoxetine was used therapeutically as the racemate, although a stereospecificity associated with its interactions with the neuronal serotonin-uptake carrier was demonstrated. In this context, the development of enantioselective methods for the chiral analysis of pharmaceuticals allowing stereoisomer ratio estimation…
Determination of Magnesium in Fertilizers by Inductively Coupled Plasma Atomic Emission Spectrometry: Studies of Some Spectral and Interelement Effec…
1995
Abstract Four analytical wavelengths of magnesium were tested for determination of Mg from fertilizers by inductively coupled plasma atomic emission spectroscopy (ICP-AES): 202.528, 285.213, and 383.826 nm (Mg I) and 279.553 (Mg II). The effects of fertilizer matrix elements on Mg determination were examined by adding matrix elements to fertilizer solutions. Multiple linear regression calculations proved a valuable technique for evaluating the effects of matrix elements on Mg determination. The observed interferences at Mg wavelengths may be both spectral and interelement. Interelement effects were typically caused by Na, K, and Ca, and spectral effects, by P, Fe, and S. The best wavelength…
Investigation of various shellac grades: additional analysis for identity.
2009
Background: A number of different grades of shellac are commercially available and most of them are known only as generic shellac and are not further differentiated. The investigated grades of shellac in this study are based on different insect strains, host trees, refining methods, and products from different suppliers. Method: The Gardner/Iodine color values of alcoholic and aqueous solutions of the various shellac grades were measured. Glass transition temperatures and pKa-values were determined. To assess chemical differences in the tested shellac grades, MALDI-TOF analysis was performed. Results: Differences were found in color, TG, and pKa-values and in the mass spectra by MALDI-TOF a…
Monitoring of five postharvest fungicides in fruit and vegetables by matrix solid-phase dispersion and liquid chromatography/mass spectrometry
2002
Abstract A method was developed for monitoring dichloran, flutriafol, o-phenylphenol, prochloraz, and tolclofos-methyl in fruits and vegetables, using matrix solid-phase dispersion and liquid chromatography with mass spectrometry detection. The method was used to determine fungicide content in 200 samples of chards, onions, peppers, bananas, lemons, and oranges. Of the samples examined, 54% contained o-phenylphenol with concentrations ranging from 0.005 to 3.34 mg/kg and 35% showed prochloraz in the range of 0.06–1.95 mg/kg. Dichloran, flutriafol, and tolclofos-methyl were detected only occasionally. Only 4% of the samples exceeded the European Union maximum residue limits. The pesticides i…
A measurement of the phases of the CP-violating amplitudes in K0→2π decays and a test of CPT invariance
1990
Abstract The phases of the CP-violating amplitudes in K0→π+π− and K0→2π0 decays, φ+−=46.9°±2.2° and φ00=47.1°±2.8°, have been measured in the same experiment, and a direct comparison gives the phase difference φ00−φ+−=0.2°±2.9°. This result leads to an upper limit on possible CPT violation in the K0 mass matrix, of |(m K 0 −m K 0 )/m K 0 | −18 at the 95% confidence level and is the most stringent test of the equality of particle and antiparticle masses.
Existence of zero-energy impurity states in different classes of topological insulators and superconductors and their relation to topological phase t…
2015
We consider the effects of impurities on topological insulators and superconductors. We start by identifying the general conditions under which the eigenenergies of an arbitrary Hamiltonian H belonging to one of the Altland-Zirnbauer symmetry classes undergo a robust zero energy crossing as a function of an external parameter which can be, for example, the impurity strength. We define a generalized root of \det H, and use it to predict or rule out robust zero-energy crossings in all symmetry classes. We complement this result with an analysis based on almost degenerate perturbation theory, which allows a derivation of the asymptotic low-energy behavior of the ensemble averaged density of st…
Orientation and Dynamics of ZnO Nanorod Liquid Crystals in Electric Fields.
2010
ZnO nanorod polymer hybrids (i.e., ZnO nanorods coated with a block copolymer with a short anchor block (dopamine) and a longer solubilizing block of polystyrene (PS)) form liquid crystalline (LC) phases if they are dispersed at high concentration e.g., in a PS oligomer matrix. Due to the high mobility of the low T(g)-matrix the nanorod polymer hybrids show a switching behavior under an applied AC electric field. Hence, the orientation of the nanorod mesogens can be changed from planar (parallel to the substrate) to homeotropic (perpendicular) in full analogy to the switching of low molecular liquid crystals in an electric field. Dielectric measurements show that such a switching is mainly …
Phononic heat transport in the transient regime: An analytic solution
2016
We investigate the time-resolved quantum transport properties of phonons in arbitrary harmonic systems connected to phonon baths at different temperatures. We obtain a closed analytic expression of the time-dependent one-particle reduced density matrix by explicitly solving the equations of motion for the nonequilibrium Green's function. This is achieved through a well-controlled approximation of the frequency-dependent bath self-energy. Our result allows for exploring transient oscillations and relaxation times of local heat currents, and correctly reduces to an earlier known result in the steady-state limit. We apply the formalism to atomic chains, and benchmark the validity of the approx…
Effects and future trends of casein phosphopeptides on zinc bioavailability
2007
This review focuses on studies of the effects of CPPs on zinc bioavailability. It evaluates the main differences in studies performed in the last two decades, such as methodology used to measure zinc, food matrix, CPP preparation, CPP dose, CPP:Zn molar ratio and presence and concentration of zinc absorption inhibitors, such as phytate, iron and calcium. The future trends of CPPs as functional ingredients in zinc-enriched or zinc-containing foods are also discussed.