Search results for "resolution."

Uptake of actinides by calcium silicate hydrate (C-S-H) phases

2018

Abstract The sorption of actinides (Th, U – Am) was studied in dependence of the solid-to-liquid (S/L) ratio (0.5–20.0 g/L) and the calcium-to-silicon (C:S) ratio. The C:S ratio was varied between 1.80 and 0.70 to simulate the changing composition of the C-S-H phases during cement degradation from high to low C:S ratios. The decrease of the calcium content in the C-S-H phases by time is accompanied by a decrease in pH in the corresponding suspensions from 12.6 to 10.2. X-ray photoelectron spectroscopy (XPS) of the C-S-H phases showed an increasing depletion of Ca on the surface with increasing C:S ratio in comparison to the composition of the solid phase as a whole. The sorption experiments…

Anatase photocatalyst with supported low crystalline TiO2: The influence of amorphous phase on the activity

2018

Abstract In a previous study on commercial TiO2 nanoparticles (J. Soria et al.) we had shown that the superficial disordered layers influence their textural and reactivity features. In the present work we used well crystallized anatase particles (commercial TiO2, BDH) as support of different amounts of titania powders, prepared by TiCl4 hydrolysis and constituted by nanocrystals diluted into an amorphous matrix. The reactivity of these photocatalysts has been tested for the selective oxidation of 4-methoxybenzyl alcohol to aldehyde in aqueous suspension. The catalyst characteristics have been studied using adsorption-desorption isotherms, TEM, HRTEM, TGA, PL, DRIFT-IR, and 1H MAS-NMR spectr…

Hydrogen peroxide sensors for cellular imaging based on horse radish peroxidase reconstituted on polymer-functionalized TiO2 nanorods

2011

We describe the reconstitution of apo-horse radish peroxidase (apo-HRP) onto TiO2 nanorods functionalized with a multifunctional polymer. After functionalization, the horse radish peroxidase (HRP) functionalized TiO2 nanorods were well dispersible in aqueous solution, catalytically active and biocompatible, and they could be used to quantify and image H2O2 which is a harmful secondary product of cellular metabolism. The shape, size and structure of TiO2 nanorods (anatase) were analyzed by transmission electron microscopy (TEM), high resolution TEM (HRTEM), electron diffraction (ED) and X-ray diffraction (XRD). The surface functionalization, HRP reconstitution and catalytic activity were con…

Chromatography of metal chelates

1973

The chromatographic behavior of metal bis(ethoxyethyl)dithiocarbamate was investigated. The chelates of 14 elements (V, Cr, Co, Ni, Cu, Zn, Se, Mo, Cd, Te, Hg, Tl, Pb and Bi) could be preconcentrated from water with an on-line system and were shown to be suitable for C18-reversed-phase liquid chromatography. A quaternary solvent mixture with admixture of a surfactant was used as eluent, UV-detection was performed at 254 nm. Thermostating the column to 40° C resulted in a significant increase in chromatographic resolution and in a decrease of analysis time. The recovery of the chelates from the aqueous solutions as well as reproducibility of the results are very sensitive to pH changes.

High resolution electron microscopy of liquid crystalline polymers

1990

Les images de microscopie electronique a haute resolution des polymeres cristaux liquides calamitiques [CO−CH(R)−CO 2 −(CH 2 ) 6 −OPh−N:N−PhO−(CH 2 ) 6 −O] n (R=CH 2 −CH=CH 2 , (CH 2 ) 6 −O−Ph N=N−Ph−CN) et discotique poly (hexadecanedioate de triphenylene) sont simulees sur ordinateur et comparees avec les structures obtenues a partir des resultats experimentaux de diffraction electronique. Une theorie est developpee pour expliquer le bon accord observe

2003

Resting cells of the yeast Rhodosporidium toruloides (UOFS Y-0471) were immobilised in calcium alginate beads for the enantioselective kinetic resolution of racemic-1,2-epoxyoctane. The initial activity exhibited by immobilised cells was almost 50% lower than that of the free counterpart but was extremely stable when compared to the free cells. The concentration of the immobilised biomass had no effect on apparent enzyme activity but did lead to a decrease in single cell activity. An increase in both the alginate and CaCl2 concentrations used for bead preparation led to a decrease in enzyme stability. An increase in the alginate concentration led to an increase in bead diameter. The stoichi…

The CEC behaviour of several synthetic peptides related to the activin ��A-��D subunits

2008

The resolution of several structurally related synthetic peptides, derived from the loop 3 region of the activin betaA-betaD subunits, has been studied using capillary electrochromatography (CEC) with Hypersil n-octadecylsilica as the sorbent. The results confirm that the CEC migration of these peptides can be varied in a charge-state-specific manner as the properties of the background electrolyte, such as pH, salt concentration and content of organic modifier, or temperature are systematically changed. Acidic peptides followed similar trends in retention behaviour, which was distinctly different to that shown by more basic peptides. The CEC separation of these peptides with the Hypersil n-…

Simultaneous gas chromatographic determination of aliphatic C2−C20 n-carboxylic acids and their methyl esters using SE-30 and OV-351 quartz capillary…

1983

Simultaneous determination of aliphatic C2−C20 carboxylic acids and their methyl esters was carried out using SE-30 and OV-351 quartz capillary columns with temperature programming. Complete resolution of all 36 components was achieved. On SE-30 the methyl ester and the corresponding free acid are eluted in turn, whereas on OV-351 acetic acid eluted after methyl octanoate, after which the Cn methyl ester and Cn-6 carboxylic acid (n>9) are eluted one after the other. A non-polar SE-30 column is better for long-chain acids giving sharp peaks without tailing, the analysis time of the mixture being less than 16 minutes. The weight response correction factors for compounds under optimum operatin…

Separation of Proteic Primary Amino Acids under Several Reversed‐Phase Liquid Chromatographic Conditions

2006

Abstract The reversed‐phase liquid chromatographic (RPLC) analysis of proteic primary amino acids with acetonitrile‐water, using pre‐column derivatisation with o‐phthalaldehyde (OPA) and N‐acetylcysteine (NAC), was compared with RPLC modes using trifluoroacetic acid or pentadecafluorooctanoic acid and evaporative light‐scattering detection, or sodium dodecyl sulphate micelles with pre‐ and post‐column derivatisation. The importance of column lifetime, risk of potential damages in the instrumentation, retention and resolution, was considered. Among the assayed approaches, the best is still aqueous‐organic RPLC with pre‐column derivatisation. It not only yields the most reliable results, but …

Prediction of the genetic variety of Spanish extra virgin olive oils using fatty acid and phenolic compound profiles established by direct infusion m…

2007

Abstract The genetic varieties of Spanish extra virgin olive oils (Arbequina, Hojiblanca and Picual) were predicted by direct infusion of the samples in the electrospray ionization source of a mass spectrometer, followed by linear discriminant analysis of the spectral data. The samples were 1:50 diluted (v/v) with an 85:15 propanol/methanol (v/v) mixture containing 40 mM KOH and infused. The abundances of the [M–H] − peaks of the free fatty acids (7 peaks) and 28 phenolic compounds (20 peaks) were measured. Ratios of pairs of peak abundances were used as predictors in the construction of the linear discriminant analysis models. An excellent resolution between the three genetic varieties was…