Search results for "Partition coefficient"
showing 10 items of 146 documents
Influence of temperature and background electrolyte on the sorption of neptunium(V) on Opalinus Clay
2012
Abstract The temperature dependence of the sorption of 8 μM neptunium(V) on Opalinus Clay (OPA, Mont Terri, Switzerland) was investigated between 40 and 80 °C and compared to previous results for 20 °C. The batch experiments were performed under ambient air conditions in synthetic pore water (pH = 7.6, I = 0.4 M) under variation of the solid-to-liquid ratio between 2 and 20 g/L. Under these conditions the sorption of Np(V) on OPA was found to be an endothermic process as the average distribution coefficient (K d ) increases continuously with increasing temperature from 23 ± 4 L/kg at 40 °C to 678 ± 254 L/kg at 80 °C. In the temperature range of 40-80 °C, the plot of log(K d ) vs. 1/T could …
Skin permeation model of phenyl alcohols: comparison of experimental conditions
1998
Abstract This study was conducted primarily to establish the significance of the experimental conditions in the determination of permeability coefficients. In order to do this, standard in vitro skin permeation methods were used to determine the permeability coefficient (kp) of a homologous series of phenyl alcohols, with a wide range of lipophilicity, by two different experimental conditions through rat skin; first, using solutions (at 75% saturation concentration) of the penetrants in the donor compartment and second using saturated solutions added with an excess of the penetrant. The kp values obtained by these techniques were compared. Solubility of the phenyl alcohols in the donor phas…
Trennung von Spaltprodukten durch Extraktionschromatographie
1967
The possibilities for the separation of a complex fission product mixture by extraction chromatography have been investigated. Here the partition coefficients between three solvents and hydrochloric acid are reported for the following elements: Zn(II), Ge(IV), As(III), As(V), Se(IV), Zr(IV), Nb(V), Mo(VI), Tc(IV) Ru(III), Ru(IV), Rh(III), Ag(I), Cd(II), In(III), Sn(IV), Sb(III), Sb(V), Te(IV), I(oxidized), Cs(I), Ce(III), Tb(III), Tm(III), Ac(III), Th(IV), Pa(V), U(VI), Np(IV), Np(VI). As solvents tri-n-butylphosphate (TBP), tri-n-octylamine (TOA) and di-(2-ethylhexyl)-orthophosphoric acid (HDEHP) have been used. The partition coefficients have been measured by batch-experiments in which th…
Determination of distribution coefficients (Kd) of various radionuclides on UTEVA resin
2016
Abstract Using radioisotope markers the distribution coefficients (Kd) of the following elements In, Sn, Sb, Te, Bi, Co, Fe, Nb, Sr, Ba, Ag, Cd, Zr, Hf and Ti were determined with different concentrations of HCl, H2SO4 and HNO3 for the extraction chromatographic resin Uranium and TEtraValent Actinides (UTEVA). This data can be used for separation of elements in complex mixtures, as well as for correct assessment of the elements chemistry with higher valences such as 3, 4, 5 or 6.
Trace-element partitioning and boron isotope fractionation between white mica and tourmaline
2011
High-grade metamorphic tourmaline and white mica from the Broken Hill area, NSW, Australia, were analyzed with laser-ablation ICP–MS and ion-probe techniques to investigate the partitioning of trace elements and fractionation of boron isotopes between these two coexisting phases. The results indicate that most trace elements show partition coefficients close to one; only elements such as Zn, Sr, the light rare-earth elements La and Ce, and Th, partition preferentially into tourmaline, whereas Rb, Ba, W, Sn, and Nb and Ta are preferentially partitioned into coexisting mica. The ion-probe measurements demonstrate that boron isotopes are strongly fractionated between mica and tourmaline, with …
Macromolecules in ordered media III. A fluorescence study on the association of poly-2-vinylpyridine with a phospholipid bilayer
2007
Association of low molecular weight poly-2-vinylpyridine taken as a polycation model with unilamellar vesicles based on dimirystoylphosphatidic acid has been experimentally investigated by means of fluorescence energy transfer experiments. The conventional profiles for the binding isotherms were obtained, confirming strong deviations from the ideality of these complex fluid composites. Two approaches, named binding and partitioning equilibrium, respectively, were used to obtain the association constant, K A; the number of phospholipids that form a binding site, N; the partition coefficient, Λ; the activity coefficient, γ; and the effective charge, v. Analysis of these parameters as a functi…
Retention of Carvacrol and Ethyl Acetate in Aqueous Gels of Potato Starch and Konjac Glucomannan
2014
The partition coefficients of two volatile compounds in dispersions containing potato starch (PS) and/or konjac glucomannan (KGM) have been determined by the phase ratio variation method using equilibrium headspace analysis by gas chromatography. The influence of the moment when volatile compounds were added and the effect of the polysaccharide dispersions were investigated. For ethyl acetate, retention by KGM was based on viscosity effect. Retention of carvacrol was important when amylose was accessible. The addition of KGM to PS suspensions decreased the retention governed by interactions with starch.
SPME of 52 pesticides and polychlorinated biphenyls: Extraction efficiencies of the SPME coatings poly(dimethylsiloxane), polyacrylate, poly(dimethyl…
2001
Fiber/water partition coefficients (Kfw) of 52 pesticides, including triazines, organophosphorus pesticides, organochlorine pesticides, and polychlorinated biphenyls (PCBs) were experimentally calculated for the five polymeric coatings poly(dimethylsiloxane) (PDMS), polyacrylate (PA), poly(dimethylsiloxane)-Divinylbenzene (PDMS-DVB), Carboxen-poly(dimethylsiloxane) (CAR-PDMS), and Carbowax-divinylbenzene (CW-DVB) commercially available for solid-phase microextraction coupled to gas chromatography. The equilibrium-time profiles for the five coatings were previously studied in order to establish the time needed for equilibrium. To calculate Kfw the amount of analyte extracted at equilibrium w…
Determination of Diffusion Parameters by a Computer Code (FDP) Based on Mathematica 6.0
2010
A computer code named Fitting for Diffusion Parameters (FDP) based on Mathematica 6.0 has been developed for modeling through- and out-diffusion experiments. FDP was used to determine the diffusion coefficients (De ) and the rock capacity factors (α) for tritiated water (HTO) and 22 Na+ and the distribution coefficient (Kd ) of 22 Na+ in Opalinus Clay (OPA). The values for De and α were obtained by fitting the results of experimental data of both transient and steady-state phases to the analytical solution of accumulated activity. The quality of the parameters De and α was tested by using them as input parameters in the equation of flux. Moreover, the diffusion parameters of HTO and 22 Na+ …
Estimation of the effect of the acidosis and alkalosis on the anesthetic potency of local anesthetics by biopartitioning micellar chromatography and …
2004
Local anesthetics are hydrophobic compounds and weak bases with protonation constants ranged between 7.5 and 8.8. These drugs block reversibly nerve conduction near their site of application or injection and thus produce temporary loss of feeling or sensation in a limited area of the body. The efficacy of anesthetic blockade of local anesthetics depends on the charged/uncharged form ratio and the hydrophobicity of the compounds. In addition their toxicological effects have been reported to be highly dependent on the physiological pH. Biopartitioning micellar chromatography (BMC) and micellar electrokinetic chromatography (MEKC), that use micellar solutions as mobile phases, have proven to b…