Acomplex mixture of sunscreens of different lipophilicity was quantified for the first time by thin-layer chromatography (TLC) followed by densitometric scanning in absorption mode. Multiple-development normal-phase TLC was performed on silica gel 60 as stationary phase. Two mobile phases were used: A — cyclohexane-diethyl ether 5:1 (v/v) and B — ethyl acetate-ethanol-water 70:35:30 (v/v). After development with mobile phase A, two oil-soluble sunscreens, avobenzone (AVO) and octyl salicylate (OS), were analyzed at 360 and 300 nm, respectively. Subsequent development of the same plates with mobile phase B made it possible to quantify a water-soluble sunscreen — phenylbenzimidazol sulfonic acid (PBS) at 300 nm. Calibration curves were non-linear. Limits of detection (LOD) and quantification (LOQ) were LOD (OS) 0.02 μg spot−1, LOQ (OS) 0.06 μg spot−1, LOD (AVO) 0.03 μg spot−1, LOQ (AVO) 0.08 μg spot−1, LOD (PBS) 0.02 μg spot−1, and LOQ (PBS) 0.06 μg spot−1. The method was validated and applied to the analysis of a commercially available cosmetic product.
The solubilities of NpO2(s) in the KURT (KAERI Underground Research Tunnel) granitic groundwater with low ionic strength were measured experimentally
and calculated by a geochemical code. Then these results were compared with each other as well as with foreign results. The
concentrations of neptunium were measured as 6·10−8−2·10−8 mol/L at a pH = 9.5–11.1 and Eh = −0.2 V, and less than 5·10−9 mol/L at a pH = 11.8–13.0 and Eh = −0.3–0.44 V. The dominant aqueous species were presumed as Np(OH)x(CO3)y4−x−2y complexes and Np(OH)4(aq) at pH = 9.5–13 under the Eh<−0.2 V reducing condition.
The behavior of a water soluble calixarene ligand has been investigated in an (NH4)2SO4/polyethylene glycol-2000 (PEG) aqueous biphasic system. Spectroscopic measurements indicate that 4-sulfonic-calix-6-arene partitions preferentially to the polymer-rich phase in this system. The utility of this ligand as a metal ion extractant was also investigated. The addition of the calixarene (10–2M in initial PEG-rich stock solution) did not significantly enhance the partitioning of Na+, Cs+, Sr2+, Ba2+, Co2+, Cd2+, or UO
from the (NH4)2SO4-rich to the PEG-rich phase. The partitioning behavior of these metal ions is dependent, rather, on their Gibbs free energy of hydration (Ghyd*).
In this paper chromatographic systems for the accurate and reliable determination of the percentage of different species (free
pertechnetate, particulate99mTc and labelled99mTc) in99mTc-labelled radiopharmaceuticals are described. The procedures are based on the simultaneous run of two different chromatograms,
one in 85% CH3OH and the other in 15% H3PO4. Also, 0.9% NaCl can be used instead of 15% H3PO4 for the second chromatogram. Alternative procedures applying two dimensional chromatography on Whatman No. 1 paper or silica
G plates with 85% CH3OH for the first run and 15% H3PO4 for the second are given. The applicability of these procedures is limited to water-soluble radiopharmaceuticals.
A field experiment study was performed at the rural site of South-East Lithuania. The main tasks of the study included an
evaluation of the peculiarities of partition of239Pu in soluble (239Pu(NO3)4,239PuCl3) and insoluble (239PuO2) forms in soddy and forest soil horizons. The results of durable experiments (418 and 326 days) have shown that from 44.1%
to 92.2% of239Pu of investigated chemical forms were accumulated in the top (0–5 cm) soil layer. Some share (5.7–39.2%) of plutonium from
studied chemical forms was found in the 5–20 cm layers of studied soil samples (columns). Obtained distribution of plutonium
in soil layers may be attributed to the consideration that the migration rate to the soil depth for plutonium is 0.1–1.0 cm·y−1 but for some part of plutonium 10 times higher migration rate is characteristic as well. Plutonium transfer factor (TF) to
the grassland plants was calculated, the values ranged from 10−2 to 10−1.
The Ostwald coefficients L2,1 of He, Ne, Ar, Kr, Xe, N2, O2, CH4 CF4 and SF6 dissolved in several homologousn-alkanes,n-C1H21+2, 6≤l≤16, andn-alkan-1-ols,n-C1H21+1OH, 1≤l≤11, were recently measured at 298.15 K and atmospheric pressure with a modified Ben-Naim/Baer apparatus. Altogether, 201 gas/liquid systems were investigated. For about half of these systems, both pressure control and measurement of the volume of gas dissolved in a given volume of solvent were achieved with a microprocessor. This improved medium-precision instrument (σ≤0.5% in most cases) combines easy handling with fully automated data retrieval, and is totallymercury-free. In this communication, the salient points of data reduction are presented, with the focus on the estimation of several important auxiliary quantities such as second virial coefficients and partial molar volumes at infinite dilution. The effect of the chain lengthl of then-alkane or then-alkan-1-ol upon solubility is demonstrated, and some correlations betweenL2,1, or the derived Henry fugacitiesH2,1, and appropriate molecular and/or bulk properties of the gases and the solvents are discussed.
Authors:J. Ramírez-García, M. Jiménez-Reyes, M. Solache-Ríos, E. Fernández-Ramírez, H. López-González, and A. Rojas-Hernández
The solubility of europium at 0.02M, 0.1M and 0.7M NaClO4 ionic strength solutions was determined by a radiometric method and pEus-pCH diagrams were obtained. Hydrolysis constants were also determined at the same ionic strengths by pH titration and the values found were log *
1 = -7.68±0.11, -8.07±0.10 and -8.20±0.11. The log Ksp values were -23.5±0.2, -22.7±0.2 and -21.9±0.2 for 0.02M, 0.1M and 0.7M NaClO4 ionic strengths, respectively, at 303 K under CO2-free conditions and the extrapolated value at zero ionic strength was log Ksp0 = -24.15. The working pCH ranges for the calculation of the hydrolysis constants were selected from the pEus-pCH diagrams in the region where precipitation of europium oxide or hydroxide was less than 20%. Europium removal from aqueous solutions with zeolites was explored.
Authors:C. Han, Z. Yu, S. Feng, D. Lv, X. Yan, G. Chen, X. Li, W. Ma, and Y. Yan
Separation and analysis of water-soluble proteins (WSP) are important in understanding wheat grain proteome fundamentals. However, due to their high degree of heterogeneity and complexity in the compositions, separating WSP is generally difficult and relevant methodologies are not efficiently developed yet. Capillary electrophoresis (CE) is one of the analytical methods currently used for protein separation and characterization. In the present study, a CE method is established for rapidly separating and characterizing WSP of wheat grains. The established method was tested in various applications including wheat variety and germplasm identification as well as protein synthesis and accumulation studies during different grain development stages subject to genotypic and environmental variations. As results, the characteristic CE patterns of a range of bread wheat cultivars and related species were readily identified. The synthesis and accumulation patterns of wheat WSP during developing grains as well as their stabilities in different environments were also investigated. The technical advancements present in this article appear to be useful for wheat cultivar and germplasm identification as well as genetics and breeding research.
The 'hydrophobic effect' of the dissolution process of non-polar substances in water has been analysed under the light of
a statistical thermodynamic molecular model. The model, based on the distinction between non-reacting and reacting systems explains the changes of the thermodynamic functions with temperature in aqueous systems. In the dissolution of non-polar
substances in water, it follows from the model that the enthalpy change can be expressed as a linear function of the temperature
(ΔHapp =ΔHø +nwCp,wT ). Experimental solubility and calorimetric data of a large number of non-polar substances nicely agree with the expected
function. The specific contribution of nw solvent molecules depends on the size of solute and is related to destructuring (nw >0) of water molecules around the solute. Then the study of 'hydrophobic effect' has been extended to the protein denaturation
and micelle formation. Denaturation enthalpy either obtained by van't Hoff equation or by calorimetric determinations again
depends linearly upon denaturation temperature, with denaturation enthalpy, ΔHden , increasing with T . A portion of reaction enthalpy is absorbed by a number nw of water molecules (nw >0) relaxed in space around the denatured moieties. In micellization, an opposite process takes place with negative number
of restructured water molecules (nw <0) because the hydrophobic moieties of the molecules joined by hydrophobic affinity occupy a smaller cavity.
The vegetative buds and later on young needles as well as needles formed in spring previous year of Picea abieswere used in the experimental work. Extracted proteins were determined spectrophotometrically and the amount of dry weight was measured. The data revealed that the dry weight of needles formed in spring previous year was about three times higher than in the vegetative buds at the beginning of investigations. During the sampling period the dry weight in those needles was keeping nearly the same level (39-54%). The increase in dry weight was noticed in the young needles 5-6 weeks after vegetative buds burst. The amount of total soluble proteins in the needles formed previous year was about 140 mg/g of dry weight and it was uniformed during the investigation period. In the vegetative buds the amount of proteins was three times higher than in needles. But, the concentration starts to decrease just before bursting of the vegetative buds as well as during next 2 or 3 weeks when young shoot proliferated. After this decreasing period amount of proteins in newly formed needles briefly reached (in 2 weeks period) the level as it was in vegetative buds. In the following period the decrease of water amount as well as the protein amount in young needles was observed.