Determination of 129I in biomonitors collected in the vicinity of a nuclear power plant by neutron activation analysis

Neutron activation analysis (NAA) was used to determine ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in bovine thyroid, moss, and river sediment samples collected in the vicinity of the Temelín nuclear power plant (NPP) in south Bohemia. The NAA procedures comprised pre-irradiation separation of ¹²⁹I by combustion of the samples in the stream of oxygen at 1,000 °C and trapping the liberated iodine in a LiOH/(NH₄)₂SO₃ solution. Post-irradiation separation of ¹³⁰I produced by the reaction ¹²⁹I(n,γ)¹³⁰I was carried out by extraction of elementary iodine with chloroform followed by precipitation of PdI₂. Nondestructive, epithermal NAA was used to determine ¹²⁷I employing the ¹²⁷I(n,γ)¹²⁸I reaction. The results showed that mean values of ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in the bovine thyroids varied from 22 to 61 mBq kg^?1 (dry mass) and 2.8 × 10^?9 to 5.4 × 10^?9, respectively. These values are close to the lower end of results reported from various regions non-polluted with ¹²⁹I. No significant differences were found between ¹²⁹I concentrations and the ¹²⁹I/¹²⁷I ratios in the bovine thyroids collected prior to the start and after several years of operation of the NPP. The mean value and standard deviation of ¹²⁹I in mBq kg^?1, dry mass and the ¹²⁹I/¹²⁷I ratio in moss Pleurozium schreberi were 23 ± 16 and 2.3 × 10^?9, respectively, whereas values of ¹²⁹I in the river sediments were below 8–10 mBq kg^?1 (dry mass) after several years of the NPP operation.     

Fingerprints of Phalaenopsis Tissues in Growth and Spike Induction Periods—A Solid‐state 13C NMR Approach

Solid‐state Nuclear Magnetic Resonance (ss‐NMR) ¹³C single‐pulse excitation spectroscopy in combination with the magic‐angle spinning (MAS) technique was applied to a series of Phalaenopsis tissues, including the leaf, sheath, stem, and root, at different growth and spiking periods. Compared with{¹H}/¹³C cross‐polarization MAS spectra, the ¹³C single‐pulse excitation MAS spectra displayed very distinct spectral patterns, recognizable as fingerprints of the tissues studied. ¹Here, we demonstrate that solid‐state ¹³C single‐pulse excitation NMR spectroscopy provides a direct and robust analytical tool for studying the various tissues of Phalaenopsis in different growth and spiking induction periods.     

Photoinduced phase transitions and helix untwisting in the SmC* phase of a novel cinnamoyl-based liquid crystal

A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation P _s was measured and it was found that UV irradiation induces a decrease in the values of P _s. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases.     

Pressurised solvent extraction of nitrated derivatives of polycyclic aromatic hydrocarbons from roadside dust

An analytical method based upon the pressurised solvent extraction and gas chromatography and mass spectrometry (GC-MS) for analysis of nitrated derivatives of polycyclic aromatic hydrocarbons (nitro-PAHs) in roadside dust has been developed. Five nitro-PAHs (1-nitronaphthalene, 1-nitropyrene, 9-nitroanthracene, 2-nitrofluorene, 6-nitrochrysene) were chosen for this study because of their variable physical properties and effect on human health. Experiments with spiked inert matrix were used for the best extraction conditions finding. Different extraction conditions (temperature, pressure, solvents and duration of extraction cycle) were examined. The highest recoveries were observed at the extraction pressure of 14?MPa, temperature of 100°C and two cycles of 5?min extraction time, when dichloromethane was used as an extraction solvent. These conditions were applied to the extraction of nitro-PAHs from roadside dust. After extraction the nitro-PAHs fraction was isolated by the silica gel column chromatography. The GC-MS detector was used for analyses of the extracts. Recoveries of nitro-PAHs after extraction from roadside dust ranged from 60% for 9-nitroanthracene to 108% for 6-nitrochrysene.     

2,8'-disubstituted-1,1'-binaphthyls: a new pattern in chiral ligands

The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product).     

Isotachophoretic analysis of the dihydrofolate reductase reaction in the presence of methotrexate and ascorbic acid

The antifolate methotrexate (MTX) is widely used in cancer chemotherapy. In this study, we show that MTX (MTX-Glu1) and MTX-polyglutamates (MTX-Glu2-5) strongly inhibited the growth of the leukemic cell line MOLT-4. This effect, however, was mitigated by ascorbic acid. We investigated whether ascorbic acid is able to reduce dihydrofolic acid (DHF) to tetrahydrofolic acid (THF) directly or by circumventing the MTX inhibition of dihydrofolate reductase (DHFR). The inhibition of this NADPH-dependent reduction of DHF by MTX-Glun in the absence or presence of ascorbate, was determined by analytical isotachophoresis. Using 0.01 M HCl/histidine, pH 6.0, as a leading electrolyte (L) and 0.005 M 2-(N-morpholino)ethanesulfonic acid (MES)/histidine, pH 6.0, as a terminating electrolyte (T), MTX-Glun derivatives including MTX-Glu1 could be easily separated, whereas the quantitative estimation of THF was not possible. A quantitative characterization of the DHFR reaction by measuring NADPH, NADP+ and ascorbate was achieved with another system (L: 0.01 M HCI/beta-alanine, pH 3.73; T: 0.01 M caproic acid, pH 3.27). Nanomolar concentrations of MTX-Glu1-5 inhibited consumption of NADPH and production of NADP+. Ascorbic acid was not able to reduce DHF, neither directly nor after inhibition of DHFR by MTX. However, ascorbic acid seemed to diminish the oxidation of THF and this may account for its capacity to reduce the inhibitory effect of MTX on MOLT-4 cells.     

Charge transfer across a polymer gel/liquid interface: determination of ionophores

An electrochemical method for the determination of the ionophores monensin and lasalocid was developed, based on the polarization of an agar gel/nitrobenzene electrolyte interface. The measured current corresponding to the facilitated ion transfer across this interface is directly proportional to the concentration of an ionophore dissolved in the organic phase. Using cyclic voltammetry in a three-electrode system the detection limit for both ionophores is about 3 × 10^?5 M.     

Preparation of a 99mTc-labeled graft polymer and its in vitro and in vivo evaluation

Journal of Radioanalytical and Nuclear Chemistry - The aim of this study is the synthesis of a novel 99mTc-labeld graft polymer and the biological evaluation of its in vitro and in vivo properties....     

Role of polar and apolar moieties in water adsorption by humic acids under arid conditions

Journal of Thermal Analysis and Calorimetry - In arid soils, humic acids (HAs) are used as amendments to improve water uptake from the atmosphere. This method of harvesting water involves several...