Progress in neutron activation analysis for uranium

A new type of extractant, sym-dibenzo-16-crown-5-oxyhydroxamic acid (HL) is introduced. The extractions of UO22+, Na+, K+, Sr2+, Ba2+ and Br- were studied with HL in chloroform. The results obtained show that UO22+ can be quantitatively extracted at pH values above 5, whereas the extractions of K+, Na+, Sr2+, Ba2+ and Br- are negligible in the pH range of 2 - 7. The dependence of the distribution ratio of U(VI) on both the concentration of the HL and pH are linear, and they have the same slope of 2. This suggests that U(VI) appears to form a 1:2 complex with ligand. Uranium(VI) can be selectively separated and concentrated from interfering elements such as Na, K, Sr and Br by solvent extraction with HL under specific conditions. The recovery of uranium is nearly 100% and the radionudear purity of uranium is greater than 99.99%. Therefore, neutron activation analysis has greatly improved the sensitivity and accuracy for the detection of trace uranium from seawater.     

Dissolved oxygen in aeration-driven piezo-catalytic for antibiotics pollutants removal in water

The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems. Herein, a piezoelectic odd-layered Mo S2is prepared and applied to piezo-catalytic remove tinidazole(TNZ) and other antibiotic pollutants with aeration as a piezo-driving force. About 89.6% of TNZ can be degraded by Mo S₂ under aeration in the presence of dissolved oxygen with a reaction rate constant of0.15 min^-1, which is 2.4 times higher than that under N₂ ...     

Adsorbents for acetone in cyclohexane effuent employed in Ziegler-Natta catalyst process

Adsorption of acetone from cyclohexane on silica, alumina, coal, natural and leached chrysotile was investigated. Adsorption phenomenon was investigated by non-linear fitting, considering the Langmuir or Freundlich models. According to non-linear regression, coal present the highest K _L (12.07) and K _F (9.115) parameters. Silica and leached chrysotile exhibited similar behavior in terms of both K _L and K _F parameters. Alumina presented the highest adsorption capacity according to both Langmuir (q _m =58.689) and Freundlich (1/n=0.844) models. Non-supported Ziegler-Natta catalyst systems were shown to be more sensitive to acetone contamination. For the polymerization reactions carried on with contaminated solvent after the percolation through the adsorbents, good results were observed in the case of silica and alumina. Coal was not suitable for use in this catalyst system, probably due to leaching of organic components by the solvent (cyclohexane).     

Chemical Research in Chinese Universities Instructions for Authors

The journal Chemical Research in Chinese Universities is a comprehensive academic journal in the field of chemistry,published bimonthly since 1984.The journal publishes research articles,letters/communications and reviews written by faculty members,researchers and postgraduates in universities,colleges and research institutes all over China and overseas.It reports the latest and most creative results of important fundamental research in all aspects of chemistry and of developments with significant consequences across sub-disciplines.This journal is sponsored by Jilin University and mandated by the Ministry of Education of P.R.China.     

TrainMiC®: a programme for life-long learning in metrology in chemistry

This article gives an overview of the programme TrainMiC^®, a European programme for Life-Long Learning in metrology in chemistry. It explains its raison d’être and puts it into perspective to other European and EU member states initiatives. The TrainMiC^® system (http://www.trainmic.org) is described in detail. It is explained how it has developed into a truly unique system which is operational across many parts of Europe (19 countries) via national teams. These teams use shareware pedagogic tools. The learning content has been harmonised at the European level by a joint effort of many experts across Europe working via an Editorial Board. The material has been translated in ten different languages. Possible future evolution of this Life Long Learning programme is discussed.     

Chemical Research in Chinese Universities Instructions for Authors

The journal Chemical Research in Chinese Universities is a comprehensive academic journal in the field of chemistry,published bimonthly since 1984.The journal publishes research articles,letters/communications and reviews written by faculty members,researchers and postgraduates in universities,colleges and research institutes all over China and overseas.It reports the latest and most creative results of important fundamental research in all aspects of chemistry and of developments with significant consequences across sub-disciplines.This journal is sponsored by Jilin University and mandated by the Ministry of Education of P.R.China.     

Photo-responsive nanoparticles for β-lapachone delivery in vitro

We reported a one-step encapsulation of indocyanine green (ICG) in ZIF-8 nanoparticles (NPs). The as-prepared ICG@ZIF-8 NPs possess an absorption band in the near infrared region and have the good photothermal conversion efficiency.     

‘Low-temperature method’ for a dramatic improvement in enantioselectivity in lipase-catalyzed reactions

Temperature control in lipase-catalyzed resolutions has been recently focused attention due to its simplicity and reliability for enhancement of the enantioselectivity. Lowering the reaction temperature usually increases the enantioselectivity. Lipase immobilized on porous ceramics was found to greatly accelerate the low-temperature reaction, and made the method practical. Our discovery, properties, and practical uses are summarized, and its applications are reviewed.     

Sampling anoxic pore waters in peatlands using “peepers” for in situ-filtration

Equilibrium diffusion chambers ("peepers") have been constructed to collect anoxic pore waters in bogs without degassing and/or oxidizing the samples. These samplers have been constructed of Plexiglass, either as a long board with a series of sampling chambers for close interval analyses near the surface of a bog, or as single chambers inserted at greater depths (1 to 6 m). Prior to installation, the chambers have been filled with deaerated, deionized water, and have been covered by a 0.2 microm membrane filter; this membrane allows the dissolved constituents in the waters to equilibrate with the deionized water in the chamber by diffusion. The samplers have been allowed to equilibrate in the bog for 4 to 6 weeks. Thereafter, they have been withdrawn into N(2)-filled glove bags. Individual chambers have been sampled in the field by inserting a syringe through the glove bag; these syringes have been used immediately upon the arrival in the lab to analyze volatile and redox-sensitive species by ion chromatography. The effectiveness of this sampling approach has been demonstrated by measuring the concentrations of the dominant volatile acids in these waters (H(2)CO(3)) and two redox sensitive species (Fe(2+) and HS(-)). The procedure described here should be applicable also to trace metal speciation studies, provided that appropriate checks are made for all possible sources of contamination.     

Recent Technological Developments in Cobalt Catalysts for Fischer-Tropsch Synthesis

Co-based catalysts are often utilized due to their high Fischer-Tropsch synthesis (FT) activity, G5+ hydrocarbon selectivity, low water-gas shift reaction (WGS) activity and relatively low cost. Selective control of C5+ hydrocarbons and the catalyst longevity are critical in the design of cobalt catalysts. Thus, various methods to improve the performance of Co catalysts have been suggested. The progress in cobalt catalysts reviewed in the last few decades, mainly involved the support, promoter, preparation and deactivation of Co-based catalysts.     

Quantitative structure-retention relationship for photosystem Ⅱ inhibitors in RP-HPLC

Using factor analysis (principle component) and multiple linear regression methods,4 solute-related structure parameters were selected from 10 structure parameters and the relationships between the retention properties (logk') of 25 2-cyano-3-methylthio-3-substituted amino-acrylates and the 4 parameters were established.There is a good agreement between the observed k' values and the predicted fe' values.     

Traceability in measurement – time for an update?

 The present international definition of "traceability" is discussed and suggestions are made for a possible refinement of the definition.     

Reference measurement procedure for Δ9-tetrahydrocannabinol in serum

An isotope dilution gas chromatography/mass spectrometry (ID-GC/MS) reference measurement procedure for Δ9-tetrahydrocannabinol (THC) in serum was developed and validated. The method complies with the concept of a ratio primary reference measurement procedure. The uncertainty was determined for two concentrations of THC in serum (1 ng/mL and 2.4 ng/mL). The calculation procedure is based on the Guide to the Expression of Uncertainty in Measurement (GUM). The relative expanded uncertainty was found to be less than 2% for both concentration levels, corresponding to a 95% confidence interval. For the reference method, it was shown that the measurement of THC within the concentration range covered by the current threshold values is very accurate. The method has the potential to provide traceability for the methods used in practical forensics.     

Resonance raman evidence for μ-oxo linkage in ferriporphyrins

The UV-Visible absorption and resonance Raman spectra of the μ-oxo iron(III) deuteroporphyrin dimethyl ester has been studied and compared to the data obtained from the well known μ-oxo iron(III) tetraphenylporphyrin. The symmetric Fe-O-Fe stretching vibration is tentatively assigned to the 414 cm-1 line; but in contrast with the tetraphenylporphyrin dimer, no resonance enhancement is observed with excitation in the α,β region. The influence of the Fe-O-Fe angle on a charge transfer transition involving the μ-oxo linkage in the visible region is discussed.     

Evidence for dose rate effect in gamma-radiolysis—II. Methylmethoxyacetate in 2,3-dimethylbutane and in cyclohexane

Solutions of 2,3-dimethylbutane (DMB) and cyclohexane containing a captodative solute, methylmethoxyacetate (MMA), were irradiated (continuous wave). Alkane dimeric products were analysed by capillary gas chromatography. G-yields were estimated as a function of the concentration of the captodative solute. By reaction with alkyl radicals, the captodative solute gives the free radical stabilized by the captodative effect. Combination reaction of this radical with itself or with alkyl radicals gives solute or mixed dimer which were also analysed. A large intensity effect was noticed, as was seen in the solutions of n-hexane-MMA. Dose effect was definitely rejected.     

Expanding Linker Dimensionality in Metal-organic Frameworks for sub-Ångstrom Pore Control for Separation Applications

Metal-organic frameworks (MOFs) are a class of porous materials with high surface areas, which are acquiring rapid attention on an exponential basis. A significant characteristic of MOFs is their ability to act as adsorbents to selectively separate component mixtures of similar size, thereby addressing the technological need for an alternative approach to conventional distillation methods. Recently, MOFs comprising a 3-Dimensional (3D) linker have shown outstanding capabilities for difficult separations compared to the parent 2-Dimensional (2D) analogue. 3D-linkers with a polycyclic core are underrepresented in the MOF database due to the widespread preferred use of 2D-linkers and the misconceived high-cost of 3D linkers. We summarize the recent research of 3D-linker MOFs and highlight their beneficial employment for selective gas and hydrocarbon adsorption and separation. Furthermore, we outline forecasts in this area to create a platform for widespread adoption of 3D-linkers in MOF synthesis.     

S-HQ： More convenient in situ polymeric cocatalyst for the PdCl2-catalyzed acetalization in

Polystyrene-supported hydroquinone （PS-HQ） is presented as an in situ polymeric cocatalyst to replace polystyrenesupported benzoquinone （PS-BQ） in the PdCl2-catalyzed acetalization of methyl acrylate with methanol in supercritical carbon dioxide （scCO2） under oxygen atmosphere. Due to deletion of H2O2 oxidation step, PS-HQ is more convenient and relatively inexpensive.     

Y-Ba-Cu-O mixed oxides for production of diphenols in liquid-solid phase

Superconductor mixed oxides were often used as catalysts at higher temperature in gas phase oxidations, and considered not suitable for lower temperature reactions in the liquid-solid phase; here the catalysis of YBa2Cu3O7+x and Y2BaCuO5+x in the phenol hydroxylation at lower temperature with H2O2 as oxygen donor was studied, and found that the superconductor YBaCu3O7±x has no catalytic activity for phenol hydroxylation, but Y2BaCuO5±x does, even has better catalytic activity and stability than most previously reported ones. With the studies of catalysis of other simple metal oxides and perovskite-like mixed oxides, a radical substitution mechanism is proposed and the experimental facts are explained clearly, and draw a conclusion that the perovskite-like mixed oxides with (AO)(ABO3) and (AO)2(ABO3) structure have better catalytic activity than the simple per-ovskite oxides with (ABO3)3 structure alone, and (AO) structure unit is the key for the mixed oxides to have the phenol hydroxylation activity.