火试金富集-电感耦合等离子体发射光谱(ICP-OES)法测定分银渣中的铂、钯

采用火试金富集得到贵金属合粒,经王水溶解,在王水(10%)介质下采用全谱直读电感耦合等离子体发射光谱(ICP-OES)法测定分银渣中铂、钯的含量。方法精密度好,准确度高,铂、钯的加标回收率在98.4%~102%,可以很好地满足分银渣中铂、钯含量的测定。     

Manganese in the water supply of the town of Beaucaire: origins and solutions

Changes in domestic water supply appearance and quality linked with increasing manganese amount and iron at a lesser degree, having been found by the inhabitants of Beaucaire (Rh?ne Valley), a study was made by chemists, hydrogeologists and biologists to detect the origin. The problem is not specific to this town and can frequently be found in the Sa?ne and Rh?ne valleys. The results show that we have to deal with an aquifer with semi-captive groundwater whose supply is double: the Rh?ne and calcareous mountain masses. The low-oxygen waters are enriched, by dissolution from gravel, with manganese and iron which are preferentially fixed on porous and cracked surface elements. The conditions for manganese liberation are connected with the presence of organic matters, bacteria (capable to reduce the manganic compounds) and anaerobiosis. The supply does not seem to be the only cause in the low-oxygen contents; the action of heterotrophic microorganism using organic matter and consuming oxygen, at the groundwater periphery, must be taken into account. Thus the central part of the groundwater system is a reducing environment which allows the modification of the bacterial metabolism towards a ferric and manganic compounds reduction process. The result is the transformation of insoluble manganic and ferric compounds into manganous and ferrous compounds which are liberated into the groundwater.     

The evaporation characteristics of LiCl–KCl eutectic salt from uranium deposits using batch type vacuum distiller with temperature slope of each zones

Recovered salt can be reused in the electrorefining process and the final removed salt from uranium (U) deposits can be fed into a following U casting process to prepare ingot. Therefore, salt distillation process is very important to increase the throughput of the salt separation system due to the high U content of spent nuclear fuel and high salt fraction of U dendrites. Yields on salt recovered by a batch type vacuum distiller transfer device were processed for obtaining pure eutectic salt and U. In this study, the influence of the various temperature slopes of each zones on salt evaporation and recovery rate are discussed. From the experimental results, the optimal temperature of each zones appear at the Top Zone and Zone 1 is 850?°C, Zone 2 is 650?°C and Zone 3 is 600?°C, respectively. In these conditions, the complete evaporation of pure salt in 1.4?h occurred and the amount of recovered salt was about 99?wt%. The adhered salt in U deposits was separated by a temperature slope zone of salt distillation equipment. From the experimental results using U deposits, the amount of salt evaporation was achieved more than 99?wt% and the salt evaporation rate was about 1.16?g/min. Also, the mount of recovered salt was about 99.5?wt%.     

Determination of the surface charge of lignocellulosic fiber by a derived spectroscopic technique

This paper proposed a derived spectroscopic technique for determining the surface charge of lignocellulosic fiber. In this method, chitosan quaternary ammonium iodide with higher molecule weight was selected to minimize its interaction with the negative charge inside of fiber pores. It was based on spectroscopically measuring the UV absorbance of I^? (the counter ion) in the filtrates from a set of solutions that containing the fixed amount of fibers and the different amount of cationic polymer (from under- to over-saturation). By plotting the derived absorbance at 245 nm versus the volume of chitosan addition, a transition point is determined, from which the fiber surface charge can be calculated. The results showed that the present method has a good measurement precision (RSD?<?3.24%) and accuracy (relative differences?<?3.11%, when compared with the conductivity titration method). It is suitable to be used for determining the surface charge of lignocellulosic fibers.

     

Does chemical cross-linking with NHS esters reflect the chemical equilibrium of protein-protein noncovalent interactions in solution?

Chemical cross-linking in combination with mass spectrometry has emerged as a powerful tool to study noncovalent protein complexes. Nevertheless, there are still many questions to answer. Does the amount of detected cross-linked complex correlate with the amount of protein complex in solution? In which concentration and affinity range is specific cross-linking possible? To answer these questions, we performed systematic cross-linking studies with two complexes, using the N-hydroxysuccinimidyl ester disuccinimidyl suberate (DSS): (1) NCoA-1 and mutants of the interacting peptide STAT6Y, covering a K_D range of 30 nM to >25 μM, and (2) α-thrombin and basic pancreatic trypsin inhibitor (BPTI), a system that shows a buffer-dependent K_D value between 100 and 320 μM. Samples were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). For NCoA-1· STAT6Y, a good correlation between the amount of cross-linked species and the calculated fraction of complex present in solution was observed. Thus, chemical cross-linking in combination with MALDI-MS can be used to rank binding affinities. For the mid-affinity range up to about K_D ≈ 25 μM, experiments with a nonbinding peptide and studies of the concentration dependence showed that only specific complexes undergo cross-linking with DSS. To study in which affinity range specific cross-linking can be applied, the weak α-thrombin · BPTI complex was investigated. We found that the detected complex is a nonspecifically cross-linked species. Consequently, based on the experimental approach used in this study, chemical cross-linking is not suitable for studying low-affinity complexes with K_D ? 25 μM.     

Chromium‐Catalyzed Alkylation of Amines by Alcohols

The alkylation of amines by alcohols is a broadly applicable, sustainable, and selective method for the synthesis of alkyl amines, which are important bulk and fine chemicals, pharmaceuticals, and agrochemicals. We show that Cr complexes can catalyze this C?N bond formation reaction. We synthesized and isolated 35 examples of alkylated amines, including 13 previously undisclosed products, and the use of amino alcohols as alkylating agents was demonstrated. The catalyst tolerates numerous functional groups, including hydrogenation‐sensitive examples. Compared to many other alcohol‐based amine alkylation methods, where a stoichiometric amount of base is required, our Cr‐based catalyst system gives yields higher than 90 % for various alkyl amines with a catalytic amount of base. Our study indicates that Cr complexes can catalyze borrowing hydrogen or hydrogen autotransfer reactions and could thus be an alternative to Fe, Co, and Mn, or noble metals in (de)hydrogenation catalysis.     

Sample introduction in high speed capillary gas chromatography; input band width and detection limits

The speed of analysis in capillary gas chromatography can be substantially increased by reduction of the column inner diameter. However, special demands are then posed upon instrumental design. In particular, the sampling system is highly critical because it has to be capable of delivering extremely small injection band widths which must be compatible with the column inside diameter. This study focuses on the evaluation of two potentially suitable sample introduction systems with respect to input band width and detection limits and their compatibility with small bore (≦ 100 μm) columns in capillary gas chromatography. One of them allows liquid on-column injection, based on liquid splitting, of only a few nl onto small bore (≦ 100 ?m) fused silica columns. For gases, input band widths as low as 1 ms are obtained with this system. The other one is part of a miniaturized gas chromatograph with extremely low dead volume interfaces and detector volumes. It allows input band widths for gases of a few ms. Without any preconcentration ppm concentrations are measured in gaseous samples with a 80 ?m thick film capillary column. It will be shown that a further reduction of the minimum detectable amount and analysis time is possible with this equipment.     

Splitting of the disulfide bonds in polysulfide polymers by hydrazine

The action of hydrazine on desulfurized tetrasulfide polymer obtained from bis-2-chloroethyl formal leads to S? S bond splitting and depolymerization. Our studies show that successful depolymerization can be initiated only in a strong alkali medium at 95–98°C. During this process cleavage of the disulfide bonds and the formation of polymers of lower molecular weight with ? SH end groups takes place. From the results of the experiments performed it can be seen that the degree of depolymerization increases with an increase in the amount of hydrazine, in the mole ratio of sodium hydroxide, and in the time of reaction. When 0.7–1.0 mole of hydrazine per segment of polymer and 4 mole of sodium hydroxide per mole of hydrazine are used, a polymer of low average molecular weight in the form of water-soluble sodium salt (fraction I) and a polymer in dispersion form (fraction II) are obtained. Similar results could be attained if the amount ot hydrazine were decreased and the mole ratio of sodium hydroxide were simultaneously increased to more than 4 mole per segment of hydrazine used. In a constant amount of sodium hydroxide with a smaller quantity of hydrazine or a shorter reaction time the amount of water-soluble polymer (as a sodium salt) decreases and the amount of polymer in dispersion form increases. If a portion of the polymer in dispersion is coagulated with a portion of the polymer in the mother liquid, the yield of the depolymerized product is higher, but the average molecular weight is also higher than those of fraction I. The influence of the average contents of sulfur on the efficiency of the depolymerization is tested in polymers that contain 2.5 (i.e., 3) atoms of sulfur per segment of polymer. The result is that the depolymerization of the polysulfide polymer could be carried out without previous desulfurization, but the molecular weights of the products obtained with an equivalent quantity of hydrazine are much higher than those obtained by depolymerization of the disulfide polymer.     

Methyl Complexes of the Transition Metals

Organometallic chemistry can be considered as a wide area of knowledge that combines concepts of classic organic chemistry, that is, based essentially on carbon, with molecular inorganic chemistry, especially with coordination compounds. Transition‐metal methyl complexes probably represent the simplest and most fundamental way to view how these two major areas of chemistry combine and merge into novel species with intriguing features in terms of reactivity, structure, and bonding. Citing more than 500 bibliographic references, this review aims to offer a concise view of recent advances in the field of transition‐metal complexes containing M?CH₃ fragments. Taking into account the impressive amount of data that are continuously provided by organometallic chemists in this area, this review is mainly focused on results of the last five years. After a panoramic overview on M?CH₃ compounds of Groups 3 to 11, which includes the most recent landmark findings in this area, two further sections are dedicated to methyl‐bridged complexes and reactivity.     

Copper-catalyzed three-component reaction of ethynylstibanes,organic azides,and selenium: A simple and efficient synthesis of novel selenides and diselenides having 1,2,3-triazole rings

A simple method for the synthesis of monoselenides and diselenides having 1,2,3-triazole ring is described herein. The three component reaction of ethynylstibanes, organic azides, and selenium powder is catalyzed by CuI (10?mol%) using 1,10-phenanthroline as the ligand (10?mol%) under aerobic conditions. Either selenides or diselenides can be synthesized by selecting the appropriate amount of selenium powder for otherwise identical reaction conditions. The obtained selenides and diselenides having a 1,2,3-triazole ring are all novel compounds. By using an antimony reagent, this one-pot reaction provides regioselective double Se-arylation under simple reaction conditions.     

Numerical study of nitrogen desorption by rapid oxygen purge for a medical oxygen concentrator

Efficient desorption of selectively adsorbed N₂ from air in a packed column of LiX zeolite by rapidly purging the adsorbent with an O₂ enriched gas is an important element of a rapid cyclic pressure swing adsorption (RPSA) process used in the design of many medical oxygen concentrators (MOC). The amount of O₂ purge gas used in the desorption process is a sensitive variable in determining the overall separation performance of a MOC unit. Various resistances like (a) adsorption kinetics, (b) column pressure drop, (c) non-isothermal column operation, (d) gas phase mass and thermal axial dispersions, and (e) gas-solid heat transfer kinetics determine the amount of purge gas required for efficient desorption of N₂. The impacts of these variables on the purge efficiency were numerically simulated using a detailed mathematical model of non-isothermal, non-isobaric, and non-equilibrium desorption process in an adiabatic column. The purge gas quantity required for a specific desorption duty (fraction of total N₂ removed from a column) is minimum when the process is carried out under ideal, hypothetical conditions (isothermal, isobaric, and governed by local thermodynamic equilibrium). All above-listed non-idealities (a?Ce) can increase the purge gas quantity, thereby, lowering the efficiency of the desorption process compared to the ideal case. Items (a?Cc) are primarily responsible for inefficient desorption by purge, while gas phase mass and thermal axial dispersions do not affect the purge efficiency under the conditions of operation used in this study. Smaller adsorbent particles can be used to reduce the negative effects of adsorption kinetics, especially for a fast desorption process, but increased column pressure drop adds to purge inefficiency. A?particle size range of ??300?C500???m is found to require a?minimum purge gas amount for a given desorption duty. The purge gas requirement can be further reduced by employing a pancake column design (length to diameter ratio, L/D<0.2) which lowers the column pressure drop, but hydrodynamic inefficiencies (gas mal-distribution, particle agglomeration) may be introduced. Lower L/D also leads to a smaller fraction of the column volume that is free of N₂ at the purge inlet end, which is required for maintaining product gas purity. The simulated gas and solid temperature profiles inside the column at the end of the rapid desorption process show that a finite gas-solid heat transfer coefficient affects these profiles only in the purge gas entrance region of the column. The profiles in the balance of the column are nearly invariant to the values of that coefficient. Consequently, the gas-solid heat transfer resistance has a minimum influence on the overall integrated N₂ desorption efficiency by O₂ purge for the present application.     

Determination of elemental sulfur in phosphorous pentasulfide by temperature modulated differential scanning calorimetry

Phosphorous pentasulfide is an important starting material for a number of commercial chemicals. Examples include lubricant additives (Spikes, Trib Lett 17:469?C489, 2004), agricultural insecticides (Kirk-Othmer, Enycl Chem Technol 14:549?C552, 1995), and mining ore flotation agents. Phosphorous pentasulfide is a mixture of several components, one of which is free elemental sulfur, present at levels of approximately 50?ppm to 20,000?ppm (2?%). The amount of free sulfur present in the phosphorous pentasulfide can impact manufacturing, such as zinc dithiosulfate processing. Therefore, an accurate and fast analytical method to measure elemental sulfur in phosphorous pentasulfide would be of value compared to what is available now.     

Electrochemical characterization of ordered arrays of metallo-porphyrins in aqueous solution

Metallated meso-tetrakis(N-methyl-4-pyridyl)porphyrin (MTMPyP) and 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis-(hydroxylcarbonylmethoxy)-calix[4]arene (C(4)TsTc) were used as key components for building up discrete supramolecular entities starting from the formation of the template species MTMPyP:C(4)TsTc (1?:?4, M = Cu, Zn). The stepwise addition of further amount of porphyrin allows the facile non-covalent synthesis of discrete supramolecular entities (2?:?4 and 3?:?4) which can be built up just by programming the right stoichiometric addition of the proper porphyrin. The redox potentials of these supramolecular complexes in aqueous media, as well as those of the parent metalloporphyrins, have been characterized by using square wave voltammetry technique. The use of the simulation procedure leads us to establish the electrochemical steps involved in the redox processes for each supramolecular species, evidencing multistep electron reductions which were not experimentally resolved clearly because of their closeness. The most striking result is that the electrochemistry of each of these supramolecular complexes is different from that of the parent components. This "anomalous" behavior can be explained only considering each of these supramolecular complexes as a unique entity, in which such an internal electronic communication might occur. The formation of the 1?:?4 supramolecular complex produces a negative shift as to the metallated porphyrin redox potentials of about 30 mV. In the case of 2?:?4 and 3?:?4 species, the redox potentials progressively shifts towards more positive values by about 10-15 mV for each complexation step.     

Physico-chemical comparison of betulinic acid, betulin and birch bark extract and in vitro investigation of their cytotoxic effects towards skin epidermoid carcinoma (A431), breast carcinoma (MCF7) and cervix adenocarcinoma (HeLa) cell lines

Betulin and betulinic acid are pentacyclic triterpenes present in the bark of the birch tree and other vegetal sources. Quantitatively, in birch bark betulin is more significant than betulinic acid; therefore, birch can be a large and feasible source of raw material for betulin extraction. Betulin can be used as extracted or, after chemical modification, as a starting compound for its acid, betulinic acid, with both substances possessing various interesting pharmacological properties. The purpose of this study is to analyse the betulin and betulinic acid content of a birch tree bark extract, as well as its cytotoxic activity. The extraction was done using a Soxhlet extractor and chloroform/dichlormethane/methanol (1?:?1?:?1) as solvent. The betulin and betulinic acid content of the extract was estimated using standards of pure betulin and betulinic acid, by thermal analysis as opposed to pure substance (thermogravimetric and differential thermal analysis). The extract and the main compounds were also analysed by NMR. The results indicated a high amount of betulin in the final extract (up to 50%), and an important quantity of betulinic acid: over 3%. The cytotoxic activity indicated a high proliferation inhibition for the birch tree extract but was still comparable with betulinic acid and betulin.     

Determination of thallium(III) with novel arsenoxylphenylazo rhodanine after pre-concentration and separation

A new catalytic kinetic fluorescent method for determination of trace thallium(III) was investigated. The method was based on the catalytic effect of thallium on oxidation of 3-p-chlorophenyl-5-(2′-arsenoxylphenylazo) rhodanine (4ClRAAP) by hydrogen peroxide in potassium hydrogen phthalate-hydrochloric acid (pH?=?5.2). Under the optimum conditions the great increase of fluorescence intensity had a linear relationship against the concentration of thallium in the range of 0.43 to 10.0?µg?L^?1 with a detection limit of 2.6?×?10^?10?g?L^?1. The coexistent metal ions can be separated, and thallium can be enriched by polyamide, which greatly improved the selectivity and sensitivity of the system. The method was applied to determine trace amount of thallium in wine, water and mineral samples, with satisfactory results.     

Morphology Control and Catalytic Dehydrogenation Performance of Zeolitic Imidazolate Frameworks-8北大核心CSCD

Zeolitic imidazolate frameworks-8（ZIF-8）is a kind of porous material with large specific surface area and strong stability,which is widely used in gas storage,separation,catalysis and other fields. In this work,the effect of different reaction conditions,such as the molar ratio of Zn2+ to 2-methylimidazole,the amount of surfactant and the reaction solvents,on the size and morphology of ZIF-8 were reported. Among these conditions,the molar ratio of Zn2+ to 2-methylimidazole is the key factor affecting the size and morphology of ZIF-8. The synthesized ZIF-8 nanoparticles were characterized by SEM,BET and XRD. The size of ZIF-8 decreases gradually from 1500 nm to 850 nm then to 250 nm,and the morphology changes from truncated hexahedron to truncated dodecahedron and finally to dodecahedron. The specific surface area of ZIF-8 nanoparticles with a particle size of 250 nm is 1730 m2/g,and the pore size and pore volume are 1. 5 nm and 0. 6 cm3/g,respectively. Therefore,it can be seen that ZIF-8 nanoparticles with a particle size of 250 nm have excellent carrier characteristics. The impregnation method was further adopted to synthesize the supported catalyst,and boron ammonia was used as the reducing agent. The ZIF-8（250 nm）nanoparticles were loaded with metals/precious metal nanoparticles in situ,the component optimization and catalytic performance were further studied. The obtained catalyst ZIF-8/Pt0. 002@Ni0. 2 shows excellent performance in hydrogen generation from aminoborane. © 2022, Science Press (China). All rights reserved.     

Solar Fuels: Visible-Light-Driven Generation of Dihydrogen at p-Type Silicon Electrocatalysed by Molybdenum Hydrides

We show that a robust molybdenum hydride system can sustain photoelectrocatalysis of a hydrogen evolution reaction at boron-doped, hydrogen-terminated, p-type silicon. The photovoltage for the system is about 600-650?mV and the current densities, which can be sustained at the photocathode in non-catalytic and catalytic regimes, are similar to those at a photoinert vitreous carbon electrode. The kinetics of electrocatalysed hydrogen evolution at the photocathode are also very similar to those measured at vitreous carbon-evidently visible light does not significantly perturb the catalytic mechanism. Importantly, we show that the doped (1-10?Ω?cm) p-type Si can function perfectly well in the dark as an ohmic conductor and this has allowed direct comparison of the cyclic voltammetric behaviour of the response of the system under dark and illuminated conditions at the same electrode. The p-type Si we have employed optimally harvests light energy in the 600-700?nm region and with 37?mW?cm(-2) illumination in this range; the light to electrochemical energy conversion is estimated to be 2.8?%. The current yield of hydrogen under broad tungsten halide lamp illumination at 90?mW?cm(-2) is (91±5)?% with a corresponding chemical yield of (98±5)?%.     

Tailor-Made Silver Release Properties of Silver-Containing Functional Plasma Polymer Coatings Adjusted Through a Macroscopic Kinetics Approach

Combining a functional plasma polymer matrix with antibacterially active silver (Ag) within a nanocomposite structure allows secure production and applications in various fields, especially in the medical sector. Therefore, nitrogen or oxygen containing hydrocarbon plasma polymers and Ag nanoparticles were simultaneously deposited. Functional groups such as amino or carboxylic groups as well as an adjusted amount of Ag can be incorporated into the growing films by controlling the plasma deposition properties. For this purpose, macroscopic kinetics were used to characterise the deposition behaviour also as a base for possible industrial up-scaling. XPS and ICP-OES were used to analyse the chemical composition of the polymer?CAg nanocomposites and the Ag content which could be incorporated depending on the plasma process conditions. Finally, the Ag release was determined in bi-distilled water for classification and comparison with the antibacterial properties. The antibacterial effect of the polymer?CAg nanocomposites was proofed with the gram? strain Pseudomonas aeruginosa PAO1 and the gram+ strain Staphylococcus aureus (ST12 Group) showing a clear efficacy dependence on the amount of released Ag and the possibility for tailor-made antibacterial active plasma films.     

The effect of submicron emulsion systems on transdermal delivery of kaempferol

In this study, submicron emulsions have been employed as a carrier for the topical application of kaempferol. The effect of components of submicron emulsions on the physicochemical properties and permeation capability of drug were evaluated. In case of drug-loaded submicron emulsions, the cumulative amount over 12?h (Q(12?h)), lag time and deposition in skin amount ranged from 13.0±3.4 to 236.1±21.2?μg/cm(2), 1.7 to 5.3?h, and 1.10 to 7.76?μg/cm(2), respectively, which indicated that the permeation parameters of kaempferol were markedly influenced by the component ratio. Kaempferol dispensed in isopropyl myristate was used as the control. The Q(12?h), lag time and deposition amount in skin were 4.2±1.8?μg/cm(2), 6.0?h and 2.25±0.60?μg/cm(2), respectively. The data showed that used appropriate submicron emulsions as vehicle could significantly increase the Q(12?h) and deposition amount in skin and shorten the lag time, demonstrating that submicron emulsions have a potent enhancement effect for kaempferol transdermal delivery.     

Visible-Light-Induced Photocatalytic Hydrogen Production over Binuclear Ru(II) -Bipyridyl Dye-Sensitized TiO(2) without Noble Metal Loading

Highly efficient, visible light induced photocatalytic H(2) production was achieved over a TiO(2) system sensitized by binuclear Ru(II) bipyridyl (bpy) complex [Ru(2) (bpy)(4) (BL)](ClO(4) )(2) (BL=bridging ligand) without Pt loading, which is almost unaffected by pH in aqueous solution in the wide range from pH?5.00 to 10.50, although the dye molecules can only be loosely attached to TiO(2) due to the absence of terminal carboxyl groups. The photocatalyst shows remarkable long-term stability and reproducibility of H(2) evolution even after exchanging the aqueous triethanolamine solution. The amount of H(2) evolved over 100?mg of photocatalyst in 27?h of irradiation corresponds to a turnover number of about 75?340, and the apparent quantum yields are estimated to be 16.8 and 7.3?% under 420 and 475?nm monochromatic light irradiation, respectively. A comparative study shows that the loosely attached dye [Ru(2) (bpy)(4) (BL)](ClO(4) )(2) has higher photosensitization efficiency than tightly linked dyes with terminal carboxyl groups, such as [Ru(2) (dcbpy)(4) (BL)](ClO(4) )(2) and N719. It can be rationalized by their different coordination, physicochemical, electron-injection, and back-transfer properties.