Thermochemistry of adducts of some bivalent transition metal bromides with 4-chloroaniline

The compounds [MBr₂(p-clan)₂] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); p-clan = 4-chloroaniline) were synthesized and characterized by melting points, elemental analysis, thermal analysis and electronic and IR spectroscopy. The enthalpies of solution of the adducts, metal(II) bromides and 4-chloroaniline in methanol, 1.2 M aqueous HCl or 25% (v/v) 1.2 M aqueous HCl in methanol were measures and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (Δ_rH°), the standard enthalpies of formation (Δ_fH°), the standard enthalpies of decomposition (Δ_DH°), the lattice standard enthalpies (Δ_MH°) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ_rH°(g)). The mean bond dissociation enthalpies of the metal(II)-nitrogen coordinated bonds and the enthalpies of adduct formation in the gaseous phase have been estimated.     

Speciation of chromium in waste waters by coupled column ion chromatography-inductively coupled plasma mass spectrometry

An application of coupled column ion chromatography (IC)-inductively coupled plasma mass spectrometry (ICP-MS) is presented for speciation of chromium in waste waters. By coupling an anion column with a cation column, both the cationic Cr(III) and anionic Cr(VI) species can be analyzed with detection limits below 0.5 μg/1. The separation of the interfering ions (chloride, chlorate, perchlorate, sulphate, sulphite, sulphide, thiosulphate, carbonate, cyanide and some organic compounds) from the chromium peaks is discussed, and the use of different chromium isotopes for data acquisition is compared. Based on the results, m/z 52 was considered as an ideal isotope for speciation of chromium in waste waters by the coupled column IC-ICP-MS, because it did not suffer from polyatomic interferences and due to the high sensitivity for chromium. The analysis of the waste water samples should be performed as soon as possible after sampling according to the stability tests of the species.     

K3MnH5, das erste salzartige Manganhydrid

K₃MnH₅, the First Salt-like Manganese Hydride K₃MnH₅ and K₃MnD₅ were synthesized by the reaction of potassium hydride (deuteride) with manganese powder under a hydrogen pressure above 3000 bar at 875 K. X-ray investigations on powdered samples and elastic neutron diffraction experiments on the deuterated compound at the time-of-flight spectrometer LAD in the temperature range 5–600 K led to the complete structure determination. The atomic arrangement is isotypic with that of Cs₃[CoCl₄]Cl (space group: 14/mcm, Z = 4). The structure of K₃MnH₅ contains isolated [MnH₄]^2?-tetrahedra and additional hydrogen ions which are exclusively coordinated by potassium cations. The magnetic susceptibilities show Curie-Weiss behaviour. At temperatures below 50 K there are obviously antiferromagnetic interactions.     

用4,4‘—壬二酰基—双（1—苯基—3—甲基—吡唑酮—5）萃取分离钍

本文研究了标题试剂(简称H_2A)与Th(Ⅳ)的络合作用及萃取行为,考查了H_2A对Fe(Ⅲ)、Co(Ⅱ)、Ni(Ⅱ)、Zn(Ⅱ)、Pb(Ⅱ)、Cu(Ⅱ)、La(Ⅲ)、Yb(Ⅲ)和U(Ⅵ)的萃取作用,试验了它对Th(Ⅳ)与上述元素及Ca(Ⅱ)、Mg(Ⅱ)、Cr(Ⅲ)、In(Ⅲ)、V(Ⅴ)、Zr(Ⅵ)的分离效果。     

泡沫镍载碳化钨催化剂上的析氢反应

结合直接化学还原法和交替微波法制备了泡沫Ni载Ni-WC催化剂,用X射线衍射、扫描电镜和透射电镜对催化剂进行了表征,研究了其析氢电催化性能.结果表明,在相同条件下,泡沫Ni载Ni-WC催化剂的析氢起始电位与泡沫Ni相比降低了60 mV左右.电解质浓度和温度对泡沫Ni载Ni-WC催化剂的析氢电催化活性有很大影响.     

Enhanced glucose production from cellulose using coimmobilized cellulase and β-glucosidase

β-Glucosidase was covalently immobilized alone and coimmobilized with cellulase using a hydrophilic polyurethane foam (Hypol®FHP 2002). Immobilization improved the functional properties of the enzymes. When immobilized alone, the K_m for cellobiose of β-glucosidase was decreased by 33% and the pH optimum shifted to a slightly more basic value, compared to the free enzyme. Immobilized β-glucosidase was extremely stable (95% of activity remained after 1000 h of continuous use). Coimmobilization of cellulase and β-glucosidase produced a cellulose-hydrolyzing complex with a 2.5-fold greater rate of glucose production for soluble cellulose and a four-fold greater increase for insoluble cellulose, compared to immobilized cellulase alone. The immobilized enzymes showed a broader acceptance of various types of insoluble cellulose substrates than did the free enzymes and showed a long-term (at least 24 h) linear rate of glucose production from microcrystalline cellulose. The pH optimum for the coimmobilized enzymes was 6.0. This method for enzyme immobilization is fast, irreversible, and does not require harsh conditions. The enhanced glucose yields obtained indicate that this method may prove useful for commercial cellulose hydrolysis.     

Insight into the extractability of metals from soils using an implementation of the linear adsorption isotherm model

This paper deals with an often overlooked artifact in sequential and single extraction of metals from soils, viz. the volume to mass (V/m) ratio as a potential source for inadequate extraction yields. We offer a theoretical framework to get a grip on this intricate parameter and came up with a model based on a linear adsorption isotherm to derive the correct maximal metal extractability for a certain extractant. We verified the model experimentally using 0.1 mol l⁻¹ nitric acid for extraction of seven metals (Cr, Co, Cu, Cd, Pb, Ni and Zn) from an urban soil sample, and concluded that commonly used V/m ratios in the range of 10-40 ml g⁻¹ may give as much as 50% too low extraction yields. Thus, a strong caveat is in place as to be very critical what V/m ratios to use and preferably apply the model derived to obtain the correct maximal extractability using a variable V/m ratio method.     

Synthesis and chelation properties of new polymeric ligand derived from 8-hydroxy-5-azoquinoline hydroxy benzene

8-Hydroxy-5-azoquinoline phenyl methacrylate-formaldehyde (8H5AQPMA-F) macromonomer was prepared from methacryloyl chloride with condensation products of 8-hydroxy-5-azoquinoline phenol-formaldehyde, and polymerized in DMF at 70 °C using benzoyl peroxide as free radical initiator. Poly(8H5AQPMA-F) was characterized by infrared and nuclear magnetic resonance spectroscopic techniques. Polychelates were obtained when the DMF solution of the resin containing few drops of ammonia was treated with the aqueous solution of Cu(II)/Ni(II). Elemental analysis of the polychelates indicates that the metal to ligand ratio was about 1:2. The IR spectra of polychelates suggest that the metals were coordinated through the oxygen of the phenolic-OH group and nitrogen of the quinoline ligand. The DRS and magnetic moment data indicate a square planar for Cu(II) complex whereas octahedral for Ni(II) complex. The TGA data revealed the thermal stability of the resin and the polychelates. X-ray diffraction study revealed the incorporation of the metal ions significantly enhanced the degree of crystallinity. The sorption properties of the chelate-forming resin towards various divalent metal ions [Cu(II) and Ni(II)] were studied as a function of pH and electrolyte.     

Effect of HF addition on the microwave-assisted acid-digestion for the determination of metals in coal by inductively coupled plasma-atomic emission spectrometry

The microwave-assisted acid-digestion for the determination of metals in coal by ICP-AES was investigated, especially focusing on the necessity of adding HF. By testing five certified reference materials, BCR-180, BCR-040, NIST-1632b, NIST-1632c, and SARM-20, it was found that the two-stage digestion without HF (HNO₃ + H₂O₂ was used) was very effective for the pretreatment of ICP-AES measurement. Both major metals (Al, Ca, Fe, and Mg) and minor or trace metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) in coal gave good recoveries for their certified or reference values. The possibility of ‘HF-memory effect’ was cancelled by the use of a set of vessels which had been never contacted with HF. Twenty-four Japanese standard coals (SS coals) were analyzed by the present method, and the concentrations of major metals measured by the present method provided very high accordance with those from the authentic JIS (Japanese Industrial Standard) method.     

Spectrofluorometric determination of certain quinolone antibacterials using metal chelation

Simple, rapid, reliable, and sensitive spectrofluorometric methods were developed for the determination of eight quinolone antibacterials namely ciprofloxacin, norfloxacin, lomefloxacin, difloxacin, amifloxacin, pefloxacin, ofloxacin, and nalidixic acid. The methods depend on the chelation of each of the studied drugs with zirconium, molybdenum, vanadium or tungsten to produce fluorescent chelates. Different factors affecting the relative fluorescence intensity of the resulting chelates were studied and optimised. At the optimum reaction conditions, the drug-metal chelates showed excitation maxima ranging from 274 to 295 nm and emission maxima ranging from 409 to 495 nm. The chelates were found to be stable at room temperature for 2 days and show good stability upon increasing temperature to 50 °C for about 1 h. Rectilinear calibration graphs were obtained in the range of 10-60 ng ml⁻¹ for each of the investigated drugs and the limits of detection and quantitation ranged from 1.214 to 2.046 and from 4.047 to 6.819 ng ml⁻¹, respectively. The molar ratios of the formed chelates were determined by Job's method and their association constants were also calculated. The developed methods were applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests. They were also applied for the determination of studied drugs in spiked urine and plasma samples.