Electrochemical masking for removal of the titanium matrix effect in DPASV determination of thallium

The possibilities for eliminating the matrix effect caused by large concentrations of titanium in an EDTA-based electrolyte have been examined. In these solutions titanium gives a DPASV peak, the height of which decreases with increase in preconcentration time. This effect depends on the pH and is probably caused by impurities in the EDTA. Complete damping of the titanium peak by means of this effect is not possible. The influence of the following surfactants on the DPASV peak for titanium in 0.2M EDTA at pH 4.5 was investigated: polyoxyethylated alkylphenols having an average of 3 and 9.5 ethylene oxide sub-units; polyoxyethylene alcohols having an average of 5 and 20 ethylene oxide sub-units; polyoxyethylene (glycerol mono-oleate) ether having an average of 20 ethylene oxide sub-units; polyoxyethylene (sorbitol mono-oleate) ether having an average of 20 ethylene oxide sub-units; poly(ethylene oxide) having M.W. 5.0 x 10(6); poly(ethylene oxide)poly(propylene oxide) block copolymer having M.W. 1.625 x 10(4); N,N,N,N',N',N'-hexamethylhexamethylenediammonium bromide (HMB); benzyl(diisobutylphenoxyethoxy) dimethylammonium chloride; hexadecyltrimethylammonium bromide; tetrabutylammonium chloride (TBAC); hexadecyldimethylbenzylammonium chloride, hexadecyltributylphosphonium bromide; tetraphenylphosphonium bromide; sodium dodecylsulphate; sodium stearate; sodium dodecylbenzenesulphonate; sodium octadecyloxyethylene ether sulphate; sodium octadecyloxyethylene ether malonate (Malester). Except for TBAC and HMB all the surfactants investigated decreased the titanium peak, although to different degrees. Generally the effect increased in the sequence cationic surfactants < non-ionic surfactants < anionic surfactants. The more hydrophobic non-ionic surfactants decreased the titanium peak more strongly than did the less hydrophobic ones. Malester was found the best of the investigated surfactants for this purpose. Sodium dodecylbenzenesulphonate also gave good results, although in this case an additional peak appeared. In the presence of these last two surfactants iron(III) does not substantially disturb the base-line current.     

用不同络合剂制备的Pd-Sn/C催化剂在碱性溶液中对乙醇氧化的电催化性能

采用3种不同的络合剂[柠檬酸三钠、 反式-1,2-环己二胺四乙酸·一水(C₁₄H₂₂N₂O₈·H₂O, CyDTA)和氨水]制备了3种Pd-Sn/C催化剂. 用X射线能量色散谱(EDS)、 X射线衍射谱(XRD)和透射电子显微镜(TEM)表征了3种催化剂的平均粒径、 形貌和组成. X射线光电子能谱(XPS)的测试结果表明, 3种催化剂表面存在Sn和SnO_x 2种状态. 电化学测试结果表明, 3种催化剂在碱性电解液中对乙醇氧化的电催化性能均优于商业化的Pd/C催化剂, 其中用CyDTA制备的Pd-Sn/C催化剂在碱性溶液中对乙醇氧化的电催化性能最好.     

Release of copper from commercial solid-state copper ion-selective electrodes

The release of copper from two commercial solid-state cupric ion-selective electrodes [Orion 94-29 Cupric Electrode (I) and Radiometer F1112 Selectrode (II)] was measured by immersion in the following media: 0.1M potassium nitrate (pH = 4.7), 0.5M sodium chloride (pH = 4.7) and 0.1M nitric acid. In the 0.1M potassium nitrate medium, the amount of copper released from both electrodes causes interference when they are used for the determination of cupric ion at the 10⁻⁷M level. In comparison with the 0.1M potassium nitrate medium, the copper release in the 0.5M sodium chloride and 0.1M nitric acid media was increased for electrode II but not for electrode I. The release of copper was not affected by removal of oxygen from the media but can be substantially lowered by coating the electrodes with a thin cation-exchange membrane (Nafion). The mechanism of copper dissolution is investigated.     

Determination of copper in the presence of a large excess of bismuth by differential-pulse anodic-stripping voltammetry without preliminary separation

Conditions have been found which make possible the determination of copper in the presence of a large excess of bismuth by differential-pulse and anodic-stripping voltammetry without preliminary separation. The electrochemical activity of the bismuth, which usually interferes in the determination of copper, is inhibited by using tetrabutylammonium chloride (TBAC) as surfactant. In 0.2M EDTA and 0.01M ascorbic acid at pH 4.5 as supporting electrolyte without the surfactant present, trace levels of copper (1.5 x 10(-8)M) can be determined accurately if the molar ratio of bismuth to copper is not higher than 3, but if the electrolyte also contains TBAC at 0.01M concentration, bismuth can be tolerated in concentrations up to 10(-4)M, and the height of the copper peak is unaffected.     

Photometric determination of copper with N-(dithiocarboxy)sarcosine after preconcentration with amberlite xad-2 resin

The copper(II) chelate of N-(dithiocarboxy)sarcosine (DTCS) is sorbed on a column of Amberlite XAD-2 resin from a pH-7 phosphate solution (0.1M) and stripped with a pH-9.0 ammonia solution (0.2M) in 60% methanol. The absorbance of the eluted chelate is measured at 432 nm against water. Sodium nitrilotriacetate, sodium tripolyphosphate, and EDTA can be used to mask interfering metal ions other than mercury(II), the resulting complexes not being sorbed on the resin. The mercury(II) chelate of DTCS is also sorbed on and stripped from the column along with the copper chelate, but does not interfere in the photometric determination of copper, because it is colourless. The recovery of copper(II) is quantitative from test solutions (50–500 ml) of any salinity up to that of sea-water. Concentration factors of up to about 20 are obtained. The method is highly selective for copper and can be applied to its determination in sea-water.     

Mesomorphic behaviour of N,N-dialkanoyl-3,4,5,6-tetramethylbenzene-1,2-diamines and related compounds

DSC, X-ray, broad-line proton NMR, and microscopy studies on several series of N,N' -dialkanoylbenzene-1,2-diamines are presented. The melting point and associated enthalpy are not much affected by methylation of the aromatic nucleus. While the dimethyl compounds carrying heptanoyl-to-hexadecanoyl groups generate metastable mesophases below 111^oC, the 3,4,5,6- tetramethyl compounds carrying propionyl-to-hexadecanoyl groups produce stable hexagonal columnar mesophases appearing mostly above 200^oC. N,N'-dialkylbenzene-1,2-carboxamides are transformed into birefringent viscous fluids exhibiting a focal-conic texture at a temperature between 76 and 99^oC when the alkyl groups are decyl, undecyl, dodecyl, and tetradecyl.     

手性温敏凝胶 P(NIPAM-co-NALL)的制备及识别性能

以L-亮氨酸(L-Leu)为手性源, 经酯化和缩合等步骤制备手性单体(NALL), 以该单体为手性识别基团, 在交联剂N,N'-亚甲基双丙烯酰胺和引发剂偶氮二异丁腈的作用下, 与N-异丙基丙烯酰胺(NIPAM)以不同的质量比发生自由基共聚, 制备了一系列新型手性温敏水凝胶P(NIPAM-co-NALL), 其结构经红外光谱确证. 相比于PNIPAM水凝胶, 疏水性单体NALL的引入使 P(NIPAM-co-NALL)凝胶的温敏性下降. 以D, L-苯丙氨酸为模型药物对P(NIPAM-co-NALL)凝胶的手性识别和拆分性能进行研究, 结果表明, 手性温敏凝胶对D型对映体具有选择吸附性, 且吸附量随着手性单体含量的增加而增加; 提高温度(40 ℃)有利于手性温敏凝胶对D, L-苯丙氨酸的手性识别和拆分. P(NIPAM-co-NALL)凝胶在重复使用后依然具有手性识别性能, 但其吸附量随着使用次数的增加而下降, 3次重复使用后吸附量下降到原来的27.6%.     

Ion chromatography of nitrite at the ppb level with photometric measurement of iodine formed by post-column reaction of nitrite with iodide

The difficulty in ion-chromatographic determination of nitrite in aqueous solutions containing a high concentration of chloride arises mainly from incomplete resolution of the peaks for these anions on the separation column whose efficiency is not high. A photometric measurement of iodine formed by a reaction of nitrite with iodide has been found to make it possible to determine, chromatographically, trace amounts of nitrite without any interference from chloride; chloride does not oxidize iodide to produce iodine. The proposed method was based on the separation of nitrite from matrix anions on a silica-based anion-exchange column with a 1.5·10⁻³ M phthalate eluent (pH 5.0), followed by photometric measurement of the iodine (as triiodide) formed via a post-column reaction of the separated nitrite with iodide. The optimal conditions for the post-column reaction were established by varying the concentrations of iodide, copper(II) and nitric acid in a post-column-reaction solution and the length of a reaction tube. A calibration graph for nitrite, plotted as peak heights versus concentrations, was linear up to 1.50·10⁻⁵ M (690 ppb). The detection limit, defined at S/N=3, was 1.00·10⁻⁷ M (4.60 ppb) nitrite. The presence of chloride ions up to 0.01 M did not give any interference to the determination of nitrite. This method was successfully applied to the determination of nitrite in lake water, river water, sewage works water and snow samples without any pretreatment.     

Effects of surfactants on foliar uptake of herbicides - a complex scenario

Novel organic–inorganic nanohybrids, each having an inorganic core covered with an asymmetric lipid-bilayer membrane, were prepared through two-step self-assembling of a Cerasome-forming organoalkoxysilane lipid, N-[N-(3-triethoxysilyl)propylsuccinamoyl]dihexadecylamine (1), as the inner layer with an appropriate bilayer-forming amphiphile, N,N-dihexadecyl-N-[6-(trimethylammonio)hexanoyl]alaninamide bromide (2), sodium N,N-dihexadecyl-N-(6-sulfohexanoyl)alaninamide (3), or dimyristoylphosphatidylcholine (DMPC; 4), as the outer layer on a monodispersed colloidal silica particle. The particle thus obtained was characterized by various physical measurements, such as FT-IR spectroscopy, transmission electron microscopy, differential scanning calorimetry, and zeta-potential measurements. These data strongly supported the successful formation of the asymmetric bilayer structure on the surface of the silica particle. The current method is widely applicable to various kinds of hybrids of inorganic particles with lipid membrane components.     

Exchange interaction energy between two one-active electron atoms at large distances

Developed formulas for the exchange interaction energy between two neutral one-active electron atoms interacting at large distances R are presented in terms of known basic integrals obtained from an asymptotic method for the alkali dimers M₂ dissociating to M(ns) + M(ns), M(n′l) + M(n′l), l = 0, …, 3 and M (np) + M(np). Detailed illustrative numerical results are displayed for the molecular states of Na₂ dissociating to the limit Na(3s) + Na(3p). Comparisons with very accurate ab initio results as well as with some available experimental data show that accurate potential energy curves for these excited states may be obtained in a very large range of internuclear distances by connecting ab initio curves for small and intermediate values of R with long-range curves obtained as the sum of usual multipolar Coulombic energy and asymptotic exchange energy.     

含三苯基氧磷结构聚芳醚醚酮酮的合成与表征

以苯酚、对二溴苯及苯基磷酰二氯为原料合成出二(4-苯氧基苯基)苯基氧磷(BPOPPO)。 三氯化铝(AlCl₃)为催化剂,通过缩聚反应,BPOPPO与对苯二甲酰氯(TPC)反应制备出一种含有三苯基氧磷结构的聚醚醚酮酮(P-PEEKK)树脂。 采用傅里叶变换红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、热重分析仪(TGA)和广角X射线衍射(WAXD)等技术手段对P-PEEKK树脂的结构和性能进行表征。 结果表明,P-PEEKK树脂属于非晶聚合物,玻璃化转变温度(T_g)较高,为190.5 ℃;热分解温度(T_5%)为515 ℃,耐热性能较好;极限氧指数(LOI)为42,阻燃性能好,为难燃材料;易溶解于氯仿、1,2-二氯乙烷、N,N-二甲基乙酰胺等有机溶剂中,溶解性能较好,便于涂膜加工;拉伸强度为62 MPa,力学性能较好。     

Ethylene oligomerization by diimine iron(II) complexes/EAO

The catalytic properties of a series of Fe(II) diimine complexes (diimine=N,N′-o-phenylenebis(salicylideneaminato), N,N′-ethylenebis(salicylideneaminato), N,N′-o-phenylenebisbenzal, N,N′-ethylenebisbenzal) in combination with ethylaluminoxane (EAO) for ethylene oligomerization have been investigated. Treatment of the iron(II) complexes with EAO in toluene generates active catalytic systems in situ that oligomerize ethylene to low-carbon olefins. The effects of reaction temperature, ratios of Al/Fe and reaction periods on catalytic activity and product distribution have been studied. The activity of complex FeCl₂(PhCH=o-NC₆H₄N=CHPh) with EAO at 200°C is 1.35×10⁵ g oligomers/mol Fe·h, and the selectivity of C_4–10 olefins is 84.8%.     

Polarographic determination of copper, arsenic and arsenic in copper arsenite

A method is proposed in which Cu^II, As^III and As^v can be determined in copper arsenite without prior separation. It is based on the fact that Cu^II and As^III yield prominent, distinguishable, widely-separated cathodic polarographic waves in a 0.1M LiCl-0.01M EDTA—0.001M LiOH solution using a dropping mercury electrode, whereas As^v does not give a wave in this medium. The As^v is determined by difference after reduction with sulphurous acid.     

Synthesis and spectroscopic analysis of tetraphenylporphyrinatoantimony(V) complexes linked to boron-dipyrrin chromophore on axial ligands

Tetraphenylporphyrinatoantimony(V) complexes, linked to boron-dipyrrin chromophores on axial ligands, were synthesized. The fluorescence spectra of 1a, 1b and 1c (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1a); 6-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]hexyloxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1b); bis{3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo}antimony(V) tetraphenylporphyrin bromide (1c)) were analyzed under the excitations of N,N′-difluorobornyl-5-dipyrrinylphenyl (Bdpy) and tetraphenylporphyrinatoantimony(V) (Sb(TPP)) chromophores. Under the irradiation of Bdpy chromophore, the excitation energy was transferred from Bdpy chromophore to the Sb(TPP) moiety at 0.13–0.40 of the quantum yields, even in a polar solvent. On the other hand, the emission of Sb(TPP) chromophores was quenched by Bdpy chromophores at rate constants of 10⁸–10⁹ s⁻¹, independent of on the solvent polarity. Under the excitation of the Bdpy chromophore of 1d (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(phenyloxo)antimony(V) tetraphenylporphyrin bromide) involving both the Bdpy and the phenoxy chromophores on the axial ligands, the excited singlet state of the Sb(TPP) chromophore generated by the energy transfer from the Bdpy chromophore was quenched by the phenoxy ligand via non-radiative processes involving electron transfer. However, rapid back electron-transfer may occur because no absorption of the anion radical of Sb(TPP) was observed by nanosecond laser photolysis.     

Determination of silver in ores, concentrates, zinc process solutions, copper metal and copper-base alloys by atomic-absorption spectrophotometry after separation by extraction of the tribenzylamine-silver bromide complex

A method for determining 0.1 μg/g or more of silver in ores and concentrates and 0.001 μg/ml or more of silver in zinc process solutions is described. Silver is separated from the matrix elements by chloroform extraction of the tribenzylamine—silver bromide ion-association complex from 0.08M potassium bromide—2M sulphuric acid and stripped with 9M hydrobromic acid. This solution is evaporated to dryness and organic material is destroyed with nitric and perchloric acids. Silver is determined by atomic-absorption spectrophotometry in an air—acetylene flame, at 328.1 nm, in a 10% v/v hydrochloric acid—1% v/v diethylenetriamine medium. Cadmium, bismuth and molybdenum are partly co-extracted but do not interfere. The method is also applicable to copper metal and copper-base alloys. Results obtained by this method are compared with those obtained by a fire-assay/atomic-absorption method.     

反相破乳剂SP169及DMEA169在溶液中的聚集行为

以芘(Py)为荧光探针,十六烷基氯化吡啶(CPC)为猝灭剂,采用稳态荧光探针法测定了反相破乳剂SP169和DMEA169的临界胶束浓度(cmc)及胶束聚集数(N_agg),并考察了两者在溶液中形成的胶束内部的微环境极性大小,采用动态光散射法测定了两者胶束的流体力学直径(D_h),并通过耗散粒子动力学(DPD)方法模拟了两者在溶液中聚集形态的动力学变化过程。结果表明,两者的临界胶束聚集数分别为N_m(SP169)=28,N_m(DMEA169)=18;SP169的流体力学直径小于DMEA169,但其增长速度前者大于后者;DPD模拟的结果显示,由于起始剂在胶束内部与其他粒子间相互作用的不同,SP169聚集成棒状胶束,而DMEA169聚集成舒展的球状胶束,这解释了实验结果：相同浓度下前者胶束的流体力学直径及胶束内部的微环境极性皆比后者小,同时由于SP169起始剂的疏水性,使得其具有较大的胶束聚集数。     

Poly(Vinyl Chloride) Containing Dibenzo-18-crown-6 as an Ion-Selective Membrane for Hyamine 1622

Abstract

A poly(vinyl chloride) membrane ion-selective electrode for the Hyamine 1622 cation is proposed. The active substance of the electrode was the neutral carrier dibenzo-18-crown-6 and di-iso-octylphthalate was used as plasticizer. The electrode had a Nernstian behaviour between 6.0 × 10^?6 and 1.6 × 10^?3 mol/dm³, a pH working range of 2 – 12 and high selectivity towards inorganic cations. Among the organic cations tested, only those having surfactant properties did interface. The electrode was suitable for determining the critical micelle concentration and as end-point detector in the potentiometric titration of the cationic surfactants.     

Immobilization of a Pd(II) complex on hydrophilic graphite oxide and its catalytic investigation in the Heck coupling reaction

Tetraamminepalladium(II) chloride monohydrate was heterogenized on hydrophilic graphite oxide (GO), synthesized by Brodie's method. Two samples, with Pd contents of 2% and 5%, referred to as Pd2 and Pd5, respectively, were prepared by a simple and scalable impregnation method and tested as catalysts in the Heck coupling reaction of styrene and bromobenzene. The reactions were carried out at 423 K for 3 hr by applying Na₂CO₃ as a base and N-methylpirrolidone or dimethylformamide (DMF) as a solvent. The Pd complexes heterogenized on graphene oxide platelets proved to be highly active and selective catalysts, and Pd2 was more efficient than Pd5. The effect of quaternary ammonium salts (tetrabutylammonium bromide and tetrabutylammonium chloride, TBAC) as modifiers and that of an ionic liquid (1-butyl-3-methylimidazolium bromide, bmim) was studied and the highest conversions were obtained when TBAC was employed. The selectivity for the formation of the main product, E-stilbene, was in the range 91–96%. Catalyst recycling was investigated and the extent of leaching was found to depend on the solvent. DMF proved to be a highly feasible reaction medium because both catalysts could be recycled five times in this solvent without any significant loss of activity. A hot filtration test was performed and gave evidence that leaching of the active Pd species did not take place under the above reaction conditions. These results substantiate the fact that simple cationic Pd species can be efficiently immobilized on pristine GO surfaces without the requirement of the functionalization of GO with nitrogen-containing mono or multidentate ligands as binding sites.     

A multivariate calibration procedure for the tensammetric determination of detergents

A multivariate calibration procedure based on singular value decomposition (SVD) and the Ho-Kashyap algorithm is used for the tensammetric determination of the cationic detergents Hyamine 1622, benzalkonium chloride (BACl), N-cetyl-N,N,N-trimethylammonium bromide (CTABr) and mixtures of CTABr and BACl. The sensitivity and accuracy depend strongly on the nature of the detergent. Acceptable accuracy is obtained with a two-step calculation procedure in which calibration constants for the total concentration range of interest are used to guide the choice of a more specific set of calibration constants which are valid for a much smaller concentration span. For Hyamine 1622, concentrations in the range 5 × 10^?6?2 × 10^?4 M could be determined with an accuracy of ± 10^?6 M. For CTABr, these numbers were 3 × 10^?6?2 × 10^?4 M and ± 5 × 10^?7 M; for BACl, they were 2 × 10^?3?9 × 10^?2 g l^?1 and ± 1 × 10^?3 g l^?1. In the mixtures of CTABr and BACl, the accuracies were ± 3 × 10^?6 M and × 1 × 10^?3 g l^?1, respectively.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.