Ion chromatographic separations of phosphorus species: a review

The aim of this paper is to review recent literature regarding the determination of phosphorus species by ion chromatography (IC), and describe the implementation of new developments in sample treatment and ion chromatography methodology for the analysis of these compounds. Ion-exchange methods using both carbonate/hydrogencarbonate and hydroxide selective columns in combination with self-regenerating membrane and solid-phase-based suppressors enable determination of phosphate down to ppb levels. New technology, particularly on-line electrolytic hydroxide generators and electrolytic self-regenerating suppressor devices, has allowed the use of elution gradients in both carbonate/hydrogencarbonate and hydroxide selective systems, improving sensitivity and reducing total analysis time for samples containing phosphate together with other inorganic anions. In addition to a review of these developments, optimization and application of chromatographic methods using reversed stationary phases and cationic and/or zwitterionic surfactants is also discussed.The objective of most of the IC methods developed for phosphorus species is the determination of phosphate and total phosphorus. Therefore, sample treatment and separation conditions specifically developed for this purpose are also described. In addition, application of IC to the analysis of other inorganic (reduced and condensed) and organic (phytates, alkyl phosphate, and phosphonates) phosphorus species is discussed along with methodology and relevant applications in water analysis and other miscellaneous fields.     

Review of electrolytic conductance standards

Measurements of aqueous electrolytic conductance are performed routinely in a variety of disciplines and industries. Conductivity is a measure of the ionic content in solution and thus has applications in pharmaceuticals, power plants, rainwater, lake surveys, and oceanography, to name a few. A thorough review of the measurement of and standards for aqueous electrolytic conductance is herein presented. At present, the most precise and accurate standards have been set forth by the International Organization of Legal Metrology (OIML), and have been adopted by most other standards organizations. However, the uncertainty assigned to these standards, especially the secondary standards, is somewhat larger than would be expected from the physical aspects of the measurement. Several changes in the units and measurement scales, including temperature, volume, molar mass, resistance, and concentration obfuscate the accuracy of these standards. In addition to the review, research is proposed, using a conductance cell with variable length, to establish new standards for aqueous electrolytic conductance.     

一种微片式电极池及其应用

制作了一种微片式微柱电极池 ,双工作电极及参比电极和辅助电极都组装在约 1 .5～ 2cm2 的聚酯片中的槽型窗口上 ,在窗口上滴加溶液即成微型电解池 ,试样仅需 30 μL左右。已采用了几种电化学方法对池的性能进行了表征。得到的实验结果表明 ,无论采用该装置开展理论研究或实际应用 ,都具有一定的使用价值。应用这种电解池测定抗坏血酸 ,检出限可达 8× 1 0 -7mol/L。     

在线电解修整磨削的电解磨削液研制

为了对金属结合剂砂轮电解修整 ,研究并配制了电解磨削液。根据电解磨削液的性能要求 ,分析确定了电解磨削液中具有电解、钝化、防锈和润滑等性能的各组元 ,并通过静态实验确认了各组元对电解磨削液性能的影响。确定最佳电解磨削液在实际系统中对金属结合剂砂轮进行电解修整得到了较为满意的修整结果。所研制的电解磨削液具有实用价值 ,可用于生产。     

Photocatalytic reduction of potassium chromate by Zn-doped TiO2/Ti film catalyst

The aim of this work was to investigate the photocatalytic (PC) reduction of potassium chromate by Zn-doped TiO₂/Ti film catalysts. The film catalyst was prepared by plasma electrolytic oxidation method in H₂SO₄ solution with different dosages of ZnSO₄. The composition and structure of the film catalysts was studied by XRD, SEM and EPMA. The removal rate of potassium chromate was investigated under the conditions of the different dosages of ZnSO₄ and the initial concentration of chromate potassium, and the reductive product during the PC reduction process was analyzed. The results showed that the film catalyst was composed of anatase TiO₂ and rutile TiO₂ with the porous structure. When the dosage of ZnSO₄ was 0.2 g/L, the film catalyst presented the highest catalytic activity, which related to the amount and the crystal grain size of anatase TiO₂ in the film. The PC reduction of potassium chromate by the film catalyst obeyed the pseudo-first-order kinetic equation. The UV-vis spectrum and XPS analyses proved that chromate Cr(VI) was reduced to Cr(III), which existed in the form of insoluble Cr(OH)₃.     

Study of electrolytic cobalt sulfide Co<Subscript>9</Subscript>S<Subscript>8</Subscript> as an electrode material in lithium accumulator prototypes

With the purpose to obtain a sulfide material for lithium and lithium-ionic thin-film batteries, cobalt sulfide Co₉S₈ was synthesized on an aluminum foil or stainless steel by electrolysis of aqueous solutions containing cobalt sulfate, sodium thiosulfate and sodium sulfide. The surface morphology of electrolytic Co₉S₈ is characterized by close packing of ball-like particles 8–12 μm in diameter, consisting of submicrometer structures 300–400 nm in size. It was found that e-Co₉S₈ electrodes exhibit stable behavior during 100 lithiation-delithiation cycles in a voltage range of 2.8–1.1 V, providing a discharge capacity of ～200 mAh/g. In a lithium cell with ethylene carbonate (EC)-dimethyl carbonate (DMC)-1M LiClO₄ electrolyte, a discharge capacity of the e-Co₉S₈-electrode was 250–450 mAh/g in a voltage range of 2.80–0.2 V. It was found that higher discharge capacities can be achieved for e-Co₉S₈-electrodes with a smaller active material mass.     

Dimerization of ionized 4‐(methyl mercapto)‐phenol during ESI,APCI and APPI mass spectrometry

A novel ion/molecule reaction was observed to occur under electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo ionization (APPI) conditions, leading to dimerization of ionized 4‐(methyl mercapto)‐phenol followed by fast H^· loss. The reaction is particularly favored during ESI, which suggests that this ion/molecule reaction can occur both in the solution inside the ESI‐charged droplets and in the gas‐phase environment of most other atmospheric pressure ionization techniques. The dimerization reaction is inherent to the electrolytic process during ESI, whereas it is more by ion/molecule chemistry in nature during APCI and APPI. From the tandem mass spectrometry (MS/MS) data, accurate mass measurements, hydrogen/deuterium (H/D) exchange experiments and density functional theory (DFT) calculations, two methyl sulfonium ions appear to be the most likely products of this electrophilic aromatic substitution reaction. The possible occurrence of this unexpected reaction complicates mass spectral data interpretation and can be misleading in terms of structural assignment as reported herein for 4‐(methyl mercapto)‐phenol. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication of functionally gradient nanocomposite coatings by plasma electrolytic oxidation based on variable duty cycle

Plasma electrolytic oxidation (PEO) was applied on the surface of commercially pure titanium substrates in a mixed aluminate-phosphate electrolyte in the presence of silicon nitride nanoparticles as suspension in the electrolyte in order to fabricate nanocomposite coatings. Pulsed current was applied based on variable duty cycle in order to synthesize functionally gradient coatings (FGC). Different rates of variable duty cycle (3, 1.5 and 1%/min), applied current densities (0.06-0.14 A/cm²) and concentrations of nanoparticles in the electrolyte (2, 4, 6, 8 and 10 g l⁻¹) were investigated. The nanopowder and coated samples were analyzed by atomic force microscope, scanning electron microscope and transmission electron microscope. The influence of different rates of variable duty cycle (or treatment times) on the growth rate of nanocomposite coatings and their microhardness values was investigated. The experimental results revealed that the content of Si₃N₄ nanoparticulates in the layer increases with the increase of its concentration in the plasma electrolysis bath. Nanocomposite coatings fabricated with lower rate of variable duty cycle have higher microhardness with smoother microhardness profile.     

电解-电化学混合电容器的制备与性能

为解决电化学电容器工作电压过低的问题, 本文以钽电解电容器的烧结型钽块为阳极, 聚苯胺(PANI)/TiO₂电化学电容器复合电极为阴极, 成功制备了高能量密度、高工作电压的电解-电化学混合电容器. PANI/TiO₂复合电极是通过在多孔阳极氧化钛纳米管阵列中电化学聚合PANI 制得. 该阴极具有优良的倍率特性, 当平均功率密度为0.55 mW·cm^-2时, 对应的比容量仍达到10.0 mF·cm^-2. 由于与电解电容器复合, 该混合电容器的单元工作电压可高达100 V. 而且电化学电容器阴极的比容量远大于阳极, 故阴极所需尺寸远小于阳极, 节省的空间可用于增大阳极尺寸, 从而使混合电容器的比容量极大提高. 所制备的混合电容器体积能量密度和质量能量密度分别是钽电解电容器的4 倍和3 倍. 将该混合电容器在100 V下进行短路充放电实验, 循环10000 次后发现容量未衰减, 等效串联电阻未增加, 显示出极好的循环稳定性和功率特性. 计算表明其最大功率密度高达847.5 W·g^-1. 电化学阻抗谱显示其具有优良的阻抗特性和频率特性.     

认知模型的修正与重构——以高三化学复习课“电解食盐水的再探究”为例

在高三化学复习教学中,依据对学生已有电解认知模型的调查分析,以学生已经学习过的电解饱和食盐水为探究背景,对为何用饱和食盐水、阴极为何采用铁钉等问题进行追问和探究,以破除学生对放电顺序的绝对化和唯一化的错误观念,认识到离子的放电顺序受浓度、电极材料、电压等多种因素共同的影响。对离子迁移放电电解认知模型的科学性进行追问,通过学生设计实验,分析实验现象,自主建构分析电解问题的氧化还原放电模型,以实现学生对已有的电解认知模型的修正与重构。