分光光度计测铁矿石中钛的测量不确定度评定

紫外-可见分光光度计在化学分析中应用较为广泛。对于借助其进行化学分析测量不确定度的评定，目前较多见于溶液测定。实际应用中，测试样品多为固体，涉及到称样、溶解、稀释、定容等步骤。此文试从随机效应和系统效应的角度考虑，对紫外-可见分光光度计应用ISO4691：1985铁矿石中钛含量的测定——二安替比林甲烷分光光度法对铁矿石中钛的测量过程中的不确定度来源进行了较为全面的分析，并最终给出评定结果。     

对在建标技术报告中正确贯彻《测量不确定度表示指南》的理解

针对计量人员在贯彻《测量不确定表示指南》,尤其是在撰写“建标技术报告”时遇到的一些体问题,进行了探讨。     

A complementary and synergistic effect of Fe-Zn binary metal oxide in the process of high-temperature fuel gas desulfurization

57Fe Mossbauer spectroscopy was used to investigate the evolution of Fe-Zn binary metal oxide sorbent in the process of high-temperature fuel gas desulfurization. The results of phase analyses show that Fe-Zn binary metal oxide sorbent is rapidly reduced in hot fuel gas and decomposed to new phases of highly dispersed microcrystalline elemental iron and zinc oxide, both of which become the active desulfurization constituents. A complementary and synergistic effect between active iron acting as a high sulfur capacity constituent and active zinc oxide acting as a deep refining desulfurization constituent exists in this type of sorbent for hot fuel gas desulfurization.     

The assessment of compliance with legal limits. Part 2. How to consider both type I and type II errors when working in the concentration domain

Considering the uncertainty of measurement when assessing compliance with reference values given in compositional specifications and statutory limits is still a controversial matter. In theory, assessing compliance requires considering both type I (false positive) and type II (false negative) errors. The more the concentration of the analyte in the sample under investigation is close to the allowed concentration limit, the more critical it is to consider both types of errors. This paper describes how this could be done. The matter is discussed in the light of the most recent literature information.     

Determination of Aldehydes and Ketones in Fuel Ethanol by High-Performance Liquid Chromatography with Electrochemical Detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymethylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical detector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol / LiClO_4(aq) at a concentration of 1.0 × 10⁻³ mol L⁻¹ (80:20 v/v) and a flow-rate of 1.1mL min⁻¹ . The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL⁻¹, with detection limits of 1.7 to 2.0 ng mL⁻¹ and quantification limits from 5.0 to 6.2 ng mL⁻¹, using injection volume of 20 μL. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.     

Ion association in calcium phosphate solutions at 37°C

Ion association in the system Ca(OH)₂–H₃PO₄–KCl–H₂O at 37°C has been studied potentiometrically over a range of pH from 3 to 9. The experimental conditions were optimized for the accurate determination of the association constants for the formation of the ion pairs CaH₂PO ₄ ⁺ , CaHPO₄ and CaPO ₄ ^– which were found to be 27.9±0.1, 591±2, and (1.35±0.02)×10⁶ L-mol^–1, respectively.     

PEMFC催化剂的研究：自制抗CO中毒Pt-Ru/C电催化剂的性质

用胶体法制备了抗CO中毒PEMFC阳极Pt-Ru/C电催化剂（标记为THYT－2）,对 比研究了THYT－2与Johnson Matthey (JM)公司同类品牌Pt-Ru/C催化剂的电化学及 其它物理化学性能。结果表明,THYT－2电催化剂在甲醇燃料电池和CO／H_2（Φ_ (CO) = 1 * 10~(-4)）的氢氧燃料电池中的电催化行为与JM催化剂相当,但THYT－ 2在低浓度CO氢气燃料中的电池性能更好。两种催化剂的其它物理化学性质具有类 似性：XPS分析结果表明THYT－2和JM催化剂 中都有三种不同价态的Pt存在：即金 属态Pt(0)、氧化态Pt(II)和Pt(IV)。HRTEM测试结果表明两种催化剂的粒径处在2 ～3 mn左右,这可能是它们拥有良好电化学性能的主要原因之一。本文还对催化剂 中Pt与Ru组分的分布和相互作用进行了讨论,提出了改进Pt-Ru/C电催化剂的思路 。     

Mg／Mgl．8La0．2Ni纳米复合材料的吸放氢性能研究

应用高能球磨法制备Mg-x％Mg1.8La0.2Ni（x=10、20和30）纳米复合储氢材料．X射线衍射（XRD）、透射电镜（TEM）和选区电子衍射（SAED）测试表明，该复合材料具有纳米晶和非晶态混合结构的性质，吸氢温度降低，较好的吸放氢动力学性能，在423K，2．5MPa氢压的条件下，50s内即可达到最大吸氢量．     

Solid-state,optical-rotation measurements on macromolecules using powder-suspensions

Summary We report techniques for measuring optical rotation of suspended solids, including dissymmetric molecular crystals (e.g. sodium chlorate and bromate), synthetic polymers, polypeptides and biopolymers. Examples include poly(triphenylmethyl methacrylate), poly-S-lactide, poly-L-hydroxyproline, hemocyanine, cellulose acetate andRNA. The results indicate that optical rotation measurements are sensitive to differences in secondary structure and can serve as a probe for structural differences between solid-state and solution.

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Messung der optischen Rotation von Makromolekülen im Festzustand unter Verwendung von Pulversuspensionen

Zusammenfassung Es wird über eine Methode zur Messung der optischen Rotation von Festkörpern in Suspensionen berichtet, wobei dissymetrische Kristalle (z. B. Natriumchlorat und -bromat), synthetische Polymere, Polypeptide und Biopolymere behandelt werden. Die Beispiele umfassen Poly(triphenylmethylmethacrylat), Poly-S-lactid, Poly-L-hydroxyprolin, Hemocyanin, Celluloseacetat undRNA. Die Ergebnisse zeigen, daß die optischen Rotationen bezüglich Unterschiede in der Sekundärstruktur empfindlich sind und daß diese Messungen als ein Maß für Strukturunterschiede zwischen Festzustand und Lösung herangezogen werden können.

     

Investigation of the electrocatalytic oxidation of formate and ethanol at platinum black under microbial fuel cell conditions

In this communication, we discuss the electro-oxidation of the fermentation products formate and ethanol at platinum black modified electrodes under microbial fuel cell conditions, i.e., at neutral pH, room temperature, and in microbial culture solutions. The electrocatalytic oxidation was studied using cyclic voltammetry, chronoamperometry, and potentiostatic coulometry. Current densities up to 6 mA cm⁻² at 0.2 V oxidation potential and 97% coulombic efficiency were observed for the electro-oxidation of 100 mM solutions of formate in pH 7 buffer solution. Electrode deactivation could be successfully prevented using an oxidative potential reactivation procedure. Polymer coating, however, fully stopped the formate oxidation. As expected, the electro-oxidation of ethanol was less efficient—with a limiting current density being 600 μA cm⁻².Dedicated to Professor Dr. Alan M. Bond on the occasion of this 60th birthday.