Evaluation of homogeneity of selected reference materials for selenium by cyclic neutron activation analysis

The homogeneity of four reference materials was evaluated for Se by cyclic instrumental neutron activation analysis (CINAA). The relative standard deviation for Se measurements at ppb levels by CINAA was <12% for NIST Wheat Flour (SRM 1567) in 5–10 mg samples, while it was <11% for Chinese Hair (HH–CH-1), <13% for IAEA Animal Muscle (H-4) and 25% for IAEA Animal Blood (A-13) in 50 mg samples. The highest relative subsampling uncertainties were observed in the mass range of samples 50 mg for Chinese Hair, 100 mg for Wheat Flour and Animal Muscle and 300 mg for Animal Blood. The results of a one-way analysis of variance indicate that all reference materials above these mass ranges are adequately homogeneous with respect to Se distribution. Our data suggest that these materials, except Animal Blood, can be used as reference standards for Se in Quality assurance programs well below the sample masses re commended by the issuing agencies.     

Application of synthetic reference materials in the medical radiological research centre

The contents of 21 chemical elements (Ag, Br, Ca, Cl, Co, Cr, Cs, Fe, Hg, K, Mg, Mn, Na, P, Rb, Sb, Sc, Se, Sr, Zn, Zr) in synthetic reference materials (SRMs) were compared with those in natural reference materials (NRMs) using short- and long-lived radionuclides. SRMs called synthetic standards (SSs) and synthetic standards, biological (SSBs) were prepared on the basis of phenol-formaldehyde resol resins in the Institute of Physics, Georgian Academy of Science. The NRMs included such IAEA reference materials as H-4 (animal muscle), A-13 (animal blood), H-5 (animal bone), SL-1 (lake sediment), SOIL-7 (soil), A-9 (mixed human diet), and IAEA-153 (milk powder). It was shown that SSB-SRMs possessed good representativity of the 30–50 mg tablets, high precision, operational convenience, and could be recommended for the INAA of a wide range of medico-biological and bioecological objects.     

An accurate method for the determination of copper in biological materials by neutron activation analysis and extraction chromatography

Distribution coefficients of 14 elements between LIX 70 in toluene and aqueous 1M NaNO₃ solution containing varying concentrations of HCl or suitable buffer, respectively, were determined by batch equilibration. It was shown that very selective separation of Cu from other elements can be achieved on columns with LIX 70 supported on Bio-Beads SM-1. Highly accurate and precise method for the determination of trace amounts of Cu in biological materials was devised by combining NAA with extraction chromatography. Results of copper determination in NBS 1570 /Spinach/, IAEA H-4 /Animal muscle/ and IAEA V-8 /Rye flour/ are presented.     

A comparison of two separation techniques using NaI(Tl) and Ge(Li) spectrometry for trace element determination in biological materials by neutron activation analysis

A comparison of two group separation techniques using either NaI(Tl) or Ge(Li) spectrometry is presented for trace element determination in biological materials by neutron activation analysis. The capabilities of both procedures are described in terms of detection limits, precision and accuracy for the determination of the elements As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Sb, Se, Sn, and Zn in various types of biological samples. For this purpose the (standard) reference materials NBS SRM-1577 Bovine Liver, Bowen's Kale, IAEA Pig Kidney H-7 and IAEA Milk Powder A-11 were analyzed. An attempt was also made to minimize blank values for several elements.     

硫酸亚铁铵滴定法测定锰渣中的锰含量

研究了高氯酸氧化-硫酸亚铁铵滴定法测定锰渣中锰含量的主要影响因素。采用磷酸分解试样,通过控制试样质量和磷酸用量的比例,优化确定了最佳溶样温度和溶样时间,探讨了放置冷却时间对测定结果的影响程度,分析了共存离子的干扰。建立了硫酸亚铁铵滴定法测定锰渣中的锰含量的方法,方法用于对锰渣标准物质和样品进行分析,测定结果的相对标准偏差为0.21%～0.35%,准确度和精密度均能满足锰渣中锰含量的分析要求。     

Determination of rare-earth elements,yttrium and scandium in manganese nodules by inductively-coupled argon-plastma emission spectrometry

A sequential-scanning, inductively-coupled argon plasma emission spectrometer is used for the determination of the rare-earth elements, plus yttrium and scandium, in manganese nodules. Wavelength selection is optimized to minimize spectral interferences from manganese nodule components. Samples are decomposed with mixed acids in a sealed polycarbonate vessel, and elements are quantified without further treatment. Results for U.S. Geological Survey manganese nodule standards A-1 and P-1 had average relative standard deviations of 6.8% and 8.1%, respectively, and results were in good agreement with those obtained by other methods.     

Characterisation of biological RMs for potential use in human brain analysis

Summary In order to investigate the precision and accuracy obtainable with instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES), five different biological reference materials were analyzed. Four of them originated from the US National Institute of Standards and Technology (NIST) (Bovine Liver (SRM 1577; 1577/a; 185/A), Orchard Leaves (SRM 1571)) and one of them came from the International Atomic Energy Agency (IAEA) (Animal muscle (H-4)). The decomposition efficiency of microwave acid digestion was examined in comparison to digestions carried out in a Parrbomb. Five to ten subsamples of each material were subjected to the two digestion procedures and the solutions were analyzed by ICP-AES. The dried samples were analyzed by INAA. Up to 16 elements (Al, B, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Zn) were determined in various materials.     

Trace rare earth element analysis of IAEA Hair (HH-1), Animal Bone (H-5) and other biological standards by radiochemical neutron activation

A radiochemical neutron activation analysis using a rare earth group separation scheme has been used to measure ultratrace levels of rare earth elements (REE) in IAEA Human Hair (HH-1), IAEA Animal Bone (H-5), NBS Bovine Liver (SRM 1577), and NBS Orchard Leaf (SRM 1571) standards. The REE concentrations in Human Hair and Animal Bone range from 10^–8 g/g to 10^–11 g/g and their chondritic normalized REE patterns show a negative Eu anomaly and follow as a smooth function of the REE ionic radii. The REE patterns for NBS Bovine Liver and Orchard Leaf are identical except that their concentrations are higher. The similarity among the REE patterns suggest that the REE do not appear to be fractionated during the intake of biological materials by animals or humans.     

电位滴定测定富锂锰基正极材料中锰

采用盐酸、硝酸溶解样品,加入焦磷酸钠溶液并调节溶液pH为6.0~7.0。用高锰酸钾标准溶液滴定至电位滴定仪上,根据消耗的高锰酸钾标准溶液的体积计算样品中的锰含量。探究了焦磷酸钠用量、溶液pH、共存元素等对测定锰含量的影响。在最优的实验条件下,方法的相对标准偏差在0.13%~0.22%之间,加标回收率在99.8%~100.5%之间。本方法是富锂锰基正极材料中质量分数10%~60%的锰测定的理想方法。     

Substoichiometric determination of manganese by neutron-activation analysis

A simple and rapid method for the substoichiometric determination of traces of manganese in various materials by neutron-activation analysis has been developed. After dissolution of the irradiated test sample, manganese(II) carrier is added and subsequently oxidised by peroxodisulphate to the heptavalent state. The permanganate thus formed is finally extracted into chloroform as tetraphenylarsonium permanganate using a substoichiometric amount of tetraphenylarsonium chloride. This single separation step isolates radiochemically pure manganese-56 in the analysis of a relatively simple material in which interfering elements (gold, rhenium, etc.) are absent. When this is not true, a preliminary separation of manganese from the irradiated sample, based on the extraction of manganese diethyldithio-carbamate into chloroform and followed by stripping of the manganese with dilute sulphuric acid, must be used. A simultaneously irradiated standard containing manganese must be treated in exactly the same way as a test sample. In the materials analysed by the new method 10(-5) to 10(-3)% of manganese has been determined.     

Matrix effects on the determination of manganese in geological materials by atomic-absorption spectrophotometry under different flame conditions

Suppression caused by five of the seven matrix elements studied (Si, Al, Fe, Ca and Mg) was observed in the atomic-absorption determination of manganese in geological materials, when synthetic solutions and the recommended oxidizing air-acetylene flame were used. The magnitude of the suppression effects depends on (1) the kind and concentration of the interfering elements, (2) the type of acid medium, and (3) the concentration of manganese to be determined. All interferences noted are removed or alleviated by using a reducing nitrous oxide-acetylene flame. The atomic-absorption method using this flame can be applied to the determination of total and extractable manganese in a wide range of geological materials without interferences. Analyses of six U.S. Geological Survey rock standards for manganese gave results in agreement with the reported values.     

Three novel triterpenoid saponins from Lysimachia capillipes and their cytotoxic activities

Three new saponins, capilliposide A (1), capilliposide B (2) and capilliposide C (3) were isolated from an ethanol extract of Lysimachia capillipes. Their structures were determined by 1D and 2D NMR (1H-1H COSY, HMBC, HMQC, DEPT and TOCSY) techniques, MS, and hydrolysis. Capilliposide B showed significant cytotoxicity against human A-2780 cells.     

Organo-Laponites as novel mesoporous supports for manganese(III) salen catalysts

A Mn(III) salen complex was immobilized onto the Laponite surface using three different methodologies: method A, direct immobilization of the complex on the parent Laponite; method B, covalent anchoring through cyanuric chloride (CC); and method C, covalent anchoring through CC into a 3-aminopropyl)triethoxysilane (APTES) modified Laponite. All of the materials were characterized by FTIR, XPS, thermogravimetry, XRD, and nitrogen isotherms at 77 K, to gather information on the modifications introduced by the organo spacers within the Laponite surface, as well as on the anchored complex integrity; the Mn based materials were screened in the heterogeneous epoxidation of styrene. The results have shown that the immobilization of the manganese(III) salen complex by methods B and C have occurred at the edges of the clay particles through the spacers (APTES and CC) that have been anchored onto the Si-OH groups, whereas in method A, the complex is distributed throughout the clay surface, including the interlayer region. Therefore, the manganese loadings on the Laponites were as follows: materials prepared by method A > method B > method C. All of the heterogeneous catalysts showed high styrene epoxide selectivity, with that prepared by method A showing comparable styrene epoxide selectivity as the homogeneous phase reaction. The styrene epoxide yields decrease in the following order: materials prepared by method A > method B > method C (1st cycles), which parallel the respective support catalytic activity and decreasing of manganese content. The heterogeneous catalysts prepared using methods B and C could be reused at least for four times, with the former exhibiting the most stable catalytic activity, but that prepared by method A showed a significant decrease after two catalytic cycles.     

Evaluation of the solid sampling technique for the determination of aluminium in biological materials by atomic absorption and atomic emission spectrometry

Summary Results for the determination of aluminium in several biological materials by atomic absorption and atomic emission spectrometry using the solid sampling technique in connection with a constant temperature furnace are given. A comparison was made with a dissolution procedure and good agreement was generally obtained. With the solid sampling technique it was possible to calibrate against aqueous standards and to achieve a precision of better than 10% r.s.d. for NBS 1577a Bovine Liver and IAEA H-4 Animal Muscle, providing that the sample mass was greater than 1.3 mg and that the peak area was evaluated. Laboratory air and the solid sampling procedure were identified as possible sources of contamination.

---

Auswertung der Feststofftechnik für die Bestimmung von Aluminium in biologischen Materialien durch AAS und AES

     

铁锰复合氧化物的氧化还原沉淀法制备及其表征

分别采用氧化还原沉淀法和常规共沉淀法制备得到铁锰复合氧化物, 并对样品进行了 Ｘ射线衍射、 Ｂ Ｅ Ｔ比表面积、程序升温还原的初步表征和比较． 结果表明, 与常规共沉淀法制备的样品相比较, 采用氧化还原沉淀法制备的铁锰复合氧化物具有粒径较小、较大的比表面积、铁锰互溶性好、铁锰物种之间的相互作用较强等特点． 作为一种较为新颖的催化剂制备方法, 氧化还原沉淀法利用在高低价可变金属离子之间发生氧化还原反应的同时使之沉淀, 不利于各相单独形成微晶, 有利于不同金属离子的均匀混合． 此种方法对制备高比表面积、含变价过渡金属离子的各类复合氧化物催化剂有其独到之处．     

The properties of gold catalysts precursors adsorbed on the MCM-41 materials modified with Mn and Fe oxides

Silica mesoporous materials modified with manganese and iron were obtained by the hydrothermal method. Gold was introduced to pure and modified silica materials by the direct hydrothermal and impregnation methods. Nitrogen adsorption/desorption studies evidenced formation of the materials with large total surface area and mesoporous structure. Unmodified silica materials showed regular pore arrangement. The uniform porous structure was distorted in the iron or manganese containing samples. XRD, UV-Vis/DRS spectroscopy and temperature programmed reduction studies revealed changes of the nature of transition metal oxide and gold species on the different preparation stages. The oxide species after drying were strongly dispersed and partially incorporated to the silica framework. High temperature treatment led to the formation of extraframework Mn and Fe oxide species. Complex processes of gold deposition were observed during hydrothermal synthesis and impregnation of modified silica materials. The increase of the size of gold species was observed during calcination. The presence of transition metal oxides decreased sintering of gold crystallites.     

IR spectra of manganese oxides with either layered or tunnel structures

Four kinds of manganese oxides with either layered or tunnel structures were prepared by different methods. The structural features of the prepared materials were characterized by power X-ray diffraction, IR spectra and SEM observation. A compare analysis of IR spectra for these materials before and after the acid treatment was carried out. Band around 761 cm(-1) could be assigned to a characteristic adsorbent band of tunnel-type manganese oxides; while it was not observed in layer-type manganese oxides. After the acid treatment, the position and relative intensity of the bands in 300-1200 cm(-1) region showed an obvious change for layered manganese oxides in compare with tunnel-type manganese oxides. The variation of IR spectra could be used to distinguish layered manganese oxides from tunnel manganese oxides.     

用于超级电容器的锰钴氧化物/碳纤维材料

The development of high-performance supercapacitor electrode materials is imperative to alleviate the ongoing energy crisis. Numerous transition metals (oxides) have been studied as electrode materials for supercapacitors owing to their low cost, environmental-friendliness, and excellent electrochemical performance. Among the developed binary transition metal oxides, manganese cobalt oxides typically show high theoretical capacitance and stable electrochemical performance, and are widely used in the electrode materials of supercapacitors. However, the poor conductivity and active material utilization of manganese cobalt oxide-based electrode materials limit their potential capacitance application. Cotton is mainly composed of organic carbon-containing materials, which can be transformed to carbon fibers after calcination. The resultant carbonaceous material exhibits a large specific surface area and good conductivity. Such advantages could potentially suppress the negative effects caused by the poor conductivity and small specific surface area of manganese cobalt oxides, thereby improving the electrochemical performance. Herein, we firstly deposited manganese cobalt oxides on cotton by a simple hydrothermal method, yielding a composite of manganese cobalt oxides and carbon fibers via subsequent calcination, to improve the electrochemical performance of the electrode material. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and electrochemical characterizations were used to investigate the physical, chemical, and electrochemical properties of the prepared samples. The fabricated manganese cobalt oxides in the composite were uniformly dispersed on the carbon fiber surface, which increased the contact between the interface of the electrode material and electrolyte, and enhanced electrode material utilization. The electrode material was confirmed to have well contacted with the electrolyte during a contact angle test. Hence, a pseudo-capacitance reaction completely occurred on the manganese cobalt oxide material. Moreover, the addition of carbon fibers reduced the resistance of the material, resulting in excellent capacitive performance. The capacitance of the prepared composite was 854 F∙g^-1 at a current density of 2 A∙g^-1. The capacitance was maintained at 72.3% after 2000 cycles at a current density of 2 A∙g^-1. These results indicate that the manganese cobalt oxide and carbon fiber composite is a promising electrode material for high-performance supercapacitors. The findings presented herein provide a strategy for coupling with carbon materials to enhance the performance of supercapacitor electrode materials based on manganese cobalt oxides. Thus, novel insights into the design of high-performance supercapacitors for energy management are provided.     

Low-level simultaneous determination of As and Sb in standard reference materials using radiochemical neutron activation analysis with isotopic 77As and 125Sb tracers

Summary The aim of the present work was to develop an older method used in our laboratory based on selective solvent extraction of As and Sb as their iodides with toluene, and by the use of the radioisotopic tracers ⁷⁷As and ¹²⁵Sb, to improve the accuracy by better control of the radiochemical yields. ⁷⁷As was produced for each sample run by concurrent irradiation of a few mg of GeO₂ followed by a rapid separation of ⁷⁷As from ⁷⁷Ge. The radiochemically purified sample fraction containing ⁷⁶⁺⁷⁷As and ^122+125Sb was counted on a Ge detector in good geometry. The -lines of the four nuclides do not mutually interfere so that a combined measurement of As and Sb may be made.The method was applied to IAEA Milk Powder A-11, Animal Muscle H-4, Bowen's Kale and some other SRMs. The results obtained are discussed in the light of literature measurements. From present and previous results, together with data by Heydorn, the presently accepted value for As in Bowen's Kale of 140 ng · g^–1 may be 20% too high.