Technical Factors of Quality Management in Gamma-Ray Spectrometry of Environmental Samples

The establishment of a quality management system is the best way to comply with international requirements concerning the achievement of confident and traceable analytical results. Some important points dealing with the technical factors of quality management in gamma-ray spectrometry of environmental samples are discussed. The experience obtained from analytical procedure validation is presented. Results of the application of standardized procedures to the analysis of ALMERA intercomparison samples, as well as the outcome of the utilization of certified reference materials for the quality control of measurement are presented. In fact, the implantation of simple technical principles reports reliable results and allows to elevate the quality of the measurements at a cost relatively low according to the real possibilities of the small laboratories, even in developing countries.     

Calculation of Self-Attenuation Factors in Gamma-Ray Spectrometry for Samples of Arbitrary Shape

The distribution of photons detected in a spectrometer as a function of their path length in the sample can be approximated by a one-parametric family of functions. The members of the family, having different average path lengths, describe the transport of photons in samples of different shapes. The value of the parameter corresponding to the actual counting geometry is obtained from the measured average path of photons in the sample. The self-attenuation factor as a function of the attenuation coefficient is calculated as the Laplace transform of the member of the family, defined by the extracted value of the parameter.     

Scientists, Spectrometry, and Gamma-Ray Spectrum Catalogues, 1957-2007

The original Gamma-ray Spectrum Catalogue, Ge(Li) and Si(Li) Spectrometry published in 1974 by R. L. Heath has been recreated and enhanced as an electronic file and is available on CD-ROM or over the Internet. This electronic version includes 1998 -ray data from the Evaluated Nuclear Structure Data File database as downloaded in 1998 as well as decay scheme drawings. Future developments of similar catalogues will include -ray spectra from radioactive decay with newer detectors and spectra from neutron interactions with elemental samples and separated isotopes. The electronic form of these catalogues will allow the creation of tutorials on -ray spectrometry and on the data included.     

Investigation of Inorganic Systems at High Temperature by Mass Spectrometry

High-temperature mass spectrometry (hitherto at temperatures between 1000 and 2500 °K and at pressures between 10^?3 and 10^?12 atm) has already made possible the identification of many previously unknown and unpredicted diatomic and polyatomic molecular species. The present paper deals with the investigation of many oxides, of halides, and of carbon molecules and intermetallic molecules. An apparatus for the production and investigation of molecular beams is described. Knudsen cells permit the production of molecular beams under equilibrium conditions; in special cases the “double-oven” type of Knudsen cell is used. Thermodynamic and kinetic quantities such as ΔH values, dissociation energies, and ionization cross sections of the species investigated are given.     

k0 Standardization Approach in Neutron-Induced Prompt Gamma-Ray Analysis at JAERI

The k ₀ standardization method has been studied and applied at JAERI for the accurate determination of multielements by neutron-induced prompt gamma-ray analysis (PGA). The k ₀ factors for 26 elements using Cl as a comparator were measured by the cold and thermal neutron guided beams of JRR-3M with an uncertainty less than 3% except for a few elements. The k ₀ factors for most elements obtained with both cold and thermal neutrons agreed within 3%, and agreed also with those measured at other cold and thermal neutron guided beams within 10%, except for a few elements. Multielement determinations in reference materials were performed using the k ₀ factors obtained to evaluate the accuracy and precision of this work.     

First Results from the Prompt Gamma-Ray Activation Facility at PSI

Since October 1997, a new Prompt Gamma-ray Activation (PGA) Facility at the neutron spallation source SINQ of the Paul Scherrer Institute (PSI) in Villigen in Switzerland has been operational. The detection system includes a Compton-suppression and a pair spectrometer. Of particular interest is the availability of a neutron focusing lens. During the beam periods 1997 and 1998, measurements were performed to characterize the PGA facility (gamma-ray background, profile and flux of the neutron beam, efficiencies of the two spectrometers, analytical sensitivities and detection limits for several elements, elemental analysis of standards). Scanning of samples and nuclear spectroscopy of isotopes having small capture cross section were also performed using the neutron focusing lens.     

High Accuracy Molecular Weight Determination and Variation Characterization of Proteins Up To 80 ku by Ionspray Mass Spectrometry

A quadrupole mass spectrometer with an ionspray interface was used to measure the molecular weight (MW) of proteins up to 80,000 u . With the improvements in instrument cahbration by a statistical averaging method and in data analysis by a gaussian curve-fitting method, precision of MW determination as high as 12 ppm was achieved with equine myoglobin (MW 16,950.4 ± 0.2 u). Exact MW determination of three components in cerato-ulmin revealed that the two minor ones had lost amino acid residues Ser and Ser-Asp, respectively, from the major component (MW 7618.4 ± 0.2 u). MW classifIcation of eight components in the Fab fragment of a monoclonal antibody revealed that one set of four had MW ? 47,540 u and the other ? 47,640 u. The MW difference of 100.2 ± 0.6 u between fragment 1 and 2, attributed to inhomogeneous cleavage at the Fab C-terminus, was probably due to one additional Thr in 1. The MW of bovine serum albumin (BSA) was found to be 66,431.5 ± 1.3 u, ? 164 u higher than the calculated sequence MW, most probably because of the incorrectness in the previously reported BSA amino acid sequence. The MW of human serum transferrin (79,556.8 ± 1.7 u) was shown to be 4414 u higher than the sequence MW, pointing to a glycosylation of 22.7 sugar units in this protein. The greater complexity in bovine serum transferrin (MW 78,030.5 ± 1.8 and 78,326 ± 3.3 u for the two major components) was correlated with the heterogeneity in the glycosylation.     

Precision and Accuracy Studies of Impaction-Electrothermal Atomization Atomic Spectrometry

Abstract

The precision of aqueous solutions of cadmium, copper, and manganese introduced as an aerosol by an pneumatic nebulizer and electrothermal vaporizer to an impaction-electrothermal atomization atomic absorption spectrometeric system was in the range of 1–3% which was similar to that obtained by manual introduction of similar concentrations of aqueous solutions of cadmium, copper, and manganese to the electrothermal atomizer and atomic absorption spectrometry. The precision of a laboratory air sample was 7.6–9.9%. Accuracy was assessed by comparison to conventional methods of sampling air by collection on a filter followed by digestion of the filter and analysis by flame atomic absorption spectrometry The levels were found to be 59–69% compared to the conventional method.     

加温加压原位红外光谱法的研究

本文报道在加温加压反应条件下原位红外光谱的测试方法,包括了加温加压红外光谱样品槽的研制;连续循环式和釜式加温加压络合催化反应-原位红外光谱联用装置的建立,以及应用该装置检测不稳定催化活性中间络合物的方法。实验表明,本方法既可以定性和定量地测出用一般红外光谱方法所不能发现的活性催化络合物的特征吸收峰,又可追踪各活性中间物的消长和确定各基元反应的次序,同时还可用于研究基元反应动力学和鉴定对空气敏感的络合物的结构,是研究均相反应机理的工具。     

低温焙烧-原子吸收法测定高含量辉锑矿中的金

采用先低温焙烧除硫后再高温焙烧,通过王水溶样,对辉锑矿矿样焙烧方法的对比表明,利用方法焙烧样品,矿样不结块,金可溶解完全.方法经国家一级标准物质分析验证,结果与标准值相符.对实际样品测定的方法精密度为1.44%～4.79%(RSD,n=5).加标回收率在95.5%～104.3%,方法快速、准确,适用于高含量辉锑矿中金的批量样品分析.     

Analysis of Rotenoids by High Temperature High Resolution Gas Chromatography-Mass Spectrometry

A short glass capillary column coated with PS-090 (20% phenyl–80% methylpolysiloxane, of 10 m × 0.30 mm i.d.; with 0.1 μm film thickness) was used to analyze samples from Tephrosia candida; eighteen rotenoids were separated and identified without derivatization by HT-HRGC and HT-HRGC-MS. The mass spectra show the typical fragmentation pattern for rotenoids, with the base peaks either at M⁺, or originating from RDA (Retro Diels-Alder) rearrangements. HT-HRGC and HT-HRGC-MS were shown to be extremely valuable and neglected techniques for structural studies as well as the routine analysis of rotenoids in crude extracts. Possible applications to other classes of aromatic natural products, e.g. flavonoids, are envisaged.     

Automated Hydrogen/Deuterium Exchange Electron Transfer Dissociation High Resolution Mass Spectrometry Measured at Single-Amide Resolution

Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a well established method for the measurement of solution-phase deuterium incorporation into proteins, which can provide insight into protein conformational mobility. However, most HDX measurements are constrained to regions of the protein where pepsin proteolysis allows detection at peptide resolution. Recently, single-amide resolution deuterium incorporation has been achieved by limiting gas-phase scrambling in the mass spectrometer. This was accomplished by employing a combination of soft ionization and desolvation conditions coupled with the radical-driven fragmentation technique electron transfer dissociation (ETD). Here, a hybrid LTQ-Orbitrap XL is systematically evaluated for its utility in providing single-amide deuterium incorporation for differential HDX analysis of a nuclear receptor upon binding small molecule ligands. We are able to show that instrumental parameters can be optimized to minimize scrambling and can be incorporated into an established and fully automated HDX platform making differential single-amide HDX possible for bottom-up analysis of complex systems. We have applied this system to determine differential single amide resolution HDX data for the peroxizome proliferator activated receptor bound with two ligands of interest.     

High Resolution Mass Spectrometry of Polyfluorinated Polyether-Based Formulation

High resolution mass spectrometry (HRMS) was successfully applied to elucidate the structure of a polyfluorinated polyether (PFPE)-based formulation. The mass spectrum generated from direct injection into the MS was examined by identifying the different repeating units manually and with the aid of an instrument data processor. Highly accurate mass spectral data enabled the calculation of higher-order mass defects. The different plots of MW and the nth-order mass defects (up to n = 3) could aid in assessing the structure of the different repeating units and estimating their absolute and relative number per molecule. The three major repeating units were -C₂H₄O-, -C₂F₄O-, and -CF₂O-. Tandem MS was used to identify the end groups that appeared to be phosphates, as well as the possible distribution of the repeating units. Reversed-phase HPLC separated of the polymer molecules on the basis of number of nonpolar repeating units. The elucidated structure resembles the structure in the published manufacturer technical data. This analytical approach to the characterization of a PFPE-based formulation can serve as a guide in analyzing not just other PFPE-based formulations but also other fluorinated and non-fluorinated polymers. The information from MS is essential in studying the physico-chemical properties of PFPEs and can help in assessing the risks they pose to the environment and to human health.

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The Thermoviscoelastic Constitutive Equation of PP and PA Blends and Its Rate Temperature Equivalency at High Strain Rates

By using Instron 1342 testing system and an improved SHPB technique, PP/PA blends are tested at a wide range of strain rates from 10⁻⁴ up to 10³ s⁻¹ and at a temperature range of 25–80 °C. Their mechanical responses are shown to be sensitive both to the strain rate and temperature. Based on the experimental data of 113 blends at a wide range of strain rates from 10⁻⁴ up to 10³ s⁻¹ and at a temperature range of 25–80 °C, it is shown that the mechanical behavior of this PP/PA blends can be described with ZWT thermoviscoelastic constitutive equation. The corresponding thermoviscoelastic parameters for 113 blends are obtained. The predicted theoretical results coincide quite well with the experimental data.The experimental results also reveal that the rate/time-temperature equivalence relation is shown for PP/PA blends. Raising the temperature is equivalent to the increasing of time (the decreasing of strain rate). Conversely, decreasing the temperature is equivalent to the decreasing of time (the increasing of strain rate). Through introducing a dimensionless parameter , two characteristic parameters: strain rate and temperature T are put together to this unified parameter Z. From experimental results, A/k is fitted, A/k = 8.595 °C, and a unified curve characterizing the rate/time –temperature equivalence relation is obtained.     

高精度相对论密度泛函计算方法

对适用于含重元素体系的高精度相对论密度泛函计算方法作简要的评述.结合本实验室的研究工作,重点介绍严格处理相对论效应的四分量相对论密度泛函计算方法和近似处理相对论效应的两分量和标量相对论密度泛函计算方法,包括零级规则展开近似(ZORA)方法及其改进和排除奇点的近似展开(SEAX)方法,以及适合处理局部包含重元素大体系的接合两分量-标量相对论(或非相对论)计算方法.     

新型PVT性质测试系统的研制

研制了一套新型压力-温度-体积（PVT）性质测试系统．该系统由自行开发的测控软件实时测控,温度测量精度可达±10mK,压力测量系统最大不确定度为±1．2KPa．利用新的测试系统对294～351K温度区间的Hydrofluorocarbons（HFC）-245fa饱和蒸气压进行了研究．实验结果表明,HFC-245fa的测量值与公认文献值的平均偏差小于0．03％,最大偏差小于0．484％,结果与文献值吻合较好．