Certification of a Diesel Particulate Related Standard Reference Material (SRM 1975) for PAHs

Standard Reference Materials (SRMs) are Certified Reference Materials issued by the National Institute of Standards and Technology (NIST). Three of these materials, SRMs 1975 (Diesel Particulate Extract), 2975 (Diesel Particulate Matter, Industrial Forklift), and 1650 (Diesel Particulate Matter) are diesel particulate-related materials that are well characterized for PAH isomer distributions. SRM 1975 is a methylene chloride extract of industrial forklift diesel particulate matter and it was developed originally in response to the needs of the bioassay community for a natural environmental extract. Thirty-nine PAHs (or combinations of PAHs) were determined in SRM 1975 using various combinations of four different methods of analysis. SRM 1975 will be issued with certified concentrations for eight PAHs. In addition, reference concentrations will be provided for additional PAHs, including many alkyl substituted isomers such as methylphenanthrenes, methylpyrenes, and methylfluoranthenes. Reference values for the mutagenic activity of the extract will also be provided. The approach and results for the certification of PAH concentrations in SRM 1975 are described in this paper.     

Development and Analysis of Three Diesel Particulate-Related Standard Reference Materials for the Determination of Chemical,Physical, and Biological Characteristics

The National Institute of Standards and Technology (NIST) has recently issued three Standard Reference Materials (SRMs) related to diesel particulate matter: SRM 1650a, Diesel Particulate Matter; SRM 2975, Diesel Particulate Matter (Industrial Forklift); and SRM 1975, Diesel Particulate Extract. These three materials have certified and reference concentrations for selected polycyclic aromatic hydrocarbons (PAHs) including many alkyl-substituted compounds. SRM 1650a is the reissue of an existing material and SRMs 2975 and 1975 represent new materials. The characterization of the PAH content of these three diesel particulate-related SRMs is presented with a discussion of the approach for the certification of PAH concentrations. In addition, the physical and biological characterization of these materials is discussed. A review of customer reported uses of these SRMs in the chemical, physical, and biological sciences is also provided.     

Standard Reference Materials (SRMs) for the Determination of Polycyclic Aromatic Compounds--Twenty Years of Progress

In 1981 the National Bureau of Standards, now the National Institute of Standards and Technology (NIST), issued the first natural matrix Standard Reference Material (SRM) for the determination of polycyclic aromatic compounds (PACs), SRM 1580 Organics in Shale Oil. In the next 10 years, additional natural matrix SRMs were developed including air and diesel particulate matter, petroleum crude oil, coal tar, sediment, and mussel tissue. The SRMs represented the "first generation" of natural matrix SRMs for the determination of PACs. The SRMs had "certified" values for only 5 to 12 PACs; however, their development established the foundation for the implementation of the "two or more independent analytical techniques" approach for certification of individual PACs in environmental matrices. The requirement for use of different analytical techniques spurred the development of both gas chromatography (GC) and liquid chromatography (LC) approaches for the determination of PACs. Since the mid-1990s, the "second generation" of natural matrix SRMs has been issued by NIST with certified values for over 20 PACs in each material. The greater number of certified values in these SRMs was the result of the combination of measurements using reversed-phase LC with fluorescence detection, multidimensional LC, and GC with mass spectrometric detection using two or more stationary phases with different selectivity for polycyclic aromatic hydrocarbon (PAH) separations. This article discusses the significant developments in analytical methods and chromatographic separation of PAHs during the past 20 years that have resulted in the certification of over 25 SRMs, which are now used worldwide for the validation of analytical methods for the measurement of PACs in environmental matrices.     

The Elucidation of Charge-Transfer-Induced Matrix Effects in Environmental Aerosols Via Real-Time Aerosol Mass Spectral Analysis of Individual Airborne Particles

Matrix effects in real-time aerosol mass spectrometry (RTAMS) were investigated using Standard Reference Materials (SRMs) obtained from the National Institute of Standards and Technology (NIST). Suppression of major component ions by much less concentrated species was observed. Attempts were made to mimic the ion suppression using binary systems but were unsuccessful. Data are presented that suggest the origin of the matrix effect is charge transfer induced neutralization in the ablation plume.     

Characterization of Standard Reference Material 1690 by Modulated Dynamic Light Scattering

ABSTRACT

We have measured the number average diameter (NAD) and the standard deviation of the diameter distribution (SDDD) of spherical particles from a sample of Standard Reference Material 1690 (SRM 1690) using the method of Modulated Dynamic Light Scattering to determine the diameter of single test particles by examining their Brownian motion as they sediment freely in dry air. Standard Reference Material 1690 is a water-suspension of 1 μm nominal diameter polystyrene spheres and has been characterized by National Institute of Standards and Technology (NIST) personnel as a primary reference standard for the calibration of particle-size-measuring instruments. We have obtained for SRM 1690 particles the values NAD = 0.9103 ± 0.0021 μm and SDDD = 0.0090 μm. The NIST-certified values for SRM 1690 are NAD = 0.895 ± 0.008 μm and SDDD = 0.0095 ± 0.0012 μm. The SDDD value from this work agrees with the NIST-certified value within the stated limits of uncertainty, but the NAD value is 1.7% larger than the NIST-certified value. We suggest that the discrepancy is due to the presence of nonspherical particles in the test suspensions measured by NIST.     

美国国家标准与技术研究院的高性能混凝土研究项目

美国国家标准与技术研究院（ＮＩＳＴ）正在进行名为“高性能混凝土之友（ＰＨＰＣＴ）”的合成研究项目,其目的是促进混凝土技术发展,推动高性能混凝土（ＨＰＣ）在建筑物和基础构筑物中的应用,项目的目标是结合业已确认的多属性模型,开发和应用一种计算机集成知识系统（ＣＩＫＳ）,来预测和优化ＨＰＣ的性能及寿命周期预算,我们的基本假设是：最实际有效地将知识传授给混凝土潜在用户（或者说考虑使用的用户）的方法,就是使     

Pigment and nanofiller photoreactivity database

The service life and durability of nanocomposites containing fillers are affected by photocatalytic properties of these fillers, particularly narrow band gap metal oxides (NBMOs) such as titanium dioxide (TiO₂). When irradiated with ultraviolet flux, NBMOs produce electrons and other species that are capable of causing rapid degradation of organic materials with which they are in contact. Electrons and holes (positively charged species) migrate to the surface and react with species to generate various free radicals. Measurement science tools for characterizing TiO₂ photoreactivity using electron paramagnetic resonance (EPR) methods have been developed by the Engineering Laboratory (EL) at the National Institute of Standards and Technology (NIST) and a linkage between EPR measurements and current industrial methods has been established. A database of TiO₂ photoreactivity values and other data measured via the EPR methods and industrial assays has been compiled and will be accessed through a searchable software database in the NIST Standard Reference Database program??http://www.nist.gov/srd/index.cfm. The database provides fundamental photoreactivity data that can be used for product selection and development purposes to enable more reliable assessments of end-performance.     

Natural cement as the precursor of Portland cement: Methodology for its identification

When cements appeared in the 19th century, they took the place of traditional binding materials (lime, gypsum, and hydraulic lime) which had been used until that time. Early cements can be divided into two groups, natural and artificial (Portland) cements. Natural cements were introduced first, but their widespread usage was short-lived as they were quickly replaced by artificial cements (Portland), still the most important and predominant today. The main differences between natural and artificial cements arise during the manufacturing process. The final properties of the cements are greatly influenced by differences in the raw materials and burning temperatures employed.The aim of this paper is to assess the efficiency of traditional analytical techniques (petrographic microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR)) used to differentiate natural and artificial cements.     

Calcium silicate and calcium aluminate cements for dentistry reviewed

Calcium silicate cements were identified as excellent materials for dentistry, particularly for dental procedures contacting the dental pulp or root system. Both calcium silicate and calcium aluminate cements cause the biomineralization (precipitation of hydroxyapatite [HA] phenomena and shield dental tissues from the underlying cement (a foreign body material). The cements also elute ions to stimulate cytokines that contribute to the healing of the dental pulp or in the tissue surrounding the root of a tooth. The cements serve as a foundation for other dental restorative materials. This paper reviews the cement phases, properties, in vivo reactions, and clinical benefits from the use of calcium silicate and calcium aluminate ceramic cements.     

Comparison of Liquid Chromatography with Fluorescence Detection and Gas Chromatography/Mass Spectrometry for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples

Liquid chromatography (LC) with fluorescence detection and gas chromatography/mass spectrometry (GC/MS) have been compared for the determination of polycyclic aromatic hydrocarbons (PAHs) in a variety of environmental samples. Three sets of data are presented in this paper in which LC/fluorescence and GC/MS were used for the analysis of the same samples. These three data sets include the comparison of results from: (1) certification measurements for three natural matrix Standard Reference Materials (SRM's), (2) an international round robin for the determination of PAHs in air and diesel particulate samples, and (3) the analysis of four marine sediment reference materials. The results from these studies indicate that the two techniques generally provide comparable results for the measurement of PAHs in environmental samples (in the range of 0.1 to 300 ng/g), with differences in the two techniques between 5–20%. However, at low levels, anthracene and perylene are best measured using LC/fluorescence because of their selective and sensitive fluorescence detection characteristics. In contrast, GC/MS provides more accurate results for the determination of benzo[ghi]perylene because of its low fluorescence sensitivity.     

Analysis of CCRL proficiency cements 151 and 152 using the Virtual Cement and Concrete Testing Laboratory

To test the ability of the Virtual Cement and Concrete Testing Laboratory (VCCTL) software to predict cement hydration properties, characterization of mineralogy and phase distribution is necessary. Compositional and textural characteristics of Cement and Concrete Reference Laboratory (CCRL) cements 151 and 152 were determined via scanning electron microscopy (SEM) analysis followed by computer modeling of hydration properties. The general procedure to evaluate a cement is as follows: (1) two-dimensional SEM backscattered electron and X-ray microanalysis images of the cement are obtained, along with a measured particle size distribution (PSD); (2) based on analysis of these images and the measured PSD, three-dimensional microstructures of various water-to-cement ratios are created and hydrated using VCCTL, and (3) the model predictions for degree of hydration under saturated conditions, heat of hydration (ASTM C186), setting time (ASTM C191), and strength development of mortar cubes (ASTM C109) are compared to experimental measurements either performed at NIST or at the participating CCRL proficiency sample evaluation laboratories. For both cements, generally good agreement is observed between the model predictions and the experimental data.     

Total fat analysis in milk- and soy-based infant formula powder by supercritical fluid extraction

A rapid method for the determination of total fat in infant formula powders using a commercially available supercritical fluid extraction (SFE) instrument was evaluated. The matrices examined were Standard Reference Material SRM 1846 Infant Formula (NIST) and commercial milk- and soybased infant formula powders. Method verification and validation were done by linear regression analysis using the Method of Standard Additions. A Data Quality Objectives (DQO) format was used to define and evaluate the performance characteristic parameters of the instrumental total fat analysis fy SFE. A peer validation study showed excellent agreement with the declared labeled percentage fat values and reproducibility among three participating laboratories. The laboratory relative SD (RSD _R %) is within Horwitz's limits of acceptability and the HORRAT ratio criteria at the level of the analyte analyzed. Linear regression analysis of all infant formula matrices spiked with added fat showed that the SFE instrument response was due only to the added analyte. By integrating the DQO process with a readily available certified reference material, along with reproducibility indicated by two outside collaborating laboratories, we established verification and validation of the accuracy of the data obtained by SFE.     

少熟料高标号复合水泥的性能

工业废渣用于水泥混合材的研究一直是水泥研究领域的热点问题。从实际应用看 ,活性高的混合材 ,如矿渣已得到充分的利用。而活性低的混合材 ,如粉煤灰 ,利用率较低。针对矿渣、磷渣和粉煤灰的特点 ,通过强度和孔结构测试 ,研究了少熟料高标号复合水泥。强度和孔结构研究表明 ,利用混合材的优势互补原理 ,并引入外加剂可以得到性能优异的少熟料复合水泥     

Improvement of fatigue strength and fracture toughness of bone cement by incorporation of aromatic structures to formulations

Abstract

It has been postulated that the incorporation of cyclic or aromatic groups to the chemical structure of monomers/polymers could improve the mechanical performance of the polymeric materials prepared from them. In this work, N-methacryloyloxyethyl-m-toluidine (MEET) monomer, a compound whose chemical structure is similar to diethylamino ethyl methacrylate (DEAEM) but having an aromatic ring, was synthesized. Acrylic bone cements were prepared using either MEET or DEAEM as co-monomer and a systematic study of the potential influence of adding aromatic structures on the fatigue properties and fracture toughness of such bone cements was performed. Results indicated that the formulations prepared with the aromatic co-monomer (MEET) exhibited a higher fatigue resistance than those containing the aliphatic counterpart (DEAEM), at all co-monomer concentrations. These results confirm the hypothesis that the inclusion of aromatic structures in the bone cement formulations increases the fatigue life of these materials. It was also found that presence of aromatic structures in bone cement formulations improve the fracture toughness of cements.     

Relationship between free chloride and total chloride contents in concrete

Linear relationships between free chloride and total chloride contents in concrete are proposed based on the results of several long-term exposure tests under marine environment for various cements, such as ordinary portland cement (OPC), high early strength portland cement (HES), moderate heat portland cement (MH), calcium aluminate cement (AL), slag cements of Types A (SCA) and B (SCB), and fly ash cement of Type B (FACB). A high chloride-binding ability is found for AL as compared to the other cements. Replacing the OPC with slag reduces the chloride-binding ability. The proposed linear relationships show reasonably good agreement with field data obtained from the wharf structures.     

国外水泥科技动态介绍

重点介绍１９９７年６月在瑞典召开的第十届国际水泥化学会议中有关水泥生产工艺和水泥水化理论方面的研究成果，包括生料制备、熟料烧成、水泥粉磨和水化机理等部分。     

Reference materials of defined particle size certified recently by the community bureau of reference of the european economic community

Some results from an international projects, supported by the Community Bureau of Reference of the European Economic Community, on the certification of five reference materials of defined particle size covering the overall range 0.35 – 650 μm are presented and discussed. Four of the reference materials were certified with respect to the mass distributions of the Stokes' diameters measured by an agreed gravitational sedimentation (Andreasen pipette) method. The coarsest of the reference materials was certified with respect to the mass distribution of the volume diameters of the particles using sieves, the ‘cut sizes’ of which were calibrated with respect to their equivalent volume diameters.Data were also obtained using several other methods, including X-ray gravitational sedimentation, sedimentation balance, centrifugal sedimentation, electrical sensing zone and photo-sedimentation methods. These were not used for certification but are presented for comparison purposes and to indicate the usefulness of the certified reference materials for the checking and calibration of many particle sizing techniques.     

利用磷石膏制备低热、微膨胀复合水泥的研究

为大量利用磷石膏,本文采用在复合水泥中掺加磷石膏的方法,开展了制备低热、微膨胀复合水泥的试验研究,并采用DSC、XRD、SEM及等温水化热仪表征了该复合水泥的水化特征.研究结果表明:磷石膏具有显著的缓凝效果,通过掺加Na2SO4和提高磷石膏掺量的方法,可大幅度缩短水泥的凝结时间、提高水泥的早期强度.当磷石膏掺量超过10％时,水泥水化产物中钙矾石量显著增加,并出现二水石膏,硬化水泥浆体呈现出微膨胀性.通过调整磷石膏的掺量,可控制复合水泥的膨胀率.     

有替代硅酸盐水泥熟料的生产的选择吗?(英文)

人们一直在寻找CO2排放量低的水硬性胶凝材料,用它替代传统的以硅酸盐水泥熟料(Portland clinker,PC)为主的水泥。介绍了几种处于不同发展时期的新型非PC基的胶凝材料体系。目前大多数水泥生产商都尽可能多地用辅助性胶凝材料替代硅酸盐水泥熟料。火山灰材料具有低的水硬活性,它可使用高浓度碱金属溶液来激发,得到介于"地聚合物"和石灰激发火山灰胶凝材料间的复合胶凝材料。较远期可以期待基于贝利特、硫铝酸钙和铁铝酸钙矿物组成的水泥熟料,如拉法基公司的AetherTM已投入生产。更远的将来,不产生CO2的原材料,如硅酸镁等,可能使得水泥生产中实现CO2零排放,然而,这些胶凝材料的耐久性有待验证,用其配制的混凝土中钢筋锈蚀的防护是实际应用中的关键问题。