Characterization of particulate matter from the Metropolitan Zone of the Valley of Mexico by scanning electron microscopy and energy dispersive X-ray analysis

Samples of total suspended particles (TSP) and PM10 respirable particles from five monitoring stations from the network system of the Metropolitan Zone of the Valley of Mexico (MZVM) were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). Morphology and chemical composition allowed to identify six groups. The analysis shows that the most abundant groups are Al-Si-O, Fe, and metals, the first one in the TSP fraction. Trace metal, commonly associated to PM10 at a receptor location, will depend on the relative influences of local anthropogenic sources. Metal group was observed in all samples, mainly in Tlalnepantla and CES zones (28–46%).     

扫描电镜-能谱法测定生活饮用水中石棉

建立了扫描电镜-能谱法(SEM-EDS)测定生活饮用水中石棉(≥10μm)的方法,使用场发射扫描电镜可对宽度大于0.050~0.124μm的石棉纤维进行定性和计数。若生活饮用水中存在以藻类为主的有机质干扰,使用紫外-过硫酸钾消解可消除相应干扰。配置低、中、高3个浓度的石棉悬浊液模拟水样交由国内不同地区的6家实验室进行方法学验证,结果表明,方法实验室内RSD为10%~37%,实验室间RSD为10%~39%,蓝藻干扰消除实验回收率平均值为98.1%,RSD为11%。方法检出限为5.0×10^4~11.6×10^4个/L,低于GB 5749限量规定的700×10^4个/L。     

Information-theoretical feature selection using data obtained by scanning electron microscopy coupled with and energy dispersive X-ray spectrometer for the classification of glass traces

In this work, a selection of the best features for multivariate forensic glass classification using Scanning Electron Microscopy coupled with an Energy Dispersive X-ray spectrometer (SEM-EDX) has been performed. This has been motivated by the fact that the databases available for forensic glass classification are sparse nowadays, and the acquisition of SEM-EDX data is both costly and time-consuming for forensic laboratories. The database used for this work consists of 278 glass objects for which 7 variables, based on their elemental compositions obtained with SEM-EDX, are available. Two categories are considered for the classification task, namely containers and car/building windows, both of them typical in forensic casework. A multivariate model is proposed for the computation of the likelihood ratios. The feature selection process is carried out by means of an exhaustive search, with an Empirical Cross-Entropy (ECE) objective function. The ECE metric takes into account not only the discriminating power of the model in use, but also its calibration, which indicates whether or not the likelihood ratios are interpretable in a probabilistic way. Thus, the proposed model is applied to all the 63 possible univariate, bivariate and trivariate combinations taken from the 7 variables in the database, and its performance is ranked by its ECE. Results show remarkable accuracy of the best variables selected following the proposed procedure for the task of classifying glass fragments into windows (from cars or buildings) or containers, obtaining high (almost perfect) discriminating power and good calibration. This allows the proposed models to be used in casework. We also present an in-depth analysis which reveals the benefits of the proposed ECE metric as an assessment tool for classification models based on likelihood ratios.     

Line scanning analysis of the component of Ru Porcelain by micro energy disperse X-ray fluorescence probe

The Ru kiln is one of the five famous kilns of the Song Dynasty in China, and it is said that the Ru Porcelain is the chief of the five. As the Ru Porcelain was produced for a short time in history, no other than approximately 20 a, and exclusively fired only for the royalty, the remains are rather rare, with the total number falling short of one hundred pieces all over the world excluding the ones excavated in Qingliang Temple, Baofeng County, Henan Province. Especially, the celadon of …     

Contribution to the clarifying of the action of thermochemical additives on the modification of a matrix silicon carbide using scanning electron microscopy and energy dispersive X-ray analysis

Summary Previous investigations have shown that the total evaporation of impurities from silicon carbide powder can be achieved by its thermochemical transformation to BaSiO₃, BaF₂ and CoSi (CoSi₂) under the action of the modifier CoF₂ + BaO, through in situ processing in an electrothermally heated graphite crucible [13]. The aim of the present work has been to describe a methodology to perform a rational selection of various potential candidates for modifiers, to make successful combinations between various chemical additives, to understand the reason(s) for an effective/ineffective action of a particular additive, i.e. to find the optimum conditions for each type of ceramic matrix chemical modifier. A combination of scanning electron microscopy (SEM), energy dispersive X-ray analyses (EDX) and X-ray diffraction analyses was used to confirm the identification of the alterations to the silicon carbide matrix. Indirectly, the present work supports the view that the aim justifies the means particularly when the aim is to reach a complete evaporation of the impurities from a carbide matrix, which as is well known, is not an ordinary or easy task.     

Imaging fibrinogen adsorbed on noble metal surfaces with scanning tunneling microscopy: correlation of images with electron spectroscopy for chemical analysis, secondary ion mass spectrometry, and radiolabeling studies

Fibrinogen adsorption on gold and platinum surfaces has been studied with electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectrometry (SIMS), ¹²⁵I labeling, and scanning tunneling microscopy (STM). Stable images of single molecules have been obtained, but are rare. ESCA, SIMS, and labeling studies confirm that absorbed fibrinogen is present on samples at monolayer and submonolayer coverages even when STM images show only a bare substrate. Imaging is more reproducible at high coverages at which single molecules cannot be resolved. Possible explanations for the failure of STM to observe adsorbed fibrinogen molecules are discussed.     

Development of a method for direct determination of solids as thin films by energy dispersive X-ray fluorescence analysis

Solid samples can be analysed as without a prior decomposition step, if they are pulverized and then embedded in a thin layer of a cold-setting polymer. This method is very appropriate for materials which are difficult to decompose or which can be easily contaminated. The sample components are evenly distributed in a thin layer, which improves considerably the signal-tonoise-ratio, and this leads to a decrease of the limits of detection. The reproducibility of the method was tested with cobalt oxide and yttrium oxide and also a mixture of these with silver oxide and manganese dioxide. Between 20 and 60 ng of these elements can be determined without difficulty, with a precision of ± 2–4%. The correlation coefficients found for the calibration graphs were between 0.994 and 0.999.     

Optimization of a centrifugation and ultrasound-assisted procedure for the determination of trace and major elements in marine invertebrates by ICP OES

A three factor Doehlert design was applied to optimize the extraction of elements in marine invertebrate samples (oyster, mussel and clam) using centrifugation with diluted acids. The factors were: concentration of acid mixture (HCl + HNO₃ + H₃CCOOH; 1–3 mol L^{− 1}), centrifugation time (10–40 min), and rotation velocity (6000–10,000 rpm). In order to evaluate the ultrasound effect on the extraction of trace metals, a portion of the certified oyster tissue sample (NIST 1556b; 0.250 g) was sonicated for 15 min and then the solution was centrifuged at the optimized conditions. The optimized procedure was then applied to nine marine invertebrate samples (oysters, clams and mussels) collected at Todos os Santos Bay, Bahia, Brazil. The optimized condition of the developed method was: 20 min of centrifugation at 9000 rpm using the acid mixture 1.0 mol L^{− 1}. The effect of sonication prior centrifugation was very variable, but it promoted a significant increase in the extraction (12 to 44%) of some trace elements. Moreover, the combination of the centrifugation with sonication offered other advantages, such as improvement of the precision and accuracy, both demonstrated using the oyster tissue reference sample. The results of major and trace elements in marine invertebrate samples showed that elements such us Cd and Cu in oyster samples and Zn in mussel and clam samples were above recommendations, suggesting that its consumption may impose health risks.     

Archaeopolymetallurgical study of materials from an Iberian culture site in Spain by scanning electron microscopy with X-ray microanalysis, chemometrics and image analysis

Archaeometallurgical materials from “La Bastida de Moixent”, a site in Valencia (Spain), from the second Iberian iron age (4th Century B.C.) have been studied using metallographic techniques, microanalysis, chemometrics and image analysis. The materials come from various phases of iron production and cupellation of argentiferous lead to obtain silver. Scanning electron microscopy (SEM) is used to determine the morphological, microstructural and topographic characteristics of the samples. Image analysis was used to obtain a numeric estimate of the main components in these materials. X-ray microanalysis (SEM/EDX) provides qualitative and quantitative information about the elements in the sample. The semiquantitative results have been treated by chemometric tools such as Principal Component Analysis (PCA) to group the different archaeological materials. These analyses provide information on the lead and iron metallurgical processes, such as silver production by cupellation used in the period. Macroscopic and microscopic analyses indicate a high quality, acceptably uniform manufactured product, indicating broad technical skill in the later metallurgical process of transformation and refinement of these materials to obtain ingots and manufactured products to trade.     

Evaluation of microwave-assisted extraction for aristolochic acid from Aristolochiae Fructus by chromatographic analysis coupled with nephrotoxicity studies

In this paper, a microwave-assisted extraction (MAE) method was established for aristolochic acid-I from Aristolochiae Fructus, and the advantage of MAE was evaluated by chromatographic analysis coupled with nephrotoxicity studies. The experimental parameters of MAE for aristolochic acid-I in Aristolochiae Fructus were investigated and MAE was compared with Soxhlet extraction and ultrasound-assisted extraction in terms of extraction yields and extraction conditions. Under the optimum conditions, MAE could provide higher extraction yields of aristolochic acid-I (1.10 mg/g) than ultrasound-assisted extraction (0.82 mg/g) and Soxhlet extraction (0.95 mg/g), in addition to using less solvent and having a shorter extraction time. Furthermore, the nephrotoxicities of the extracts of Aristolochiae Fructus from different extraction procedures were investigated in Sprague-Dawley rats. The results of nephrotoxicity studies of, for example, general conditions, biochemistry parameters and histopathology examination showed no significantly differences in the nephrotoxicity levels of the extracts from MAE and that from Soxhlet extraction. These results indicated that MAE technique is a simple, rapid and effective extraction method, and the microwave irradiation during MAE procedure did not have any influence on the nephrotoxicity of Aristolochiae Fructus compared with Soxhlet extraction.     

Primary secondary amine as a sorbent material in dispersive solid‐phase extraction clean‐up for the determination of indicator polychlorinated biphenyls in environmental water samples by gas chromatography with electron capture detection

A simple, rapid, and novel method has been developed and validated for determination of seven indicator polychlorinated biphenyls in water samples by gas chromatography with electron capture detection. 1 L of water samples containing 30 g of anhydrous sodium sulfate was first liquid–liquid extracted with an automated Jipad‐6XB vertical oscillator using n‐hexane/dichloromethane (1:1, v/v). The concentrated extract was cleaned up by dispersive solid‐phase extraction with 100 mg of primary secondary amine as sorbent material. The linearity of this method ranged from 1.25 to 100 μg/L, with regression coefficients ranging between 0.9994 and 0.9999. The limits of detection were in the ng/L level, ranging between 0.2 and 0.3 ng/L. The recoveries of seven spiked polychlorinated biphenyls with external calibration method at different concentration levels in tap water, lake water, and sea water were in the ranges of 85–112, 76–116, and 72–108%, respectively, and with relative standard deviations of 3.3–4.5, 3.4–5.6, and 3.1–4.8% (n =  5), respectively. The performance of the proposed method was compared with traditional liquid–liquid extraction and solid‐phase extraction clean‐up methods, and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of polychlorinated biphenyls in different water samples.