Studying Ice with Environmental Scanning Electron Microscopy

Scanning electron microscopy (SEM) is a powerful imaging technique able to obtain astonishing images of the micro- and the nano-world. Unfortunately, the technique has been limited to vacuum conditions for many years. In the last decades, the ability to introduce water vapor into the SEM chamber and still collect the electrons by the detector, combined with the temperature control of the sample, has enabled the study of ice at nanoscale. Astounding images of hexagonal ice crystals suddenly became real. Since these first images were produced, several studies have been focusing their interest on using SEM to study ice nucleation, morphology, thaw, etc. In this paper, we want to review the different investigations devoted to this goal that have been conducted in recent years in the literature and the kind of information, beyond images, that was obtained. We focus our attention on studies trying to clarify the mechanisms of ice nucleation and those devoted to the study of ice dynamics. We also discuss these findings to elucidate the present and future of SEM applied to this field.     

Ion Chromatographic Determination of Anions in Environmental Samples

Abstract

The use of ion-exchange chromatography with an IonPac AS 14 column, 3.5 mM Na₂CO₃/1.0 mM NaHCO₃ eluent and suppressed conductivity detection provides a simple, cost-effective, fast, accurate, and highly sensitive method for the determination of F^?, Cl^?, NO₂ ^?, Br^?, NO₃ ^?, PO₄ ^2?, SO₄ ^2?, and C₂O₄ ^2? at low μ/L levels in environmental samples. Data on sensitivity, selectivity, accuracy, and % relative standard deviation are described. The method is suitable for many environmental applications including atmospheric aerosols (exposed on cellulose, glass fiber, and quartz filters), rainwater, cloud water, potable- and non-potable waters, and carbonated waters. Dominant components of the aerosol were SO₄ ^2?, NO₃ ^?, and Cl^?. Rainwater, on the other hand, has relatively very low concentrations of these three species. The wide-spread concentration range for Cl^? in variety of water samples and the high concentrations for SO₄ ^2? in drinking water are striking. Determination of the anionic composition of carbonated waters revealed a considerable variation of the individual anions.     

生物和环境样品中硒元素的形态分析研究

金属组学是继基因组学/蛋白质组学和代谢组学后提出的一种新的组学,其研究重点在于对所研究的金属和类金属元素的各种存在形态进行分析。硒是生物环境中存在的一种重要的类金属元素。形态与浓度不同的硒化合物可能是生物体的必需元素,同时也可能导致中毒。本文对目前存在的硒元素形态分析方法的研究现状进行了总结,并对前景进行了展望。     

Determination of Arsenic Speciation in Complex Environmental Samples by the Combined Use of TEM and XPS

Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) have been used to refine the solid-state speciation of As in mine waste materials and stream-bed sediments from the Baccu Locci mine area in Sardinia, Italy. The combined use of TEM and XPS confirmed previous studies and pointed out that: (i) As is contained in plumbojarosite in substitution of S, (ii) As-bearing Fe(III) hydroxides are represented by arsenical 2-line ferrihydrites with most Fe/As molar ratios in the range of 1.6–3.2, (iii) scorodite often lacks long range order. Arsenatian plumbojarosite will tend to dissolve incongruently in ferrihydrite, releasing Pb and As into water. However, Pb is fated to precipitate as Pb(OH)₂ or to be adsorbed onto ferrihydrite, whereas As mobility is favoured since the adsorptive capacity of ferrihydrite for As(V) is notably reduced under the neutral to alkaline pH conditions occurring in the Baccu Locci stream water. Arsenical ferrihydrites will tend to be converted into goethite or hematite with time, releasing As into the water as a consequence of the notably lower density of the adsorption sites of the crystalline Fe(III) phases. Also scorodite is relatively unstable under the Baccu Locci system conditions, and its stability is further decreased owing to the higher solubility of the amorphous form compared to the crystalline one.     

Electrochemical Synthesis of Perfluorinated Ion Doped Conducting Polyaniline Films Consisting of Helical Fibers and their Reversible Switching between Superhydrophobicity and Superhydrophilicity

Superhydrophobic conducting polyaniline (PAni) films were electrochemically deposited in acetonitrile‐H₂O electrolyte containing aniline monomer and perfluorooctanesulfonic (PFOS) acid. The films exhibited an extended network structure composed of helical PAni sub‐micron fibers. The helical fibrous structure is thought to form through a supermolecular templating process. The surface of the PFOS‐doped PAni films showed a water contact angle of 153°. Reducing the PFOS‐doped PAni (in emeraldine salt form) by negative potential led to de‐doped PAni films (in leucoemeraldine base form) which were superhydrophilic (water contact angle close to 0°). By controlling the electrical potential, PAni films were changed between the doped state and de‐doped state, resulting in reversibly switchable superhydrophobic and superhydrophilic surfaces.

     

电感耦合等离子体-质谱联用及其在环境和生物样品中铂族金属分析的应用进展

本文简述了电感耦合等离子体-质谱联用(LCP-MS)技术和仪器的发展,分析了环境和生物样品中铂族金属分析的主要困难,综述了90年代以来国内外ICP-MS技术在环境和生物样品中铂族金属分析的最新进展,引用文献47篇.     

Graphene-modified Monolithic Capillary Column for the Microextraction of Trace Benzodiazepines in Biological Samples

A graphene monolithic column was fabricated in a capillary using π-electron-rich poly(N-vinylcarbazole-divinylbenzene) as the supporter through in situ one-step polymerization for the enrichment of trace benzodiazepines in biological samples. This new three-dimensional monolith showed uniformity and a continuous column bed; more importantly, it retained the unique properties of graphene that are typically associated with individual graphene sheets. Based on the large delocalized π-electron system, graphene forms π–π stacking interactions with benzodiazepines and benzene rings of poly(N-vinylcarbazole-divinylbenzene), which not only enhance the extraction performance for benzodiazepines compared to the neat polymer but also provide chemical stability of the graphene monolith. Moreover, several factors likely to affect the extraction, including ionic strength, sample pH, sample volume, and eluant volume were studied in detail. The optimized method gave a linear range of 0.005–1?ng?mL^?1, and detection limits of 1.12–2.35?ng?L^?1. Finally, the graphene monolith was successfully applied to the separation and enrichment of benzodiazepines from urine and hair samples coupled with high-performance liquid chromatography–mass spectrometry. The recoveries were in the range of 78.6–85.6% for urine and 87.2–94.3% for hair with relative standard deviations of 3.4–6.9 and 2.9–8.3%, respectively.     

生物,环境样品和食品中铅的痕量分析

主要根据近七年来发表的有关论文，综述了我国生物、环境样品和食品中铅和痕量分析技术进展，内容包括分子光谱、原子光谱、电化学和其他分析方法，以及联用技术和前处理等方面，收集文献３９３篇。     

生物样品中儿茶酚胺类物质分析方法的研究进展

儿茶酚胺是人体内重要的神经递质,血浆及尿中儿茶酚胺的浓度水平可用于诊断高血压、嗜铬细胞瘤及成神经细胞瘤等病症,因而准确测定人体生物样品中儿茶酚胺类物质代谢浓度的变化,在疾病的诊断和治疗中具有重要的意义。该文综述了人体液和组织中儿茶酚胺类物质的不同分析方法,包括高效液相色谱法、毛细管电泳法、质谱法、电化学法、化学发光法、荧光光度法等。     

Speciation of Arsenic in Environmental and Biological Samples

A novel arsine generator glass assembly is constructed and reported for the spectrophotometric determination and speciation of arsenic in real samples. In an arsine generator, sodium borohydride is added dropwise to the acidic sample solution and arsine thus formed is reacted with silver diethyldithiocarbamate (Ag‐DDTC) ‐ Tritron‐X (TX‐100) solution in pyridine to form a red coloured complex. The complex showed the absorption maximum at λ_max 540 nm. The molar absorptivity of the method was found to be (1.55) × 10⁴ L mole^?1 cm^?1 at this wavelength. The presence of non‐ionic surfactant, i.e. TX‐100 in the Ag‐DDTC solution, makes the method ≈ 3 times more sensitive than the conventional Ag‐DDTC method. Beer's law is obeyed in the concentration range of 0.05–2.80 mg L^?1 of arsenic. The detection limit of the method was calculated to be 20 μg L^?1 As. Speciation of arsenite from other forms of arsenic in sample solutions was carried out by extraction of arsenite with Pb‐DDTC in chloroform, followed by spectrophotometric determination. After arsenite separation the sample is used for the arsenate determination. Total arsenic was determined by acid decomposition of the same sample. The speciation data were found to be comparable (±2%) with ICP‐MS, with better precision (< 1%). The method has been successfully applied for the speciation of arsenic in drinking water and dust samples of arsenic affecting the Rajnandgaon district of Chhattisgarh, India, and urine and blood samples of patients with arsenical diseases. Concentration of total arsenic in tube‐well water of this area was 3–6 times more than the permissible limit. Dust samples contained less amounts of arsenic than the ground water.     

基于原子力显微镜的单分子力谱在生物研究中的应用

原子力显微镜被广泛应用于生物研究领域,基于原子力显微镜的单分子力谱可以在单分子、单细胞水平上研究生物分子内和分子间的相互作用。 本文介绍了原子力显微镜单分子力谱在生物分子间相互作用、蛋白质去折叠、细胞表面生物分子、细胞力学性质和基于单分子力谱成像等研究中的最新进展。     

Forensic Analysis of Textile Synthetic Fibers Using a FT-IR Spectroscopy Approach

Synthetic fibers are one of the most valuable trace lines of evidence that can be found in crime scenes. When textile fibers are analyzed properly, they can help in finding a linkage between suspect, victim, and the scene of the crime. Various analytical techniques are used in the examination of samples to determine relationships between different fabric fragments. In this exploratory study, multivariate statistical methods were investigated in combination with machine learning classification models as a method for classifying 138 synthetic textile fibers using Fourier transform infrared spectroscopy, FT-IR. The data were first subjected to preprocessing techniques including the Savitzky–Golay first derivative method and Standard Normal Variate (SNV) method to smooth the spectra and minimize the scattering effects. Principal Component Analysis (PCA) was built to observe unique patterns and to cluster the samples. The classification model in this study, Soft Independent Modeling by Class Analogy (SIMCA), showed correct classification and separation distances between the analyzed synthetic fiber types. At a significance level of 5%, 97.1% of test samples were correctly classified.     

电感耦合等离子体质谱方法在生物样品分析中的应用

介绍了电感耦合等离子体质谱方法在生物样品分析中应用研究的新进展。针对ICP－MS的特点阐述了样品处理、进样方式、干扰校正的主要方法和应注意的问题。     

单扫描极谱法测定环境水中的微量砷

提出了在饱和酒石酸/酒石酸锑钾(8.0 mg/L)/硒(Ⅳ)(0.40 mg/L) 底液中,单扫描极谱法于原点电位-0.5V(vs.SCE)起扫,在峰电位为-0.87V(vs.SCE)测定砷的方法,线性范围为0.08~12.0 g/mL;最低检出浓度0.06 g/mL。该法简捷快速,可满足环境水样分析的要求。     

Trace Analysis of Iron in Environmental Water and Snow Samples from Poland

Abstract

A voltammetric method for the determination of iron at detection limit of 4 μg/l is described, using the catalytic current of the reduction of the Fe(III)-triethanolamine (TEA) complex in the presence of bromate ions. the determination was performed at a mercury hanging drop electrode without preconcentration, using the TEA alkaline solution as a supporting electrolyte and the differential pulse technique. A peak current for the Fe(III)-TEA catalytic reduction was observed at a potential of-1.0 V (Ag/AgCl saturated electrode). the influence of TEA, BrO³ and NaOH concentrations on the peak height was studied. It was found that a 100-fold excess of Mn, a 50-fold excess of Cr(VI) and Zn did not interfere in the determination. This method was applied to the determination of iron in water, snow and waste water samples.     

环境水样及食品中亚硝酸根的分析进展

评述了自1997年至2002年国内外环境水样及食品中亚硝酸根(NO2^-)的分析进展。包括分子光谱法、电化学分析法和色谱分析法，引用文献96篇。     

环境和生物样品中多来宝残留量的气相色谱分析方法研究

湿性样品中的多来宝残留物用丙酮（水样和干样用石油醚）提取，提取液经石油醚再萃取、浓缩后，用被石油醚饱和的乙腈分配，过硅胶氧化铝混合柱净化，室温下与（ＣＨ３）３ＳｉＩ衍生化反应，生成３－苯氧基苄基碘，用ＧＣ检测。当添加浓度为０．０５，０．１０，１．００μｇ／ｇ时，样品的平均回收率为８０．７％～１１０．０％，方法最小检出量为０．０１ｎｇ，样品最小检出浓度是：水０．００１ｍｇ／Ｌ，稻米和土壤０．０１μｇ／ｇ，稻草、谷壳、水浮莲和罗非鱼为０．００８μｇ／ｇ。     

Head-Space SPME for the Analysis of Organophosphorus Insecticides by Novel Silica IL-Based Fibers in Real Samples

This work demonstrates the suitability of a newly developed ionic liquid (IL)-based silica SPME fiber for the determination of seven organophosphorus insecticides in cucumber and grapefruit samples by headspace solid-phase microextraction (HS-SPME) with a gas chromatography–flame ionization detector (FID). The sol-gel method released four different sorbent coatings, which were obtained based on a silica matrix containing ILs immobilized inside its pores. In order to obtain ionogel fibers, the following ionic liquids were utilized: 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide; Butyltriethyl ammonium bis(trifluoromethylsulfonyl)imide; 1-(2-Methoxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-Benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The developed fibers were applied for the extraction of seven different insecticides from liquid samples. The most important extraction parameters of HS-SPME coupled with the GC-FID method were optimized with a central composite design. The new SPME fiber demonstrated higher selectivity for extracting the analyzed insecticides compared with commercially available fibers. The limit of detection was in the range of 0.01–0.93 μg L⁻¹, the coefficients of determination were >0.9830, and 4.8–10.1% repeatability of the method was found. Finally, the obtained ionogel fibers were utilized to determine insecticides in fresh cucumber and grapefruit juices.     

Water‐sorption kinetics in oil palm fibers

Oil palm fibers represent a very abundant and natural resource for raw materials that can be efficiently utilized as reinforcement in polymers. The sorption characteristics of two types of oil palm fibers—oil palm empty‐fruit‐bunch (OPEFB) fiber and oil palm mesocarp fiber‐in distilled water, mineral water, and water containing salt at four different temperatures were investigated. The uptake of water decreased with an increase in temperature. The OPEFB fiber showed higher sorption than the mesocarp fiber. This was due to the uptake associated with the capillary action in the OPEFB fiber. The thermodynamic parameters of the sorption process were calculated. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1215–1223, 2001     

Handling of Environmental and Biological Samples via Pre-Column Technologies

Abstract

Sample handling is still a weak point in chromatography and in analytical chemisty in general. One consideration is the automation potential of new procedures. Solid-liquid extraction techniques in combination with pre-column technology are particularly promising in this regards. The construction and geometry of pre-columns both for conventional and narrow-bore HPLC are of major importance, since band broadening should be kept at a minimum for an optimal functioning of the analytical system. The various operations that can be carried out with such a pre-column are trace-enrichment, clean-up of the sample which depends on the type of adsorbents used in the precolumn, i.e., polar or apolar materials, ion exchangers or metal covered surfaces, etc., protection of the analytical column, field sampling and storage of samples and as a substrate for on-column chemical derivatizations. These various operations are demonstrated with practical examples from the fields of environmental and biological analysis. The selectivity can be further enhanced by coupling precolumn technology with selective detection modes such as diode array UV, electrochemical or fluorescence detection. This enables the construction of optimal and integrated analysis sytems which are fully automated and microprocessor controlled. They can also be made compatible with miniaturized LC-technology.