Characterization of nuclear materials by total reflection X-ray fluorescence spectrometry

Nuclear energy is one of the available energy options for long term energy security of world. In order to produce electricity using this mode of energy generation in an efficient and safe manner, it is necessary that the materials used for such energy generation comply with the specifications assigned. The major and trace composition of these materials is an important specification for their quality control. Different analytical techniques are used for such quality control. Total reflection X-ray fluorescence (TXRF) is a comparatively new technique having several features well suited for trace and major element determinations in nuclear materials. However, this technique has not been used so far extensively for characterization of nuclear materials. The present paper gives a brief introduction of TXRF, its suitability for nuclear material characterization and some details of the TXRF studies made in our laboratory for the characterization of nuclear materials.     

Polysaccharides derived from natural sources applied to the development of chemically modified electrodes for environmental applications: A review

Potentially toxic organic and inorganic compounds have been released into the environment by different sources. Due to this detrimental problem, the modern analytical chemistry has increasingly acted in the interface of knowledge in terms of developing methods which are robust, efficient, sensitive, inexpensive, and aim at meeting green chemistry principles. From an electroanalytical standpoint, the application of polysaccharides derived from natural sources in the development of chemically modified electrodes has increased in the last decades. Chitosan, cellulose and other polysaccharides have been widely used in the development of modified electrodes due to their high mechanical strength, relatively low cost, and green features. Several studies have reported in the past few years that chemically modified electrodes elaborated with these polysaccharides usually present superior analytical properties as compared to the conventional electrodes. This review describes the general aspects of these polysaccharides, extraction sources, characterization methods, derivatives and crosslinking processes as well as a comprehensive overview of their several applications in the development of new sensors applied to environmental samples.     

Analytical Chemistry in Modern Society: What we can Expect

Analytical chemistry today contributes many analytical techniques which are required in industry, environmental control, medical laboratories and other areas of society. However, increased portability and miniaturization has the potential to enable us to solve new problems such as the analysis of new matrices including the possibility to analyse even cellular compartments. In this development process it is also being attempted to produce instruments and techniques which can be used by non-specialists. The integration, in a recent future, of microanalytical systems into our water taps permitting to control the presence of contaminants or microanalytical systems to control our health profile are some examples of the future contribution of analytical chemistry to society which probably will change our life.     

Stripping voltammetry for the determination of trace metal speciation and in-situ measurements of trace metal distributions in marine waters

Progress in marine chemistry has been driven by improved sampling and sample handling techniques, and developments in analytical chemistry. Consequently, during the last 20 years our understanding of marine trace metal biogeochemistry has improved a great deal. Stripping voltammetric techniques (anodic stripping voltammetry and adsorptive cathodic stripping voltammetry) have made an important contribution to this understanding. The selectivity and extremely low detection limits have made stripping voltammetry a widely used technique for trace metal speciation and trace metal distribution measurements in seawater. Stripping voltammetry is very suitable for ship-board and in-situ applications because of the portability, low cost and capability for automation of the voltammetric instrumentation. Future developments in stripping voltammetry can be expected in the field of stand-alone submersible voltammetric analysers, capable of continuous trace metal measurements. Future applications of stripping voltammetry can be found in the interactions between trace metal speciation and growth and the functioning of organisms in pristine and metal polluted marine waters.     

分析化学发展中的几个问题

分析化学在迅速发展中出现了一些令人关注的问题。它们是：如何确定现代分析化学煌范围，如何给字以明确的定义；对分析化学煌前沿的预测；当今分析化学在化学中的地位；对分析介的批评意见的反思；分析化学应注意克有孤自身的弱点；如何培养高水平的分析化学专业人材等。本文就这些问题介绍国内外同行的一些看法发表本人的浅见。     

Simulation vs. Understanding: A Tension,in Quantum Chemistry and Beyond. Part A. Stage Setting

We begin our tripartite Essay with a triangle of understanding, theory and simulation. Sketching the intimate tie between explanation and teaching, we also point to the emotional impact of understanding. As we trace the development of theory in chemistry, Dirac's characterization of what is known and what is needed for theoretical chemistry comes up, as does the role of prediction, and Thom's phrase “To predict is not to explain.” We give a typology of models, and then describe, no doubt inadequately, machine learning and neural networks. In the second part, we leave philosophy, beginning by describing Roald's being beaten by simulation. This leads us to artificial intelligence (AI), Searle's Chinese room, and Strevens’ account of what a go-playing program knows. Back to our terrain—we ask “Quantum Chemistry, † ca. 2020?” Then move to examples of AI affecting social matters, ranging from trivial to scary. We argue that moral decisions are hardly to be left to a computer. At this point, we try to pull the reader up, giving the opposing view of an optimistic, limitless future a voice. But we don't do justice to that view—how could we? We return to questioning the ascetic dimension of scientists, their romance with black boxes. Onward: In the 3rd part of this Essay, we work our way up from pessimism. We trace (another triangle!) the special interests of experimentalists, who want the theory we love, and reliable numbers as well. We detail in our own science instances where theory gave us real joy. Two more examples-on magnetic coupling in inorganic diradicals, and the way to think about alkali metal halides, show us the way to integrate simulation with theory. Back and forth is how it should be—between painfully-obtained, intriguing numbers, begging for interpretation, in turn requiring new concepts, new models, new theoretically grounded tools of computation. Through such iterations understanding is formed. As our tripartite Essay ends, we outline a future of consilience, with a role both for fact-seekers, and searchers for understanding. Chemistry's streak of creation provides in that conjoined future a passage to art and to perceiving, as we argue we must, the sacred in science.     

Simulation vs. Understanding: A Tension,in Quantum Chemistry and Beyond. Part A. Stage Setting

We begin our tripartite Essay with a triangle of understanding, theory and simulation. Sketching the intimate tie between explanation and teaching, we also point to the emotional impact of understanding. As we trace the development of theory in chemistry, Dirac's characterization of what is known and what is needed for theoretical chemistry comes up, as does the role of prediction, and Thom's phrase “To predict is not to explain.” We give a typology of models, and then describe, no doubt inadequately, machine learning and neural networks. In the second part, we leave philosophy, beginning by describing Roald's being beaten by simulation. This leads us to artificial intelligence (AI), Searle's Chinese room, and Strevens’ account of what a go‐playing program knows. Back to our terrain—we ask “Quantum Chemistry, ? ca. 2020?” Then move to examples of AI affecting social matters, ranging from trivial to scary. We argue that moral decisions are hardly to be left to a computer. At this point, we try to pull the reader up, giving the opposing view of an optimistic, limitless future a voice. But we don't do justice to that view—how could we? We return to questioning the ascetic dimension of scientists, their romance with black boxes. Onward: In the 3rd part of this Essay, we work our way up from pessimism. We trace (another triangle!) the special interests of experimentalists, who want the theory we love, and reliable numbers as well. We detail in our own science instances where theory gave us real joy. Two more examples‐on magnetic coupling in inorganic diradicals, and the way to think about alkali metal halides, show us the way to integrate simulation with theory. Back and forth is how it should be—between painfully‐obtained, intriguing numbers, begging for interpretation, in turn requiring new concepts, new models, new theoretically grounded tools of computation. Through such iterations understanding is formed. As our tripartite Essay ends, we outline a future of consilience, with a role both for fact‐seekers, and searchers for understanding. Chemistry's streak of creation provides in that conjoined future a passage to art and to perceiving, as we argue we must, the sacred in science.     

The surface chemistry of a nanocellulose drug carrier unravelled by MAS-DNP

Cellulose nanofibrils (CNF) are renewable bio-based materials with high specific area, which makes them ideal candidates for multiple emerging applications including for instance on-demand drug release. However, in-depth chemical and structural characterization of the CNF surface chemistry is still an open challenge, especially for low weight percentage of functionalization. This currently prevents the development of efficient, cost-effective and reproducible green synthetic routes and thus the widespread development of targeted and responsive drug-delivery CNF carriers. We show in this work how we use dynamic nuclear polarization (DNP) to overcome the sensitivity limitation of conventional solid-state NMR and gain insight into the surface chemistry of drug-functionalized TEMPO-oxidized cellulose nanofibrils. The DNP enhanced-NMR data can report unambiguously on the presence of trace amounts of TEMPO moieties and depolymerized cellulosic units in the starting material, as well as coupling agents on the CNFs surface (used in the heterogeneous reaction). This enables a precise estimation of the drug loading while differentiating adsorption from covalent bonding (∼1 wt% in our case) as opposed to other analytical techniques such as elemental analysis and conductometric titration that can neither detect the presence of coupling agents, nor differentiate unambiguously between adsorption and grafting. The approach, which does not rely on the use of ¹³C/¹⁵N enriched compounds, will be key to further develop efficient surface chemistry routes and has direct implication for the development of drug delivery applications both in terms of safety and dosage.

DNP-enhanced solid-state NMR unravels the surface chemistry of functionalized nanocellulose.     

Development of visual analytical methods for trace determination.

In this paper our recent progress in the field of simple analytical methods is reviewed, with particular focus on the development of rapid, inexpensive, yet sensitive techniques to visualize trace elements of medical, industrial, and environmental importance. Our objective is to solve long-standing practical problems in these fields. We have repeatedly shown that visual perception is remarkably sensitive when used with our new techniques. The applicability of the proposed methods to real samples is also discussed. Making measurements visually is a method free from machinery malfunctions and serves as a simple and sensitive analytical technique, avoiding all of the practical disadvantages associated with sophisticated instrumentation as well as tedious procedures.     

The role of analytical chemistry in Niger Delta petroleum exploration: A review

Petroleum and organic matter from which the petroleum is derived are composed of organic compounds with some trace elements. These compounds give an insight into the origin, thermal maturity and paleoenvironmental history of petroleum, which are essential elements in petroleum exploration. The main tool to acquire the geochemical data is analytical techniques. Due to progress in the development of new analytical techniques, many hitherto petroleum exploration problems have been resolved. Analytical chemistry has played a significant role in the development of petroleum resources of Niger Delta. Various analytical techniques that have aided the success of petroleum exploration in the Niger Delta are discussed. The analytical techniques that have helped to understand the petroleum system of the basin are also described. Recent and emerging analytical methodologies including green analytical methods as applicable to petroleum exploration particularly Niger Delta petroleum province are discussed in this paper. Analytical chemistry is an invaluable tool in finding the Niger Delta oils.     

Where is analysis of trace elements in biotic matrices going to?

Summary Accomplishing the act of balancing our technological progress with the accompanying risks for safety and health in our life quality, calls for modern analytical science. It should serve as an indicator for the correct balance of forces in the substantial sphere. However, today such an indicating role is based on rough estimations, or on insufficient or unconfirmed information with respect to concentrations, binding forms and local distributions of toxic or of essential substances within a sample. Moreover, many complex mechanisms of synergetic and antagonistic physiological interactions have not yet been clarified — and consequently, we have to take into account severe misjudgements of risks.In addition, one has reached the limits of financial means required for the increasing control and survey tasks of daily analytical routine. Accordingly, only a long-term planned strategy for the development of more powerful, more reliable and more economic analytical methods, which moreover guarantee a better local distribution (microdistribution analysis), are the prerequisites for an improvement of this situation in analytical sciences.In view of the future tasks and the ultimate limits of trace- and micro-distribution analysis of the elements, the present state and an outlook on reaching the limit of analysis are critically discussed. Main emphasis is placed here on the possibility of improving conventional determination methods such as AAS, OES, XRFA, MS, NAA with regard to better power of detection and reliability. But also innovative analytical principles such as laser atomic spectroscopy (RIS, LEI, LIF) are introducted. They promise to develop into an essential basis for micro and trace element analysis of tomorrow.As instrumental methods are always the last step in an analytical procedure, a brief reference will be made to the problem of sample preparation, mainly with regard to the sources of systematic errors. As for trace analysis at the ng/ ml- or pg/ml-levels there are no reliable or certified standard reference materials available up to now, multistep procedures are still necessary. They must combine decomposition, preconcentration and determination methods in an optimal way to minimize systematic errors. The state-of-the-art of such multistep procedures in extreme elemental trace analysis will also be presented.

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über die zukünftige Entwicklung der Spurenelementanalyse in biotischen Matrices

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Dedicated to Prof. Dr. W. Fresenius in gratitude on the occasion of his 75th birthday.     

Modern analytical chemistry education in Europe at university level

Stimulated by the rapid growth of analytical chemistry in research and development, a discussion on the past, present and future role of analytical chemistry as part of the chemistry curricula at European universities is presented in this article. The present status of analytical chemistry curricula is described, based on a recent investigation of the Working Party on Analytical Chemistry (WPAC) of the Federation of European Chemical Societies (FECS) at 229 European universities. The evaluation of the questionnaires has been done for all institutions together, as well as for the 119 institutions with a separate chair or department of analytical chemistry and the 110 institutions without such a separate chair. The distribution of teaching hours between the classical and modern fields is generally significantly better and more flexible to new developments (like chemometrics, environmental and material sciences) at institutions with an own chair of analytical chemistry. This survey is also a key to earlier reviews on education in analytical chemistry stimulated and published by WPAC-members.     

CRISPR‐Cas: From the Bacterial Adaptive Immune System to a Versatile Tool for Genome Engineering

The field of biology has been revolutionized by the recent advancement of an adaptive bacterial immune system as a universal genome engineering tool. Bacteria and archaea use repetitive genomic elements termed clustered regularly interspaced short palindromic repeats (CRISPR) in combination with an RNA‐guided nuclease (CRISPR‐associated nuclease: Cas) to target and destroy invading DNA. By choosing the appropriate sequence of the guide RNA, this two‐component system can be used to efficiently modify, target, and edit genomic loci of interest in plants, insects, fungi, mammalian cells, and whole organisms. This has opened up new frontiers in genome engineering, including the potential to treat or cure human genetic disorders. Now the potential risks as well as the ethical, social, and legal implications of this powerful new technique move into the limelight.     

Computer-Assisted Solution of Chemical Problems—The Historical Development and the Present State of the Art of a New Discipline of Chemistry

The topic of this article is the development and the present state of the art of computer chemistry, the computer-assisted solution of chemical problems. Initially the problems in computer chemistry were confined to structure elucidation on the basis of spectroscopic data, then programs for synthesis design based on libraries of reaction data for relatively narrow classes of target compounds were developed, and now computer programs for the solution of a great variety of chemical problems are available or are under development. Previously it was an achievement when any solution of a chemical problem could be generated by computer assistance. Today, the main task is the efficient, transparent, and non-arbitrary selection of meaningful results from the immense set of potential solutions—that also may contain innovative proposals. Chemistry has two aspects, constitutional chemistry and stereochemistry, which are interrelated, but still require different approaches. As a result, about twenty years ago, an algebraic model of the logical structure of chemistry was presented that consisted of two parts: the constitution-oriented algebra of be- and r-matrices, and the theory of the stereochemistry of the chemical identity group. New chemical definitions, concepts, and perspectives are characteristic of this logic-oriented model, as well as the direct mathematical representation of chemical processes. This model enables the implementation of formal reaction generators that can produce conceivable solutions to chemical problems—including unprecedented solutions—without detailed empirical chemical information. New formal selection procedures for computer-generated chemical information are also possible through the above model. It is expedient to combine these with interactive methods of selection. In this review, the Munich project is presented and discussed in detail. It encompasses the further development and implementation of the mathematical model of the logical structure of chemistry as well as the experimental verification of the computer-generated results. The article concludes with a review of new reactions, reagents, and reaction mechanisms that have been found with the PC-programs IGOR and RAIN.     

The Royal Society of Chemistry and the delivery of chemistry data repositories for the community

Since 2009 the Royal Society of Chemistry (RSC) has been delivering access to chemistry data and cheminformatics tools via the ChemSpider database and has garnered a significant community following in terms of usage and contribution to the platform. ChemSpider has focused only on those chemical entities that can be represented as molecular connection tables or, to be more specific, the ability to generate an InChI from the input structure. As a structure centric hub ChemSpider is built around the molecular structure with other data and links being associated with this structure. As a result the platform has been limited in terms of the types of data that can be managed, and the flexibility of its searches, and it is constrained by the data model. New technologies and approaches, specifically taking into account a shift from relational to NoSQL databases, and the growing importance of the semantic web, has motivated RSC to rearchitect and create a more generic data repository utilizing these new technologies. This article will provide an overview of our activities in delivering data sharing platforms for the chemistry community including the development of the new data repository expanding into more extensive domains of chemistry data.     

Development of synthetic double helical polymers and oligomers

There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical counterparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5195–5207, 2009     

Applications of Laser-Enhanced Ionization In Analytical Chemistry

Various applications of laser-enhanced ionization (LEI) in analytical chemistry are reviewed. This technique was applied to determine some physical quantities associated with a flame through development of an appropriate model. Determinations of flame temperature and atomization efficiency of an element in the flame are examples. As trace analysis is an important application of this technique, we compare the ion yield induced in a two-step LEI with that in a one-step LEI. The factors governing the ion enhancement via two-step excitation are examined in order to make efficient use of the two-step LEI apparatus. A novel technique was designed to couple flow-injection analysis to a conventional LEI device; in this manner, electrical interference, a severe problem inherent in LEI, was successfully removed.     

新型量子点基分子印迹荧光传感器在快速检测中的应用

作为一种新型荧光纳米材料,量子点具有十分优异的光学特性,是分析化学、生物科学、医学等领域研究的热点标记材料.分子印迹聚合物是能够进行特异性识别和选择性吸附的"仿生"材料,它易于制备且具有较好的重现性和稳定性,因而分子印迹技术已成为具有广阔应用前景的识别技术.量子点基分子印迹荧光传感器结合了量子点和分子印迹技术的优势,由...