The environmental challenge for analytical sciences

In this paper the major elements of the European Union’s policy on environmental protection and sustainable development and the resulting challenges for analytical sciences are presented. The priority issues dealt with are:

Russian doctors of sciences working in analytical chemistry

Statistical data on Doctors of Sciences in Russian analytical chemistry are given.     

Carbon black,multiwall carbon nanotubes,expanded graphite and functionalized graphene flame retarded polypropylene nanocomposites

Herein, we examine the influence of adding functionalized graphene (FG), distinct expanded graphites and carbon nanofillers such as carbon black and multiwall carbon nanotubes on mechanical properties, morphology, pyrolysis, response to small flame and burning behavior of a V‐2 classified flame‐retarded polypropylene (PP). Among carbon fillers, FG and multilayer graphene (MLG) containing fewer than 10 layers are very effectively dispersed during twin‐screw extrusion and account for enhanced matrix reinforcement. In contrast to the other fillers, no large agglomerates are detected for PP‐FR/FG and PP‐FR/MLG, as verified by electron microscopy. Adding FG to flame‐retardant PP prevents dripping due to reduced flow at low shear rates and shifts the onset of thermal decomposition to temperatures 40°C higher. The increase in the onset temperature correlates with the increasing specific surface areas (BET) of the layered carbon fillers. The reduction of the peak heat release rate by 76% is attributed to the formation of effective protection layers during combustion. The addition of layered carbon nanoparticles lowers the time to ignition. The presence of carbon does not change the composition of the evolved pyrolysis gases, as determined by thermogravimetric analysis combined with online Fourier‐transformed infrared measurements. FG and well‐exfoliated MLG are superior additives with respect to spherical and tubular carbon nanomaterials. Copyright © 2013 John Wiley & Sons, Ltd.     

Electronic conduction in polymers, carbon nanotubes and graphene

In the years since the discovery of organic polymers that exhibited electrical conductivities comparable to some metals, other novel carbon-based conductors have been developed, including carbon nanotubes and graphene (monolayers of carbon atoms). In this critical review, we discuss the common features and the differences in the conduction mechanisms observed in these carbon-based materials, which range from near ballistic and conventional metallic conduction to fluctuation-assisted tunnelling, variable-range hopping and more exotic mechanisms. For each category of material, we discuss the dependence of conduction on the morphology of the sample. The presence of heterogeneous disorder is often particularly important in determining the overall behaviour, and can lead to surprisingly similar conduction behaviour in polymers, carbon nanotube networks and chemically-derived graphene (122 references).     

第49届分析科学暨光谱与其他谱学国际会议

本届国际会议于2003年6月1日～4日在加拿大Ottawa市召开,由该市Carleton大学主办。大会报告有2个:(1)加拿大Windsor大学RFAroca,表面增强共振拉曼与单分子谱图,获Herzberg奖;(2)加拿大Ionalytics公司RGuevre mont,高场不对称波形离子迁移谱(FAIMS)的发展,获Barringer研究奖。专题研讨会共16个。(1)感耦等离子体质谱联用技术的多用途性及其新方向;(2)毛细管电泳与其相关技术;(3)红外、拉曼与核磁共振谱;(4)水溶液的振动光谱;(5)人类健康和环境中的金属;(6)光谱学与医学的机遇-由崇高至荒诞;(7)以激光为基础的分析技术———激光诱…     

Carbon nanotubes paste electrode

The performance of carbon nanotubes paste electrodes (CNTPE) prepared by dispersion of multi-wall carbon nanotubes (MWNT) within mineral oil is described. The resulting electrode shows an excellent electrocatalytic activity toward ascorbic acid, uric acid, dopamine, 3,4-dihydroxyphenylacetic acid (dopac) and hydrogen peroxide. These properties permit an important decrease in the overvoltage for the oxidation of ascorbic acid (230 mV), uric acid (160 mV) and hydrogen peroxide (300 mV) as well as a dramatic improvement in the reversibility of the redox behavior of dopamine and dopac, in comparison with the classical carbon (graphite) paste electrodes (CPE). The substantial decrease in the overvoltage of the hydrogen peroxide reduction (400 mV) associated with a successful incorporation of glucose oxidase (GOx) into the composite material, allow the development of a highly selective and sensitive glucose biosensor without using any metal, redox mediator or anti-interference membrane. No interference was observed at −0.100 V even for large excess of ascorbic acid, uric acid and acetaminophen. A linear response up to 30 mM (5.40 g l⁻¹) glucose with a detection limit of 0.6 mM (0.11 g l⁻¹) were obtained with the CNTPE modified with 10% w/w GOx. Such an excellent performance of CNTPE toward hydrogen peroxide, represents a very good alternative for developing other enzymatic biosensors.     

Carbon nanotubes as nanocarriers in medicine

Carbon nanotubes (CNTs) possess outstanding properties and a unique physicochemical architecture, which may serve as an alternative platform for the delivery of various therapeutic molecules. This review focuses on recent progress in the field of CNTs for biomedical applications. After a short, general physico-chemical introduction to CNTs, we introduce different methods for CNT surface modification, facilitating their dispersions in physiological solutions, on the one hand, and binding a wide range of molecules or drug-loaded liposomes, on the other. We summarize imaging evidences on the structure of CNT-drug conjugates and their relevant uptake mechanisms by the cell. Lastly, we review current repots on CNT toxicity and new developments in CNT-based medical applications: photo-thermal therapy, drug delivery and gene therapy.     

Trends in analytical atomic and molecular mass spectrometry in biology and the life sciences

Trends in analytical atomic and molecular mass spectrometry (MS) are reviewed here with an emphasis on problems related to biology and the life sciences. The move towards novel desorption/ionization techniques including matrix-free laser desorption-ionization MS and recent technological developments in MS imaging of elements, small molecules, and proteins are discussed. Recent developments in the interfacing of microfluidics with MS are also reviewed. Metabolic profiling, evaluation of biomarkers, pharmaceutical metabolite identification, and many related topics are addressed.     

Carbon nanotubes: Solid-phase extraction

Since the first report in 1991, carbon nanotubes (CNTs) have shown great possibilities for a wide variety of processes and applications, which include their use as electrodes, sensors (gas, enzymatic, etc.), nanoprobes, electronic materials, field emitters, etc. The combination of structures, dimensions and topologies has provided physical and chemical attractive properties that are unparalleled by most known materials. Their applications have also reached the Analytical Chemistry field in which CNTs are being used as matrices in matrix assisted laser desorption ionization, stationary phases in either gas chromatography, high performance liquid chromatography or capillary electrochromatography, also as pseudostationary phases in capillary electrophoresis, etc. as well as new solid-phase extraction (SPE) materials. Concerning this last application the number of works has considerably increased in the last five years. This review article pretends to focus on the most important features and different applications of SPE using CNTs (including matrix solid-phase dispersion and solid-phase microextraction) covering articles published since their introduction up to now (September 2009).     

Carbon nanotubes for electrochemical biosensing

The aim of this review is to summarize the most relevant contributions in the development of electrochemical (bio)sensors based on carbon nanotubes in the last years.Since the first application of carbon nanotubes in the preparation of an electrochemical sensor, an increasing number of publications involving carbon nanotubes-based sensors have been reported, demonstrating that the particular structure of carbon nanotubes and their unique properties make them a very attractive material for the design of electrochemical biosensors.The advantages of carbon nanotubes to promote different electron transfer reactions, in special those related to biomolecules; the different strategies for constructing carbon nanotubes-based electrochemical sensors, their analytical performance and future prospects are discussed in this article.     

Method validation in analytical sciences: discussions on current practice and future challenges

Accreditation and Quality Assurance - Eurachem held a workshop on method validation in analytical sciences in Gent, Belgium, on 9–10 May 2016. A summary of the working group discussions is...     

Carbon nanotubes for in vivo cancer nanotechnology

The latest progress of using carbon nanotubes (CNTs) for in vivo cancer nanotechnology is reviewed. CNTs can be functionalized by either covalent or non-covalent chemistry to produce functional bioconjugates for many in vivo applications. In vivo behaviors and toxicology studies of CNTs are summarized, suggesting no significant toxicity of well functionalized CNTs to the treated mice. Owing to their unique chemical and physical properties, CNTs, especially single-walled carbon nanotubes (SWNTs), have been widely used for various modalities of in vivo cancer treatment and imaging. Future development of CNT-based nanomedicine may bring novel opportunities to cancer diagnosis and therapy.     

Carbon nanotori and nanotubes encapsulating carbon atomic-chains

In this paper we investigate toroidal carbon nanotubes (carbon nanotori) encapsulating a single symmetrically located carbon atomic-chain. The interaction energy of the carbon chain is found from the Lennard-Jones potential using the continuous approach which assumes that atoms are uniformly distributed over the surface of the torus and the line of the circular chain with constant atomic surface and line densities, respectively. We assume that the chain is centrally located and that the carbon nanotorus is synthesized from a perfect carbon nanotube. We predict that the carbon chain can be encapsulated inside the carbon nanotorus when the cross-sectional radius \(r\) of the nanotorus is larger than 3.17 Å. At the minimum energy, a value of the toroidal radius \(R\) lies between 3.6 and 3.7 Å corresponding to each value of \(r\) . We also investigate the energy of carbon chains inside carbon nanotubes, which are (4,4), (5,5) and (10,0) tubes. We find that they are energetically favourable in (5,5) and (10,0) tubes, but not in a (4,4) tube, because it is geometrically too small, and these results are in agreement with existing studies. The same results for these three carbon nanotubes can also be obtained from the corresponding nanotori when \(R\) goes to infinity.     

Symmetries and fuzzy symmetries of Carbon nanotubes

Carbon nanotubes (CNTs) possess the fuzzy cylinder group characteristic. Comparing with the linear and planer molecules, there are included the fuzzy symmetry of the cylinder screw rotation (CSR) in relation to some higher ( $>$ 2) fold rotation axis. The CSR may be noted as the product of translation (T) and rotation (C). The CSR symmetry will be imperfect owing to the introduction of T. As the extent of whole translation is more than 10-fold than every time, the membership function of CNT in relation to CSR will be more than about 0.9, and such CNT may be seems as provided with the perfect CSR symmetry. For analyse the CNT we may using the cylindrical orthogonal curvilinear coordinate system. The MO ought to be provided with a pure irreducible representation, but the component of symmetry adapted atomic orbital (SA-AO) set may be not sole, and it is difficult to get and analyse the ‘pure’ $\uppi $ -MO. There are some various AO (1S-, 2S-, 2Pz-, 2Pr-, 2Pt of carbon and 1S- for hydrogen)-set components in a certain MO. For the CNT with the same diameter and different length, the MO energy and the SA-AO component versus the relative serial number will be with the similar distribution. The MOs of CNT with higher fold C symmetry may be provided with two-dimensional irreducible representation. For the molecular skeleton and the MO which belong to one-dimensional irreduable representation, their membership functions in relation to the CSR with the product of the same T and different C would be equality. However, for the single MO which belong to two-dimensional irreducible representation that may be somewhat difference. The torus carbon nanotube (TCNT) may be provided the symmetry with the torus group and torus screw rotation (TSR), such symmetry would be or near be not rare in nature. Similar as the planer rectangle (called as the MH rectangle) may composed the Hückel- or Möbius-strip band, the more MH rectangles in the cylinder CNT may be composed the more Hückel- or Möbius-strip bands, such strip bands set may be called strip tube, meanwhile the fuzzy CSR symmetry will be transform to the perfect TSR symmetry. The intersecting line (Z-axis) of the MH rectangles will be transform to the common basic circle of these strip bands. When the CNT to form a TCNT, as one of the MH rectangle form a Hückel-strip band or an $n(t)$ -twisted Möbius-strip band itself, the other MH rectangle will be form the strip band with the same topological structure synchronously, and the set of these strip bands may be called the strip tube. The boundary closed curves of the strip band may reflect the torus group symmetrical characteristic of the relative strip bands. The closed curve may correspond to a cyclical group or subgroup. The number of carbon atomic pairs on the closed curve denoted the order of such group or subgroup. As the CNT to form the TCNT, it is different as the single MH rectangle, they may be to form the fractal-twisted Möbius-strip tube synchronously, in which the single Möbius-strip band may be formed from more one MH rectangle, however, single MH rectangle may enter into only one Möbius-strip band. As the hetero-CNT with the helical-structure distribution, such hetero-CNT may form the relative torus hetero-CNT, but according to the continuity of CNT tube side, a certain twisted to form Möbius-strip tube may often be required. There is some interaction between the distributional helical-structure and twisting way, such interaction may touch to the degree of tightness of the helical-structure distribution in torus hetero-CNT.     

Principles of analytical calibration/quantification for the separation sciences

Calibration is an operation whose main objective is to know the metrological status of a measurement system. Nevertheless, in analytical sciences, calibration has special connotations since it is the basis to do the quantification of the amount of one or more components (analytes) in a sample, or to obtain the value of one or more analytical parameters related with that quantity. Regarding this subject, the aim of analytical calibration is to find an empiric relationship, called measurement function, which permits subsequently to calculate the values of the amount (x-variable) of a substance in a sample, from the measured values on it of an analytical signal (y-variable). In this paper, the metrological bases of analytical calibration and quantification are established and, the different work schemes and calibration methodologies, which can be applied depending on the characteristic of the sample (analyte+matrix) to analyse, are distinguished and discussed. Likewise, the different terms and related names are clarified. A special attention has been paid to those analytical methods which use separation techniques, in relation with its effect on calibration operations and later analytical quantification.     

Carbon nanotubes in benzene: internal and external solvation

The structure and dynamics of benzene inside and outside of single-walled carbon nanotubes (SWNTs) in the (n,n) armchair configuration are studied via molecular dynamics computer simulations. Irrespective of the nanotube diameter, benzene molecules form cylindrical solvation shell structures on the outside of the nanotubes. Their molecular planes near the SWNTs in the first external solvation shell are oriented parallel to the nanotube surface, forming a π-stacked structure between the two. By contrast, the benzene distributions in the interior of the SWNTs are found to vary markedly with the nanotube diameter. In the case of the (7,7) and (8,8) nanotubes, internal benzene forms a single-file distribution, either in a vertex-to-vertex (n = 7) or face-to-face (n = 8) orientation between two neighboring molecules. Inside a slightly wider (9,9) nanotube channel, however, a cylindrical single-shell distribution of benzene arises. A secondary solvation structure, which begins to appear inside (10,10), develops into a full structure separate from the first internal solvation shell in (12,12). The ring orientation of internal benzene is generally parallel to the nanotube wall for n = 9-12, while it becomes either slanted with respect to (n = 7), or perpendicular to (n = 8), the nanotube axis. The confinement inside the small nanotube pores exerts a strong influence on the dynamics of benzene. Both translational and rotational dynamics inside SWNTs are slower and more anisotropic than in liquid benzene. It is also found that reorientational dynamics of internal benzene deviate dramatically from the rotational diffusion regime and change substantially with the nanotube diameter.     

Present and future applications of carbon nanotubes to analytical science

This article reviews the impact of carbon nanotubes on analytical science, and the main current and future applications of carbon nanotubes in this field. Given that it is necessary to solubilize carbon nanotubes for many applications, we consider the procedures developed to achieve this. The use of carbon nanotubes in analytical chemistry as a target analyte and as an analytical tool is also discussed. Chromatographic and electrophoretic methods used to separate and characterize carbon nanotubes are presented. The use of carbon nanotubes as an analytical tool in filters and membranes, as sorbent material for solid phase extraction, in electrochemical (bio)sensors, and in separation methods is discussed. It is clear that while nanotubes are being tested for use in many different fields, their truly enormous potential has yet to be realized in analytical chemistry.Dedicated to the memory of Wilhelm Fresenius     

Dispersion of multi-wall carbon nanotubes in polyhistidine: Characterization and analytical applications

We report for the first time the use of polyhistidine (Polyhis) to efficiently disperse multiwall carbon nanotubes (MWCNTs). The optimum dispersion MWCNT–Polyhis was obtained by sonicating for 30 min 1.0 mg mL⁻¹ MWCNTs in 0.25 mg mL⁻¹ Polyhis solution prepared in 75:25 (v/v) ethanol/0.200 M acetate buffer solution pH 5.00. The dispersion was characterized by scanning electron microscopy, and by cyclic voltammetry and amperometry using ascorbic acid as redox marker. The modification of glassy carbon electrodes with MWCNT–Polyhis produces a drastic decrease in the overvoltage for the oxidation of ascorbic acid (580 mV) at variance with the response observed at glassy carbon electrodes modified just with Polyhis, where the charge transfer is more difficult due to the blocking effect of the polymer. The reproducibility for the sensitivities obtained after 10 successive calibration plots using the same surface was 6.3%. The MWCNT-modified glassy carbon electrode demonstrated to be highly stable since after 45 days storage at room temperature the response was 94.0% of the original. The glassy carbon electrode modified with MWCNT–Polyhis dispersion was successfully used to quantify dopamine or uric acid at nanomolar levels, even in the presence of large excess of ascorbic acid. Determinations of uric acid in human blood serum samples demonstrated a very good correlation with the value reported by Wienner laboratory.