Soluble polymeric ligands for metal complexation and catalyst recovery

Soluble polymers that bind metals and that in turn can be separated from other components of a reaction mixture are described. The polymers used include derivatives of acrylamides, acrylates, polystyrene and other polymers. Both sequestration of trace metals and recovery of homogeneous catalysts is discussed. Separation methods using liquid/liquid mixtures that are monophasic during a reaction but biphasic during a separation are emphasized.     

High performance analytical characterization of refractory metals

It is first shown what effects trace impurities generally exert on metal properties and why trace analysis is essential to modern applications of refractory metals in today's high technology. The effect of trace impurities in metals on complex systems like microelectronic components is also discussed.It is then shown, what principal analytical requirements are mandatory for trace characterization of refractory metals at levels of rising purity (4 N to 6 N). A survey of analytical methods for trace and ultratrace characterization of refractory metals is given including the following methods: flame and graphite furnace atomic absorption spectrometry, ICP and DCP-atomic emission spectrometry, X-ray fluorescence spectrometry, activation analysis, mass spectrometric methods, especially SIMS and GDMS.     

Some Aspects on Preconcentration for Neutron Activation Analysis

A preconcentration method incorporated with neutron activation analysis was developed for the accurate determination of trace metals in biological and environmental samples. Bismuth diethyldithiocarbamate, thallium diethyldithiocarbarnate, and ammonium pyrrolidinedithiocarbamate were used as the preconcentration agents for three groups of metals. Trace metals were enriched and interfering elements such as Na, Br, P. K. etc. were removed simultaneously during the preconcentration process so that the sensitivity for each metal was greatly improved. Optimal conditions for sample digestion, group preconcentration of trace metals and neutron activation analysis of biological and environmental samples were discussed.     

Voltammetric methods for speciation analysis of trace metals in natural waters

Trace metals play an important role in the regulation of primary productivity and phytoplankton community composition. Metal species directly affects the biogeochemical cycling processes, transport, fate, bioavailability and toxicity of trace metals. Therefore, developing powerful methods for metal speciation analysis is very useful for research in a range of fields, including chemical and environmental analysis. Voltammetric methods, such as anodic stripping voltammetry (ASV) and competing ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV), have been widely adopted for speciation analysis of metals in different natural aquatic systems. This paper provides an overview of the theory of voltammetric methods and their application for metal speciation analysis in natural waters, with a particular focus on current voltammetric methods for the discrimination of labile/inert fractions, redox species and covalently bound species. Speciation analysis of typical trace metals in natural waters including Fe, Cu, Zn, Cd, and Pb are presented and discussed in detail, with future perspectives for metal speciation analysis using voltammetric methods also discussed. This review can elaborate the particular knowledge of theory, merits, application and future challenge of voltammetric methods for speciation analysis of trace metals in natural waters.     

Determination of trace heavy metals in waters by atomic-absorption spectrometry after preconcentration by liquid-phase polymer-based retention

A new method for the determination of metals in waters by flame atomic-absorption spectrometry is described. The metals are retained by water-soluble polymers in a membrane filtration cell and the factors which influence their determination are discussed. The method has been applied to the determination of Ni, Cu, Zn, Hg and Cd in drinking and river water with poly(ethyleneimine) and its thiourea derivative as complexing polymers. The metals were determined in the aqueous concentrate after a 250-fold preconcentration by 2% polymer solution at pH 7. The metal recoveries were at least 92%, and the limits of detection (ng/mg) were 0.012 for Cu, 0.006 for Zn, 0.03 for Ni, 0.004 for Cd and 0.0001 for Hg (cold vapour method). When a new type of membrane filtration cell is used even higher preconcentration factors can be achieved and lower concentrations can be determined.     

Determination of trace metals in sea water by chelex-100 or solvent extraction techniques and atomic absorption spectrometry

Determinations of cadmium, lead, nickel, copper and zinc in sea water are discussed. Two different methods of preconcentration are compared: the trace metals are preconcentrated either by extraction with ammonium pyrrolidinedithiocarbamate/diethylammonium diethyldithiocarbamate into freon followed by back-extraction into nitric acid, or by collection on a Chelex-100 resin followed by elution with nitric acid. Cd, Pb, Ni, and Cu are determined by graphite-furnace atomic absorption spectrometry, while zinc is determined by flame atomic absorption spectrometry. The comparison of methods shows that cadmium can be determined accurately whereas results for the other trace metals may be biased by reagent contamination in the Chelex-100 method. Recovery data are given for both methods of preconcentration. Filtering experiments with Chelex-100 method are described. Results are compared for sea-water samples preconcentrated immediately after sampling and some weeks after sampling, with only freezing for preservation. The present results are consistent with other recent work. The importance of blank values is discussed.     

Preconcentration of traces of silver and bismuth from cobalt and nickel and their nitrates, with activated carbon

A method is described for the preconcentration of trace metals Ag and Bi, present as impurities in high-purity cobalt and nickel metals and their nitrates. After the metal samples have been dissolved in nitric acid (or the salts in water) the trace elements are complexed with ammonium pyrrolidinedithiocarbamate (APDC). The sample solution is then filtered through a 2-cm filter paper coated with 50 mg of activated carbon, whereby the complexed trace metals are adsorbed on the activated carbon and separated from the matrix. The trace elements are dissolved off with nitric acid and determined by flame atomic-absorption spectrometry (AAS). The detection limits for the analysis of 10 g of metal samples and 50 g of the nitrate samples were 0.002-0.035 ppm Ag and 0.04 ppm Bi for the metal samples, and 0.0003-0.0004 ppm Ag and 0.004-0.005 ppm Bi for the nitrate samples. The coefficient of variation, in general, is 10-25% for Ag and 33% for Bi.     

Trace metal impurities in silica as a cause of strongly interacting silanols

Summary The paper describes nuclear activation analysis of several chromatographic grade silicas for the determination of trace metals. The effect of acid washing is described and the effect of trace metals on the acidity of surface silanols is discussed. A correlation has been found between the concentration of metal traces in the layer of silica adjacent to the surface and the concentration of strongly interacting sites.     

Chitin and chitosan as chromatographic supports and adsorbents for collection of metal ions from organic and aqueous solutions and sea-water

The rates of adsorption of several metal ions on chitin and chitosan in water and sea-water have been measured; chitin and chitosan are proposed as Chromatographic chelating supports. These natural polymers are also suitable for recovery of trace metals from sea-water.     

X-ray determination of traces of hafnium in zirconium metal or traces of zirconium in hafnium metal after separation by ion exchange

A method is proposed for the determination of traces of hafnium in zirconium metal or zirconium in hafnium metal. The trace metals are first separated from the matrix metals on an ion-exchange column and then determined by X-ray analysis.     

A Comparison of Methods for the Determination of Available Trace Metals in Sea Water

Abstract

Two methods for the determination of available trace metals CCd, Pb, and Cu) in sea water are compared. One method employs anodic stripping voltammetry at controlled pH (8.1, 5.3, and 2); the other method involves sample pretreatment with Chelex-100 resin before ASV analysis. Differences in the results are discussed in terms of the definition of available metal and differences in the analytical methods.     

Grundzüge der Deformationsprozesse in Metallen

The physical principles of our present understanding of the elastic, the anelastic, and the plastic deformation of metals are discussed. The following specific cases are considered in details.

1. Elastic deformation due to one of the following processes. Energy elasticity, vibrational entropy elasticity, anomalies in the elastic behaviour resulting from lattice instability or ferromagnetism. This behaviour is compared with the entropy and energy elasticity of polymers.
2. Anelastic deformation due to one of the following mechanisms. Difussion of solute atoms and/or point defects, dislocation relaxation, dislocation resonance interaction between dislocations and other lattice defects, migration of grain boundaries, phase boundaries or domain walls.
3. Plastic deformation of pure metals by cooperative shear, dislocation motion, mechanical twinning, martensitic transformations and by diffusion. The effect of alloying on these processes is discussed in the case of solid solutions, ordered alloys and precipitation hardened materials. The dominant deformation modes of polymers are different from those of metals because metals are formed by atoms with relatively isotropic interatomic forces, whereas polymers generally consist of long chains characterized by a strong anisotropy in chemical bonding. This difference makes the deformation stress of polymers and metals depend differently on temperature, pressure, and deformation rate. An other characteristic difference between the deformation of polymers and metals is that metals deform plastically, whereas a large fraction of the so-called plastic deformation of polymers is really anelastic.

     

水溶性高分子对激光热透镜分析的增强作用

本文研究了水溶性高分子对激光热透镜分析的增强作用。结果表明，水溶性高分子的加入，改变了测定体系的热物理特性和显色体系的微环境。不但提出了热透镜分析的灵敏度，而且增强了显色体系的稳定性。在水溶性高分子存在下，对土壤中水溶性磷及痕量碘进行了高灵敏度的测定。     

Chelating polymers and related supports for separation and preconcentration of trace metals

This review is concerned mainly with the applications of chelating polymeric resins for the separation and concentration of trace metals from oceans, rivers, streams and other natural systems. Commercially available resins, specially prepared polymers and a selection of other sorbents are described and their uses outlined. Special emphasis is placed on the preconcentration of uranium from sea-water.     

Gold and silver determination in Waters by SPHERON® Thiol 1000 preconcentration and ETAAS

A reliable procedure for the electrothermal atomic absorption spectrometry (ETAAS) determination of gold and silver in waters at trace level is described. The method is based on prior separation and preconcentration of the metals using a chelating sorbent SPHERON® Thiol 1000 after acidification of water samples (pH < 3) with nitric acid. Optimization of analytical variables during enrichment and ETAAS determination of the metals are discussed. The accuracy of the method is verified by analysis of certified reference materials. The limits of determinations based on 10 σ definition were 0.005 ng cm^?3 for Au and 0.02 ng cm^?3 for Ag. Precision of studied elements determination expressed by relative standard deviation varied in the range from 2.9 % to 16.4 %.     

A vidicon spectrometer and its application to the analysis of gold

A TV camera which is attached to a monochromator, is used for the photoelectric measurement of optical spectra. The properties of this detection system and its application to the analysis of trace metals in high purity gold with d.c. arc excitation are described. Problems which originate from this application are discussed and results are compared with those obtained with different analytical methods.     

Determination of trace elements in metals by atomic absorption spectrometry with introduction of solid samples into furnaces: An appraisal

The determination of trace elements in metals by atomic absorption spectrophotometry with introduction of solid samples into furnaces has been reviewed from the first paper in 1965 until the present day. The need for this type of analysis is considered along with other analytical techniques that can provide useful information. Early developments up to 1975 are presented and discussed but the main emphasis is on work undertaken during the past five years. Information is provided on homogeneity of samples, methods of calibration, accuracy, precision and limits of detection to show that this technique is the most convenient available for the determination of volatile trace elements in metals at concentrations less than 10 μg g⁻¹.     

The application of electrodeposition techniques to flameless atomic absorption spectrometry : Part IV. Separation and preconcentration on graphite

A new flameless atomic absorption technique for the determination of trace metals in a salt matrix is described. The elements to be determined are electrolyzed on to a graphite electrode, the exposed part of which is ground, and a portion of the graphite powder is finally analyzed directly by flameless atomic absorption in a graphite furnace. Many elements can be determined from a single electrochemical deposition. The graphite powder may also be stored for later control analysis. The effects of various experimental parameters are described. The method is applied to the determination of trace metals in commercial salts.     

Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis

The analysis of seawater for trace metals is important for pollution monitoring and better understanding of marine systems. The present paper describes an efficient preconcentration method for the determination of trace metals in seawater. Trace metals [Ni(II), Cu(II), Ga(III), Cd(II), Pb(II), and Bi(III)] in 1,000 mL of seawater sample were complexed with ammonium pyrrolidinedithiocarbamate and sorbed onto silica particles covered with cetyltrimethylammonium chloride. After the addition of sodium dodecyl sulfate, the particles were floated to the solution surface by bubbling and then collected by suction. The trace metals were desorbed with dilute nitric acid and determined by inductively coupled plasma–mass spectrometry. The rapid 200-fold preconcentration was demonstrated with certified seawater samples.     

Application of adsorptive stripping voltammetry (AdSV) for the analysis of trace metals in brine

Summary Routine analysis of brine for trace metals is important for safe and economical production in the alkali chloride electrolysis. As opposed to many spectroscopic techniques, trace metal determination by adsorptive stripping voltammetry (AdSV) is shown to be performed directly in brine. With minimal sample preparation chromium(VI), iron(III), nickel(II), cobalt(II), titanum(IV), manganese(II), molybdenum(VI) and vanadium(V) can be determined within minutes. The influence of parameters such as pH-value, supporting electrolyte solution, concentration of complexing reagents and possible interferents are investigated for optimal experimental conditions. Minimum detection limits are less than 5 ng/g for all trace metals except 1 ng/g for chromium(VI), cobalt(II) and molybdenium(VI) for 40 s adsorption periods with precisions of better than 7%. AdSV with linear or differential pulse scan is discussed.