Chemical physics of dispersed material surfaces

Adsorption and chemisorption processes involving hydroxy groups and coordinated water molecules on the surface of silica are discussed on the basis of information derived from infrared spectra, ESCA and thermogravimetric data. The formation of strongly adsorbed surface complexes is described in terms of changes in coordination number of silicon atoms and the concomitant lowering of surface tension.     

Chemical control of peptide material phase transitions

Progressive solute-rich polymer phase transitions provide pathways for achieving ordered supramolecular assemblies. Intrinsically disordered protein domains specifically regulate information in biological networks via conformational ordering. Here we consider a molecular tagging strategy to control ordering transitions in polymeric materials and provide a proof-of-principle minimal peptide phase network captured with a dynamic chemical network.

Substrate initiated assembly of a dynamic chemical network.     

Chemometrics for material analysis

Chemometric methods are described that provide effective means to enhance the information of analytical methods in material analysis and to enable knowledge engineering tools to be applied within the field. Typical applications are outlined for depth-profile analysis, for pattern recognition on ceramic systems as well as for the utilization of expert systems.     

Pseudocyclic activation analysis of geological material

A pseudocyclic activation system has been installed at the Ecole Polytechnique SLOWPOKE reactor. It is shown that, for analyses of geological material with short-lived nuclides, pseudocyclic activation is preferable to cyclic activation because it avoids the buildup of²⁸Al activity. The total experiment time is reasonable when several sample are analyzed. The possibilities of the technique were illustrated with the analysis of nine well-known silicate rocks. With n cycles an improvement in precision approaching n^1/2 was achieved. The detection limits in silicate rocks were determined for 18 elements using thermal and epithermal irradiation and 25 cycles.     

Chemical analysis and medicine

The main directions in using chemical analysis in medicine are considered, such as diagnosis of diseases, sanitation and hygiene control, doping control, direct identification of microorganisms, DNA-analysis, etc.     

Thermogravimetric analysis of a polycyanurate thermosetting material

The thermal degradation of a fully cured polycyanurate thermosetting material was examined by monitoring the mass loss at various temperatures ranging from 200 to 220C. The effect of the copper naphthenate catalyst, generally used to facilitate curing, is also studied. A decrease in weight is observed with increasing time at elevated temperatures in the systems containing copper naphthenate, with the onset of degradation occurring sooner with higher concentrations of the copper compound. The apparent activation energy for degradation is 220±30 kJ mol^–1.The support of the National Science Foundation in the form of an equipment grant (CTS 9500318) is gratefully acknowledged.     

Chemical analysis and water quality

Summary The development of analytical standards for water quality is considered on an historical basis and the present day position reviewed in relation to other bases for quality assessment. The analytical aspects have developed strongly, and continuously, during the past hundred years for fresh water; and there are now many well established compendia of analytical methods, based on collaborative and other cooperative studies. By contrast the standards and analytical methods for sea water have only developed much more recently. Some of the particular analytical problems which arise in the examination of fresh water, rivers and oceans will be considered, together with questions of the automation of methods.Analytical standards still play a very important role in the assessment of water quality. However, there is now a need for quicker methods, automatic methods and in some cases approximate methods which may not have the accuracy and precision of the more detailed procedures but which give results of sufficient accuracy for specific purposes.

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Chemische Analyse und Wasserqualität

Zusammenfassung Die Entwicklung analytischer Standards zur Beurteilung der Wasserqualit ät wird auf historischer Grundlage betrachtet und die gegenwärtigen Verhältnisse werden in Beziehung zu anderen Kriterien der Qualitätsbeurteilung diskutiert. Für Süßwasser haben sich die Methoden während der letzten hundert Jahre kontinuierlich weiter entwickelt und es existieren zahlreiche gut eingeführte Handbücher und Sammelwerke. Auf dem Gebiet der Meereswasseranalyse hat die Entwicklung jedoch erst viel später eingesetzt. Einige spezielle analytische Probleme, die bei der Wasseruntersuchung auftreten, werden zusammen mit Fragen der Automation erörtert.Bei der Beurteilung der Wasserqualität spielen analytische Standards immer noch eine sehr wichtige Rolle. Es werden allerdings gegenwärtig schnellere und automatisierte Methoden benötigt, sowie auch angenäherte Verfahren, die vielleicht nicht die Reproduzierbarkeit und Genauigkeit der eingehenderen Methode aufweisen, jedoch für spezielle Zwecke ausreichende Ergebnisse liefern.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Chemical analysis of norrisolide-induced Golgi vesiculation

The chemical origin of the norrisolide-induced irreversible Golgi vesiculation was studied using a variety of norrisolide probes. This natural product was found to bind to a receptor on the Golgi membranes using the perhydroindane core fragment as the recognition element. The acetylated gamma-lactol-gamma-lactone side chain of norrisolide is essential for the irreversible Golgi vesiculation and can be replaced by other electrophilic motifs without loss of biological function. In particular, compound 10 reproduces the cellular phenotype of the natural product.     

Chemical analysis of vanadium pentoxide catalysts

Reliable procedures are described for the analysis of alkali metal sulphate-promoted vanadium pentoxide catalysts supported on silica gel. Vanadium and alkali metals are determined by flame atomic absorption spectrometry in suitable dilutions of solutions obtained by digestion with sulphuric and hydrofluoric acids. “Free acidity” is determined by dissolution of the samples in alkali and back-titration with acid ; corrections for V₂0₅ acidity are included. Relative standard deviations are about 2.5% for metal contents of3–5%($\text{w}\text{w}$).     

Chemical and instrumental analysis of ferrites

More than thirty years since the manufacture of the first commercial ferrites, research and development efforts continue to produce ferrites with enhanced performance and new applications. Analytical chemistry has maintained a substantial role in the ferrite industry in the characterization of both raw materials and products, and the analytical literature of ferrites has grown accordingly. The continuing importance of ferrites to the electronic device industry requires further development of analytical methods suitable for characterization of ferrites so that their chemical composition may be related to performance and to the manufacturing processes used. As modem analytical techniques have been developed, their application to the characterization of ferrites and the detection of heterogeneity in these materials is increasing.     

Chemical sensors for environmental analysis

Chemical sensors for environmental monitoring are under active development but at the moment are of only limited value. However some fiber-optical sensor systems combined with opto-electronics and lasers have the potential to fulfil the legal requirements in monitoring environmentally relevant analytes in the ppt-range. The principles of sensors, and new developments reported in the literature or from our own research are discussed.     

Chemical analysis through atomic ionoluminescence

An account is given of the principle of optical microanalysis of the surface of a metallic or insulating solid through atomic ionoluminescence. Essentially, this method involves bombarding the surface to be studied with high-velocity positive ions, and recording the local emission of light resulting from the de-excitation of the pulverized atoms on the surface of the target. Two original and complementary instruments are described: an optical microanalyser and an ionprobe microanalyser; examples of possible applications are given, followed by a discussion of the performances and potentials of these systems, which are open to still further refinements.     

Preparation and analysis of a marble reference material

A 7 kg stone of a Carrara marble was reduced to grains smaller than 100 m, mixed and homogeneized in order to prepare a marble reference material. The homogeneity was tested for 16 elements by instrumental neutron activation analysis (INAA). Through a one-way analysis of variance based on several analyses of each of 15 bottles and within the same bottle, it was concluded that the inter-bottle heterogeneity is not greater than the intra-bottle heterogeneity. Results on the concentration of major and trace elements in the marble reference material, obtained by different laboratories and different techniques, are given. The limestone certified reference material KALKSTEIN KH was used to evaluate measurement accuracy, to intercalibrate laboratories, and to provide compatibility of measurement data.     

Ultratrace and microdistribution analysis in material sciences

Summary All-rounders and experts are two basic types of scientists. A harmonic cooperation between these two groups is essential for today's large study groups engaged in materials development. Materials development programmes in many high-tech countries are major fields of research supported by special financial arrangements (e.g. COST, EURAM or BRITE-programmes in Europe). Modern materials development is not possible without analytical guidance. This is not always realized by all engaged partners and it is a main obligation of analytical chemists to make aware of the role of a potent materials characterization in relevant development programmes. This should be demonstrated in two essential relevant areas: a) Bulk trace and ultra trace analysis of metals. Many important metal properties are directly or indirectly influenced by trace elements. In complex systems like fusion reactors or microelectronic components, trace contents of even minor metal parts might decisively influence system properties. As refractory metals and their silicides gain rising importance in VLSI microelectronic applications, their ultratrace characterization becomes a major challenge. Essential progress was possible by the complementary application of mass-spectrometric methods. Latest results and a critical survey will be given, including GDMS, SIMS, SSMS, IDMS and ICP-MS.Surprisingly, however, highest sensitivities and best detection limits were recently achieved by a combination of trace-matrix separation procedures and final end determination with ICP-MS. This combination also proved to be the most economic and safest approach from the view point of accuracy and precision. b) The analytical characterization of discontinuities and heterogeneities in solid matter. Practical examples are again taken from the study of refractory and hard metals and ceramics. A survey is given as to the manifold effects, heterogeneities and discontinuities exert on modern high-tech materials: as a function of their average diameter, they can either strengthen the material (dispersion strengthening), or they can cause deterioration of material properties e.g. as points of crack initiation, by grain boundary embrittlement etc. Together with most important methods for detection and characterization of heterogeneities and discontinuities, their evaluation and possible prevention during materials fabrication are discussed and pertinent examples are given. The phenomena of heterogeneous particles and pores are elucidated in more detail.

Acronyms used

1 Abbreviations for European research programmes AGATA Advanced Gas Turbines for Automobiles - BRITE Basic Research for Industrial Technologies for Europe - COST Cooperation in Science and Technology - EURAM European Research Activities Programme on Materials 2 Abbreviations in the field of refractory metals technology ADM Ammonium-Di-Molybdate - APT Ammonium-Para-Tungstate - HP High Purity - MHC Molybdenum-based alloy containing 1.2% Hf and 0.1% C - NS Non-sag (tungsten, used for lamp filaments and evaporative metallization techniques) - ODS Oxide Dispersion Strengthened - RM Refractory Metal - TZM Molybdenum-base alloy containing 0.5% Ti, 0.08% Zr and 0.025% C - UHP Ultra High Purity - VLSI Very large scale integration - ZHM Molybdenum-base alloy containing 0.40% Zr, 1.2% Hf and 0.15% C 3 Analytical technique names AA Activation Analysis - AAS Atomic Absorption Spectrophotometry - AES Auger Electron Spectrometry or Atomic Emission Spectrometry (only used in this work where it is clear that Auger Electron Spectrometry is not meant) - EDX(RS) Energy Dispersive X-Ray Spectrometry - EELS Electron Energy Loss Spectrometry - EP(X)MA Electron Probe X-Ray Microanalysis - GDMS Glow Discharge Mass Spectrometry - GFAAS Graphite Furnace Atomic Absorption Spectrometry - ICP-OES, MS Inductively Coupled Plasma — Optical Emission Spectrometry, Mass Spectrometry - ID-MS Isotope Dilution — Mass Spectrometry - LAS Classical photometry (Liquid Absorption — Spectrophotometry) - LEED Low Energy Electron Diffraction - MS Mass Spectrometry - NAA Neutron Activation Analysis - OES Optical Emission Spectrometry - SEM Scanning Electron Microscopy - SIMS Secondary Ion Mass Spectrometry - SSMS Spark Source Mass Spectrometry - TEM Transmission Electron Microscopy - TMS Trace-Matrix Separation (procedure) - WLD(-XRS) Wave Length Dispersive — XRS - XR(F)S X-Ray (Fluorescence) Spectrometry     

Bulk material analysis using 14 MeV neutrons

There is considerable interest in bulk material analysis using energetic neutrons e.g. on-line coal analysis and down-hole logging. Recent work has indicated that an in-situ analysis of all the major elements of coal, using prompt capture and inelastic neutron scattering reactions, may be an operational possibility. The application of these techniques to oil well logging would allow the determination of lithology, porosity and oil and water saturation. Gamma-ray spectra arising from 14 MeV neutron bombardment of well characterised coal and fluid saturated rocks are presented. The gamma-ray intensities from both capture and scattering reactions are determined. Neutron transport modelling is used to evaluate the effect of variations in material content and the presence of trace neutron poisons. Predictions of carbon and oxygen scattering response are compared with the experimentally determined ratios.     

Stradivarius violins: Chemical analysis of wood

From the Editor-in-Chief

Stradivarius violins: Chemical analysis of wood     

Chemical modification of a cellulose-based material to improve its adsorption capacity for anionic dyes

A cellulosic material was modified to enhance its anionic dye adsorption capacity. The chemically modified cucumber peel was characterized by FTIR, SEM, TGA, XRD, proximate and ultimate analyses, and pH_zpc measurements, and was used for the removal of toxic textile dyes. The kinetic data followed the pseudo-first-order model. The isotherm data fitted to the Langmuir model giving maximum capacities of 95.24 and 129.87 mg g^?1 for Reactive Black 5 and Direct Blue 71, respectively. Thermodynamic parameters suggest that the process is spontaneous and endothermic. The recovery of the adsorbed dyes was achieved by NH₃ and NaOH solutions.