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Abstract  

Although potentially very useful as a screening tool, currently-applied “gross” alpha/beta analyses are often considered unreliable by the environmental monitoring community. We describe here an alternative approach based on direct counting of pressed soil “wafers” to estimate total alpha/beta activities. The system was calibrated using a series of natural soils and sediment standards with total α/β activities estimated by use of a combination of available certified values, equilibrium assumptions, and our own measurements. A set of 10 such standards that span a wide range of activities were prepared by thoroughly mixing several grams of selected NIST and IAEA natural matrix standards together with reagent grade cellulose in a 4∶1 sample-to-binder ratio and pressing in a 40-mm stainles steel die. The resulting wafers, assumed to be at infinite thickness for expected radionuclides, were counted in a gas flow proportional counter set for simultaneous α/β counting. Both the alpha and beta count rates increased in a linear, systematic manner with increasing total estimated activities. This technique should prove to be an inexpensive, simple, and waste-free approach for screening total radioactivity in soil samples.

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Abstract  

Betel nut chewing (Areca catechu), whether plain or wrapped insidea betel leaf quid together with other substances including tobacco,has been reported as a cause of the high incidence of oral and oesophagealcancers in Asian communities worldwide. Chewing of such substances resultsin the formation of nitrosamines, some of which may be diabetogenic to man.The incidence of Type 2 diabetes is particularly prevalent amongst Asian immigrantsliving in the UK and as part of a larger study we have analysed a number ofpopular betel nut based chewing materials to determine their elemental composition.Instrumental neutron activation analysis was used for determination of elementalconcentrations of short-lived radionuclides. Ag, Al, Br, Ca, Cl, Cu, Dy, K,Mg, Mn, Na, Ti, and V were detected, some of which are implicated in diabetes.Concentrations of these, except for Ag, Dy and Ti, are reported and comparedwith values found in betel-nut and chewing materials from Taiwan. It is indicatedthat for certain elements the amount ingested by betel-nut chewers may bea significant fraction of their daily dietary intake.

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Abstract  

The results from numerous intercomparison exercises and proficiency tests indicate that the measurement of 90Sr in solid environmental matrices poses a problem to many analysts. The causes of the observed scatter of analytical results are not well understood and therefore difficult to remedy. In order to assess the effect of various analytical operations and measurement routines on the quality of the 90Sr data, the IAEA's Analytical Control Services have organised a proficiency test using a mineral sample spiked at three different levels with known amounts of 90Sr. This proficiency test generated considerable interest from the radioanalytical community as a total of 192 sets of samples were distributed to 158 radioanalytical laboratories world-wide. The reported data were evaluated with respect to their relative bias against the reference value and with respect to their reported overall uncertainty. The major sources of bias leading to overestimated values are ineffective purification procedures, high background values and a lack of statistical control over background values. The major sources of bias leading to an underestimation are overestimated recovery factors in part due to failure to correct for stable Sr in the sample and possibly failure to correct for quenching in liquid scintillation counting. Preliminary results for a small randomly selected group of laboratories are presented.

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Abstract  

In April 2007 the new nuclear research reactor, OPAL, was opened at Lucas Heights in Sydney. OPAL is a 20 MW open pool light water reactor with a heavy water reflector vessel and contains a cold neutron source. It is a multi-purpose facility for radioisotope production, irradiation services and neutron beam research. The OPAL design includes purpose-built facilities for instrumental neutron activation analysis (INAA) and delayed neutron activation analysis (DNAA). For INAA there is a short residence time facility in a neutron flux of around 2·1013 cm−2·s−1 and a number of long residence time facilities providing fluxes from 3·1012 to 1·1014 cm−2·s–1. The flux at the short residence time DNAA facility is around 6·1012 cm−2·s−1. The main focus for INAA at OPAL is the research community, meeting the needs of a wide range of disciplines, including mineral processing, geology, the environment, health and archaeology. Both the relative (comparator) method and the k 0-method of standardization for INAA are being established in OPAL. A description of progress, plans and capabilities are presented.

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Acta Chromatographica
Authors: Stefano Dugheri, Nicola Mucci, Alessandro Bonari, Giorgio Marrubini, Giovanni Cappelli, Daniela Ubiali, Marcello Campagna, Manfredi Montalti, and Giulio Arcangeli

Sample pretreatment is the first and the most important step of an analytical procedure. In routine analysis, liquid–liquid microextraction (LLE) is the most widely used sample pre-treatment technique, whose goal is to isolate the target analytes, provide enrichment, with cleanup to lower the chemical noise, and enhance the signal. The use of extensive volumes of hazardous organic solvents and production of large amounts of waste make LLE procedures unsuitable for modern, highly automated laboratories, expensive, and environmentally unfriendly. In the past two decades, liquid-phase microextraction (LPME) was introduced to overcome these drawbacks. Thanks to the need of only a few microliters of extraction solvent, LPME techniques have been widely adopted by the scientific community. The aim of this review is to report on the state-of-the-art LPME techniques used in gas and liquid chromatography. Attention was paid to the classification of the LPME operating modes, to the historical contextualization of LPME applications, and to the advantages of microextraction in methods respecting the value of green analytical chemistry. Technical aspects such as description of methodology selected in method development for routine use, specific variants of LPME developed for complex matrices, derivatization, and enrichment techniques are also discussed.

Open access
Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Spyrou, W. Arshed, A. Farooqi, G. Ibeanu, O. Akanle, C. Jeynes, O. Asubiojo, I. Obioh, E. Oluyemi, and A. Oluwole

Abstract  

Three nuclear and atomic-based techniques for elemental analysis of air-particulate samples are discussed in terms of their usefulness in an environmental monitoring and impact assessment programme, supported by the European Economic Community, in Nigeria. Instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) analysis are compared with respect to the number of elements detected and the detection limits obtained for air-particulate matrices. The latter is used in conjunction with Rutherford backscattering spectrometry (RBS) in order to correct for variations in matrix composition. A scanning electron microprobe (SEM) with analytical facilities is also employed mainly for characterization of the air-particulates through measurement of particle size and morphology. The value of carrying out statistical analysis for differentiating between collection sites or sources of pollution is emphasised. Reference to results obtained from the analysis of air-particulates collected during the Harmattan season at Kano and Ife, separated by about 1000 km place the problem in context and serve to illustrate the requirements.

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Abstract  

The main purpose of this study is to review the current state of the problem of the impact of gaseous environment on the kinetics of solid-state decompositions. Three different theoretical approaches to the interpretation of the decomposition kinetics have been considered. As it follows from the literature published over the past 80 years, the Arrhenius and Knudsen–Langmuir approaches based on the assumption of two different reaction mechanisms (congruent and incongruent) could not solve the problem. At the same time, successes in the application of the thermochemical approach that is based on the assumption of a unitary congruent dissociative vaporization mechanism with condensation of oversaturated vapor remain unnoticed by the TA community. Taking into account this situation, the author has outlined the key points of the thermochemical kinetics in a compact but rigorous and complete form once more. The revised kinetic equations for the different modes of decomposition, several important interrelations between the kinetic parameters, and, finally, the results in the interpretation or reappraisal of the main effects related to the impact of gaseous environment on the kinetics have been considered. In the framework of the thermochemical approach, the problem being discussed may be considered nowadays practically resolved.

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Abstract  

This is an overview of the early investigations into the mechanism of solid decompositions since the fundamental studies by Ostwald on catalysis during 1890–1902 and the first experimental study of the autocatalytic decomposition of Ag2O by Lewis in 1905. In order to explain the formation mechanism of the solid product, Volmer suggested in 1929 that the decomposition of Ag2O includes two sequential stages: first, a thermal decomposition of the oxide into gaseous silver atoms and oxygen molecules and second, the condensation of the supersaturated silver vapor. This revolutionary idea was immediately used by Schwab to explain the autocatalytic peculiarity of solid-state decomposition reactions. However, this mechanism did not receive the acceptance of the scientific community. On the contrary, as can be seen from the results presented at the conference “Chemical reactions involving solids” in Bristol in 1938, this model was dismissed as unrealistic and, as a result, was since forgotten. Instead, considerable attention at this conference was devoted to the disorder theory proposed earlier by Wagner and Schottky, and to the mechanism of ion transport in the solid crystals. During the subsequent 70 years, decomposition mechanisms have been interpreted, without visible progress, on the latter basis. The mechanism of congruent dissociative vaporization proposed independently in 1990 turned out to be in complete agreement with the Volmer–Schwab model. It has been treated with the same distrust. These historical events, in the author’s opinion, are responsible for the prolonged stagnation in the development of solid-state decomposition theory.

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Abstract

The reuse and recycling of biomass materials can minimize the environmental impact of society, and can help create a sustainable community. Although cellulosic biomass from demolished buildings is a promising resource for recycling, contaminants, such as wood preservatives that likely contain metal oxides, are found in recycled wood dust. These oxides could act as catalysts for the oxidation of organic materials, resulting in spontaneous ignition of large piles of recycled wood dust. Copper(II) oxide (CuO) is major component in wood preservative and plays a catalytic role in the oxidation of cellulose, which could cause spontaneous ignition. The present study focused on the influence of CuO on oxidation of cellulose. The exothermal behavior and mass loss of cellulose/CuO mixtures were investigated. Changes in exothermal behavior and mass loss with an increasing amount of CuO were measured by differential scanning calorimetry and thermogravimetry. In addition, kinetics and spectroanalysis were conducted to determine the catalytic effect of CuO on oxidation of cellulose and help determine the oxidation model of cellulose upon addition of CuO. Results revealed a change in exothermal behavior and increase in mass loss with increasing amounts of CuO. In addition, CuO had a catalytic effect on the oxidation of cellulose, which helped determine the oxidation model of cellulose upon addition of CuO.

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Abstract  

Although the number of research reactors (RRs) is steadily decreasing, more than half of the operational RRs are still heavily underutilized, and in most cases, underfunded. The decreasing and rather old fleet of RRs needs to ensure the provision of useful services to the community, in some cases with adequate revenue generation for reliable, safe and secure facility management and operations. Enhancement of low and medium power research reactor (RR) utilization is often pursued by increasing the neutron activation analysis (NAA) activities. In this paper we will present the strategy and concrete actions how NAA as one of the most popular RR applications can contribute to the above goals in particular through (a) RR coalitions and networks, (b) implementation of automation in different stages of NAA, (c) QA/QC, including skills improvement of involved personnel, (d) dedicated proficiency tests performed by a number of targeted analytical laboratories. We also show that despite the IAEA’s efforts, some of the NAA laboratories still perform badly in proficiency tests, do not have formal QA/QC procedures implemented, have not implemented automation to process large number of samples or lack of clear marketing strategies. Some concrete actions are proposed and outlined to address these issues in the near future.

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