Present and future positron-molecular scattering experiments

Progress to date (June, 1999) of the Oak Ridge positron scattering project is reviewed. Results from our positron time-of-flight mass spectrometer include ionization and fragmentation of some halomethanes, positronium formation below the threshold for double ionization of Ne and the heavier noble gases, and the production of HeH⁺ by positron impact on mixtures of He and H₂. New directions for future experimental work are discussed. These entail the construction and testing of a new spectrometer which measures both the masses and recoil energies of charged products, including secondary electrons. We hope to use an intense positron beam, such as the one at Lawrence Livermore National Laboratory or a similar beam, as the ionizing agent for the new spectrometer, which contains a pulsed supersonic molecular beam. With such an instrument, a range of new phenomena can be studied.     

Present and future of surface plasmon resonance biosensors

Surface plasmon resonance (SPR) biosensors are optical sensors exploiting special electromagnetic waves—surface plasmon-polaritons—to probe interactions between an analyte in solution and a biomolecular recognition element immobilized on the SPR sensor surface. Major application areas include detection of biological analytes and analysis of biomolecular interactions where SPR biosensors provide benefits of label-free real-time analytical technology. This paper reviews fundamentals of SPR affinity biosensors and discusses recent advances in development and applications of SPR biosensors.     

Calibration of activity readings from radiopharmaceuticals with impurities

Accurately determining the amount of a radionuclide actually administered to a patient is an important aspect of quality control in nuclear medicine. In this study, in order to accurately assess the “apparent” radioactivities of radionuclides with impurities by a dose calibrator, two methods, (1) curve fitting, and (2) relative sensitivities calculation, have been employed to determine the parameter, M (relative response). From the comparisons between the measurement and re-calculated radioactivity using the M values, each method was found to have its own advantage and disadvantage, depending upon the fraction ratio of the impurity as well as the energy level of the impurity’s photons. This study might be helpful for improving the assessment of radiopharmaceuticals’ “true” activity and its “apparent” activity measured by a dose calibrator.     

Present and foreseeable future of metabolomics in forensic analysis

The revulsive publications during the last years on the precariousness of forensic sciences worldwide have promoted the move of major steps towards improvement of this science. One of the steps (viz. a higher involvement of metabolomics in the new era of forensic analysis) deserves to be discussed under different angles. Thus, the characteristics of metabolomics that make it a useful tool in forensic analysis, the aspects in which this omics is so far implicit, but not mentioned in forensic analyses, and how typical forensic parameters such as the post-mortem interval or fingerprints take benefits from metabolomics are critically discussed in this review. The way in which the metabolomics–forensic binomial succeeds when either conventional or less frequent samples are used is highlighted here. Finally, the pillars that should support future developments involving metabolomics and forensic analysis, and the research required for a fruitful in-depth involvement of metabolomics in forensic analysis are critically discussed.     

Present and future of expert systems in food analysis

This paper presents an overview of the most relevant contributions in the field of expert system (ES) applications in chemical analysis of foods, along with a critical discussion of future, would-be developments. It illustrates the possibilities offered as well as the fact that quality control laboratories should be aware of the power of artificial intelligence that modern computer technology affords. It is worth noting that the applications described are straightforward with a certain versatility and can, therefore, be implemented for other analytes and/or food samples. Special attention is devoted to the promising distributed knowledge-based systems due to their potential advantages over the existing centralized approaches, as inferred from a recent example of application to the on-line monitoring of some key chemical parameters in the course of a food production process. Short and middle term predictions concerning the potential of ES in food analysis are also made.     

In vivo activation analysis: Present and future prospects

In vivo activation analysis has proved to be an analytical assay for the elemental composition of the human body. Applications have included the diagnosis of disease, the evaluation of therapeutic clinical interventions, the study of basic human physiology (especially of the aging process), and the development of reference standards for indirect measures of body composition. This paper will focus on the in vivo activation techniques currently in use and their future prospects, with an emphasis on body Ca, N, C and Cd. The prospects for delayed, prompt, and pulsed neutron activation will be included in the discussion.     

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     

Capillary electrophoresis and herbicide analysis: Present and future perspectives

The aim of this article is to provide an overview on the potential of the CE–herbicides binomial. To this end, the methods proposed so far are discussed: their characteristics, types of samples and analytes to which the methods have been applied, sample preparation steps, if required (e.g. cleanup–preconcentration, derivatization steps), and type of detection in each case. Also, the methods are compared with counterparts based on LC, when appropriate. The role of MS detection in present and future analytical research in this field (both for identification and quantitation) are commented. The foreseeable and desirable trends in analysis of herbicides are also outlined in the light of the present trends in metabolomics as a way of knowing the pathways, the intermediate and final degradation products that can influence the crops and the food chain of humans and other animals, as a result.     

Biodegradable materials — Present situation and future perspectives

Biodegradable polymers constitute a loosely defined family of polymers that are designed to degrade through the action of living organisms. They offer a possible alternative to traditional nonbiodegradable polymers if recycling is impractical or not economical. The main driving force behind this technology is the solid waste problem, particularly with regard to the decreasing availability of landfills, the litter problem and the pollution of marine environment by non-biodegradable plastics. Technologies like composting used for the disposal of food and yard waste are the most suitable for the disposal of biodegradable materials. European Standardisation Committee (CEN), Organic Reclamation and Composting Association (ORCA) and German Institute for Standardisation (DIN) have already defined, at a draft level, the basic requirements for a product to be declared compostable. They are based on: complete biodegradability of the product in a time period compatible with composting, measured through respirometric tests (ASTM D5338-9, ISO/CD14855, etc); disintegration of the material during the fermentation phase; no negative effects on compost quality; checking of laboratory-scale results on pilot/full-scale composting plants. These requirements set forth a common base for a universal marking system to readily identify products to be composted. Thermoplastic starch-based polymers and aliphatic polyesters are the two classes of biodegradable materials with the greatest near-term potential. This paper reviews a great variety of properties, structures and biodegradation behaviour of thermoplastic starch in combination with poly(vinyl alcohol) or some aliphatic polyesters like poly(hydroxybutyrate-co-hydroxyvalerate), poly(lactic acid), poly(ϵ-caprolactone) and poly(butanediyl succinate).     

Iodine labelled radiopharmaceuticals from arylthallium bis(trifluoroacetate) intermediates

A simple, one-step micro-synthesis of aromatic radioiodides which utilizes the in-situ formation of arylthallium bis (trifluoroacetate) intermediates has been developed. Thallium(III) trifluoroacetate was used in the thallation of aryl compounds to yield the intermediate arylthallium bis (trifluoroacetate). The latter was isolated, purified and used for radioiodination. Alternatively, in-situ radioiodination was accomplished by the addition of radioactive aqueous NaI plus excess non-radioactive iodide to complete the reaction. Yields of up to 81% of radiochemically pure compounds were obtained. Using the modified thallation-radioiodination method, aromatic radiopharmaceuticals can be easily and quickly labelled with¹²³I.     

Evaluation of additional absorbed radiation dose from radioactive impurities in radiopharmaceuticals

The additional absorbed radiation doses to total body from radioactive impurities in radiopharmaceuticals were estimated for a total of 10 samples (i.e., 99mTc generator eluates, 99mTc solutions, 67Ga, 81mKr generator eluates, 111In, 123I, 201Tl, 75Se, 197Hg, 198Au) selected from commonly used radiopharmaceuticals. The radioactive impurities in radiopharmaceuticals used in this estimation were previously identified. The radiation doses were calculated according to the MIRD procedures, assuming each radionuclide to be uniformly distributed throughout the body. In the case of the cyclotron-produced radioisotopes and 198Au, the additional total body absorbed doses from impurities were found to be rather high: 280% for 123I, 55% for 81mKr, 5% for 198Au, 4% for 111In and 2% for 201Tl. The absorbed doses due to impurities in the other radioisotopes were less than 1%.     

Neutron activation analysis of radiopharmaceuticals

In order to understand the chemical form of soluble technetium in paddy soil and its availability to a rice plant, soil incubation and uptake experiments have been carried out using^95mTc as a tracer. The chemical form of the soluble Tc was observed by gel chromatography and found not to be pertechnetate, but rather to be associated with soluble organic matter. An uptake experiment with rice seedlings using nutrient solution showed that this Tc-organic matter complex was less available than pertechnetate.     

Applications of PET–CT in clinical practice: Present and future

Radionuclide imaging and specially positron emission tomography (PET) has already demonstrated its benefits in three major medical subjects, i.e. neurology, cardiology and particularly clinical oncology. More recently the combination of PET and X-ray computed tomography (CT) as PET–CT led to a significant increment of the already large number of clinical applications of this imaging modality. This “anatomy-metabolic fusion” also known as Metabolic Imaging has its future assured if we can: (1) improve resolution reducing partial volume effect, (2) achieve very fast whole body imaging, (3) obtain accurate quantification of specific functions with higher contrast resolution and, if possible, (4) reduce exposure rates due to the unavoidable use of ionizing radiation.     

Cyclotron isotopes and radiopharmaceuticals XXVI. A carrier-free separation of77Br from se

A silver chloride co-precipitation and ion exchange separation method is described for the carrier-free isolation of⁷⁷Br bromide from isotopically enriched⁷⁷Se targets following dissolution of the irradiated⁷⁷Se in nitric acid. A cation exchange procedure has been devised to remove the silver and yield a dilute hydrochloric acid solution containing ≈90% of the precipitated⁷⁷Br as bromide. The radiochemical and chemical composition of several preparations have been analyzed. A method for the quantitative recovery of the isotopically enriched selenium is described. Research carried out under contract with the U.S. Department of Energy and supported by its Division of Basic Energy Sciences. Supported in part by the Massachusetts Heart Association and by NIH Grant No. HL 18487-01. All inquiries should be directed to R. M. Lambrecht. For earlier papers in this series see Ref.¹²     

Nanomaterial-based adsorbents: the prospect of developing new generation radionuclide generators to meet future research and clinical demands

Nanostructured materials by virtue of huge surface to volume ratios, altered physical properties, tailored surface chemistry, favorable adsorption characteristics, and enhanced surface reactivity resulting from the nanoscale dimensions, have attracted considerable attention as a new class of adsorbent material in column chromatographic separation. This emerging class of adsorbent represents an innovative paradigm and is expected to play an important role in the development of radionuclide generators for nuclear medicine. The optimal combination of suitable nanomaterial and appropriate parent/daughter radionuclide pair forms the basis of such generators. Development of such generators is currently under intensive investigations and the utility of such systems is expected to pave the way for broad panoply of diagnostic and therapeutic applications in nuclear medicine. While nanomaterial-based radionuclide generator is still in its infancy, the use of such novel class of adsorbents is expected to have potential impact on shaping the radionuclide generator technology of future generation. This review provides a comprehensive summary on the utility of nanomaterials as effective adsorbents in the development column chromatographic radionuclide generators for medical applications. This overview outlines a critical assessment of role of the nanosorbents, recent developments, the contemporary status, and key challenges and apertures to the near future.     

Determination of residual activities in 99mTc generators and 81mKr generators

The residual activities present in spent 99Mo-99mTc generators and 81Rb-81mKr generators were determined from a view point of the disposal of radiopharmaceuticals. The results showed that seven kinds of residual nuclides such as 95Zr-95Nb, 103Ru, 90Sr, etc. were found in 99mTc generators with maximum level of 740 Bq/3.7 GBq (0.02 muCi/100 mCi) at one year after the reference date. In 81mKr generators one year old, six nuclides such as 57Co, 83Rb, 84Rb and others remained and these activities were less than 3.7 kBq/370 MBq (0.1 muCi/10 mCi). On the basis of these data, the disposal of 99mTc generators and 81mKr generators is discussed.