Metallobiochemistry of current environmental levels of trace metals: A new method of cyclotron production of48V for toxicological studies

No-carrier-added⁴⁸V at 37 Mbq (mCi) levels was produced at the JRC-Ispra cyclotron by (, n) reactions on a scandium target and used to label environmental and physiological levels of vanadium for metallobiochemical investigations. The radiochemical separation of⁴⁸V from Sc is very simple and rapid and involves a single chromatographic step after fast dissolution of the bombarded target. The yield of the separation and the radioisotopic purity of the separated⁴⁸V were nearly 100% A summary of the main results concerning different metabolic investigations on rats including absorption, retention, transfer of⁴⁸V from mothers to newborns, binding with enzymes as well as uptake by cell culture system is reported.At the time of this study visiting scientists at the^4,5Radiochemistry and³Functional Materials Divisions of the JRC-Ispra.     

Aspects of proficiency testing studies of trace elements in environmental samples with a focus on laboratory performance

Four proficiency tests of environmentally significant elements in soil and water are described. The effects of sample matrix, analyte, sample preparation procedure, extraction method efficiency and instrumental technique on laboratory performance were assessed. Participants’ performance was evaluated using z scores and E _n scores. One study included dried sediment and sediment digest as test samples. By testing both dried sediment and sediment digest in the same study, differences in laboratories’ results due to the extraction method or instrumental technique were evaluated. Cadmium and nickel were the elements with the most unsatisfactory z scores for dried sediment compared to sediment digest. The second study had as test samples river water and river water fortified with biosolid. For an evaluation of the efficiency of participants’ extraction method, the results reported for the analysis of river water were compared to the results for analysis of the same river water fortified with biosolid. No consensus could be found between participants’ results for Cr and Ni in this study as the extraction method employed by them produced results that were too variable. The last two studies included saline and fresh water samples. The analysis of fresh and saline water samples with similar analyte concentrations assisted laboratories in developing their methods for trace elements in saline water. For Cr, Pb and Se, the assigned values were reference values traceable to SI, measured using isotope dilution inductively coupled plasma mass spectrometry. Saline water containing low concentrations of analytes presented difficulties to some laboratories. Arsenic and selenium were the analytes most difficult to analyse in all types of environmental samples.     

Biomonitoring of environmental pollution based on studies of trace elements in soil and crops

Most elemental concentrations in crops should be related to those in soil and other circumferential environments. In the present study, more than thirty minor and trace elements in soils and crops were determined by the use of ICP, XRF and NAA. Soil and crop samples were collected at eleven abandoned mine regions in Chungnam province located in the middle part of Korea. The elemental concentrations in soils were compared to the crustal mean concentrations in both Chungnam area and worldwide. The concentration ratios of the elements in soils and crop compartments were calculated and the distribution characteristics of each element were investigated between soil and crop compartments.     

Fractionation studies of trace elements in Polish uranium-bearing geological materials: potential environmental impact

The samples of U deposits from Podlasie Depression (East Poland) and Peribaltic Syneclise (Northeast Poland) were studied to state the U and accompanied metal content and to estimate a potential environmental impact caused by the studied area. Sequential extraction is an effective method for assessing the heavy metal behaviour in environment in such environmental materials as soils, sediments, different wastes and ores.

The modified Bureau of Reference of the European Commission sequential extraction procedure has been used for fractionation study of nine elements (U, V, Mn, Co, Ni, Cu, Zn, Cd and Pb) in two kinds of U ores: dictyonema shale and sandstone. The total content and the content in each fraction of metals of interest were determined by the inductively coupled plasma mass spectrometry method.

The obtained results show the high mobility of such elements as Co, Zn and Ni in shale and U, Co and Mn in sandstone. These results make it possible to assess the environmental risk associated with heavy metals occurring in tested U-bearing ores.     

Multivariate analysis of trace elements determined in archaeological materials and its use for characterisation

Data on the concentrations of K, Ca, Ti, Fe, Cu, Zn, Ga, Rb, Sr and Zr obtained by PIXE and of B, F, Na, Mg, Al, Si and Cu obtained by proton-induced prompt gamma-ray spectrometry were used to characterize archaeological artefacts and source materials by multivariate analysis. The mathematical approaches employed were cluster analysis using nearest-neighbour data, multidimensional scaling and correspondence analysis.     

Overview of the methodology of nuclear analytical techniques for speciation studies of trace elements in the biological and environmental sciences

Recent achievements in speciation studies of trace elements in the biological and environmental sciences by nuclear analytical techniques, mainly molecular activation analysis, position-sensitive spectrometry with a variety of exciting sources, and synchronous radiation-based analytical techniques (although radioisotope or enriched stable isotope-based speciation techniques are also used), particularly in our laboratory, are outlined. In this paper the merits and drawbacks of the nuclear analytical techniques are discussed, as are reagent blanks, contamination, and artifacts.     

Cyclotron production, radiochemical separation and quality control of platinum radiotracers for toxicological studies

The increasing concentration of Pt, Pd and Rh in the environment is mainly due to the release of these elements from the catalytic converters of the motorvehicles. This situation makes it necessary to carry out metallotoxicological experiments on both cell cultures and laboratory animals, in order to assess their impact on living organisms after a Long Term and Low Level Exposure (LLE). Both nuclear reactions^natIr(p,xn) and^natOs(α,xn) were investigated in the energy range up to 45 MeV for protons and 38 MeV for alpha-particles, in order to optimize the irradiation parameters for the production of^188,189,191Pt. Several sets of thin- and thick-target excitation functions were determined experimentally by cyclotron irradiation at both Milano and Ispra cyclotrons. This paper reports the irradiation parameters studied and adopted and two radiochemical procedures for the separation of radio-Pt from an Os target, as well as from ruthenium, iridium and gold impurities. These procedures were used to obtain very high specific activity Pt radionuclides in No Carrier Added (NCA) form. Radionuclidic, radiochemical and chemical purity measurements were carred out by the use of several techniques like ψ-spectrometry, ion-exchange radio-chromatography, atomic absorption spectrometry and neutron activation analysis.     

Preconcentration of environmental trace elements on organic support for neutron activation and high resolution photon spectrometry

In this paper, six methods of preconcentration on ion exchange or chelating filters and resins for neutron activation with X-ray and gamma spectrometry are described. These techniques are applied to the determination of trace elements in natural waters. The analysis of water samples from the lake of Geneva by these different methods gave results in good agreement among themselves and also when compared with those obtained by other techniques, with a very reasonable blank and good sensitivity for most determined elements.     

A decade of heterogeneous photocatalysis in our laboratory: Pure and applied studies in energy production and environmental detoxification

Heterogeneous Photocatalysis (HP) has been examined and explored as a potentially viable alternative technology to classical “best” technologies in both environmental detoxification and in energy production. Both fundamental and applied investigations have been pursued over the last decade (1983–1993). This novel technology employs illuminated semiconductor materials as photocatalysts such as CdS and TiO2 to produce both reducing and highly oxidizing species on the particle surface, poised to unleash redox reactions in aqueous media some of which are not possible by normal chemical means. Our laboratory has been involved in this area and has made a significant contribution in (i) demonstrating the generality of the techniques to mineralize a large variety of environmental organics to carbon dioxide together with disposing of trace and toxic metals from aqueous media, and in (ii) understanding the events taking place initially when the light photons interact with the photocatalysts and later when the mineralization process proceeds to its pathological conclusion(s). In this paper we briefly review some of the salient features of our work in Heterogeneous Photocatalysis over the last decade.     

Considerations in the preparation of biological and environmental reference materials for use in the study of the chemical speciation of trace elements

Summary The role that information on chemical speciation can play in the selection of reference materials for the analysis of biological and environmental samples is reviewed. Some considerations that might go into the preparation of materials designed for chemical speciation studies are explored. Individual steps in the preparation of lyophilized serum and urine reference materials are examined in relation to changes that could occur in the chemical speciation of trace elements.     

Comparison of NAA and ICP-MS for the determination of major and trace elements in environmental sample

Summary Major and trace elements in soil and plant samples, including standard reference materials were determined by means of neutron activation analysis (NAA) and inductively coupled plasma-mass spectrometry (ICP-MS). The analytical procedure for NAA utilized dried powder samples. The concentration of iodine in soil samples was determined by radiochemical NAA. The irradiated samples were cooled and then counted with a Ge gamma-ray detector connected to a multi-channel analyzer. For ICP-MS analysis, the samples were decomposed by microwave digestion with an acid mixture. The concentration of I in the soil samples was measured by ICP-MS after separation by ignition. The analytical values for most elements in the environmental samples by both methods were in good agreement, whereas sample treatments were different. Measured value of Zr in the soil samples by ICP-MS was about 50% lower than that by NAA. It should be assumed that some minerals of Zr in soil particles were not entirely dissolved by the acid mixture. Analytical results of Cd for three different Cd levels in unpolished rice flour samples (NIES 10-a, b and c) determined by ICP-MS were in agreement with certified values. The concentration of Cd in the sample with the lowest Cd level, as determined by NAA with 57% counting error, was 3 times higher than the certified value.     

Present-day methods for the determination of trace elements in oil and its fractions

The development and use of instrumental methods for the determination of a wide range of trace elements in oil is considered. Special attention is paid to methods of the direct introduction of samples into spectrometers. It is shown that preliminary sample preparation is in certain cases necessary for the determination of trace elements in oil. The main methods of sample preparation of oils, including methods of extraction of a series of trace elements from crude oil (extraction, membrane, sorption, etc.), are described.     

A system for the neutron activation analysis of trace elements in samples of biological and environmental interest

A neutron activation, ion exchange group separation and iterative least squares γ-ray spectroscopy method has been evaluated. This technique is suitable for multiple trace element analysis in a wide range of biological and environmental materials, since the major contaminants,²⁴Na,³²P, and⁴²K, are removed by an anion exchange resin and do not interfere with the analysis of the majority of the trace elements present. The iterative least squares method was tested with a mixture of standards. The reproducibility and accuracy varied from 3 to 26%. The larger uncertainties resulted from (1) the limited statistical accuracy associated with a low counting rate, and (2) bias introduced by the contaminants in the library of standard spectra even though radiochemical purity exceeded 99.8%. The rigorous least squares method can accurately compensate for instrumental drifts so that the sensitivity approaches the limit imposed by the statistical accuracy of the data and of the standard spectra. Minor components of the complex γ-spectrum were resolved and proved to be present at levels as low as 0.8% of the integral counting rate.     

Phenylalanine ammonia-lyase: the use of its broad substrate specificity for mechanistic investigations and biocatalysis--synthesis of L-arylalanines

Several fluoro- and chlorophenylalanines were found to be good substrates of phenylalanine ammonia-lyase (PAL/EC 4.3.1.5) from parsley. The enantiomerically pure L-amino acids were obtained in good yields by reaction of the corresponding cinnamic acids with 5M ammonia solution (buffered to pH 10) in the presence of PAL. The kinetic constants for nine different fluoro- and chlorophenylalanines do not provide a rigorous proof for but are consistent with the previously proposed mechanism comprising an electrophilic attack of the methylidene-imidazolone cofactor of PAL at the aromatic nucleus as a first chemical step. In the resulting Friedel-Crafts-type sigma complex the beta-protons are activated for abstraction and consequently the pro-S is abstracted by an enzymic base. Results from semi-empirical calculations combined with a proposed partial active site model showed a correlation between the experimental kinetic constants and the change in polarization of the pro-S Cbeta-H bond and heat of formation of the sigma complexes, thus making the electrophilic attack at the neutral aromatic ring plausible. Furthermore, while 5-pyrimidinylalanine was found to be a moderately good substrate of PAL, 2-pyrimidinylalanine was an inhibitor.     

Determination of trace elements in archaeological ceramics and application of Kernel Density Estimates: Implications for the definition of production locations

Summary Chemistry fingerprint of materials helps determine provenance and technological production techniques, and, therefore, is useful way to study interaction between prehistoric people. In this work 38 ceramic fragments from Justino and S?o José sites, in Brazilian northeast, were analyzed using instrumental neutron activation analysis (INAA). The recognition of the compositionally homogeneous group within of the database was performed by means of principal component (PC). The PC scores were calculated on the matrix covariance of the log base 10 transformed concentration values, and grouping was sought in the PC scores using Kernel Density Estimates (KDE). By using KDE from PC scores two chemically different groups were found. Discriminant analysis was performed to assess the groups' validity. Despite of the pottery from Justino and S?o José sites present same technical profile, different of the Tupiguarani and Aratu traditions, it was obtained that Justino and S?o José samples are constitute of distinct ceramic pastes. This result can be understood in terms of the cultural influences in the preparation of the ceramic past and that potteries analyzed are originate locally.     

Comparison between the use of direct current glow discharge mass spectrometry and inductively coupled plasma quadrupole mass spectrometry for the analysis of trace elements in nuclear samples

The quantitative determination of trace elements in nuclear samples by GDMS and ICP-MS is presented and compared. Spectral interferences, matrix effects, detection limits, precision and accuracy are discussed. Results for selected samples demonstrated that both techniques are complementary. The use of a multi-standard solution provides the most accurate results in ICP-MS, whereas in GDMS this is achieved by relative sensitivity factors (RSF) matrix matched. Nevertheless, the use of standard RSF allows a fast screening.     

Comparison between the use of direct current glow discharge mass spectrometry and inductively coupled plasma quadrupole mass spectrometry for the analysis of trace elements in nuclear samples

The quantitative determination of trace elements in nuclear samples by GDMS and ICP-MS is presented and compared. Spectral interferences, matrix effects, detection limits, precision and accuracy are discussed. Results for selected samples demonstrated that both techniques are complementary. The use of a multi-standard solution provides the most accurate results in ICP-MS, whereas in GDMS this is achieved by relative sensitivity factors (RSF) matrix matched. Nevertheless, the use of standard RSF allows a fast screening.