Application of neutron activation analysis in the investigation of trace element metabolism

The applications of neutron activation analysis in the investigation of trace element metabolism in animals and man are described and discussed. They include the determination of element distributions in the body, the study of correlations between trace element concentrations and physiological processes, the special methods of investigation of trace element metabolism in man and the identification of the chemical forms of the elements in the organism. Examples for each stage of application are given.     

Influence of Water Treatment and Wastewater Treatment on the Changes in Residues of Important Elements in Drinking Water

Drinking water is the essential medium for food production, and is also needed for direct consumption; while it must be free of harmful substances, it also must have a composition that is beneficial to health. The aim of this study was to evaluate the influence of water and wastewater treatment on reducing the concentrations of zinc (Zn), nickel (Ni), iron (Fe), manganese (Mn), copper (Cu), lead (Pb), and arsenic (As) in the Western Pomerania Voivodeship in Poland. The research was carried out in 2017–2019. The analysis was performed with inductively coupled plasma atomic emission spectrophotometry (ICP-AES). The concentrations of trace elements in drinking water were below maximum acceptable concentrations (MACs). Reductions in the most dangerous elements during water treatment fluctuated from 48.5% (As) to 97% (Pb). Wastewater treatment reduced the concentrations of analyzed elements by a range of 28.6 to 60.8%, and the most toxic elements (Pb and As) by over 50%. Trace element concentrations in treated wastewater were below MAC values, and ranged from 1.15% (Pb) to 6.23% (As) of MACs for toxic elements. The concentrations of both essential elements (Zn, Ni, Fe, Mn, Cu) and toxic elements (Pb, As) in drinking water were below the MACs. Water treatment had a significant (p < 0.05) effect on decreasing trace element concentrations.     

The effect of washing procedures on trace element content of human hair

The effects of four washing procedures on the concentrations of manganese, iron, copper, zinc and cadmium and were investigated for three pooled samples of human head hair. The solutions evaluated were a non-ionic detergent (Triton X-100), an ionic detergent (sodium lauryl sulfate), acetone and a complexing agent (EDTA). The results indicate that for every element determined there is a level below which the concentration cannot be reduced by further washings. The numbers of washings required to reach these levels vary considerably. This effect must be considered in the trace element analysis of hair.     

INAA of coals from the Midwestern USA

The concentrations of 43 elements were determined in coal samples collected from the state of Missouri using INAA at the University of Missouri Research Reactor. The results of the whole coal analysis reveal that the chemical compositions of Missouri coals are highly variable. Enrichment factors were determined for each of the elements determined in this project to provide a measure of the relative enrichment of the element as compared to the average crustal abundance for that element. Most elements are relatively depleted in coals, however the elements As, Br, B, Ca, Cd, Cl, Fe, Mo, Ni, Sb, S, U, Zn and Zr were found to be enriched in Missouri coals. The determination of the relative enrichment of a given element in coal will allow a greater assessment of the environment impact the will be incurred from the use of that coal.     

Variations in trace element concentrations in human blood serum in the normal state investigated by instrumental neutron activation analysis

Using instrumental neutron activation analysis, the variations in the serum levels of Br, Cs, Na, Rb, Se, and Zn were investigated in 18 persons in the normal state. By determining the element levels in relation to changes is the serum water content, information about the binding to the serum protein was obtained. The influence of physiological factors on the serum element levels was investigated. Changes in the concentrations due to variations in the protein/water ratio and in the zinc level as a result of different posture were observed. When standardized sampling procedures were used, the variations in the serum element concentrations during one hour and from day were found to be less than 10%.     

Air pollution monitoring at the Environmental Specimen Bank of Germany: spruce and pine shoots as bioindicators

An investigation has been carried out to study the pattern of heavy metal abundance in buds, needles, twigs and cones from single trees and to compare the results with the integrated (composite, homogenized) ESB material of the same origin. It has been evident that (i) pine and spruce shoots are comparable in terms of the pattern of trace element abundance with the exception of Ni, Ba, Sr and Pb, (ii) twigs contribute substantially to the overall concentration of the homogeneous material, and (iii) heavy metal concentrations are remarkably different in samples from remote and industrialized sampling sites. To distinguish the influence of soil at different sampling sites on the overall concentration levels, an extensive investigation using chemometrical data evaluation has still to be carried out.     

Air pollution monitoring at the Environmental Specimen Bank of Germany: spruce and pine shoots as bioindicators

An investigation has been carried out to study the pattern of heavy metal abundance in buds, needles, twigs and cones from single trees and to compare the results with the integrated (composite, homogenized) ESB material of the same origin. It has been evident that (i) pine and spruce shoots are comparable in terms of the pattern of trace element abundance with the exception of Ni, Ba, Sr and Pb, (ii) twigs contribute substantially to the overall concentration of the homogeneous material, and (iii) heavy metal concentrations are remarkably different in samples from remote and industrialized sampling sites. To distinguish the influence of soil at different sampling sites on the overall concentration levels, an extensive investigation using chemometrical data evaluation has still to be carried out.     

Multiplexed detection of ions and mRNA expression in single living cells

In order to push forward into new areas of medical and biological research, new techniques must be developed that will enable a complex investigation into cellular processes. This involves investigating not only the different expression levels inside of a cell but also the ability to analyze how those expression levels are connected to one another. In order to accomplish this level of exploration, different types of analytes must be investigated simultaneously inside of single cells, thereby allowing their expression levels to be directly compared. To accomplish this, we have developed a method of detecting and monitoring mRNA expression levels and ion concentrations simultaneously inside of the same single cell. We have utilized this technique in studying the effects of an anti-cancer agent on human breast carcinoma cells. Using this approach, we are able to shed light onto the complex connections between genes and ions inside the cell that is not possible with any other existing technique.     

Changes in the elemental content of blood components by selenium supplement in humans

A study was undertaken to determine the concentration of selenium in whole blood, erythrocytes and plasma in samples obtained from three groups (each group consisting of one male and one female subject) given as a supplement a commercial product containing the element, together with vitamins A, C and E. Blood samples were obtained on one-day-a-week basis from each group, over a period of 75 days, both in the morning and in the afternoon, as part of a gastric function investigation, in which the subjects were given orange juice after fasting. Results indicate that the level of selenium in whole blood and its components increases with dose and time and that concentrations of the element are maintained for at least 45 days following cessation of supplementation. The influence of the supplement on some electrolytes such as Na, Cl, Br and Rb was also investigated.     

Synchrotron radiation induced μ-X-ray fluorescence spectroscopy on municipal solid waste fly ashes

The high brightness of synchrotron radiation sources of the 3rd generation and the development of focusing optical elements for X-rays make it possible to create beams of micrometer size with high intensity. These beams can be used to reveal spatially resolved information about structural and chemical properties of particles. Here, the possibility of using synchrotron radiation micro-X-ray fluorescence (μ-SRXRF) for the determination of the major and minor components and their distribution within municipal solid waste (MSW) fly ashes has been investigated. By using an excitation energy of 27.0 keV, trace elements of environmental concern, like Cd, Pb and Zn can be detected to their low concentrations (ppm) routinely. The aim of the work was to gain a better understanding of the factors that determine the environmental mobility of each trace element and, in particular, the potential for their dissolution and leaching. Such detailed investigation of the content and distribution of toxic metals on/in individual particles is a valuable complement to the usual elemental analysis of bulk samples.     

Aggregation of methyl orange probed by electrical impedance spectroscopy

We present results of an electrical impedance spectroscopy investigation of the evolution of the aggregation of methyl orange (MO) in pure aqueous solutions as the concentration of the dye is varied. By applying the constant phase element (CPE) approximation to model the electrical response of the MO solutions, we have verified that the formation of dimers and oligomers can be recognized by specific signatures in the loss and capacitive components of the dielectric response of the system. We interpret these well-defined changes in the dielectric properties of the solutions as a result of molecular rearrangements caused by the aggregation process that alter the current circulation pathways and the electric dipole distribution. The fact that these specific changes in the dielectric behavior coincide with critical concentrations where dimer and oligomer formation in pure aqueous MO solutions are known to occur suggests that electrical impedance spectroscopy can be a competitive technique for the investigation of aggregation behavior in dyes and surfactants.     

Selektive chemische Trennverfahren für die Aktivierungsanalyse

Relative sensitivity factors (RSF) of 32 elements in the concentration range 1–10⁴ ppm (mass of element/ mass of electrode) have been determined for spark source mass spectrometric analysis. Graphite and silver powder was used as conductive material. The RSF of about two thirds of the elements under investigation were found to be dependent on their concentration in the electrodes. This is thought to be due to volatilization at high temperatures whereby the concentration of these elements at the electrode surfaces is diminished. In general RSF's at silver powder electrodes are higher and necessary sparking times are shorter than those at graphite electrodes. Therefore the use of silver powder for determinations of concentrations <10³ ppm is advantageous although experimental results show greater scatter due to inhomogeneity of the electrode.     

Calibration of laser-ablation ICP-MS. Can we use synthetic standards with pneumatic nebulization?

An approach for the determination of trace element concentrations in high purity metals, using an inductively coupled plasma mass spectrometer (ICP-MS) with a laser-ablation system for direct solid sample introduction after calibration with nebulized liquid standards was made. Due to the inherent differences in the rate of sample introduction with laser-ablation and pneumatic nebulization, a matrix element must be used as an internal standard. This is problematical for elements that have no isotope with a relative abundance of less than 0.1 %, since the ion signals would be too high for direct measurement, and reduction of the ablation rate would compromise the sensitivity for trace elements. Due to the high stability of ICP-unit and mass filter of the instrument used, it was found that the tail of a mass-peak of the matrix element could be used as an internal standard. Therefore, a position at –0.5 amu from the matrix-isotope (e.g. ^62.5Cu in copper samples) was used for internal standardization. The standard deviation of this signal in a period of 2.5 h was 3.6% RSD with no notable drift when the laser ablation was used for sample introduction. The calibration of the matrix-element by nebulizing liquid standards showed that the ion signal measured on the peak-tail is directly proportional to the element concentration in the ICP. This indicates that the peak shape is not only stable, but also independent of the peak height. The advantages of this method lie in the easy preparation of calibration standards for quantitative measurements with a laser-ablation system and access to homogeneous standards for materials, that are difficult to homogenize in the solid state. The calibration of the traces is performed relatively to a fixed concentration of the matrix element. Calibrations were carried out for trace concentrations in high purity copper and good recoveries were obtained for high-purity reference standards. Received: 23 February 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998     

Calibration of laser-ablation ICP-MS. Can we use synthetic standards with pneumatic nebulization?

An approach for the determination of trace element concentrations in high purity metals, using an inductively coupled plasma mass spectrometer (ICP-MS) with a laser-ablation system for direct solid sample introduction after calibration with nebulized liquid standards was made. Due to the inherent differences in the rate of sample introduction with laser-ablation and pneumatic nebulization, a matrix element must be used as an internal standard. This is problematical for elements that have no isotope with a relative abundance of less than 0.1 %, since the ion signals would be too high for direct measurement, and reduction of the ablation rate would compromise the sensitivity for trace elements. Due to the high stability of ICP-unit and mass filter of the instrument used, it was found that the tail of a mass-peak of the matrix element could be used as an internal standard. Therefore, a position at –0.5 amu from the matrix-isotope (e.g. ^62.5Cu in copper samples) was used for internal standardization. The standard deviation of this signal in a period of 2.5 h was 3.6% RSD with no notable drift when the laser ablation was used for sample introduction. The calibration of the matrix-element by nebulizing liquid standards showed that the ion signal measured on the peak-tail is directly proportional to the element concentration in the ICP. This indicates that the peak shape is not only stable, but also independent of the peak height. The advantages of this method lie in the easy preparation of calibration standards for quantitative measurements with a laser-ablation system and access to homogeneous standards for materials, that are difficult to homogenize in the solid state. The calibration of the traces is performed relatively to a fixed concentration of the matrix element. Calibrations were carried out for trace concentrations in high purity copper and good recoveries were obtained for high-purity reference standards. Received: 23 February 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998     

Analysis of wines by ICP-MS: Is the pattern of the rare earth elements a reliable fingerprint for the provenance?

In a comparative analysis of young and finished product wines by semi-quantitative ICP-MS, a striking difference was observed: finished products exhibited significant concentrations of the rare earth elements whereas the concentrations in young wines which had not been subdued to any treatment after their initial preparation from the grapes were below the determination limits with a quadrupole instrument and could only be determined with a magnetic field instrument operated at a low mass resolution (R = 300). The reason was found in contamination from bentonites as usually applied for the purification of wines from tarnishing components such as proteins. Therefore, bentonites of different origin were extracted with a reference wine, and an increase of the rare earth element concentrations by more than one order of magnitude was observed in the extracts. The investigation leads to the conclusion that the concentration pattern of the rare earth elements can be strongly affected by the wine producing process and therefore is not generally suitable as a fingerprint for the provenance of wines.     

Towards routine NAA of materials rich in heavy elements with iterative gamma-ray attenuation and neutron self-shielding calculations

Solids and powders can be analysed directly and with good accuracy by neutron activation analysis without sample preparation because of the excellent penetrating powers of neutrons and gamma rays. However, if the sample contains high concentrations of gamma-absorbing heavy elements or neutron-absorbing elements, the analysis results must be corrected for neutron self-shielding and gamma-ray attenuation. These effects are coupled and depend on the chemical composition of the sample, which is the final result of the analysis. Thus, the correction calculation must be iterative. In this work we performed the first coupled iterative corrections of the two effects. Six test samples were prepared by mixing powders containing compounds of Cd, a neutron absorber, and the rare-earth elements Ce, Pr and Nd with concentrations as high as 47 %. The samples were irradiated in the SLOWPOKE research reactor and counted with a germanium gamma-ray detector. In the samples with the highest heavy element concentrations, the uncorrected Neutron activation analysis results were in error by as much as 55 %. The results were corrected iteratively using the neutron self-shielding model coupled with the gamma-ray attenuation model, and the final corrected results were accurate to 5 % or better.     

Extending NAA to materials with high concentrations of neutron absorbing elements

Summary The recently discovered universal functions for thermal and epithermal neutron self-shielding were adapted to NAA of cylindrical samples, expressing the magnitude as the product of a nuclear factor, a geometrical factor and the amount of the neutron absorbing element. The theory was tested and the nuclear factors were measured for 1 ml samples containing the halogens Cl, Br and I. Tests on samples containing these elements at a priori unknown concentrations, irradiated in a mixed thermal and epithermal neutron spectrum, showed that self-shielding as high as 30% could be corrected with an accuracy of about 1%, except in cases with significant epithermal shielding of one element by another.     

Progress in the accuracy enhancement for elemental analysis by quadrupole-based plasma-SNMS

The elemental quantification in plasma-based SNMS is hampered by the matrix dependence of the detection efficiencies. The signals of elements of unknown compounds can only be converted to concentrations with mean detection factors resulting in concentrations with an uncertainty mainly given by the matrix effect. This situation can be considerably improved by energy measurements of the sputtered particles. The energy distribution (ED) can be used in two ways. First, the exact knowledge of the ED to each detected element allows an element specific integration of the directly sputtered atoms eliminating thermal species from resputtered wall deposition. For a set of copper compounds the spread of the Cu detection factors could be reduced from ± 63% for the conventional measurement to ± 35% using energy resolved data. Second, the shape of the ED of postionised atoms differs considerably from all interfering species, such as clusters as well as twice charged atoms which could superimpose on the atomic signals. A quantitative shape analysis of the measured ED was developed to correct for these interfering species. Examples are given for both superpositions with cluster intensities and interferences with twice charged intensities. To reduce the additional time necessary to obtain the ED, the number of energy resolved data points was reduced in steps down to 3 points only which still reduced a superposition error to half of the value without ED based correction.