Reliability in scientific evidence based on multi trace forensic neutron activation analysis

The forensic activation analyst must often evaluate his own results as they relate to certain legal or moral situations, since investigative officers, and courts of law are not usually competent to make judgements of the validity or meaning of scientific data. In providing scientific evidence in court, two criteria for criminal identification must be met: (1) suspect's sample should be similar to sample found at the scene of the crime, (2) samples relared to other people in the same statistical population should not generally match that found at the crime site. When two or more specimens are submitted for comparison by NAA they will usually fall into one of three classes: (a) materials about which we have partial or inconclusive data, (c) materials with an excellent analytical data background. Ideally all cases would fall in category c; in practice, very few. Some examples of cases and/or situations that fall into these three categories in both individual and corporate investigations are given. Research sponsored by U.S. Atomic Energy Commission under contract with Union Carbide Corporation.     

Human hair instrumental neutron activation analysis and medicine

Periodically increasing and decreasing enthusiasm has accompanied the studies of medical significance of human hair elemental composition for at least two decades. In this field, nuclear analytical methods play an extremely important role, especially the instrumental neutron activation analysis (INAA). This paper tries to add some new knowledge to this problem. Two approaches are used — comparison of individual hair composition with certain diagnoses in clinic groups and comparison of population data with medical statistics. Rather large samples and multielement mathematical procedures helped reveal strong correlations valuable for diagnostic and health screening.     

The study of human nails as an intake monitor for arsenic using neutron activation analysis

Arsenic is toxic to humans with the lethal dose being approximately 1 mg/kg/day. At much lower long-term exposures, arsenic is hypothesized to increase the risk of certain cancers. We have developed an irradiation position for the neutron activation analysis (NAA) of nail specimens for arsenic, in support of a case-control study involving New Hampshire residents consuming well water above the EPA Safe Drinking Water Standard of 0.050 ppm. Arsenic is bound to nail keratin through sulfhydryl groups proportional to intake providing a convenient means of integrating arsenic intake in population-based studies. Our objective was to develop the necessary facilities and procedures by which relatively small samples (i.e. 20 to 100 mg) could be accurately analyzed for arsenic, so that affordable nutritional epidemiology investigations, requiring large numbers of samples (>1000 in this case), could be undertaken. A high-flux reflector position, with minimal axial variation throughout the fuel cycle, suitable for pneumatic-tube irradiations, was characterized by measurement of the neutron flux distribution (thermal and epithermal) within the irradiation capsule over time. Results from application of the method to a case-control study of basal and squamous cell skin cancer will be presented.     

Processing of neutron activation analysis data using a general purpose PDP-11 minicomputer

A minicomputer system is described for the off-line reduction of gamma spectral data from neutron activation analysis. The hardware and software systems are described. Both data printouts and spectral plots are produced. The versatility of system permits the availability of computer capability for both on- and off-line functions in a variety of analytical techniques at a moderate cost and under the control of the experimenter.     

Determination of uranium in human head hair of a Brazilian populational group by epithermal neutron activation analysis

Hair analysis is extensively used in forensic sciences, assessment of occupational or environmental exposure and in some cases also for clinical and nutritional studies. Hair has a series of advantages in relation to other biomonitors, like blood and urine, since it is very easy to collect, very stable at room temperature and it represents not only instantaneous concentrations, but it can reveal the exposure along a given period of time. The assessment of environmental or occupational exposure to uranium is generally done by means of urine analysis, although a few papers have described attempts to use hair as a biomonitor. In the present work, epithermal neutron activation analysis has been used to establish base-line concentrations for a Brazilian populational group, living in Sao Paulo and not exposed to uranium, either environmentally or occupationally. For quality control, the reference materials Pine Needles NIST 1575 and Basalt USGS BCR-1 were used. The concentrations obtained for the control population studied up to now varied from about 2 to 50 ng·g⁻¹.     

Separation of antimony from synthetic cloth: Application in forensic science using neutron activation analysis

Summary A simple ion-exchange separation procedure was developed for selective removal of antimony from synthetic cloth to facilitate determination of several trace elements frequently used to identify gunshot residues by neutron activation analysis. Radiotracers of Sb, Ba, Cu, Co, As, Zn, Hg and Ag were employed to optimize the developed procedure. The method involves the quantitative retention of the above elements, except of Sb, from 0.2M ammonium carbonate solution using Chelex 100 resin and subsequent quantitative elution of the elements of interest with 2M nitric acid for gamma-ray spectrometry. The procedure was tested by simulated gunshot residues.     

Instrumental neutron activation analysis of the hair of metallurgical workers

Hair samples were collected from 20 metallurgical workers (10 males and 10 females) and from 59 control subjects (32 males and 27 females), whose jobs do not indicate a specific occupational exposure. The concentrations of ten minor and trace elements (Al, Co, Cu, Fe, Mg, Mn, Sb, Se, V and Zn) were determined by instrumental neutron activation analysis (INAA). The statistical data distributions, the sex and age influences in these elemental concentrations and the average values obtained for the control group were compared with published data. The effect of occupational exposure to the metallic elements was reflected in elemental composition of hair by significant higher concentration levels of Al, Co, Cu, Fe, Mg, Mn, Sb, V and Zn in the hair of the exposed group, when compared with the control group.     

Multielement neutron activation analysis of human scalp hair a local population survey in the Tokyo metropolitan area

Applying instrumental neutron activation analysis, multielement analysis of human hair was carried out to elucidate the levels of various trace element concentrations in hair of local population in the Tokyo metropolitan area. 202 hair samples were collected from the inhabitants classified by sex and five age groups. Using several combinations of irradiation time, cooling time and counting time, forty elements were quantitatively analyzed. The method of analysis for data including samples under detection limit is discussed, assuming that the frequanecy distribution of trace element contents in hair is log-normal.     

Instrumental neutron activation analysis of fly ash,aerosols and hair

Samples of coal, slag, emissions retained on the separating devices, fly ash, aerosols and hair taken in the area of coal-fired power plant were analyzed by means of instrumental neutron activation analysis. 13 to 23 elements were determined in the samples. The data obtained for emissions and aerosols were further evaluated by calculation of enrichment factors, correlation coefficients and by the ratio matching method. The concentrations of elements determined in the hair of exposed group were compared with the data of control and out control groups as well as with the recent data found for hair in other countries. It can be seen from the results that arsenic is the most serious pollutant in the area.     

Determination of molybdenum in hair and wool by neutron activation analysis

Neutron activation analysis was applied to the determination of molybdenum in hair and wool. Ashed samples of hair and wool were irradiated for 15 min at a flux of 5·10¹³ n/cm²/sec to produce ¹⁰¹Mo. An acid solution of the ash was first boiled in the presence of sodium bromide and bromate to volatilize bromine (⁸⁰Br and ⁸²Br radioisotopes interfere) and then extracted with 0.1% α-benzoinoxime in chloroform to remove ¹⁰¹Mo from other interfering radionuclides. The ¹⁰¹Tc daughter from ¹⁰¹Mo was measured over the 0.31-MeV γ-ray photopeak after allowing the separated ¹⁰¹Mo to decay for 15 min. The molybdenum concentration in hair varied from 0.02 to 0.13μg/g while wool was found to contain 0.04–0.58 μg/g.     

Use of neutron activation analysis for determination of gold in some human scalp hair samples

In the Egyptian society, it is usual until now that females wear extensively gold jewelry since their birth. The present work is carried out to determine gold content in scalp hair samples from some selected female donors of various ages. Instrumental Neutron Activation Analysis, with gamma ray spectrometry was applied for this study. The obtained data are compared with the available published data for analysis of hair samples from other countries. The correlation between age and gold concentration in hair samples is discussed. Interpretation of the influence of other factors which possibly may affect the contents of gold in the analyzed hair samples is also presented.     

Distribution of some elements in human hair and internal organs,determined by neutron activation analysis

Twenty four male autopsies were obtained from Shanghai, China. The samples of liver, lung, kidney cortex, brain and scalp hair were collected from the autopsies. The elements As, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, Mg, Mn, Na, Rb, S, Se and Zn were determined by neutron activation analysis (NAA). The present study shows the distribution of the elements in different tissues and provides the element level for normal persons in the local area. In general, the results are comparable with those of other countries.     

The neutron flux of a252Cf neutron activation analysis device using the MCNP code

This report presents results from the application of the Monte Carlo N-Particle (MCNP) computer code to the²⁵²Cf neutron activation analysis (NAA) Device in the Technical Physics Institute of the Heilongjiang Science Academy of the People's Republic of China. The thermal and epithermal neutron flux at the sample positions and the neutron and photon fluxes on the surfaces of the device were calculated. A comparison between the calculated and experimental thermal and epithermal neutron fluxes at sample positions yield relative errors of less than 10% for the thermal neutron flux.     

Instrumental neutron activation analysis applications in materials science and in forensic surveys

Neutron Activation Analysis (NAA) was applied to the characterization of lithious ceramic materials to be used as tritiogenic breeders in future fusion reactors. After neutron irradiation, measurements by -spectrometry were performed on the activated impurities, particularly on the ones with large neutron cross section. Irradiated samples were then annealed at rising temperatures, to obtain a fractional release of the tritium [formed by (n,) reaction on lithium] as element (HT/T₂) or tritiated water (HTO/T₂O). Barium and antimony were determined by NAA, on request of Italian Courts, as evidence of gunshot residues (GSR), on hands and clothes of suspected people. The sample is left unchanged, even if slightly radioactive, allowing further examinations, in case of controversial results. In some actual cases, NAA was performed on sample already examined by scanning electron microscopy (SEM/EDX), allowing the determination of several more elements and a more definite identification of the ammunitions involved in the crime.     

Trace element concentrations in human bone using instrumental neutron activation analysis

Instrumental neutron activation analysis has been applied to analyze 23 bone samples obtained from Libyan patient aged (3–80) years for the study of the concentration levels of trace elements Ba, Br, Ca, Fe, Sr and Zn and their concentration pattems regarding to the age and sex of the patients.     

Trace element concentration in human gallstones using instrumental neutron activation analysis

The concentrations of trace elements in two types of gallstones in 24 female patients in Tripoli aged 24–60 years have been determined using instrumental neutron activation analysis. These elements are Co, Fe, Mn, Se and Zn. The results are expressed in ppm and are in agreement with reported values. The data suggested that the concentrations of trace elements increase with age.Presented at the MTAA-8 Conference, September 16–20, 1991, Vienna, Austria.     

Determination of antimony in nail and hair by thermal neutron activation analysis

The concentration of antimony in nail and hair was determined by thermal neutron activation analysis. Samples were collected from the workers of an antimony refinery, inhabitants near the refinery, and residents in control area. They were irradiated by Kyoto University 5 000 kW Reactor for 1 h, and cooled for 30 to 100 days. After cooling, the concentration of Sb in nail and hair was estimated by measuring the intensity of gamma-ray from 124Sb of the samples, then the samples were washed by 0.1% aqueous solution of nonionic surface active agent in an ultrasonic cleaner. The gamma-ray spectrometry was done again (after washing). The concentration of Sb in nail before washing was 730 ppm for the workers, 2.46 ppm for habitants near the refinery, and 0.19 ppm for the control; after washing, it became 230 ppm for the workers, 0.63 ppm for habitants, and 0.09 ppm for the control. The concentration of Sb in hair before and after washing was 222 ppm and 196 ppm for the workers, and 0.21 ppm and 0.15 ppm for the control, respectively.     

Prompt gamma activation analysis using a chopped neutron beam

A beam chopper has been developed at the cold neutron PGAA facility of the Budapest Research Reactor. In the open phase of the chopper the usual prompt gamma-spectrum is recorded, while in the decay phase short-lived decay lines can be collected with good counting statistics on an extremely low baseline. A series of elements has been measured with the chopped beam technique to assess the capabilities of the new technique. An archaeological sample was also examined, to demonstrate how spectral interferences can be resolved.     

Determination of trace elements in human brain tissues using neutron activation analysis

Neutron activation analysis was applied to assess trace element concentrations in brain tissues from normal (n = 21) and demented individuals (n = 21) of both genders aged more than 50 years. Concentrations of the elements Br, Fe, K, Na, Rb, Se and Zn were determined. Comparisons were made between the results obtained for the hippocampus and frontal cortex tissues, as well as, those obtained in brains of normal and demented individuals. Certified reference materials, NIST 1566b Oyster Tissue and NIST 1577b Bovine Liver were analyzed for quality of the analytical results.     

Studies on neutron activation analysis using ion exchange preconcentration

Three convenient procedures are described for applying anion exchange resins to the preconcentration and irradiation support in neutron activation analysis. For each procedure the amounts of interferences were determined. The effect of the form, cross-linkage, pore size, and particle size of the resins on the elimination of interferences was investigated. Some other associated problems are also presented, viz. effect of concentration and temperature of washing solution, effect of irradiation time, and comparison with filter