RNAA for arsenic,cadmium, copper,and molybdenum in CNS tissues from subjects with age-related neurodegenerative diseases

Reactor thermal neutron irradiation of biological matrices induces high levels of intense gamma-ray or bremsstrahlung radiation from⁸²Br,⁴²K,²⁴Na, and³²P, that interfere with the determination of As, Cd, Cu, and Mo by INAA. Central nervous system (CNS) issue samples from subjects with Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and controls were analyzed using a simple RNAA procedure involving a rapid two-step solvent extraction procedure to determine these four elements. Significant increases (p0.05) in concentrations of Cd and Mo were observed for brain of AD subjects compared to controls, but significant imbalances were not observed for ALS subjects. Concentration data for these elements in selected international reference standards are also presented.     

Sensitivity improvements in the determination of mercury in biological tissues by neutron activation analysis

The possible association of dental amalgam surface exposure, brain mercury (Hg) levels, and pathological markers of Alzheimer's disease (AD) in the brain is the subject of an on-going study in our laboratory. Two radiochemical neutron activation analysis methods and the use of instrumental neutron activation analysis (INAA) with Compton suppression spectrometry have been evaluated for improving our INAA Hg detection limit (2.8±0.6 ng/g, wet-weight basis) in human tissue. Large numbers of samples dictated the use of a purely instrumental method or rapid, simple radiochemical separations. Human brain tissues and NIST biological standards were analyzed using a precipitation of Hg₂Cl₂, a solvent extraction utilizing sodium diethyldithiocarbomate, conventional INAA, and INAA with Compton suppression. The radiochemical precipitation of Hg₂Cl₂ proved to be the most useful method for use in our study because it provided a simultaneous, quantitative determination of silver (Ag) and a Hg detection limit in brain tissue of 1.6±0.1 ng/g (wet-weight basis).     

NAA methods for determination of nanogram amounts of arsenic in biological samples

Summary The determination of arsenic at natural levels in biological materials remains difficult. Many analytical techniques cannot detect the low levels present in typical biological tissues and other techniques suffer from interferences. This paper reviews uses of neutron activation analysis (NAA) at NIST to determine nanogram amounts of arsenic in biological reference materials with radiochemical (RNAA) or instrumental (INAA) procedures. INAA is compromised by high activities from ²⁴Na, ⁸²Br, and ³²P that may be formed during irradiation of biological tissues, and result in detection limits as high as 0.1 mg. Lower detection limits have been achieved using state-of-the-art gamma-ray spectrometry systems in INAA and a variety of procedures in RNAA. These techniques and procedures were applied recently at NIST to the determination of arsenic in urine, nutritional supplements, and total diet samples.     

INAA assay of bullet lead for lead via204mPb

Using reactor instrumental neutron activation analysis (INAA), experiments have shown that the percent lead in typical bullet leads can be measured to a relative standard deviation of around ±1%, even without use of cadmium. Under the conditions used, the forensically important elements Sb, As, Cu and Sn can be measured at the same time. The other important element, Ag, must still be measured satisfactorily in a separate, short irradiation that utilizes the 24.6 s¹¹⁰Ag (or 2.41 m¹⁰⁸Ag) activities.     

Further investigating the determination of phosphorus in plants by INAA using<Emphasis Type="Italic"> bremsstrahlung</Emphasis> measurement

Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy. Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because ³²P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from ³²P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg⁻¹ were irradiated at a thermal neutron flux of 9.5 × 10¹² cm⁻² s⁻¹ and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated, the production of ³²P from sulfur, and the contribution of Compton scattering should be considered for producing good results.     

A pilot study to measure levels of selected elements in Thai foods by instrumental neutron activation analysis

A pilot study was carried out to evaluate the scope of instrumental neutron activation analysis (INAA) for measuring the levels of selected elements in a few commonly consumed food items in Thailand. Several varieties of rice, beans, aquatic food items, vegetables and soybean products were bought from major distribution centers in Bangkok, Thailand. Samples were prepared according to the protocols prescribed by the nutritionist for food compositional analysis. Levels of As, Br, Ca, Cd, Cl, Cr, Cu, Fe, K, Mg, Mn, and Zn were measured by INAA using the irradiation and counting facilities available at the Thai Research Reactor with the maximum in-core thermal neutron flux of 3 × 10¹³ cm^?2 s^?1 of the Thailand Institute of Nuclear Technology in Bangkok. Selenium was determined by cyclic INAA using the Dalhousie University SLOWPOKE-2 Reactor facilities in Halifax, Canada at a thermal neutron flux of 2.5 × 10¹¹ cm^?2 s^?1. Both cooked and uncooked foods were analyzed. The elemental composition of food products was found to depend significantly on the raw material as well as the preparation technique.     

Performance of Compton suppression system (CSS) and applicability in food matrices

As a non-destructive and multi-element technique, with high-level metrological properties, instrumental neutron activation analysis (INAA) has an important role to determine chemical elements in food. However, its use may be limited when looking for mass fractions near the detection limits. The Compton scattering of higher energy gamma-rays raised the spectrum baseline thus impairing the determination of several elements. Therefore, the gamma-ray spectrometry with Compton suppression becomes an alternative for improving the performance of INAA, since it can reduce the uncertainty of measurements and the detection limits by increasing the proportion between photopeak area and baseline. Here the performance of a Compton suppression system set by Ortec, with 50% relative efficiency and 2.04?keV resolution (FWHM) for the 1,332?keV photopeak, was evaluated for food analysis. Samples of beans, chickpeas, lentils, peas, and rice were irradiated with neutrons and measured in the suppression system. Detection limits calculated from suppressed and unsuppressed spectra were compared. The suppression factor achieved by the system for ¹³⁷Cs was 5.88?±?0.11 (n?=?20) in the plateau region (358 to 382?keV), which was stable along a 20?week period and similar to the data provided in literature for other systems. Amongst fifteen elements determined, the detection limits for Br, Co, La, Na, Sc, and Se were not improved by the use of Compton suppression. On the other hand, the variable improvement obtained for As, Ca, Cd, Cr, Fe, Hg, K, Rb, and Zn corroborated the idea that the performance of the Compton suppressor must be individually assessed for each type of sample.     

Rare earth element (REE) in surface mangrove sediment by instrumental neutron activation analysis

A study is carried out on the concentrations of rare earth element (REE) elements present in surface mangrove sediments from 10 locations throughout west coast Malaysia. In carrying out the analysis, the best and most convenient method being the instrumental neutron activation analysis (INAA). Samples were obtained, dried, crushed to powdery form and samples prepared for INAA. All the samples for analysis were weighted approximately 150 mg for short irradiation and 200 mg for long irradiation time. As calibration and quality control procedures, blank samples, standard reference material SL-1 were then irradiated with thermal neutron flux of 4 × 10¹² cm^?2 s^?1 at the MINT TRIGA Mark II research reactor which operated at 750 kW by using a pneumatic transport facility. The REE elements of surface sediment samples in this study are Dy, Sm, Eu,Yb, Lu, Tb, La and Ce. It was found that the level of concentrations of all the REE elements varies in the range (0.35–117.4 mg/kg). The geochemical behavior of REEs in surface sediments and normalized pattern (chondrite and shale) has been studied. The degree of sediments contaminations were computed using an enrichment factor. The results showed that the enrichment factor varied in the range (0.75–6.75).     

Determination of zinc in geological samples using Compton suppression with thermal and epithermal instrumental neutron activation analysis

The determination of Zn in geological samples using instrumental neutron activation analysis is usually done using the ⁶⁴Zn(n,γ)⁶⁵Zn reaction and its 244 day half-life. However this analysis has proven to be potentially difficult. This is due to its relatively low neutron absorption cross section and gamma ray intensity, and the relatively high neutron absorption cross section and gamma intensity of ⁴⁶Sc, which has an energy peak that is only 5 keV greater than ⁶⁵Zn. The use of a high resolution detector makes it possible to differentiate between the ⁶⁵Zn and ⁴⁶Sc photopeaks peaks. However, the dominating ⁴⁶Sc gamma ray can even make peak fitting routines unsuccessful in the proper determination of ⁶⁵Zn. The use of a Compton suppression system suppresses the ⁴⁶Sc peak, which has two coincident gamma-rays, and this greatly improves the ratio of the height of the ⁴⁶Sc 1120.5 keV photopeak to the ⁶⁵Zn 1115.4 keV photopeak. Irradiating the sample with epithermal neutrons also improves the measurement since ⁶⁵Zn has a higher cross section for epithermal neutrons rather than thermal neutrons, whereas ⁴⁶Sc has a higher thermal cross section. Another technique to determine zinc is the use of ⁶⁸Zn(n,γ)^69mZn reaction with its 13 h half-life using epithermal neutrons and Compton suppression INAA. However, the 438 keV gamma ray of ^69mZn has no interference with any adjoining photopeak. A critical comparison of these two methods is given.     

Determination of 22 elements in geological samples by instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·10¹² n·cm⁻²·sec⁻¹ and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively.     

Reversed-phase extraction chromatography–neutron activation analysis (RPEC–NAA) for copper in natural waters using Amberlite XAD-4 resin coated with 1-(2-thiazolylazo)-2-naphthol

A preconcentration neutron activation analysis method has been developed for the determination of trace levels of Cu in natural waters including seawater with an absolute detection limit of 0.106 μg. The method involves the preconcentration of Cu onto Amberlite XAD-4 resin coated with 1-(2-thiazolylazo)-2-naphthol using reversed-phase extraction chromatography (RPEC). Copper is assayed through its neutron activation product ⁶⁶Cu (half-life = 5.10 min) by direct irradiation of the resin bed. Factors affecting the uptake of Cu onto the ligand-impregnated resin have been investigated; these include flow rate, pH, column height, presence of other trace elements, major elements, and interfering matrix. The RPEC–NAA method has been validated by analyzing NIST and NRC water reference materials.     

Elemental analysis in bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis

The concentration of rare earths and other elements have been determined in the bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis (INAA). The samples and the standards soil-5, soil-7, coal fly ash and pond sediment were prepared and simultaneously irradiated for short and long time at the TRIGA Mark-II research reactor facility of Atomic Energy Research Establishment, Savar, Dhaka. The maximum themal neutron flux was of the order of 10¹³ n·cm^–2·s^–1. After irradiation the radioactivity of the product nuclides was measured by using a high resolution high purity germanium detector system. Analysis of -ray spectra and quantitative analysis of the elemental concentration were done via the software GANAAS, it has been possible to determine the concentration level of 27 elements including the rare earths La, Ce, Sm, Eu, Tb, Dy and Yb and uranium and thorium.     

Chemical characterization of graphite by instrumental neutron activation analysis

Nuclear and commercial grade graphite samples were analysed by instrumental neutron activation analysis (INAA) using high flux reactor neutrons. Eleven elements (Na, K, As, Sc, Fe, Cr, Co, Zn, La, Ce, and Sm) were determined in eight samples of graphite (two nuclear grade and six commercial grade) by irradiating at a neutron flux of 3?×?10¹³ cm^?2 s^?1 in CIRUS reactor and assaying the activity by high-resolution gamma ray spectrometry using 40% relative efficiency HPGe detector coupled to an MCA. Concentrations of elements were determined by relative method of INAA. Results of both types of graphites as well as detection limits achieved by INAA method are discussed in the paper.     

Practical aspects of instrumental neutron activation analysis with the Miniature Neutron Source Reactor (MNSR)

Instrumental neutron activation analysis (INAA) often relies on reactions withthermal neutron fluxes of 10¹²cm^-2s^-1 like with the Chinese madeMiniature Neutron Source Reactor (MNSR). Next to the obvious advantages of a small reactor,there are the inherent limitations of intermittent operation, the low flux and its eventualdecrease over the working period and the necessity of using cyclic INAA rather than singlerabbit irradiations. They bear on the precision and accuracy of results. This paper dealswith the use of the MNSR for routine INAA in terms of the capacity of existing and eventualadditional irradiation facilities and with the elimination of systematic biases and theoptimization of precision. A survey of eventual applications is added.     

Trace element content of medicinal plants from Algeria

Neutron activation analysis (INAA) has been applied to multielemental determination of eleven medicinal plants used to cure the urinary tract diseases observed in Algeria. These plants include Androgena Citratus, Ceratonia Siliquata, Punica Granatum, Glyryrrhiza Glabra, Lausaunia Alba, Fragaria Vesca, Arbutus Unedol, Hordeum Vulgaris, Papieteria Officinalis, Zea Mays L, and Davallia Seae. Concentrations of twenty elements Ba, Br, Ca, Cl, Co, Cu, Cr, Fe, I, Mn, Na, Mg, Rb, Sb, Se, Sc, Sr, Ti, V, and Zn have been determined by short, and long irradiation times with a thermal and epithermal flux of 1.4·10¹² n·cm⁻²·s⁻¹ and 1.4·10¹¹ n·cm⁻²·s⁻¹, respectively. These analyses were performed in conjunction with Compton suppression. In almost herbs studied the Co, Cr, Cu, Rb, Sb, Sc, Se and V are found to be present at trace levels, Br, Mn, and Zn at the minor level, and Ca, Cl, Fe, Mg and Na are generally at the major level. The accuracy of the measurements has been evaluated by analyzing NIST-botanical references materials.     

Determination of trace elements in high purity copper by INAA, GFAAS and ICP/AES

Trace impurity elements in high purity copper metal (4 mine class) put on the market were analyzed by Instrumental Neutron Activation Analysis (INAA) and the results compared with those from Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS) and Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES). The sample irradiation was done at the irradiation facilities (thermal neutron flux, 5·10¹² n·cm⁻²·s⁻¹) of the TRIGA Mark-III research reactor in the Korea Atomic Energy Research Institute. Four unalloyed copper standards (NIST SRM # 393, 394, 395 and 398) were used to identify the accuracy and precision of the analytical procedure. The homogeneity of samples was assessed by means of the elements such as Ag, As, Co, Sb, Se and Zn. The analytical results of INAA, GFAAS and ICP-AES were in good agreement within expected uncertainties each other and showed the possibility of using them for the analytical quality control.     

Study of the correlation of trace elments in human hair and internal organs by NAA

24 male autopsy cases aged 35–60 years have been collected from Shanghai China to study the relationships between human hair and internal tissues. Autopsy samples of hair, kidney-cortex, liver and lung were analyzed. A radiochemical neutron activation analysis (RNAA) based on a simple group extraction scheme was used for measuring the trace elements As, Cd, Hg, Cu and Zn. Zinc diethyldithiocarbamate Zn(DDC)₂ and methly isobutyl ketone-iodide have been chosen as reagent. Trace element of Se was determined by instrumental neutron activation analysis (INAA). A SLOWPOKE reactor with a thermal neutron flux of 8·10¹¹ n·cm^–2·s^–1 and a swimming pool type reactor with a thermal neutron flux of 1·10¹³ n·cm^–2·s^–1 were used for short and long irradiation of samples, respectively. The reliability of methods has been checked by analyzing biological standard reference materials Horse Kidney (IAEA H8), Tomato Leaves (NBS 1573) and Human Hair (NIES-5). The analytical results show that toxic elements As, Cd and Hg exist in a larger individual variability than the essential elements of Cu, Se and Zn for each tissue. A linear regression analysis related to the six elements of primary interest for the IAEA Coordinated Research Program (CRP) has been done by a computer program for each pair of hair-tissue. A positive correlation is found between concentration of As in hair and kidney-cortex, the correlation coefficient r is 0.751 (p<0.01). Positive correlations between concentration of Se in hair and liver, kidney-cortex and lung are also observed in this study. It shows that the elements As and Se in hair may be useful indicators for assessing certain internal tissues of normal persons. A comparison of Cd concentration in lung shows a significant difference between smokers and non-smokers. A significant correlation between element Cd and Zn in kidney-cortex is also presented in this paper.     

A search for losses of chemical elements during freeze-drying of biological materials

Possible losses of seven chemical elements were investigated in biological tissues during freeze-drying in vacuum. Thyroid glands were taken during post-mortem examination of 23 people died of different diseases. Instrumental neutron activation analysis (INAA) was used to estimate contents of Br, Ca, Cl, I, K, Mg, and Na. The nuclear reator vertical channel with flux density of 1.2·10¹³n·cm^–2·s^–1 was used for neutron irradiation. The analysis was carried out using short-lived radionuclides induced in samples after neutron irradiation. Then thyroids were freeze-dried at below 0 °C in vaccum up to the constant mass (lyophilisation) and then homogenized. Samples of lyophilised and homogenized tissues were again studied by INAA. The lack of difference between the results of the analysis before and after lyophilisation is an evedence of no loss of Br, Ca, Cl, I, K, Mg and Na during freeze-drying of biotissues in vaccum.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.