Non-destructive determination of aluminum in biological reference samples using neutron activation analysis

The non-destructive methods of thermal and epithermal neutron activation analysis have been employed to determine the aluminum concentration of seven National Institute of Standards and Technology certified biological reference materials. Through the judicious use of both thermal and epithermal neutron activation analysis using bare and boron-lined irradiation carriers, the major and minor contributions of the³¹P/n, /²⁸Al and of the²⁸Si/n, p/²⁸Al reactions, respectively, to the²⁷Al/n, /²⁸Al reaction could be corrected for explicitly. Based on replicate determinations precision of the analysis ranged from 2.5% for citrus leaves determined at the 75 ppm level to 18% for bovine liver measured at the 1 ppm level. Accuracy was demonstrated whenever possible by comparison to existing published data.     

Neutron activation analysis of zeolite catalysts

A new method for the determination of aluminum and silicon has been developed for zeolite catalysts. In contrast to previous methods, thermal neutrons are used for the analysis of both elements, and cadmium absorbers are not needed. The silicon determination utilizes a one-hour irradiation to observe the³¹Si produced by the (n, ) reaction of³⁰Si. A 15-second irradiation is used for the²⁷Al(n, )²⁸Al reaction. The²⁸Al activity is corrected for the contribution from the²⁸Si(n,p)²⁸Al reaction by using the analyzed weight of silicon in the sample and the data for a silicon standard irradiated simultaneously with the zeolite and the aluminum standard. The quantitation limits are 0.012 g for silicon and 3.3×10^–5 g for aluminum. Sodium presents a significant interference, but this element can be removed by taking advantage of the ion exchange properties of these materials.     

Fast neutron activation analysis of silicon in aluminum alloys

The silicon content in an aluminum-silicon alloy was measured by nondestructive fast neutron activation analysis with fission spectrum neutrons. A boron nitride irradiation container reduced the flux of thermal and epithermal neutrons at the sample position, enhancing the²⁹Si (n, p)²⁹Al reaction. A detection limit of 0.4% silicon in a 0.5 g alloy sample was obtained.     

Non-destructive bone aluminum assay by neutron activation analysis

A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The²⁸Al signal obtained upon neutron irradiation includes contributions from both the reaction²⁷Al(n,)²⁸Al and³¹P(n,)²⁸Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the³¹P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction⁴⁸Ca(n, )⁴⁹Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 g g^–1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.     

A system for the determination of silicon in the human lung using neutrons from A 2MV Van de Graaff generator

Neutron activation analysis, using inelastic scattering, provides a quantitative, non-invasive technique of studying silica burdens and is potentially useful as a screening procedure for occupationally exposed workers. In this method, silicon is measured using the fast neutron inelastic scattering reaction²⁸Si(n,n )²⁸Si which emits 1779 keV -rays. The method requires a source of fast neutrons (> 2MeV). A 2MV Van de Graaff generator has been developed to produce a pulsed beam of 5.2 MeV neutrons. The pulsed beam has the advantage of improving measurement sensitivity by separating in Bone the inelastic scattering -rays from those due to thermal-neutron capture reactions. The incident neutron energy was chosen to maximise the silicon -ray count rate, while keeping the signal from the competing reaction³¹P(n,)²⁸Al negligible.     

Determination of Mg,Al, P,Cu and Mn in biological fluids by neutron activation analysis

Thermal and epithermal neutron activation analysis has been applied to determine the concentrations of magnesium, aluminium, phosphorus, copper and manganese in two biological fluids: blood serum and market milk. Both epithermal neutron irradiation and radiochemical separation (a chromatographic column of HAP) were used to get rid of the interferences from 24-Na. Strongly acidic solutions of the irradiated samples were passed through the columns of HAP, where sodium was completely adsorbed while, Al, Cu, Mg and Mn were eluted with an efficiency of 99±1%. Since both Al and P were determined through the formation of²⁸Al (2.24 min) thermal and epithermal neutron activation have been applied in order to determine the contribution of each radionuclide to²⁸Al activity. The determination of Mg, Al and P in milk samples was done instrumentally, whereas in the case of blood serum with higher concentration of Na, a radiochemical separation is essential in both cases. The concentrations of Al, Cu, Mg, Mn and P in blood serum and market milk were found to be 0.24±0.02 and 1.85±0.09 g Al/ml, 1.35±0.04 and 0.068±0.005 g Cu/ml, 22.9±1 and 98.9±8.6 g Mg/ml, 22±3 and 16±2 ng Mn/ml and 167±13 and 865±32 g P/ml, respectively.     

Neutron activation analysis for determination of trace elements in sediments in the Sea of Galilee,Israel

The feasibility of applying both thermal and epithermal neutron activation analysis for simultaneous determinations of elemental composition in sediments, collected from the Sea of Galilee (Kineret Lake), Israel, during 1988–1993, was experimentally investigated. In the present work, the concentrations of 30 elements (Al, Ba, Br, Ca, Ce, Co, Cs, Cr, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Rb, Sc, Si, Sr, Ta, Tb, Th, Ti, U, V, Yb and Zn) in sediments were determined. The validity of the method was checked by analyzing the U.S. NBS Standard Reference Material SRM-1633a; the elemental content found agreed well with the published certified data. Aluminium was determined by reactor neutron activation analysis (RNAA) taking into account the contribution of silicon to the total²⁸Al activity by the²⁸Si(n,p)²⁸Al reaction. Measurements of irradiated mixtures of Si and Al showed that the dependence of log SiAl mass ratio vs. log cadmium ratio (R _Cd) of²⁸Al is almost linear. The data can be analyzed more accurately by a parabolic correlation (log Si:Al mass ratio vs logR _Cd). The concentrations of fission radionuclide¹³⁷Cs, an activation radionuclide¹³⁴Cs (derived from Chernobyl accident) and the naturally occuring radionuclides⁴⁰K,²²⁶Ra and²³²Th in sediments were also measured by -ray spectrometry using Marinelli (Reentrant) Beaker-Sample Containers.     

Evaluation of atmospheric airborne particles in Lisbon, Portugal using neutron activation analysis

Summary We have employed Compton supression neutron activation analysis in conjunction with thermal and epithermal neutrons to detemine trace elements in airborne particulate matter in Lisbon, Portugal. As a result of the proximity of ocean marine, elements such as sodium and chlorine can signficantly decrease the analytical sensitivities of many elements of interest due ot the high backgrounds arising from ³⁸Cl and ²⁴Na. Compton suppression has resulted in the increase of the analytical sensitivities using thermal neutrons of Al, Ba, Ce, Cr, Cu, Ni, Rb, Se, Th, Ti, V, and Zn. The use of Compton suppression and epithermal neutrons significantly reduced the detection limits for As, I, K, Si, and W, while the utilization of solely epithermal neutrons improved the analyses of In.     

A quick method for the determination of the Al/Si weight ratio in alumino-silicates using an Am-Be neutron source

An irradiation procedure with fast and thermal neutrons from a 5 Ci Am-Be isotopic neutron source irradiation facility in combination with a 3'3' NaI(Tl) detector system has been used to determine Al/Si weight ratios in alumino-silicates. Samples were irradiated with and without Cd cover for 10 minutes and counted for 10 minutes after a waiting time of 1 minute. The peak area analysis of the 1779 keV gamma-ray line of ²⁸Al product radionuclide produced via ²⁷Al(n,γ)²⁸Al and ²⁸Si(n,p)²⁸Al reactions in combination with the neutron flux parameter at the irradiation site and nuclear data were used to determine Al/Si ratios. Due to discrepancy in literature data, Am-Be neutron source spectrum averaged cross sections of (n,p) reactions on ²⁷Al, ²⁸Si and ⁵⁶Fe were determined by the activation technique using ¹¹⁵In(n,n')^115mIn as the fast neutron flux monitor reaction. The method was tested using mixtures of high-purity Al₂O₃ and SiO₂ with known weight ratios of Al/Si and validated by a certified reference material BCS-CRM 348 (Ball Clay). Results are presented for bentonite, kaolin, bauxite, feldspar and ball clay samples from Nigeria. The method is non-destructive, rapid and suitable for use in-situ for large-scale exploration works and industrial process control. This revised version was published online in July 2006 with corrections to the Cover Date.     

Correction of interferences by fast neutrons for determination of sodium in silicon

The interferences caused by reactions with fast neutrons may be corrected with the help of substances containing the interfering element, which are irradiated together with samples and standards. For the correction of the apparent sodium content caused by the²⁸Si(n,p)-reaction we need silicon with an extremely low sodium content. Irradiation without such a standard needs calculation for interference with the help of flux monitors. Because of the highly effective threshold energy of the reaction an additional correction factor taking into account various neutron spectra in different irradiation positions is necessary.     

Rapid analysis of biological reference materials by instrumental neutron activation

Summary Instrumental neutron activation analysis (INAA) was applied to the rapid determination of cadmium and other elements in the IAEA biological reference material horse-kidney (H-8). Nuclear reactor neutrons and epithermal neutrons were used as neutron sources. Cadmium, bromide, iodine and phosphorus were determined by epithermal neutron activation analysis. Aluminum was determined by reactor neutron activation analysis taking into account the contribution of phosphorus to the ²⁸Al activity.     

Halogen determination in Arctic aerosols by neutron activation analysis with Compton suppression methods

The study of halogens particularly bromine and chlorine in Arctic aerosolshas received a great deal of attention in the past decade in ozone depletionduring polar sunrise studies. Iodine has also been studied as part of geochemicalcycling. We have shown that all three of the above elements can be determinedsimultaneously with very low detection limits using epithermal NAA in conjunctionwith Compton suppression methods. Besides lowering the background considerably,Compton suppression can eliminate or minimize the overlapping peak of the620 keV photopeak arising form the 1642 keV double escape peak of ³⁸Cl interfering with the 616.9 keV photopeak of ⁷⁹Br(n,) ⁸⁰ Br reaction. Iodine is ideally determined by epithermal NAAbecause of its very good resonance integral cross-section. Although chlorineis usually determined using thermal neutrons via the ³⁷Cl(n,) ³⁸Cl reactions, epithermal NAA is still feasible for the Arcticaerosol, since it has a major sea-salt component.     

Determination of pit-coal ash content with the use of an (α, n) neutron source

Activation with fast neutrons from a Pu/Be source enables the ²⁸Si(n, p)²⁸ Al and ²⁷Al(n p)²⁷Mg reactions to be utilized. Seventy-two samples of pit coals with ash contents ranging from 3 to 40% were measured. The calibration function between ash content and both 1.78- and 0.84-MeV γ-ray counts was linear. The standard deviation was 0.9% for a 17% ash content and 1.4% over the whole range of ash contents. Comparison with other methods is discussed.     

Epithermal neutron activation determination of uranium in environmental waters by neptunium-239 after preconcentration on activated carbon

A method for the analysis of uranium in natural waters based on preconcentration of uranium on activated carbon, irradiation with epithermal neutrons, and a high resolution gamma-spectrometry of²³⁹Np was developed. The chemical yield of uranium preconcentration is determined by treating a parallel sample to which a known uranium quantity is added. The lower limit of determination amounts to 1.4·10⁻⁸ g uranium per liter. The possible interfering in gamma-spectrometry of neptunium-239 was discussed too. The applicability of the proposed method is shown by the analysis of uranium in sea-, river-, geothermal-, drinking- and rain-water samples.     

Use of the Absolute Parametric Method to Evaluate the Analytical Significance of Threshold Reactions on P, Si, Al and Mg by NAA

We investigated the use of threshold reactions on magnesium, aluminum, silicon and phosphorus to determine elemental concentrations and also to correct analytical interferences, using the parametric method. The reactor neutron spectrum averaged cross sections of the threshold reactions on these elements were referred to the (111±3) mb value for the ⁵⁸Ni(n,p)^58g+mCo reaction cross section. The results of the cross section measurements are: ²⁵Mg(n,p)²⁵Na, 1.57±0.12 mb; ²⁸Si(n,p)²⁸Al, 5.68±0.25 mb; ²⁹Si(n,p)²⁹Al, 3.02±0.15 mb; ³⁰Si(n,)²⁷Mg, 0.1346±0.0090 mb; and ³¹P(n,)²⁸Al, 1.912±0.083 mb. The values for the cross sections of the following reactions: ²⁴Mg(n,p)²⁴Na, 1.441±0.092 mb; ²⁷Al(n,p)²⁷Mg, 3.84±0.18 mb; and ²⁷Al(n,)²⁴Na 0.721±0.028 mb were re-measured to check the methodology. We present the application of these values to the analysis of some reference materials.     

Determination of plutonium and americium in moss and lichen samples

A simple, sensitive and selective method is described for the simultaneous determination of plutonium and americium in lichen and moss samples which can be used as the atmospheric radioactivity bioindicators. Plutonium is separated from a HCl leaching solution by a Microthene-TNOA column; americium is separated by a KL-HDEHP column and purified by PMBP-TOPO extraction. A special attention has been paid to the decontamination of plutonium and americium from²¹⁰Po. Ten lichen and 12 moss samples from tree trunks have been analyzed: starting from 2 g sample, the average yields and the detection limits were 70.2±12.5% and 28 mBq/kg for plutonium and 70.0±15.1% and 34 mBq/kg for americium. The concentrations (mBq/kg) ranged from 28 to 4960 for^239,240Pu, from 28 to 171 for²³⁸Pu and from 34 to 1930 for²⁴¹Am, respectively.     

Aktivierungsanalyse von Silicium in Stahl mit schnellen Neutronen

Three experimentally different methods for analysing silicon in steel by activation with fast neutrons are described. By bombardment of²⁸Si with fast neutrons²⁸Al is obtained after a (n, p) reaction.²⁸Al emits a γ-radiation of 1.78 MeV. The difficulty lies in discriminating the 1.78 MeV peak out of the emitted radiation. The first method consists in determining the ratio of the 1.8 MeV peak to the 2.1 MeV peak of an activated iron sample. From this ratio one can deduct the contribution of²⁸Al to the 1.8 MeV peak of a silicon containing sample. The other method of separation makes use of the different half-lives of the 1.78 MeV γ-rays from²⁸Al and the 1.81 MeV γ-rays from⁵⁶Mn. The direct separation of the peaks with a Ge(Li) detector is the third method. This paper illustrates the possibilities of activation analysis with fast neutrons. For this reason the values measured are compared with the results of chemical analyses.     

Direct multielement determination of trace elements in boron carbide powders by direct current arc atomic emission spectrometry using a CCD spectrometer

The use of direct current arc atomic emission spectrometry (DC-arc-AES) with a CCD spectrometer for the direct determination of the trace impurities Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr in three well characterized boron carbide powders is described. The detection limits obtained by the procedure were found to be between 0.2 (Mg) and 25 (Na) ??g?g^?1 for the above elements. Three boron carbide powder samples with trace element concentrations between 0.9 (Cu) and 934 (Si) ??g?g^?1 for Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr ?? including the standard reference material ERM?-ED102 ?? were analyzed by DC-arc-AES. The relative standard deviations for 9 measurements when using 5.0?±?0.3?mg of the respective samples were found to vary from 6.2 to 27% for Al and Cu, respectively. The trace elements Al, Ca, Cr, Cu, Fe, Mn, Ni, Si, Ti and Zr could be determined in the standard reference material and their concentrations determined by DC-arc AES were found to be between 89 and 116% of the accepted values. Fe and Ti were determined by DC-arc AES in the three boron carbide samples as well as in Al₂O₃, BN, SiC, coal fly ash, graphite and obsidian rock. The correlation coefficients of the plots of the net intensities versus the accepted values over the concentration ranges from 18 to 1750 and from 6 to 8000???g?g^?1 are 0.999 and 0.990 for Fe and Ti, respectively.

137Cs,trace and toxic elements distribution in Austrian mushrooms

Various mushroom species have been analyzed for their elemental composition (i.e., Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) by means of ICP-AES. The accuracy of the measurements was confirmed by analyzing a series of the same samples by short time activation analysis. The data were evaluated statistically including the values of¹³⁷Cs. The results denote that the distribution of these elements and their correlation of these elements and their correlation coefficients are highly distinctive for each mushroom species. K, Na and P were found to correlate negatively with¹³⁷Cs in most species. Suillus grevillei and Cantharellus cibarius show high Be values (0.27 and 0.30 g g^–1, respectively), while Pb was high in Suillus grevillei (16.3 g g^–1) and Amanita rubescens (9.3 g g^–1). Higher levels of Cd were found in Rozites caperata and Russula vesca with a mean of 9.2 and 16.1 g g^–1, respectively. Cluster analysis was applied to classify these samples according to their botanical species using their elemental composition. The concentrations of Al, Cr, Mn, Na and¹³⁷Cs have no influence on the classification of these samples.     

The effect of high amounts of chlorine and sodium on measurement of aluminum by instrumental neutron activation analysis and decrease of spectrum noises by means of digital low pass filter equations

Aluminum is a pathogenic factor in some diseases, like Alzheimer and aluminum toxicity in dialysis patients. This subject signifies Al measurement in biological samples. Different methods have been proposed for Al determination. One of the known methods for the analysis of this element is instrumental neutron activation analysis (INAA). ³¹P, ²⁸Si, ³²Cl and ²⁴Na interfere the determination of Al in this method. In this study, the effects of high amounts of ³⁸Cl and ²⁴Na on the measurement of ²⁸Al are discussed. The data gathered by the detector is filtered by an equation named digital low pass filter equation with the help of a computer. The net-areas of filtered and non-filtered peaks of ²⁸Al are compared. Finally these areas are compared with the net-area of ²⁸Al peak in the standard reference material, NIST-SRM-1547. This revised version was published online in July 2006 with corrections to the Cover Date.