Phosphorus determination in milk and bone samples by neutron activation analysis

The determination of phosphorus in milk and bone samples by both radiochemical and instrumental neutron activation analysis is described. The radiochemical method consists of thermal neutron irradiation of samples and standards, sample dissolution, phosphorus precipitation as ammonium phosphomolyb-date, use of zinc holdback carrier and counting of the phosphorus-32 ß-activity. The instrumental method involves thermal neutron irradiation of samples and standards, waiting for a decay time and ß-counting. The methods were applied to commercial samples and reference materials.     

A study of flux monitoring for instrumental neutron activation analysis

The accuracy of instrumental neutron activation analysis is dependent upon measurement of the neutron flux to which samples are submitted. Flux monitoring techniques described and evaluated include: target cooling water activity, BFa counters, plastic scintillators, and a simple reference sample system. Evaluation is made on the basis of results obtained for oxygen analysis using primary standard materials. The superiority of the reference sample system for flux measurement during irregular neutron flux production is shown.     

Substoichiometry in neutron activation analysis technique

Neutron activation analysis has become one of the most sensitive and selective analytical technique for the determination of trace elements in a wide variety of matrices. Neutron activation involves the irradiation of the test sample and a standard of the element to be determined with thermal neutrons in a reactor, followed by dissolution of the test sample in the presence of carrier of the element to be determined. The carrier and radioisotopes are separated from the bulk of other induced activities (employing precipitation, solvent extraction, ion exchange etc.) and then the activity induced in the sample is measured on a suitable detector. The standard is treated identically. From the ratios of the activity of the sample and standard and the weight of the standard irradiated, the concentration of element in the test sample is calculated. A rapid, selective and sensitive method of radiochemical separation is subtoichiometric extraction in which the same amount of carrier is added to the irradiated test sample and standard. Exactly the same amount of reagent is added to both the sample and standard but in substoichiometric amounts, followed by the separation of the species formed by extracting it with an organic solvent. The activities of the extracts are measured. The amount of element present in the sample is calculated with help of the ratio of the activities and the weight of the standard taken. The advantages of the method are discussed. Application of substoichiometry in neutron activation has been elucidated with reference to the determination of Au in various samples by substoichiometric neutron activation analysis.     

Destructive and nondestructive analysis of some elements in tissue and environmental samples by thermal neutron activation analysis technique

A rapid and selective method has been developed and applied for determining elements present in tissue and environmental samples by both destructive and nondestructive activation analysis. Nondestructive activation analysis involves the irradiation of the sample and standard of the elements such as Mn, Na, and K with thermal neutrons from²⁵²Cf neutron source followed by radioassay of the (n,r) products on a HPGe detector coupled to a PC-based MCA. Elements are determined by irradiating the samples in the thermal neutron flux of the CIRUS reactor and radiochemically separating the isotopes of interest using substoichiometric extraction and precipitation technique. The statistical evaluation of the method with respect to accuracy and precision of the method and its sensitivity are discussed.     

Determination of selenium in individual food items using the short-lived nuclide77mSe

The selenium content of a variety of food items representing a normal hospital diet has been determined by cyclic instrumental neutron activation analysis (CINAA) through the 162-keV gamma-ray of the^77mSe nuclide. The CINAA method is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s, and counting for 20 s. The precision of the method has been significantly improved by recycling the samples up to 4 times. The accuracy has been evaluated by analyzing a number of certified reference materials of varied selenium levels.     

Activation analysis of vanadium in high alloy steels using manganese as internal standard

A method has been developed for the determination of vanadium in high alloy steels by radioactivation analysis. Manganese present in the steel sample is used as an internal standard, thus permitting accurate correction of neutron flux irregularities between sample and reference. The method was tested on 4 National Bureau of Standard samples having a vanadium content from 0.014 up to 2.04% and a widely differing composition as regards other alloy constituents. The results obtained by radioactivation in the Belgian Reactor BRI and the Amsterdam 28 MeV deuteron cyclotron show satisfactory accuracy as well as precision.     

Optimal use of instrumental neutron and photon activation analyses for multielement determinations in sewage sludges

A combination of instrumental neutron activation analysis (INAA) and instrumental photon activation analysis (IPAA) methods has been developed for multielement determinations in a variety of sludges and fertilizers. The precision and accuracy of both the methods have been evaluated by analyzing replicate samples, NBS standard reference materials, and an interlaboratory intercomparison sewage sludge sample. The concentration rages of up to 50 elements in raw and chemical sludges, sludge-based fertilizers, and other organic and inorganic fertilizers are reported here. The advantages and limitations of the INAA and IPAA methods are also discussed here.     

Use of standard reference materials as multielement irradiation standards in neutron activation analysis

Standard reference materials, normally used to check accuracy and precision of analytical methods or for interlaboratory comparisons, are proposed for use as multielement irradiation standards in neutron activation analysis (NAA). The advantages are simplicity of operation, and elimination of errors inherent in the preparation of a large number of synthetic standards at the trace element level. Examples of the approach are illustrated in the analysis of geological materials, soils, sediments, meteorites, lunar samples, coal and fly ash using the USGS diabase W-1 as the irradiation standard. Plant materials and animal tissue are analyzed using NBS Orchard Leaves as the irradiation standard. Best values for four popular SRM's (W-1, Bowen's Kale, Orchard Leaves, and Bovine Liver) are tabulated to facilitate further use of the proposed approach to multielement neutron activation analysis.     

Simultane instrumentelle Analyse einiger Haupt- und Nebenelemente in Calciumcarbid durch Aktivierungsanalyse mit 14 MeV-Neutronen

Mg, Al, Si, P, Ca, Ti, V, Se, Sr and Ba have been analyzed simultaneously in technical calcium carbide using 14 MeV neutron activation analysis. One irradiation and one or two measuring periods were necessary for each sample. Gamma spectra were taken with a high-resolution Ge(Li)-spectrometer, data were processed with a 32 k computer. Seven samples could be analyzed within one day. In order to control the accuracy of the results a multielement reference material was used as a secondary standard. The obtained data were in very good agreement with those of other analysis methods.      

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.     

Uptake of oxygen in a coal standard reference material® determined by fast (14-MeV) neutron activation analysis

A fast (14-MeV) neutron activation analysis procedure was employed to directly measure mass fractions of oxygen in coal samples. The procedure demonstrated sufficient precision and accuracy to determine a relative change of about 5% or more, in the oxygen mass fraction of about 12%. The procedure was applied to test samples of the newly developed SRM 1632c Trace Elements in Coal (Bituminous). The samples had been stored at three conditions: in liquid nitrogen vapor and at room temperature in the original containers packaged under argon, and for accelerated aging at 50 °C open to air. Following six months storage increments, duplicate samples of each of twelve bottles of the SRM were measured for each storage condition. In addition each sample was processed through ten separate analytical runs yielding a total of some 720 measurements per storage duration. Oxygen was determined by comparison to a primary standard potassium dichromate and the accuracy of the method was assessed through the analysis of replicate samples of three reference materials that are certified for oxygen content. The initial 6-months test period indicated uptake of oxygen in the open-air storage.     

Nitrogen determination in plant samples by fast neutron activation analysis

For the non-destructive deermination of the nitrogen content in plant samples 14-MeV neutron activation analysis was applied. Using powder samples of 0.7 g, irradiation time of 1 h and measuring time of 10 min, the accuracy of the determination is about +15%. The potassium content of the plant samples was determined by X-ray fluorescence analysis and correction was made for their contribution to the nitrogen activities.This work was supported in part by the Hungarian Academy of Sciences.     

Use of 14 MeV neutrons in analysis of explosive class materials

Samples of explosive class materials were analyzed by 14 MeV neutron activation technique to estimate concentrations of oxygen, nitrogen, aluminium and chlorine. For aluminized explosives, test of stability against temperature was carried out by heating samples at 75 °C and loss of nitrogen was studied by measuring the ratio of aluminium to nitrogen in the sample. Loss of oxygen and nitrogen in a triple base propellant heated at 71.6 °C, was also estimated by measuring residual oxygen and nitrogen in the heated samples. This technique is convenient to adopt in the laboratory and useful to decide quickly the suitability of explosive class materials for practical applications.     

A rapid calibration method for the determination of traces of oxygen by 14-MeV neutron activation analysis

A dual axis rotation irradiation system has been used in the development of a calibration method for the determination of oxygen in almost any matrix by 14-MeV neutron activation. The method allows the correction of matrix effects which arise from neutron removal and γ-self absorption, thus providing an accuracy of ± 2% for the oxygen analysis. The experimental results are interpreted on the basis of theoretically calculated mass absorption coefficients and neutron removal cross-sections.     

Non-destructive determination of zinc in biological certified reference materials

Non-destructive neutron activation analysis was employed to determine zinc in ten biological standard reference materials from the National Bureau of Standards and the National Research Council of Canada. The use of a 4 h. irradiation at a medium neutron flux allows excellent accuracies, precision and sensitivities to be attained for all the samples analyzed. It is suggested that neutron activation analysis be one of the benchmark methods for the determination of zinc in biological reference materials for concentrations as low as the one part per million level.     

Internal standard method for determination of gallium and some trace elements in bauxite by neutron activation analysis

A method is described for the determination of gallium and other trace elements such as Ce, Cr, Hf, Lu and Th in bauxite by the technique of neutron activation analysis using gold as internal standard. Isopropyl ether was used as organic extractant to extract radioactive gallium from the sample. This method yields very good accuracy with a relative error of ±3%.     

Determination of carbon,nitrogen and phosphorus in cattail using cold neutron prompt-gamma activation analysis

Summary A method for the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt-gamma activation analysis (CNPGAA) has been developed and evaluated through the analysis of standard reference materials (SRM). After extensive preparation, approximately 400 mg cattail samples from the lower Apalachicola River floodplain were irradiated in the CNPGAA facility at the National Institute of Standards and Technology (NIST). The results of numerous field samples and two standard reference materials using the nuclear method show favorable comparison to results obtained by a CHNS/O analyzer.     

Comparison of Different Analytical Techniques for the Determination of Organic Mercury

Abstract

Methods for the determination of (1) total organic mercury (Hg) using an extraction +neutron activation analysis, (2) the sum of methyl-Hg+phenyl-Hg using ¹³¹I^?-Cl^? exchange and (3) methyl-Hg using two different Westöö modifications, have been compared. Sample materials were 8 falcon livers, 5 pike livers and 2 pike muscles. Although differences were found between the methods, interaction effects caused by either sample inhomogeneity or bad performance of the analytical methods impeded a clear interpretation of the comparison. Total Hg in the samples was determined by neutron activation analysis (NAA) and atomic absorption spectrometry. The accuracy of the total Hg determination using NAA was verified by the analysis of certified reference material.

In addition to the other organic Hg determinations phenyl-Hg was determined separately in some of the samples by an isotope exchange method using ²⁰³Hg²⁺.

The main conclusion of the study was that there is a demand for reference materials certified for at least total organic Hg and methyl-Hg.     

常见炸药的稳定同位素比值分析方法研究进展

炸药的深度比对与溯源对于爆炸案事件的侦破具有重大意义,以不同地域来源的原料或不同生产工艺生产的炸药,其组成元素的稳定同位素比值具有差异,因而稳定同位素比值可作为炸药深度比对与溯源的重要指标。稳定同位素比值质谱法(IRMS)作为一种高精度的稳定同位素比值测量手段,已逐渐发展成熟,与元素分析仪、气相色谱仪、液相色谱仪等仪器联用,在食品安全、环境保护、法庭科学等领域应用广泛。IRMS在炸药比对与溯源上亦发挥了重要作用,自1975年IRMS被应用于区分不同国家生产的三硝基甲苯(TNT)以来,IRMS已成功用于多种炸药的分析。但目前尚未见有文献系统地总结常见炸药的稳定同位素比值分析研究进展。该文介绍了稳定同位素比值分析的相关原理、仪器组成及特点,分别总结了硝酸铵、黑火药、TNT、太恩、黑索金等常见炸药的稳定同位素比值分析方法,汇总了文献报道的不同国家生产的硝酸铵、黑火药、TNT等炸药的稳定同位素比值。文章就不同炸药的稳定同位素比值差异、炸药生产、存储过程中相关因素对同位素比值的影响,爆炸前后稳定同位素比值的变化情况等内容进行了分析。本文还指出了目前炸药的稳定同位素比值分析研究中存在的问题,对可能的解决办法进行了讨论,对未来的发展方向提出了建议。     

Determination of arsenic and bromine in hot spring waters by neutron activation analysis

Concentrations of arsenic and bromine dissolved in hot spring waters have been determined by neutron activation analysis using 0.5 cm³ of sample waters without any chemical pretreatment. The samples prepared for neutron irradiation were simply pieces of filter papers which were infiltrated with samples. With the results of satisfactorily high accuracy and precision, this analytical method was found to be very convenient for the determinations of arsenic and bromine dissolved in water at ppm to sub-ppm levels.This revised version was published online in November 2005 with corrections to the Cover Date.