The application of a252Cf neutron multiplier for routine instrumental neutron activation analysis

The successful application of instrumental neutron activation analysis for routine determinations depends on the ability to produce accurate and precise analytical results in a relatively short time. An important factor in obtaining the desired speed has been the availability of a low-cost, moderate-flux neutron source for on-site use. The²⁵²Cf neutron multiplier (CFX), designed and constructed by Intelcom Rad Tech Corporation of San Diego, California, is a subcritical assembly capable of continuous, stable operation and has provided us with the ability to determine more than 35 elements as major and minor components. The CFX produces a thermal neutron flux of ∼2×10³ n/cm²-sec by a 100-fold multiplication of the neutrons emitted from a 1 mg²⁵²Cf source. Of particular importance in its application at Kodak has been the determination of the halogens Cl, Br, and I, both singly and simultaneously, in various matrices including photographic materials.     

Determination of chromium, iron and cobalt in high-purity niobium by radiochemical neutron activation analysis

Summary Chromium, iron and cobalt were determined in niobium by radiochemical neutron activation analysis. The main steps of the technique involved the irradiation of the samples in a medium or high-flux reactor, the post-irradiation decontamination of the sample surface, a two-step separation procedure based on anion-exchange from HF and HCl medium, and counting the separated indicator radionuclides with a well-type NaI-detector. For a 42-day irradiation at a thermal neutron flux of 8×10¹³ n cm^–2 s^–1 and a sample weight of 100 mg, the limits of detection are: 10 ppt for chromium, 1.5 ppb for iron and 4 ppt for cobalt. The results obtained by this technique are compared with data obtained by radiochemical proton activation analysis and atomic absorption spectrometry.

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Bestimmung von Chrom, Eisen und Cobalt in hochreinem Niob durch radiochemische Neutronenaktivierungsanalyse

Zusammenfassung Die Hauptschritte der Methode sind die Bestrahlung der Probe in einem Mittel- oder Hochflußreaktor, eine anschließende Oberflächendekontamination und die spezifische Abtrennung der Indicatorradionuklide mittels Anionaustausch aus Flußsäure- und Salzsäure-Medium, sowie die Messung der Radionuklid-Fraktionen mit einem Natriumjodid-Detektor.Für eine 42tägige Bestrahlung mit Reaktorneutronen bei einem thermischen Fluß von 8×10¹³ n cm^–2 s^–1 konnte bei einem Probengewicht von 100 mg für Chrom eine Nachweisgrenze von 10 ppt, für Eisen von 1,5 ppb und für Cobalt von 4 ppt erreicht werden.Die mit dem Verfahren erhaltenen Ergebnisse werden mit denen der radiochemischen Protonenaktivierungsanalyse und der Atomabsorptions-Spektrometrie verglichen.

     

Substoichiometric determination of chromium by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of chromium. It is based on the substoichiometric extraction of chromium diethyldithio-carbamate into methyl-isobutyl-ketone from acetate buffer solution in the presence of EDTA and potassium cyanide. The method has been applied for the determination of chromium in high-purity calcium carbonate and NBS glasses as standard reference materials.     

Multielement standards in routine reactor neutron activation analysis

The application of multielement standards (MES) in routine neutron activation analysis brings a whole range of advantages. This paper deals with the experience obtained during many years of application of these MES. Nine of these MES contain a total of 50 elements in suitable combinations and concentrations; thus, the determination of most of the common elements by NAA can be carried out simultaneously. This refers to the following elements: Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Ag, Cd, In, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, W, Re, Au, Hg, Th and U. For the determination of the remaining elements such as Zr, Ta, Ir etc., single element standards (SES) are used.     

On the use of parent—Daughter relations in routine instrumental neutron activation analysis

Measurements on daughter radionuclides of parent-daughter relations can be used in routine instrumental neutron activation analysis if appropriate corrections for differences in irradiation, decay and counting time are applied. These corrections and their precision are discussed.     

Reactor-detector calibration for routine instrumental neutron activation analysis of geological materials

A reactor-detector combination has been calibrated for routine determination of trace elements by instrumental neutron activation analysis using the semi-absolute method with flux corrections. The reproducibility of the calibration constants is studied using the standard rock AGV-1 for the activities¹⁴⁰La,¹⁴¹Ce,¹⁵³Sm,¹⁶⁰Tb,¹⁵²Eu,¹⁷⁵Yb,¹⁷⁷Lu,¹³¹Ba,⁶⁰Co,⁵¹Cr,¹³⁴Cs,¹⁸¹Hf,²³³Pa,⁴⁶Sc, and¹⁸²Ta. The results show that a calibration reproducibility with a relative precision of better than 5% can be achieved in many of the cases without any special precautions. To study the applicability of the calibration constants, concentrations of the corresponding elements have been determined in standard rocks, G-2, W-1 and GSP-1 and are compared with the recommended values.     

Determination of chromium in blood by neutron activation analysis

A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10⁻³ μg Cr. Dried blood was irradiated with a neutron flux of 10¹² n·cm⁻²·sec⁻¹ in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid. The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of⁵¹Cr. In order to make correction for the interfering reaction⁵⁴Fe(n,α)⁵¹Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between 1.03×10⁻² and 5.2×10⁻² ppm Cr.     

Determination of iron isotopes by neutron activation analysis

Instrumental neutron activation analysis has been applied to the determination of Fe isotopic abundances in iron materials with the experimental accuracy of 5%. The proposed method can be considered as a quite simple and fast quality check system on the iron isotope enriched oxides used as standard in Mössbauer spectroscopy.     

Multielement neutron activation analysis of an iron ore

Multielemental analysis of an iron ore from the Kingdom of Saudi Arabia was carried out using Instrumental Neutron Activation Analysis (INAA) with Ge(Li) detectors. The spectra were analysed with the help of an off-line computer programme. Twenty five elements are observed to be present in the ore. The elements of major interest are Fe, Al and Ca with 51.5%, 3.6% and 2.2% concentrations, respectively.     

Studies of erythrocyte kinetics using stable chromium and neutron activation analysis

The survival of erythrocytes is measured using⁵⁰Cr labelling followed by neutron activation analysis. The measured half-life of⁵⁰Cr tagged autologous erythrocytes in the rhesus monkey (17.9±2.7 d) compares favorably with the value of 17.1±1.4 d measured using the standard method of radioactive⁵¹Cr labelling. With the use of stable chromium as a tagging agent, erythrocyte kinetics can be monitored without the problems associated with the use of radioactive isotopes. The method presented is highly reproducible and eliminates the necessity of any chemical separation of chromium. The results of both⁵⁰Cr and⁵¹Cr labelled erythrocyte survival studies are presented.     

The use of neutron activation in dietary reference material analysis

Summary Results for a number of trace elements in a total human diet material (USDIET-1), obtained by the application of both INAA and RNAA are presented. Several dietary reference materials such as NBS SRM 1577A, and BCR CRM Single Cell Protein were also analyzed, and these results are also given. Combining measurements on short and long lived radionuclides, the INAA approach is useful for the determination of about 20 elements. In order to expand the elemental coverage or improve detection limits, RNAA was also explored in two modes: separation of radionuclides using organic ion exchange resins and the use of hydrated manganese dioxide. This combination is applicable to 15 trace elements. For example, using RNAA, the following results were obtained for USDIET-1: Cd=31.8, Mo=280, Cr=71, Ag=4, As=117 and Sb=9.4 g/kg. In the INAA mode, special attention was given to Al, F and Se. The F content of USDIET-1 was found to be 840 mg/kg, a rather high value, resulting from handling USDIET-1 by Teflon tools. By applying INAA and RNAA under two different laboratory conditions, it has been demonstrated that, even for the so-called difficult to determine elements like Cr, As or Mo, consistent results can be obtained. Thus, NAA promises to be a strong tool for human nutritional studies.

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Einsatz der Neutronenaktivierung für Nahrungsmittel-Referenzmaterialien

     

In-beam neutron activation analysis of stainless steel and iron ore

Pulse radiolysis of MIT and DIT irradiated to doses from 2.8·10⁴ to 85·10⁴ rads is studied by ascending chromatography. The 3-iodo-4,5-dihydroxyphenylalanine (DOPA-I) and 3-iodo-4-hydroxyphenylalanine have been identified as first stages of degradations of MIT and DIT, respectively. G values are 0.015 for MIT (10⁻⁵M) and 0.004 for DIT (0.5·10⁻⁵M). By self decomposition MIT is degraded less rapidly than DIT and there is no formation of DOPA-I.      

The use of the microtron for the activation analysis of pure metals and alloys

Oxygen and carbon concentrations up to 0.06 ppm and 0.03 ppm respectively were determined in high purity metals such as Fe, Cu, Nb, Mo, In and some others. Analytical procedures and results of the determination of alloying additives in a number of rare metal alloys are given. The relative standard deviation constitutes 0.02 to 0.04. Accuracy of the procedures used is confirmed by a comparison of experimental results with those of the other analytical methods. Experimental data on the sensitivity of determining 35 elements are reported on irradiating them with thermal neutrons and a bremsstahlung emitted by the microtron. For most elements (for radioactive isotopes having a half-life of above 2 min.) sensitivity of the analysis is 10⁻⁶ to 10⁻⁸, g, at the microtron current of 30 μA and irradiation time of less than 10 min.     

Determination of sodium and chlorine in pure water by neutron activation analysis

Neutron activation analysis was applied to determine sodium and chlorine in high purity water samples. After irradiation of the sample,³⁸Cl was purified from⁸²Br and other nuclides by carbon tetrachloride extraction and silver chloride precipitation, and²⁴Na was separated from other alkali elements and other nuclides by adsorption of²⁴Na on HAP. The activities of both elements were measured by conventional G.M. counter. The contamination of the elements from container walls during neutron irradiation and the interference with³⁸Ar(n, p)³⁸Cl reaction on argon dissolved in water were also examined. Water samples containing 3 ppb of chlorine could not be determined accurately, owing to the above mentioned interfering reaction.     

Determination of chromium in aquatic environment by substoichiometric thermal neutron activation analysis

Chromium has been determined in environmental samples. The method described here involves the irradiation of environmental samples and a g quantity of standard with thermal neutrons at the self-serve position in the CIRUS reactor, followed by dissolution of the sample and standard in the presence of a milligram amount of carrier. Both the sample and the standard are subjected to substoichiometric extraction under controlled experimental conditions with alizarin into cyclohexane. An aliquot of the organic phase was counted on a gamma-ray spectrometer. The concentration of Cr in water samples from Bombay and Karad City, and the accuracy, precision and sensitivity of the method are discussed.     

The use of threshold energy differences in fast neutron activation analysis for oxygen and fluorine

A method is described for the simultaneous determination of oxygen and fluorine; the latter has a lower neutron-activation threshold energy so that the fluorine-to-oxygen¹⁶N formation ratio changes after partial moderation of the incident 14.7 MeV neutron beam. In mixtures containing approximately equal amounts of fluorine and oxygen, these elements can each be determined with a precision of ca. ±1%; as expected, errors in the determination of a minor component (ca. 17%) are larger, being ca. ±5%.     

Simultaneous determination of chromium and silicon in steel by 14-mev neutron activation analysis

Chromium and silicon are determined simultaneously in steel by 14-MeV neutron activation analysis. The activities of ⁵²V(E_γ=1.43 MeV,T_{$\text{1}\text{2}$}=3.76 min) from ⁵²Cr(n,p)⁵²V and ²⁸Al (E_γ=1.78 MeV; T_{$\text{1}\text{2}$}=2.24 min) from ²⁸Si(n,p)²⁸Al are evaluated by mixed γ-ray spectrometry. The influence of manganese and phosphorus, the main interfering elements, is negligible for most stainless steels. The count rate should be limited, to avoid ⁵²V pulse pile-up effects interfering in the ²⁸Al energy region. Precisions in the 2-10% range are reached, depending on the concentrations, for a 10-min analysis time. Results for a series of steel samples are compared with industrial analyses.     

Instrumental neutron activation analysis of iron and zinc in compact cosmetic products

Summary An instrumental neutron activation analysis method is described for the determination of iron and zinc in compact eye shadow, compact face powder and compact rouge make-up cosmetic products. The steps of the procedure are: irradiation of samples with thermal neutrons, counting of gamma-radioactivity of the radioisotopes of iron and zinc produced by this irradiation and calculation of the concentration of these elements from the gamma-ray spectra of samples and standards. Analysis of the I.A.E.A. standard reference material by this procedure give results in close agreement with certified values. The limit of quantitation is 45 g for iron and 0.35 g for zinc. The developed procedure could possibly be established as an official method for the simultaneous determination of iron and zinc in compact cosmetic products.

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Instrumentelle Neutronenaktivierungsanalyse von Eisen und Zink in festen kosmetischen Erzeugnissen

Zusammenfassung Ein neutronenaktivierungsanalytisches Verfahren wird beschrieben zur Bestimmung von Eisen und Zink in festen kosmetischen Erzeugnissen (Eye shadow, Gesichtspuder, Rouge Make-up). Die Methode umfaßt die Bestrahlung der Probe mit thermischen Neutronen, Messung der Gammaradioaktivität der erzeugten Radioisotope von Fe und Zn, sowie Berechnung der Konzentrationen aus den Gammaspektren von Probe und Standard. Bei der Analyse von Standardreferenzmaterial wurde gute Übereinstimmung mit den zertifizierten Werten erhalten. Die Bestimmungsgrenzen liegen bei 45 g Fe bzw. 0,35 g Zn. Das Verfahren wird als offizielle Methode zur gleichzeitigen Eisen- und Zinkbestimmung in diesen Erzeugnissen empfohlen.

     

Analysis of ancient iron objects with 14 MeV neutron activation analysis

Ancient iron objects excavated from five different sites around Nagpur city in Maharashtra State /India/ were cut into small pieces and samples were prepared. Each sample was irradiated with 14 MeV neutrons for 8 min. From the recorded gamma ray spectrum for each sample, the presence of trace elements Cu, Si, Al, Mg and Mn were detected and their mutual ratios of activities were determined. The results show that all the iron objects obtained from five different sites are of the same origin.