A comparison of neutron-activation analysis and hot extraction analysis of the oxygen content of steel

A system developed for the fast neutron-activation analysis of the oxygen content of metals has been tested comparatively with the conventional vacuum fusion and carrier-gas fusion techniques. The results of these tests indicate that neutron-activation analysis is much faster (the total analysis takes only 2 min or less), and more reliable than vacuum fusion and carrier-gas fusion methods because all oxygen present is analysed. Samples can be much larger than the 0.2-3 g commonly used for the fusion methods. Furthermore, the analysis is non-destructive-the same samples can be re-analysed as often as desired. The fast neutron-analysis system includes a 14-MeV neutron generator producing 10(11) neutrons/sec, a dual-tube pneumatic transfer system, a 5 x 5 inch NaI(T1)crystal, a single-channel analyser, two scalers, and timers and switch-gear. A sample, in a polyethylene bottle, and a Lucite reference are irradiated simultaneously, after which the sample is returned to a detector for counting the (16)N gammas from the (16)O(n,p)(16) N reaction. The reference is then counted in a second detector; the ratio of the sample counts to the reference counts is proportional to the oxygen content of the sample. Samples with oxygen contents from 0.002 to 0.1 % of oxygen have been analysed by neutron activation, then cut in several pieces for hot extraction analysis of the total sample.     

Separation of gold from lead-rich minerals for neutron-activation analysis

An easy method for the recovery of gold from lead-rich minerals has been developed. The gold is extracted with methyl isobutyl ketone from an aqua regia solution of the mineral, then stripped into aqueous medium by evaporating the solvent, and finally co-precipitated with lead sulphide. The gold is uniformly distributed in the lead sulphide.     

Multielement neutron-activation analysis of plants and fertilizers

The report considers the results of the development of the automated technique for simultaneous, multielement activation analysis of plants and fertilizers for the macronutrient elements N, P, K, Ca, Mg, Cl, and Si. On the basis of analytical procedures, algorithms and software developed, the first automatic (computer based) installation for multielement analyses of plants and fertilizers has been completed and is in routine use in the agrochemical and plant breeding research program at Soviet Union. The proposed technique together with the full automatic real time process of measurement and processing of data by computer, provides a throughput of 250–500 samples (1250–2500 elements determinations) per 8-hour shift, with the accuracy of ±3% for N and ±5–10% for P, K, Mg, Cl and ±15% for Ca.     

Substoichiometric determination of manganese by neutron-activation analysis

A simple and rapid method for the substoichiometric determination of traces of manganese in various materials by neutron-activation analysis has been developed. After dissolution of the irradiated test sample, manganese(II) carrier is added and subsequently oxidised by peroxodisulphate to the heptavalent state. The permanganate thus formed is finally extracted into chloroform as tetraphenylarsonium permanganate using a substoichiometric amount of tetraphenylarsonium chloride. This single separation step isolates radiochemically pure manganese-56 in the analysis of a relatively simple material in which interfering elements (gold, rhenium, etc.) are absent. When this is not true, a preliminary separation of manganese from the irradiated sample, based on the extraction of manganese diethyldithio-carbamate into chloroform and followed by stripping of the manganese with dilute sulphuric acid, must be used. A simultaneously irradiated standard containing manganese must be treated in exactly the same way as a test sample. In the materials analysed by the new method 10(-5) to 10(-3)% of manganese has been determined.     

Substoichiometric determination of copper by neutron-activation analysis

A rapid and selective method has been developed for the determination of Cu in complex matrices by thermal neutron-activation analysis employing substoichiometric extraction with 1,2,3-benzotriazole /1,2,3-BT/ into chloroform. The time required for radiochemical purification and counting of two samples was 2 h. 1.015 g Cu can be determined with an accuracy of 6.40% and a purification of 5.26%.     

Determination of noble metals by neutron-activation analysis

The scope and limitations of neutron-activation analysis in the field of the platinum metals are discussed. Special attention is given to interferences that occur in determination of noble metals in platinum metals and in natural samples. The problem of standards, carriers and chemical yield determination is emphasised. A recommendation is given of modern techniques for counting radionuclides formed by neutron activation of the platinum metals.     

Determination of gold in germanium by neutron-activation analysis

Gold was determined in gold-doped germanium by neutron-activation analysis. The irradiated samples were dissolved in aqua regia, in the presence of gold carrier. The matrix activity was eliminated by distillation, and gold precipitated in the residue with hydroquinone. The gold fraction was essentially radiochemically pure. For a neutron dose of 5 x 10(15)n/ cm(2), a sensitivity of 1 ppM Au can be obtained, with a 2.4-g sample. The samples investigated contained from 24 to 36 ppM Au.     

Determination of cadmium in soils by neutron-activation analysis

A radiochemical neutron-activation method for the determination of cadmium in soils is presented. The irradiation is carried out in a neutron flux with a high epithermal component, taking advantage of the high ratio of the resonance-activation integral to the thermal-neutron cross-section for (114)Cd to obtain an increased sensitivity. The irradiated samples are decomposed with hydrofluoric acid-nitric acid and cadmium is separated by anion-exchange. Zinc may also be determined. There is good agreement with results obtained by atomic-absorption spectrophotometry based on solvent extraction separation of cadmium.     

Determination of rhenium in molybdenite by neutron-activation analysis

A neutron-activation method is described for the determination of rhenium in molybdenite. Radiochemical separation by a carrier technique was carried out very rapidly by means of successive liquid-liquid extraction processes. The recovery of rhenium, which was determined by a spectrophotometric method, was about 93%. About 10 samples could be analysed within 6 hr in parallel runs.     

Substoichiometric determination of traces of palladium by neutron-activation analysis

A highly selective, rapid one-step radiochemical separation procedure for palladium has been developed. It is based on the solvent extraction of palladium diethyldithiocarbamate from a 5M hydrochloric acid solution with a substoichiometric amount of copper diethyldithiocarbamate in chloroform. The separation has been applied to the determination of traces of palladium by neutron-activation analysis, in platinum, the rocks W-1 and PCC-1 and a biological material (kale). Amounts of palladium down to 10(-8) g have been determined.     

Determination of Samarium in rocks by epithermal neutron-activation analysis

Summary A non-destructive neutron-activation method for the determination of samarium in rocks, based on activation with epithermal neutrons, is described. By this means the formation of¹⁵³Sm, as compared to most interfering radionuclides, is considerably higher than by thermal neutron activation. The precision of the method is 2–3% in the range of 3–25 ppm, and the sensivity is about 0,1 ppm. Results are presented for some standard rocks. The influence of other rare earth nuclides on the measurement of the 41 KeV X-ray of¹⁵³Sm has been investigated.

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Zerstörungsfreie Bestimmung von Samarium in Gesteinen durch Aktivierungsanalyse mit epithermischen Neutronen

Zusammenfassung Die Bildung von¹⁵³Sm ist hierbei im Vergleich zu den meisten störenden Radionukliden beträchtlich größer als bei der Aktivierung mit thermischen Neutronen. Die Präzision des Verfahrens beträgt 2–3% im Bereich von 3–25 ppm, die Empfindlichkeit etwa 0,1 ppm. Für einige Standardgesteine werden die Ergebnisse angeführt. Der Einfluß anderer Nuklide Seltener Erden auf die Messung der 41 keV Röntgenstrahlung von¹⁵³Sm wurde untersucht.

     

Determination of palladium in biological samples by neutron-activation analysis

Summary A neutron-activation method for determination of nanogram levels of palladium in biological samples is described. It is based on radiochemical separation of 13.5-hr¹⁰⁹Pd by solvent extraction of its dimethylglyoximate complex into chloroform from the acid solution obtained by wet ashing of the irradiated sample. The effect of the acidity of the aqueous phase on the extraction coefficient was also investigated by radiotracer experiments. Results are reported for biological standard reference materials and a few environmental samples.

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Bestimmung von Palladium in biologischen Proben durch Neutronen-Aktivierung

Zusammenfassung Eine Neutronen-Aktivierungsmethode zur Bestimmung von Nano-grammengen Palladium in biologischen Proben wurde beschrieben. Sie beruht auf der radiochemischen Trennung des¹⁰⁹Pd durch Extraktion seines Dimethylglyoxim-Komplexes mit Chloroform aus der sauren, durch nasse Veraschung gewonnenen Lösung der bestrahlten Probe. Der Einfluß der Acidität der wäßrigen Phase auf den Extraktionskoeffizienten wurde ebenfalls durch Radiotracer-Versuche geprüft. Untersuchungsergebnisse für biologische Standardproben und einige Milieuproben wurden mitgeteilt.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Substoichiometric determination of molybdenum in steels by neutron-activation analysis

A simple and rapid substoichiometric method for the determination of small amounts of molybdenum in steel by neutronactivation analysis is based on the extraction of molybdenum alpha-benzoinoximate into chloroform. The sensitivity of the method is 0.2 microg and the relative standard deviation is 1%. Two activated samples can be processed and counted within 30 min.     

The determination of gallium in rocks by neutron-activation analysis

Neutron-activation analysis has been applied to the determination of gallium in rocks. The Harwell Pile BEPO has been used as the source of neutrons, and a radiochemical procedure employing carrier chemistry has been utilised to separate the induced gallium activity.

Neutron-activation analyses of gallium in the standard rocks Gl and Wl are reported and compared with results obtained by other analytical methods.     

Multielement trace analysis for inorganic species in large-volume water samples by mono-standard neutron-activation analysis

Summary Mono-standard neutron-activation analysis of large-volume water samples without preliminary chemistry is applied to the multielement determination of trace inorganic species in pure water, river water, urban effluent, etc. The accuracy, precision and sensitivity have been assessed by analysing a standard reference material, a water sample from a round-robin analysis and pure waters. The method is applied to investigate the behaviour of trace inorganic species in the course of the cleaning process in an urban sewage treatment plant. The distribution of the elements in the effluents and stably suspended materials has been systematically analysed and the behaviour of the elements in the system discussed.

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Multielementanalyse anorganischer Spurenelemente in grovolumigen Wasserproben mit der Mono-Standard-Neutronen-Aktivierungs-Analyse

Zusammenfassung Die Mono-Standard-Neutronen-Aktivierungs-Analyse großvolumiger Wasserproben ohne chemische Vorbehandlung wird zur Bestimmung anorganischer Spurenelemente in reinem Wasser, Flußwasser, Abwasser usw. eingesetzt. Die Richtigkeit, Genauigkeit und Empfindlichkeit der Methode wurden durch Analysen von Standard-Referenz-Material, eine Ringanalyse einer Wasserprobe und reinen Wassers überprüft. Die Methode wird zur Untersuchung des Verhaltens anorganischer Spurenelemente während des Reinigungsprozesses in einer Kläranlage angewandt. Die Verteilung der Elemente zwischen dem Abwasser und dem stabil suspendierten Schwebstoff wurde systematisch analysiert und das Verhalten der Elemente in dem System diskutiert.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Activation method for determining the carbon content of natural crystals

A method for determination of carbon content in natural silicate crystals has been elaborated using the¹²C(d,n)¹³N reaction. Etching of crystal surfaces by acid solutions is proposed to remove the pollutant surface layers. Carbon contents varying from 8 to 100 ppm were measured for olivine, orthopyroxene and gamet crystals.     

A rapid method for determining the casein content of milk

A method is presented for the rapid determination of the casein content of milk by Direct Injection Enthalpimetry (DIE).A significant heat pulse of precipitation of casein is produced by adjusting the pH of the solution to the pH of the isoelectric point of casein. The method is calibrated against a real sample whose casein content has been determined by a standard method incorporating the time consuming Kjeldahl method, but once calibrated the proposed method can be operated routinely by non-skilled personnel. The method is sensitive and gives results as acceptable as those obtained by standard methods. The method can be applied to most liquid samples without the need for prior preparation. the main advantages of the method are those of time and costs of analysis and the potential of the enthalpimetric method for automation.

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Zusammenfassung Es wird ein Verfahren zur Schnellbestimmung des Kaseingehaltes von Milch mittels Direct Injection Enthalpimetry (DIE) beschrieben.Durch das Einstellen des pH-Wertes der Lösung auf den pH-Wert des isoelektrischen Punktes von Kasein kann infolge des Ausfällens von Kasein ein eindeutiger Wärmeimpuls erzeugt werden. Das Verfahren wurde anhand einer wirklichen Probe geeicht, deren Kaseingehalt mittels dem zeitaufwändigen Kjeldahl-Verfahren bestimmt wurde. Einmal kalibriert kann das neue Verfahren routinehaft auch von Laien durchgeführt werden. Die Empfindlichkeit der Methode ist gut, die erhaltenen Ergebnisse können genauso akzeptiert werden, wie die in Standardverfahren erhaltenen Ergebnisse. Dieses Verfahren kann bei den meisten flüssigen Proben ohne jede vorherige Vorbereitung angewendet werden. Der Hauptvorteil besteht in der Ersparnis von Zeit und Analysenkosten und in der Anwendbarkeit des enthalpiemetrischen Verfahrens zur Automatisierung.

     

Applications of gamma-spectrometry in determining chlorine in aqueous solutions

A method is described for the radioanalytical determination of traces of chlorine in aqueous solutions without radiochemical separation or purification. Using a gamma-spectrometer with monocrystal scintillator, the sensitivity of the analysis is about 1·10⁻⁸ g of chlorine/ml, the time of analysis being 15 minutes. For the selective determination of chlorine in aqueous solutions containing a large amount of impurities, a bicrystal scintillation sum-coincidence spectrometer was employed with 120×100 mm NaI(Tl) crystals and thus the³⁸Cl cascade radiation could be used. Application of the sum-coincidence spectrometer allowed a reliable determination of 1·10⁻⁷ g of Cl/ml against a background of 1·10⁻⁵ g of Na/ml.     

A study of some nuclear reaction interferences in determination of nitrogen content of plant materials by 14-MeV neutron-activation analysis

The nitrogen content of 10 medicinal plant species has been determined by fast-neutron activation analysis (FNAA). Correction factors for the effects of the (16)O(p, alpha)(13)N knock-on proton-induced reaction and the (n, 2n) reactions, which produce interfering positron-emitting radionuclides, have also been determined. The total relative interference from the (16)O(p, alpha)(13)N and (n, 2n) reactions of K, Cl, Fe and Br was found to be 5.1-32.1% for the plant samples.