Isotopic determination of calcium-43 by proton activation

An activation analysis method has been developed for the routine determination of⁴³Ca. The calcium is chemically separated and converted to fluoride. When activated for 2 hours with 4.50 MeV protons,⁴³Sc and⁴⁸Sc are produced and the ratio of their activities is a measure of the isotopic concentrations of⁴³Ca.⁴⁸Ca serves as an internal standard to represent total natural calcium. The relative standard deviation is ±1.5% and the method can determine a change of +0.004 atom %⁴³Ca in natural calcium.⁴²Ca may interfere, if present in enriched concentrations.     

From potential to reality: Yeasts derived from ethanol production for animal nutrition

A chemical and radiochemical neutron activation analysis (CNAA/RNAA) method has been developed for the determination of three calcium isotopes (⁴⁸Ca,⁴⁶Ca, and⁴⁴Ca) in a single sample derived from urine. This method was developed in support of clinical research using a dual enriched stable isotope methodology to study bone mineralization in premature infants, juvenile rheumatoid arthritics, and cystic fibrosis. In these studies, one enriched isotope of calcium is administered orally, and one is administered intravenously. By making determinations of three isotopes (two enriched, one unenriched) within the same sample, the perturbation from natural isotopic ratios can be determined and used to calculate true absorption of calcium. In our method,⁴⁸Ca is determined via the⁴⁸Ca(n,γ)⁴⁹Ca reaction and 3084 keV gamma-ray,⁴⁶Ca via the⁴⁶Ca(n,γ)⁴⁷Ca reaction and 1296 keV gamma-ray, and⁴⁴Ca via the⁴⁴Ca(n,γ)⁴⁵Ca reaction and 256 keV (max) beta-particle. A pair of chemical separation steps are employed to separate calcium from urine as calcium oxalate with a yield in the range of 80–90%, and a radiochemical step is employed prior to the measurement of⁴⁵Ca to remove interfering radionuclides.     

Determination of thorium and uranium in activated concrete by inductively coupled plasma mass spectrometry after anion-exchange separation

A sensitive analytical method was established for the determination of Th and U in activated concrete samples. The method combines an anion-exchange separation step with an ICP-MS determination technique. In the ICP-MS measurement, a few μg mL^–1 of Al and Ca, a few ng mL^–1 of Mn, La, Ce, Nd and Pb and pg mL^–1 amounts of Li, Zr, Nb and Ba coexisting in the anion-exchange fraction of Th and U did not interfere. No adverse interference effects were observed in real sample analyses. The obtained detection limits (3σ, n = 10) of Th and U were 2.3 and 1.8 pg mL^–1, respectively. The analytical precisions for ca. 5 μg g^–1 Th and ca. 1 μg g^–1 U in real activated concrete samples were equally less than 7% RSD. The accuracies obtained by the analysis of GSJ rock standard samples were –18.1 to 0.4% for the Th determination and –14.0 to –5.7% for the U determination. The method uses the conventional absolute calibration curve. The internal standard calibration is unnecessary. Received: 14 March 1999 / Revised: 13 July 1999 / Accepted: 15 July 1999     

Application of neutron activation analysis to the measurement of isotope abundance shifts in calcium and potassium

A simple method for the measurement by neutron activation analysis of the isotopic abundance shifts of⁴⁴Ca and⁴¹K in compounds of low volatility is described. Extraction and measurement procedures for the radioactive argon isotopes (³⁷Ar,³⁹Ar and⁴¹Ar produced by (n, α) and (n, p) reactions are also given. The results obtained demonstrate that the accuracy for the measurement of δ⁴⁴Ca is better than by the mass spectrometric method; in the case of δ⁴¹K measurement the accuracy is the same as that obtained with the mass spectrometer. Interfering reactions which yield other rare gases, and their relative contribution to the error in the measurement of δ values are also discussed.     

Epithermal neutron activation analysis of uranium by neptunium-239 using high resolution gamma-spectrometry

The possibility to use the most intensive gamma-peak of²³⁹Np for INAA of uranium with epithermal neutrons and high resolution Ge(Li)-spectrometry is evaluated. A way for calculation of the peak area of overlapping peaks of¹⁵³Sm and²³⁹Np is proposed. This can be used in other similar cases in the practice of NAA. On this basis a scheme for NAA of uranium in geological objects is proposed. Lower detection limit is 8·10⁻⁸ g U the precision 5–10% (relative standard deviation). The accuracy is demonstrated by the analysis of some geological standard reference materials.     

Cupel assay of gold by an activation method

The difficulties of determining gold in rocks and ores are due to two causes: low gold concentrations in rocks (Clark 1 to 4·10⁻⁷%), and non-uniform distribution of gold in ores. A method is proposed which is based on neutron activation of the lead alloy obtained by cupel melting in the procedure of determining gold by cupel assay. Samples of 50 to 100 g are used for cupel melting. Such large samples guarantee their representativeness. Discs of 2 to 3 g are cut from the lead alloy block and activated in a neutron flux of 10¹¹ to 10¹³ n·cm⁻² sec⁻¹. The gold content is determined from the photopeak of¹⁹⁸Au using a standard for comparison. The sensitivity of the method is 0.02 g/metric ton, its accuracy at a gold content in the order of 1.0 g/metric ton is 10% relative. The method is distinguished by the fact that it is fast and requires little labour.     

Determination of228Th,230Th,and232Th in environmental samples from uranium mining and milling operations

A method is described for the determination of²²⁸Th,²³⁰Th, and²³²Th in environmental samples from uranium mining and milling operations. The analytical procedure is based on the direct determination of²²⁸Th in the sample by high resolution γ-spectrometry followed by extraction and purification of the thorium fraction using high molecular weight amines and an anion-exchange technique, respectively, prior to α-spectrometry to determine isotopic ratios. The lowest level of detection for each thorium isotope is 0.01 pCi/g for solid samples and 20 pCi/l for aqueous samples. Replicate analyses of a typical mine waste stream gave a standard deviation of ±3% for²²⁸Th. Standard deviations of the²³⁰Th and²³²Th increased to ±11% apparently due to traces of²¹⁰Po interfering in the α-spectrometry.     

A method for the determination of Mn,Cu, Zn,K and Na in small tissue biopsies by neutron activation analysis

A method has been worked out for the determination of Mn, Cu, Zn, K and Na in tissue biopsies weighing between 10 and 50 mg. The samples were dried, packed in polyethylene containers and irradiated at a flux of 1.8·10¹² n·cm⁻²·sec⁻¹ for 48 hrs. They were dissolved and separated into five fractions by ion exchange chromatography. Managenese was precipitated and counted as MnO₂ and zinc as quinaldate. Copper and potassium were counted in solution. Sodium was taken up in hydrated antimony pentoxide (HAP) and counted in that stage. Accuracy, precision and specificity were determined by recovery experiments and by analysis ofBowen's biological standard.     

Synthesis,plasma clearance,and in vitro stability of protein containing a conjugated indium-111 chelate

A new bifunctional chelating agent, N′-(p-diazoniumbenzyl)-N,N N″,N″-diethylenetri-aminetetraacetic acid (DTTA) was synthesized. The compound as coupled to methyl p-hydroxybenzimidate and the resulting azoimidate was attached to lysine residues of monomeric human serum albumin (HSA) via the amidination reaction. Blood clearnace of¹¹¹In-labelled DTTA conjugated to HSA (AAHSA) in rabbits was biphasic. The first phase has a clearance indistinguishable from that of¹²⁵I-labeled HSA. During the second phase, the¹¹¹In-labeled AAHSA was cleared more rapidly so that between 24 hours and 48 hours the percent of the injected dose of¹¹¹In-labeled AAHSA in the blood was significantly lower than that of¹²⁵I-labeled HSA. Highly conjugated¹¹¹In-labeled AAHSA (0.9 DTTA/HSA) showed accelerated clearance at 24 and 48 hours compared to lightly conjugated protein (<0.9 DTTA/HSA). As a result we postulate that the level of conjugation is the critical parameter controlling the blood clearance.     

The determination of calcium in yttrium oxide by alpha-particle activation analysis

The determination of calcium in yttrium oxide through the⁴⁰Ca(α, p)⁴³Sc reaction was studied, using a post-irradiation radiochemical separation procedure. The half-life of⁴³Sc was determined to be 3.87 hr. The chemical recovery was about 70%. The detection limit was about 10 ppb, for a 30 min irradiation at an alpha-particle beam current of 1 μA (E_α=13.4 MeV) and γ−γ coincidence counting (background counts being<1, cpm), with counting starting at 4 hours after the end of irradiation. Four samples of a batch of yttrium oxide (A.R.) were analyzed, and found to contain 13.9±1.0 ppm of calcium.     

In vivo iontophoretic delivery of calcium ions through guinea pig skin enhanced by direct and pulsating current

Studies were initiated to investigate the effect of the delivery mode of⁴⁵Ca ions through guinea pig skin in vivo. Direct current (DC), pulsating current (PC) and a Bernard current form, the “courtes periodes” current profile (CP) were applied with the same current density (0.16 mA/cm²) and for the same duration (30 minutes). The⁴⁵Ca ions were delivered from a Ca-bentonite patch radiolabeled with⁴⁵Ca (a natural mineral clay rich in calcium, 50 mgCa/g). The total quantity of applied bentonite was 1.5g×10 days=15g.⁴⁵Ca was counted in different biological samples of the animals. The delivery of⁴⁵Ca ions into the body (systemic effect) is the highest when CP current is applied (6.87±0.95·10⁻¹²g/samples). The local effect appears to be more effective in case of DC current mode (5.89±0.12·10⁻¹²g/0.5g bone). Total calcium measurements proved that the result of transdermal radiocalcium delivery is not only an ion exchange process at the surface of the bone but a deposition of calcium ions into the hydroxiapatite matrix (the net calcium introduction, which represent the difference between the total calcium into the treated bone and total calcium into untreated bone varied from 15.52±2.42·10⁻³g/0.5g bone to 44.30±3.50·10⁻³g/0.5g bone). The results suggest that iontophoresis could be used to accumulate calcium into different target tissues using the appropriate current system.     

The use of charcoal from agriculture waste in the speciation of iodine from well and river waters

The concentrations of iodine in fresh waters are known to be within the range of 0.5 to 35 ng·ml⁻¹, much lower than in oceanic waters. The iodine concentrations, particularly that of¹²⁹I which is significant from the radiation safety aspect, in public drinking waters have to be specified in order to verify the required level before distribution for domestic use. A modified version of an established method was used in the adsorption of iodine, iodate, total inorganic iodine and charcoal-adsorbable iodine using activated carbon prepared from oil palm kernel wastes. A thorough investigation of the physical properties of the activated carbon was carried out to determine its viability as an adsorbent for volatile species such as iodine. The iodine species were preconcentrated from water samples collected from wells in villages and from water intake points along rivers. The quantitative analysis of the species adsorbed was done by irradiating the activated charcoal loaded with the respective species in a neutron flux of 5.1·10¹² n·cm⁻²·s⁻¹ from a TRIGA MkII, nuclear reactor. Recovery experiments using spiked samples was done to provide quality assurance controls.     

The selective removal of32P from activated specimens in neutron activation analysis

The presence of large quantities of³²P in neutron activated biological specimens is often a limiting factor in the direct application of γ-ray spectroscopy. A technique for the selective removal of phosphates in neutron activated specimens is described. The technique is based on the adsorption of phosphates on chromatographic grade alumina. The adsorption selectivity was studied by determining the behaviour of 49 ions when submitted to the procedure for phosphate removal. A few applications are reported as examples.     

Neutron activation analysis for platinum in Cr2O3

A method for the analysis of platinum in Cr₂O₃ has been developed for amounts of Pt ranging up to 2.5 mg. The method employs the separation of activated Pt into ethyl acetate after its reduction by SnCl₂. The areas under the 192 keV γ-ray from the decay of¹⁹⁷Pt in standards and samples are used to calculate the amount of Pt in the samples by the standard comparison technique. It has been shown that up to 2.5 mg of Pt can be recovered by the solvent extraction procedure. The precision of the analysis has varied up to 5%.     

Determination of isotopic composition of lithium by neutron activation analysis; comparison with mass spectrometry

An activation analysis method is described for routine determination of⁶Li-abundances in various lithium compounds on the basis of the reaction sequence⁶Li(n,α)T and¹⁶O(t, n)¹⁸F and the measurement of¹⁸F. Irradiations of diluted equeous solutions of samples containing CrO₃ as internal flux monitor were carried out at a thermal neutron flux density of ϕ≤10¹¹ n·cm⁻²·sec⁻¹. Interferences from variations in neutron self-shielding oxygen concentration and triton range do not exceed 0.5% when using the dilution technique. The results for⁶Li abundances from 3.52 to 7.60% with standard deviations of 1 to 2.5% were confirmed by mass spectrometric measurements.     

Isotopic analysis of lithium by prompt alpha measurement during deuteron irradiation

Charged particle spectrometry was used to determine the isotopic concentration of lithium in lithium fluoride targets irradiated with a deuteron beam of 4.0 MeV. Alpha particles emitted by the⁶Li(d, α)⁴He and⁷Li(d, α)⁵He reactions were used as a measure of⁶Li and⁷Li, respectively. From the⁶Li/⁷Li α-count ratio the isotopic concentration of⁶Li was determined for isotopic concentrations over the range 7.42 (natural) to about 30 atom%⁶Li, with a relative standard deviation of±4.1%. Alpha particles from the¹⁹F(d, α)¹⁷O reaction could also be measured as an internal standard, extending the measurements from natural to 100 atom%⁶Li and giving a relative standard deviation of ±1.9%. The effect of target thickness on the accuracy of the determinations was investigated.     

The electrodeposition of thorium in natural materials for alpha spectrometry

A technique has been developed for the electrodeposition of thorium on stainless stell planchettes following standard radiochemical separation and uptake in acetate buffer. The method has been used on over 130 samples including calcrete, clay, granite and shell matrices. To assess the efficiency at ultra low levels, three solutions of carrier free²²⁸Th (<1.5–10⁻⁷ μg in 5 ml electrolyte) and four solutions of²²⁹Th (4.4–10⁻⁴ μg in 5 ml) were studied. The efficiencies of the former avaregad 66 per cent; those of the²²⁹Th varied from 41 to 91%.     

Differential determination of203Hg and14C or35S in double labelled biological samples

The differential determination of²⁰³Hg and¹⁴C or³⁵S in double labelled biological samples is presented. The biological samples were mineralized with 70% HClO₄ and 30% H₂O₂ in minivals MILLI-6. The γ-activity of²⁰³Hg was measured on a well scintillation counter. The total activity, due to²⁰³Hg and¹⁴C or³⁵S, was measured by the liquid scintillation technique after addition of Aquasol into the same vials. The method of external standard channel ratio was used for standardization. Very good recoveries were obtained: 100±0.7% for²⁰³Hg and 94.6–101.0% for¹⁴C and³⁵S. This method could be used for other β, γ and β-active nuclides with similar β-spectra.     

A simple procedure for the fabrication of high activity beta-radiation sources of147Pm for use in beta-ray thickness gauges

A simple procedure is described for the fabrication of mCi level strong sources of¹⁴⁷Pm radioisotope on a noble metal substrate like Palladium as a source for β⁻-ray thickness gauge. The procedure is based on the principle of internal electro-deposition of¹⁴⁷Pm from aqueous solutions containing¹⁴⁷Pm³⁺ ions, using metallic magnesium for the purpose. Investigations conducted towards ascertaining the adherence of the¹⁴⁷Pm radioactivity onto the palladium substrate. Leaching studies conducted on these source indicated that the radioactive film is satisfactorily adherent to the palladium substrate, suggesting that the method can be used for fabricating satisfactorily safe high β⁻-activity sources of¹⁴⁷Pm contained in small active dimensions. Results of leaching studies keeping the sources fully immersed in boiling water for 15 minutes are also presented.     

Determination of small quantities of51Cr(III) in the presence of large quantities of51Cr(VI) by coprecipitation with zinc hydroxide

A procedure is described for the determination of⁵¹Cr(III) in⁵¹Cr(VI) samples having a⁵¹Cr(VI) to⁵¹Cr(III) ratio of 10⁵, by means of a single zinc hydroxide coprecipitation at apH of ca. 13. Acceptable precision (standard deviation of 10–15%) is possible with solid⁵¹Cr(VI) samples containing 10 ppm of⁵¹Cr as⁵¹Cr(III).