Anodically oxidised aluminium layer as a useful substrate for the fabrication of147Pm sources for beta-ray thickness gauges

An anodically oxidised layer of aluminium was found to be a satisfactory substrate for holding millicurie amounts of carrier-free¹⁴⁷Pm activity, which is used as a source of -radiation in -ray thickness gauges. The sources fabricated by this method showed satisfactory performance regarding leaching and adherence of the radioactivity held up in the oxide layer. Details regarding the anodic oxidation conditions used for making these source substrates are given. Leaching studies conducted on these sources indicated influence of the acid concentration at which¹⁴⁷Pm activity was deposited in the oxide layer. Better performance characteristics of these sources could be achieved whenever¹⁴⁷Pm activity was absorbed in the oxide layer under near neutral conditions of acidity.     

Stability of radio-metallofullerenes against beta-decay

The effect of β⁻-decay on the stability of metallofullerenes was investigated for three decay chains of¹⁵⁵Sm-¹⁵⁵Eu,¹⁶¹Gd-¹⁶¹Tb and¹⁷⁷Yb-¹⁷⁷Lu. For the former two cases, the metallofullerenes were found stable even after the β⁻-decay while in the case of¹⁷⁷Yb, the metallofullerene became unstable after β⁻-decay. The present results point to the fact that metallofullerenes are stable against ordinary β⁻-decay unstable after β⁻-decay. The present results point to the fact that metallofullerenes are stable against ordinary β⁻-decay recoil energies, but they become unstable if the oxidation state of the metal atom is changed by nuclear transformation.     

Determination of <Superscript>151</Superscript>Sm and <Superscript>147</Superscript>Pm using liquid scintillation tracer methods

The long-lived rare earth isotopes ¹⁵¹Sm (90 years, β _max = 76.3 keV) and ¹⁴⁷Pm (2.62 years, β _max = 224.6 keV) are low-yield fission products that generally require lengthy separation procedures to isolate and count by their beta emissions. We will describe novel liquid scintillation counting techniques using radioactive tracers to determine radiochemical yields from an environmental matrix. The recovery of ¹⁵¹Sm is determined from the alpha decay (2.25 MeV) of ¹⁴⁷Sm in the natural Sm carrier and is in excellent agreement with the gravimetric recovery. The ¹⁴⁷Pm recovery is determined by the use of ¹⁴⁵Pm (17.7 years, EC) tracer, custom-produced at LANL using an isotopically enriched target of ¹⁴⁴Sm. We have determined the ¹⁴⁵Pm recovery both from the 37.4 keV k_α1 X-ray, and the electron-capture emissions by LSC. A comparison of these recovery methods is presented.     

Absorption method for determination of pure beta-emitters in samples containing more than one beta-emitter

Absorption method is shown to be suitable for direct determination of pure β-emitting, isotopes in samples containing more than one β-emitter. This method consists of (1) measurement of the β-counting rate as a function of the thickness of the absorber placed in between the sample and the β-detector and (2) decomposition of the complex absorption curve by computation in order to obtain the contributions of the nuclides to the total counting rate one by one. The method is presented through two examples of its practical application in the field of environmental radioanalysis:⁹⁰Sr and¹⁴⁷Pm isotopes were determined in aerosol samples contaminated by Chernobyl radioactivity and in hot particles of Chernobyl origin using a simple end-window Geiger-Müller counter as a β-detector.     

Chemical study on the separation and purification of promethium-147

A chemical process for the separation of¹⁴⁷Nd/¹⁴⁷Pm from fission products of synthetic radioactive waste solution has been developed. The process includes: (1) denitration, (2) removal of high concentration of uranium by 30% TBP/kerosene extraction, (3) removal of⁹⁵Nb,¹⁰³Ru,¹³⁷Cs and part of⁹⁰Sr by 50% TBP/dodecane extraction, (4) separation of¹⁴⁷Nd/¹⁴⁷Pm from part of⁹⁰Sr and⁹⁵Zr by oxalic acid precipitation, and (5) removal of¹⁴⁴Ce by mixture of 0.4M D2EHPA and 0.2M TBP extraction. Experimental results indicate that the recovery of¹⁴⁷Nd/¹⁴⁷Pm in the final separated solution is about 90%. The purification of¹⁴⁷Nd and¹⁴⁷Pm from some other rare earth elements, viz.¹⁵³Sm,¹⁵⁴Eu and¹⁴⁴Ce was further investigated by using a Dowex 50W×8 ion-exchanger. Parameters of flow rate, eluent concentration and pH were examined. The results show that the recovery and radionuclide purity of¹⁴⁷Nd plus¹⁴⁷Pm under the present separation conditions are 77.8% and 98.6% for diethylenetriaminepentaacetic acid (DTPA) and 87.3% and 99.5% for nitrilotriacetic acid (NTA), respectively.     

Contribution to the study of the sorption of radionuclides on hydrated oxides

The mechanism of¹⁰⁶Ru(III),¹⁰⁶RuNO(II),¹⁴⁴Ce(III),¹⁴⁷Pm(III),⁸⁵Sr(II),¹³¹I⁻,³⁵SO ₄ ²⁻ , and H₂ ³²PO ₄ ²⁻ radionuclide sorption on hydrated ferrous, ferric, aluminium and chromic hydrated oxides was studied. The dependence of sorption on the pH has shown that in a certain range of pH values it is the ion exchange of the radionuclide for a proton or a hydroxyl group of the oxide that probably plays a decisive role in the sorption process. The sorption depends considerably on the pH in the whole range of studied, but its decrease with cations in alkaline media and its increase with I⁻ ion in acidic media does not agree with the above sorption mechanism. Similarly, the course of the dependence of sorption on the sorbent concentration does not indicate ion exchange to be the only mechanis, but it indicates a more complicated sorption process. Probably the sorption of colloidal forms of the radionuclides proceeds, too.     

Colloidal forms of radionuclides and their separation from water solution

Colloidal properties of¹⁴⁴Ce(III),¹⁴⁷Pm(III),⁹¹Y(III), and other, radionuclides were determined from the course of their self-diffusion. A reduced self-diffusion indicated the formation of colloidal radionuclides. The decrease in the self-diffusion coefficient began from a certain value of pH, and a pH region of slowest self-diffusion existed for each of the radionuclides studies. The maximum formation of colloidal radionuclides may be assumed to lie in the range of these pH values. An increase in the rate of self-diffusion was observed with radionuclides in colloidal forms under the effect of gamma-radiation. The possibility of mutual interaction between radionuclides was also inferred from the course their self-diffusion. High effective sorption of¹⁴⁷Pm(III) was attained on hydrated ferric oxide in the pH range were hydrolytic products and colloidal forms of¹⁴⁷Pm(III) were formad to a large extent.     

After effects of β− on time differential perturbed angular correlation spectra

The after effects of β⁻ -decay on time differential perturbed angular correlation (TDPAC) spectra of II–VI semiconductor CdS have been studied using β⁻ -emitting¹¹¹Ag as well as^111mCd as probe nuclei. The TDPAC spectrum of¹¹¹Ag in CdS exhibits a time dependent interaction indicating that the preceding β⁻ -decay leaves the daughter nucleus in an excited state. The recovery time (τ_g) of the probe atom was found to be 16±6 ns while Abragam and Pound's relaxation time (τ_kr) was found to be 9±2 ns. The results show that β⁻ -decay does change the chemical environment around the probe atom.     

The inflection point of the variation of interionic distance between Sm3+ and Cl− in a methanol and water mixture

The stability constants, β₁, of the monochloride complex of Sm(III) have been determined in mixed system of methanol and water at 1.00 mol dm⁻³ ionic strength using a solvent extraction technique. The values of β₁ increase with an increase in the mole fraction of methanol (X _s ) in the mixed solvent system when 0≤X _s ≤0.351. The interionic distance of Sm³⁺−Cl⁻ (d _Sm−Cl) in the mixed solvent system was estimated by applying the Gibb's free energy derived from β₁ to a Born-type equation. It was determined that an inflection point of the variation in the estimatedd _Sm−Cl againstX _s was present in the vicinity ofX _s =0.054. The inflection point ofd _Sm−Cl shows a value ofX _s between those ofd _Eu−Cl andd _Nd−Cl previously obtained by us.     

Application of non-steroidal anti-inflammatory drugs for palladium determination

A highly sensitive spectrophotometric method for palladium determination using piroxicam and tenoxicam as new chromogenic reagents has been developed. In the presence of sodium lauryl sulfate (SLS), palladium reacts with piroxicam (PX) or tenoxicam (TX) to form stable yellow orange complexes in an acetate buffer solution of pH 5.0 at 424 nm and 426 nm with molar absorptivity of 7.16 × 10⁴ L mol⁻¹ cm⁻¹ and 1.20 × 10⁵ L mol⁻¹ cm⁻¹, respectively. Sandell sensitivity, detection, and quantitation limits were also calculated. Optimum conditions were evaluated considering pH, reagent concentration, time, temperature, and surfactant concentration. The complex system conforms to Beer’s law over the range of 0.07–1.28 μg mL⁻¹ palladium. The stoichiometric ratio and stability constant were also evaluated. Tolerance limits of many cations and anions were determined. Finally, the proposed method was applied successfully in the determination of palladium in jewellery, anode mud, synthetic mixtures, catalysts, and alloy samples.     

A separation procedure for the analysis of90Sr,154Eu, and the actinides237Np,239Pu,241Am and244Cm

A procedure for the analysis of⁹⁰Sr,¹⁵⁴Eu,²³⁷Np,²³⁹Pu,²⁴¹Am and^242−244Cm was developed. Separation was done with the separating agent, di-2(ethyl hexyl)-phosphoric acid (HDEHP), and results in fractions containing the different elements to be analysed.⁹⁰Sr analysis was done by analysing its daughter nuclide⁹⁰Y, detected through the Cherenkov radiation emitted by this high energy β⁻-emitter.¹⁵⁴Eu was detected using γ-spectrometry with a lower Compton background as a result of the removal of other fission products.²⁴¹Am could also be detected with γ-spectrometry or together with^242−244Cm with α-spectrometry. The long-lived radionuclides²³⁷Np and²³⁹Pu were detected using inductively coupled plasma mass spectrometry (ICP-MS).     

Salient Features in the Preparation of Promethium-147 Activated Zinc Sulphide Phosphor Light Sources

Activation of zinc sulphide phosphor with beta radiation of ¹⁴⁷Pm will provide self-sustaining light sources and are widely used as nocturnal illumination devices. Use of ¹⁴⁷Pm as energy source is most promising since it forms non-volatile salts. By virtue of this property, it has been precipitated as hydroxide from its aqueous solution for in situ deposition on zinc sulphide phosphor. In this paper, the details of various reaction parameters such as the rate of deposition of ¹⁴⁷Pm(OH)₃ on ZnS, duration of shaking, specific activity of phosphor and effect of fatty acid (additive) concentration versus luminosity are illustrated with experimental evidence so as to obtain, under optimum conditions, an overall luminosity of 1000 micro lamberts (lm).     

Determination of noble metals by resonance neutron activation technique

Rhodium, palladium, platinum and iridium have been determined in silver matrix by nondestructive activation analysis upon activation with cadmium- and silver-filtered resonance neutrons. Experiments with different types of filter combinations are reported. The sensitivity of the method is 5·10⁻³% for rhodium, 5·10⁻³% for palladium, 3·10⁻²% for platinum and 5·10⁻³% for iridium.     

Sorption of144Ce(III) and147Pm(III) on hydrated iron sesquioxide

The sorption of¹⁴⁴Ce(III) and of¹⁴⁷Pm(III) on hydrated iron sesquioxide suspension and the sorption of¹⁴⁴Ce(III) on hydrated iron sesquioxide in a laboratory column were studied. The dependence of the sorption on pH and time, the sorption isotherm, the temperature-dependence of sorption, and the effects of ionic strength on sorption and desorption were determined under static conditions. The maximum sorptions of¹⁴⁴Ce(III) and¹⁴⁷Pm(III) were reached at pH=7.4 (K_d=8.9·10⁵) and pH=9.1 (K_d=6.2·10⁵), respectively.     

Simultaneous First Derivative Spectrophotometric Determination of Palladium and Nickel Using 2-(2-Thiazolylazo)-5-Dimethylaminobenzoic Acid as an Analytical Reagent

 A simple, rapid, selective, sensitive and economical method has been developed for the simultaneous determination of trace amounts of palladium and nickel in aqueous methanolic medium using 2-(2-thiazolylazo)-5-dimethylam inobenzoic acid as an analytical reagent by first derivative spectrophotometr y. Palladium is determined by measuring base to peak distance at λ=695.0 nm while nickel is estimated by zero crossing method in the mixture. The linearity is maintained between 0.12–1.75 μg mL⁻¹ for palladium and 0.07–1.60 μg mL⁻¹ for nickel in the pH range 2.8–7.2 and 3.4–8.8 respectively. Seven replicate determinations of 1.0 μ g mL⁻¹ of palladium and 0.8 μg mL⁻¹ of nickel in a mixture give a mean signal height of 0.391 for Pd and 0.541 for Ni with relative standard deviations of 0.9% and 1.2%, respectively. The sensitivity of the proposed method is 0.391 (dA/dλ)/(μg mL⁻¹) for palladium and 0.685 (dA/dλ)/(μg mL⁻¹) for nickel. Various parameters have been optimised for the simultaneous determination of palladium and nickel in various complex samples. Received March 30, 1999. Revision November 25, 1999.     

The concentration of <Superscript>238</Superscript>U and the levels of gross radioactivity in surface waters of the Van Lake (Turkey)

Gross α and gross β activities and ²³⁸U concentrations were determined in 18 surface water samples collected from Van Lake. The instrumentations used to count the gross α and gross β activities and to determine the ²³⁸U concentrations were α/β counter of the multi-detector low background system (PIC-MPC-9604) and Inductively Coupled Plasma-Mass Spectrometry (Thermo Scientific Element 2), respectively. Concentrations ranging from 0.001 to 0.021 Bq L⁻¹ and from 0.111 to 2.794 Bq L⁻¹ were observed for the gross α and β activities in surface waters, respectively. For all samples the gross β activities were higher than the corresponding gross α activities. The results indicated that the gross α radioactive contamination in water samples was lower than recommended values for the guideline of drinking waters and most of the gross β activities in water samples were higher than those in the same procedure. The ²³⁸U concentrations ranged from 74.49 to 113.2 μg L⁻¹ in surface waters. The obtained results have showed that ²³⁸U concentrations are higher than guideline values for uranium.     

A comparison of combustion and low beta counting methods for the determination of low levels of14C activity in animal tissue

Low β-counting was compared to combustion and liquid scintillation counting for detection of low levels of¹⁴C activity in animal tissues. In two separate experiments tissues from sheep and from pigs were analyzed. The first experiment utilized tissues from sheep into which a known amount of¹⁴C radioactivity was added. Combustion analysis gave somewhat higher recovery than low β-analysis, 92.8% compared to 85.7%. Statistical analysis indicated that the greatest source of random variation was in sampling. In the second experiment tissues from pigs given a¹⁴C labeled drug were analyzed. Sampling was again the greatest source of random error, however, it was greatly reduced over that in the first experiment. This was attributed to higher levels of radioactivity or to more homogeneous incorporation of radioactivity into tissues. The analytical performance of the two methods was essentially the same and a decision as to the best method for tissue residue studies is dependent on other considerations.     

Production of Lipids Containing High Levels of Docosahexaenoic Acid by a Newly Isolated Microalga, <Emphasis Type="Italic">Aurantiochytrium</Emphasis> sp. KRS101

In the present study, a novel oleaginous Thraustochytrid containing a high content of docosahexaenoic acid (DHA) was isolated from a mangrove ecosystem in Malaysia. The strain identified as an Aurantiochytrium sp. by 18S rRNA sequencing and named KRS101 used various carbon and nitrogen sources, indicating metabolic versatility. Optimal culture conditions, thus maximizing cell growth, and high levels of lipid and DHA production, were attained using glucose (60 g l⁻¹) as carbon source, corn steep solid (10 g l⁻¹) as nitrogen source, and sea salt (15 g l⁻¹). The highest biomass, lipid, and DHA production of KRS101 upon fed-batch fermentation were 50.2 g l⁻¹ (16.7 g l⁻¹ day⁻¹), 21.8 g l⁻¹ (44% DCW), and 8.8 g l⁻¹ (40% TFA), respectively. Similar values were obtained when a cheap substrate like molasses, rather than glucose, was used as the carbon source (DCW of 52.44 g l⁻¹, lipid and DHA levels of 20.2 and 8.83 g l⁻¹, respectively), indicating that production of microbial oils containing high levels of DHA can be produced economically when the novel strain is used.     

New products and reaction pathways for the reaction of dimethylsulfoxide with peroxonitrite in aqueous solutions

The first observed basic products of the reaction of dimethylsulfoxide with peroxonitrite were methyl nitrite and methane with pH=7 and methyl nitrate at pH>10. The dependence of the yield of these and other reaction products on pH, concentrations of the substrate and peroxonitrite, and the additives NO ₂ ⁻ and CO₂ was studied. It is proposed that CH₄ and CH₃ONO are formed in the reaction between DMSO and the cis-form of⁻OONO, while DMSO₂ and CH₃ONO₂ are formed in reactions with the trans-form of⁻OONO or the dimer HOONO/OONO respectively. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 1, pp. 41–46, Jaunuary–February, 2000.     

Determination of pheniramine enantiomers in eye drop by capillary electrophoresis using hydroxypropyl-β-cyclodextrin as chiral selector

A capillary zone electrophoresis procedure has been developed for the chiral determination of pheniramine in eye drop. Native and derivative cyclodextrins (CDs) including γ-CD, β-CD, hydroxypropyl-β-CD and dimethyl-β-CD were tested as chiral selectors. Using 30 mM hydroxypropyl-β-CD in 50 mM phosphate buffer (pH 3.0), the acceptable resolution value (R = 1.55) was obtained. The assay was validated for linearity (3.3 × 10⁻⁶–5.0 × 10⁻⁴ M; R ² = 0.9996), limit of detection (3.3 × 10⁻⁶ M), limit of quantification (8.5 × 10⁻⁶ M), analytical precision by terms of intra- and inter-day variability (RSD ≤ 2.57%), and accuracy (recovery ≥ 89.3%). The content of pheniramine in eye drop obtained by the proposed method was in good agreement with the declared value. The results indicated that pheniramine in the eye drop was present as the racemate.