Neutron activation analysis for determination of cerium trace impurity in high purity lanthanum oxide

Cerium trace impurity in high purity lanthanum oxide (99.99%) has been determined by NAA after pre-separation of La matrix. In this method, the sample was dissolved in conc. nitric acid and diluted with water. The final concentration of solution is about 0.1M of nitric acid. It was passed through a MnO₂ column. Under these conditions cerium is retained on the column quantitatively without retaining lathanum. Cerium is eluted with 4M nitric acid. The recoveries of Ce were checked with tracers and by standard addition to lanthanum oxide matrices. Results obtained on a high purity lanthanum oxide are reported here.     

<Superscript>137</Superscript>Cs/<Superscript>137m</Superscript>Ba radioisotope generator based on 6-tungstocerate(IV) column matrix

Summary Barium-137m radioisotope generator of the chromatographic column elution mode based on loading 1.5 g 6-tungstocerate(IV) gel matrix with ~54 kBq of fission-produced ¹³⁷Cs is described. The elution performance of the generated ^137mBa radionuclide was investigated as a function of chemical composition of the eluent, flow rate, elution frequency, and age of the generator system. At comparable conditions, ^137mBa eluates with 0.9% NaCl-0.1M HCl eluent had higher elution yields and radionuclidic purity than with 0.1M NH₄Cl-0.1M HCl eluent. The generator has been repeatedly eluted for 311 days by passing 4810 ml of the saline eluent (10 ml × 481 elution operations) at a flow rate of 3.0 ml/min. Barium-137m eluates of high and reproducible elution yields, chemical and radionuclidic purities of (≥ 99.99%) were obtained.     

Performance of immobilized moss in the removal of 137Cs and 90Sr from actual low-level radioactive waste solutions

The efficiency of immobilized moss as a bio-sorbent for the removal of ¹³⁷Cs and ⁹⁰Sr radionuclides from actual low-level radioactive waste (LLW) solutions was investigated. Preliminary batch experiments with the moss (Funaria hygrometrica) for the sorption of Cs and Sr have shown a pH dependent binding trend from pH 1–13, with maximum binding between pH 5–10. Time dependence of the batch studies showed that a contact time of 30 minutes was sufficient to reach equilibrium. Column experiments for the sorption of Cs and Sr by moss after immobilizing in polymer silica matrix demonstrated that the sorbent is capable of removing considerable amounts of Cs and Sr from actual LLW solutions under constant flow conditions. The adsorption capacity was estimated to be 8.5 mg/g for Cs and 15 mg/g for Sr. These sorbed metal ions from the column could be leached out using 0.20M nitric acid. The regenerated sorbent exhibited relatively the same initial binding capacity of both Cs and Sr even after 3 cycles of reuse. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of a method for nuclide leaching from glass fiber in HEPA filter

For the disposal of the high efficiency particulate air (HEPA) glass filter to environment, the glass fiber should be leached to lower its radioactive concentration. To derive the optimum method for removal of Co and Cs from HEPA glass fiber, four methods were applied in this study. Results of electrochemical leaching of glass fiber by 4.0 M HNO₃–0.1 M Ce(IV) solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs from glass fiber after 5 h was 96.4, 93.6, and 93.8%, respectively. Results by 5 wt% NaOH solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 30 h was 81.7, 82.1, and 10.0%, respectively. Results by repeat 2.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 2 h of three repetitions were 96.2, 99.4, and 99.1%, respectively. Finally, results by repeat 4.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 4 h of three repetitions were 100, 99.9, and 99.9%, respectively, and their radioactivities were below 0.1 Bq/g. Therefore, the chemical leaching method by 4.0 M HNO₃ solution was considered as an optimum one for removal of cesium and cobalt from HEPA glass fiber for self disposal. Also the removal efficiencies of ⁶⁰Co, ¹³⁴Cs, and ¹³⁷Cs from the waste-solution after its precipitation-filtration treatment for reuse of 4.0 M HNO₃ waste-solution were 88.0, 95.0, and 99.8%.     

5‐O‐Caffeoylshikimic acid from Solanum somalense leaves: Advantage of centrifugal partition chromatography over conventional column chromatography

Solanum somalense leaves, used in Djibouti for their medicinal properties, were extracted by MeOH. Because of the high polyphenol and flavonoid contents of the extract, respectively, determined at 80.80 ± 2.13 mg gallic acid equivalent/g dry weight and 24.4 ± 1.01 mg quercetin equivalent/g dry weight, the isolation and purification of the main polyphenols were carried out by silica gel column chromatography and centrifugal partition chromatography. Column chromatography led to 11 enriched fractions requiring further purification, while centrifugal partition chromatography allowed the easy recovery of the main compound of the extract. In a solvent system composed of CHCl₃/MeOH/H₂O (9.5:10:5), 21.8 mg of this compound at 97% purity was obtained leading to a yield of 2.63%. Its structure was established as 5‐O‐caffeoylshikimic acid by mass spectrometry and NMR spectroscopy. This work shows that S. somalense leaves contain very high level of 5‐O‐caffeoylshikimic acid (0.74% dry weight), making it a potential source of production of this secondary metabolite that is not commonly found in nature but could be partly responsible of the medicinal properties of S. somalense leaves.     

Ion-exchange chromatography using citrate buffer,EDTA and α-HIBA for improving the separation of no-carrier-added <Superscript>139</Superscript>Ce from La<Subscript>2</Subscript>O<Subscript>3</Subscript> target irradiated with 14.5 MeV protons

The adsorption behaviour of La/Ce system on Dowex 50W-X8 in different media, namely, nitric acid, acetate buffer and citrate buffer was studied as a function of the concentration of nitric acid and buffer pH. In addition, in cation-exchange column chromatography experiments, three different eluants, namely, citrate buffer of pH 5.5, 0.1 M EDTA and 0.2 M α-HIBA, were employed for separation of Ce(III) from La(III). The optimum conditions for improvement of radiochemical separation of no-carrier-added ¹³⁹Ce from proton irradiated lanthanum were applied using the most suitable chelating agent 0.2 M α-HIBA. The purification of ¹³⁹Ce from macro amount of La(III) was done using two columns in a sequence. The target was prepared by pressing. The production of high radionuclidic and chemical purity ¹³⁹Ce via irradiation of lanthanum oxide target at MGC-20 cyclotron of proton energy 14.5 MeV was described. The experimental yield was found to be 200 kBq/μA h.     

Purification of americium from assorted analytical waste in hydrochloric acid medium

During the simultaneous extraction of plutonium and uranium using anion exchange chromatographic technique from analytical waste in hydrochloric acid medium, ²⁴¹Am which is invariably present in the plutonium bearing fuel samples remains in the effluent. A two step separation scheme was developed for the recovery and purification of Am from the assorted waste to facilitate the disposal of large volume of aqueous waste and the purified Am solution was utilized for spectroscopic investigation. The separation scheme involved solvent extraction using 0.1 M TODGA + 0.5 M DHOA for separation of americium from Fe, Pb, Ni and Na followed by extraction chromatographic technique using CMPO on inert support as stationary phase for separation of Ca from Am. A systematic study on the extraction behavior of Am from hydrochloric acid medium revealed that out of four extraction systems well known for actinide partitioning namely 0.1 M TODGA + 0.5 M DHOA, 1 M DMDBTDMA, 0.2 M CMPO + 1.2 M TBP and 30% TRPO, only 0.1 M TODGA + 0.5 M DHOA extracts americium from 7.5 M HCl feed acidity. A comparative study involving CMPO solvent extraction and column chromatographic technique revealed that elution of Am from column is satisfactory as compared to inefficient stripping of Am from organic phase in solvent extraction technique using 0.1 M HNO₃. The purity of the final solution was checked for 17 elements of interest and was found to be 98% pure, while the overall recovery of this two step separation scheme was found to be 95%.     

“Age” determination of irradiated materials utilizing inductively coupled plasma mass spectrometric (ICP-MS) detection

A gas pressurized extraction chromatography (GPEC) system has been developed to perform elemental separations on radioactive samples to determine total and isotopic compositions of Cs and Ba from an irradiated salt sample, fuel sample and two sealed radiation sources. The GPEC system employs compressed nitrogen to move liquid through the system, compared to gravity or pumped liquids that are typically used for separations. A commercially available Sr-Resin™ was used to perform the separation for the above mentioned analytes. A 1% acetic acid solution was determined to be the best extractant for Ba. A flow rate of 0.1 mL/min was determined to be optimal for the separation of Ba. Complete recovery of the Cs and Ba was achieved, within the systematic uncertainties of the experiments.     

Rapid analysis of pyridinoline and deoxypyridinoline in biological samples by liquid chromatography with mass spectrometry and a silica hydride column

Pyridinoline and deoxypyridinoline crosslinks are biomarkers found in urine for collagen degradation in bone turnover. For the first time, a rapid, sensitive, and ion‐pairing free method is described for the analysis of pyridinoline and deoxypyridinoline using ultra‐high performance liquid chromatography with Cogent Diamond Hydride column and detection by Q Exactive hybrid quadrupole‐orbitrap high resolution accurate mass spectrometry. The separation was achieved using both isocratic and gradient conditions and run time <5 min under isocratic conditions of 20% acetonitrile in water containing 0.1% formic acid. Pyridoxine was used as an internal standard and relative standard deviation of the retention times of both pyridinoline and deoxypyridinoline were <1%. The limit of detection was 0.082 ± 0.023 μM for pyridinoline and 0.118 ± 0.052 μM for deoxypyridinoline. The limit of quantitation was 0.245 ± 0.070 μM for pyridinoline and 0.354 ± 0.157 μM for deoxypyridinoline. The method was validated by the detection and quantitation of both pyridinoline and deoxypyridinoline in skin and urine samples.     

Separation properties of high temperature reverse osmosis membranes for silica removal and boric acid recovery

The separation system containing thin-film polyamide reverse osmosis membrane (tf-PA RO) of high temperature was studied.In performed laboratory tests, RO silica rejection percentage was over 97%, and boron passage was about 60–65% (molecular weight cut off of 200 or 250 Da) of the solution which contained silica in the range of 1–90 ppm and boron in the range of 7500–15,000 ppm. The separation factor (SF) between boron and silica related to boron concentration could be expressed as the relation, SF = k[boron]^0.7. The separation process could be described by a mass balance model. The modeling calculation fitted the experimental results very well, within the acceptable parameters’ errors. It was proposed that the boric acid in a boric acid storage tank (BAST) of one studied pressurized water reactor (PWR) plant could be treated with such tf-PA RO. In the prediction, the silica concentration in it would be removed to about 1 ppm, and that the boron could be reused. The waste amount of boron after such treatment was predicted to be less than 1.5%.     

Separation of fission produced 106Ru and 137Cs from aged uranium targets by sequential distillation and precipitation in nitrate media

Summary Ruthenium-106 and ¹³⁷Cs have been separated from thermal-neutron irradiated UO₃ targets aged for ~2.5 years by distillation and surface interactions in nitrate media of controlled chemical composition. After digestion of the aged targets with their aluminum wrapper in 2M NaOH solution, nitric acid was added to complete dissolution of the formed residue. The prepared fission product solution was separated from ¹²⁹I and 91.8% ¹⁰⁶Ru by sequential distillation from 20% and 40% HNO₃ solutions containing H₂O₂ and KMnO₄, as oxidants, and by boiling for 4 and 2.5 hours, respectively. The recovery yield of ¹⁰⁶Ru collected in 0.1M NaOH solution was ~68.2% with a radionuclidic purity of 399.99%. Thereafter, the fission product solution was brought to pH 9.5 by addition of NaOH solution to precipitate Al(OH)₃, MnO₂, and Na₂U₂O₇ which selectively retained the remaining fission products leaving, mainly, ¹³⁷Cs in the supernatant solution. The recovery yield of ¹³⁷Cs was ≥97.3% with ~99.75% radionuclidic purity. The gamma-ray emitter contaminants which could be detected and identified in the recovered ¹³⁷Cs solution, were ~0.25% ¹³⁴Cs and ~1.4 ^. 10^-3% ^152,155Eu.     

Synthesis and in vitro biological evaluations of novel tetrapeptide as therapeutic agent for wound treatment

We report a new small peptide containing four amino acid residues (glycine-aspartic acid-proline-histidine) conjugated with palmitic acid (Palmitoyl-GDPH) that was synthesized, characterized and evaluated for its biological activities. The Palmitoyl-GDPH was prepared by solid phase peptide synthesis (SPPS) with high percentage purity of 98.6%. The results of circular dichroism (CD) demonstrated the feasibility and stability of Palmitoyl-GDPH secondary structure at many temperatures up to 60 °C. Palmitoyl-GDPH showed its greatest collagenase inhibition activity and nitric oxide (NO) scavenging effect of 80.00 ± 2.22% at 1.0 mg/ml and 83.40 ± 8.08% at 2.5 mg/ml, respectively. In addition, in-vitro cell based study revealed that Palmitoyl-GDPH was not toxic and possessed strong proliferative activity towards normal human dermal fibroblast (NHDF) cell line. Wound scratch assay method showed that Palmitoyl-GDPH significantly promoted the cell migration which progressed faster compared to tetracycline-treated group (positive control) by about 98.39 ± 2.79% and 95.79 ± 3.83%, respectively. Collectively, these results suggested that newly synthesized Palmitoyl-GDPH possessed a strong candidate for use as therapeutic agent and can be a novel approach in the treatment of cutaneous wounds.     

Cloning,High Expression and Purification of Recombinant Human Intereferon-β-1b in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Sequential evaluation and process control strategy were employed for impurity profile and high recovery with quality of rhIFN-β-1b expressed in Escherichia coli. The high-level expression was achieved by using codon substitution (AT content of 52.6% at N-terminal region) and optimization of culture conditions. The addition of rifampicin at a concentration of 200 μg/ml has increased the specific product yield of 66 mg optical density⁻¹ l⁻¹ (43.5% of total cellular protein). Eighty-three percent of lipopolysaccharides, 32% of host deoxyribonucleic acid (DNA), and 78% of host cell proteins were removed by 0.75% Triton X-100 and 2 M urea wash. Eleven percent of lipopolysaccharides, 39% of host DNA, and 12% of host cell proteins were removed at the solubilization step. Ninety-two percent of protein refolding was achieved by high-pressure diafiltration method. Refolding by high-pressure diafiltration, bed height, and height equivalent to the theoretical plate value in chromatography column were identified as key parameters for high recovery with purity. Finally, the established process yielded 34% of purified protein with greater than 99% purity and is acceptable for preclinical toxicological studies. The purified rhIFN-β-1b obtained in this study is the highest that has been reported so far.     

Evaluation of tertiary pyridine resin for the separation of lanthanides by simulated moving‐bed chromatography

Lanthanide separation by simulated moving‐bed chromatography was studied as a model system for separating lanthanide fission products and minor actinides from used nuclear fuels. The simulated moving‐bed system was modeled for a tertiary pyridine anion‐exchange resin supported on silica particles as the stationary phase and a mixture of methanol and 1M nitric acid as the mobile phase. Pulse injection tests using a single packed column were used to obtain chromatographic parameters for mathematical modeling of the simulated moving‐bed system. Higher concentrations of methanol improved the separation, but the chromatograms showed evidence of nonlinearity of the isotherms. The mathematical model of the simulated moving‐bed process predicted a production rate of purified samarium and neodymium at 118 g solute/L resin/day and a purity of 99.5%. The optimal methanol ratio for the production rate for various product purities was determined from the model. The excellent separation of Nd and Sm suggests that the simulated moving‐bed system could be applied to the separation of minor actinides such as americium and curium.     

Evaluating the residence time for cesium removal from simulated Hanford tank wastes using SuperLig® 644 resin

Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig^® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig^® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig^® 644 to determine the equilibrium distribution coefficients (K _d) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig^® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig^® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.     

Flexible soft glass capillary columns vs. flexible fused silica capillary columns for gas chromatography-a critique

The gas chromatographic use of flexible thin walled soft glass capillary columns coated with non-polar stationary phases is compared to similar columns made of fused silica glass. With non-polar soft glass columns, the use of surface roughening viagaseous HCI followed by a Carbowax 20 M pretreatment gave adsorptive phenomena, and thermal instability. With very polar soft glass columns where a variety of cyanopropyl silicone phases were coated directly onto the NaCI crystal matrix, adsorptive effects were again prominent and frequent break-down in film stability with time, was also observed. These undesirable effects were due to the presence of metal oxides in the soft glass. Attempts to remove these materials from the thin walled soft glass surface by means of acid leaching produced significant brittleness. This deleterious result was further increased by attempts at high temperature silylation or polysiloxane deactivation. In sharp contrast, the fused silica surface was essentially free of metal oxides and the surface silanol groups are easily neutralized by silylation or polysiloxane deactivation techniques. No brittleness was observed following these procedures. An increasing series of high molecular weight, viscous, polymeric vinyl containing non-polar and highly polar stationary phases have been produced which readily wet the surface of the fused silica and are easily crosslinked in the presence of free radical generators. These columns are essentially free of all the problems noted with flexible thin walled soft glass. When all of the parameters involved in the fabrication of a glass capillary column are assessed, it appears at this time, that the flexible fused silica glass column with cross linked phases approaches the “ideal” capillary column.     

Production of low and high specific activity <Superscript>64</Superscript>Cu in a reactor

Production of radioactive scandium by irradiating natural titanium metal in Pakistan Research Reactor-1 was evaluated. The production rate of ⁴⁷Sc and other radioactive scandium was estimated. High specific activity ⁴⁷Sc can be produced by irradiating enriched ⁴⁷Ti in sufficient quantities needed for therapeutic applications. A new separation technique based on column chromatography was developed. Neutron irradiated titanium was dissolved in hydrofluoric acid, which was evaporated and taken in distilled water. The resulting solution was loaded on silica gel column. The radioactive scandium comes out first and the inactive titanium is removed with 2 M HCl. More than 95% radioactive scandium was recovered, while chemical impurity of titanium determined by optical emission spectroscopy was less than 0.01 μg/mL in final product.     

Use of alcoholic solutions for the isolation and purification of americium and curium with anion-exchangers

The sorption of transplutonium (TPE), rare-earth (RE) and other elements by anion-exchangers (Dowex 1 type) from aqueous alcoholic solutions of nitric acid and ammonium thiocyanate was investigated. This investigation allowed the development of simple and effective methods of americium—curium separation from frradiated plutonium. Plutonium, TPE (in a +3 oxidation state) and RE are firmly sorbed by the anion-exchanger from 1 M HNO₃ in 90% alcohol, Fe, Al and fission products Cs, Sr, Nb, Zr, and Ru pass through the column under these conditions. The RE separation from TPE is achieved by washing the column with 0.5M NH₄SCN in 80% alcohol. The column is then washed with 0.5 M HNO₃ in 85% alcohol, and americium—curium separation proceeds. Use of this method for recovery of an irradiated plutonium target containing 100 mg Pu, Am and Cm is described.     

Determination of traces of rubidium in high purity cesium chloride by electrothermal atomic absorption spectrometry (ETAAS) using boric acid as a modifier

The use of boric acid as a modifier for the determination of trace amount of rubidium in high purity cesium chloride matrix by electrothermal atomic absorption is described. It was found that the negative influence of the chloride matrix could not be eliminated using stabilized temperature platform (STPF) alone. Due to the high dissociation energy (D₀ = 427 kJ mol⁻¹) of rubidium chloride, it was difficult to dissociate in the gas phase and hence is lost. Elimination of interferences was achieved by the addition of boric acid as a chemical modifier. Diluted cesium chloride samples (5%, m/v) were analyzed applying the standard addition method. The characteristic mass of 24 pg was obtained. The detection limit of the proposed method is around 26 ng g⁻¹. The developed method was applied to the determination of traces of rubidium in high purity cesium chloride samples. The data obtained by this method were in good agreement with those obtained by other independent method like FAAS.     

Rare earth impurities in high purity lanthanum oxide determined by neutron activation analysis

Individual rare earth impurities in high purity La₂O₃ (99.9%) have been determined by NAA after pre-separation of the matrix (La). The separation is carried out on an anion exchanger (Dowex 1×8) using different mixtures of methanol/nitric acid as eluants. The rare earth elements from Dy to Lu are eluted quantitatively using a 10% 1M HNO₃-90% methanol mixture, while the light rare earths from Ce to Gd are eluted quantitatively using a 10% 0.05M HNO₃-90% methanol mixture. La, which is retained on the column, is eluted using 0.1M HNO₃. The recoveries of the various rare earth elements have been checked using radiotracers and also by spiking the sample with known amount of elements, and the recoveries are found to be quantitative. Results obtained on a typical high purity lanthanum oxide are reported here.