Radiochemical separation of radiothallium from proton-irradiated lead

Absorption of carrier-free T1 from nitric acid solutions of lead by ammonium 12-molybdophosphate fixed in the matrix of porous Teflon (AMP-sorbent) has been investigated. Effective separation of T1 and Pb is shown to take place. Elution processes of T1 from AMP-sorbent have been investigated. It is found that complete extraction of T1 is achieved upon dissolving AMP in concentrated ammonia. Further purification and concentration of T1 are performed by means of cation exchange chromatography on Dowex-50 or KU-2 resins. Investigation of high temperature behaviour of T1 ultramicroamounts in Pb melt showed that T1 is quantitatively separated out into the gas phase when fluorinating additions of PbF₂ or NaF solid salts covering the melt surface are used. The volatile compounds of radiothallium formed were transported by a stream of inert gas (He or N₂) from the evaporation zone to the thermochromatographic column, where they were sorbed on the surface in a limited zone with the maximum at 240 °C. Liquid and gas thermochromatographic methods for separation of carrier free radiothallium from protonirradiated lead material have been developed. The radiochemical, chemical and radionuclidic purity of T1 samples complies with requirements of nuclear medicine for²⁰¹T1 product. Both methods ensure 95% chemical yield of T1 and take about two hours each.     

A rapid carrier-free separation method for divalent rare earths

A separation of carrier-free divalent rare earths by electrolytic reduction and amalgamation is described. The separation is carried out in a water-jacketed cell, 1 cm diameter by 10 cm long, fitted with a stopcock at the bottom. The cell utilizes a Pt anode and Hg cathode. The electrolyte used is potassium citrate-rare earth acetate at a concentration of 10 mg rare earth oxide per ml. The decontamination factor observed for Lu in a typical separation for Yb is ≥10⁴. Sm, Eu, and Yb are all amalgamated if present in the sample. For the present study, the parameters have been evaluated primarily for the case of Yb. A current of 100 mA is applied to 0.5 ml of electrolyte containing 1–1000 μg of Yb(III) for 5 min. The amalgam is decomposed and the Yb recovered by shaking for 1 min with 6M HCl. The overall time required is about 10 min and the yield is reproducible at 84–85%. Under these conditions, the electrolyte may contain up to 3.5 mg of Yb although at 2 mg the yield begins to decrease. The effects of current time, density and electrolyte concentration are discussed. This method has the advantage of being rapid and carrier-free, and the separated rare earth is in a form suitable for further chemical separation if required. Based on work performed under the auspices of the U.S. Atomic Energy Commission.     

Semi-empirical calculation method for transition metals

A semi-empirical molecular orbital method capable of giving useful bond energy and bond geometry information about transition metal compounds is presented. In this method, which for the first time applies a MINDO procedure to transition metals, the one electron part of the off diagonal Fock matrix elements are put proportional to overlap divided by inter-nuclear distance rather than being proportional to overlap as is conventional. Good results are obtained for FeH, FeH₄, Fe₂, Fe₆, Fe(CO)₅, FeO, O-Fe-O, and FeO₂ (side- and end-bonded).     

A rapid method for the separation of 210 Po from 210 Pb by TIOA extraction

A rapid method for the separation of ²¹⁰ Po from ²¹⁰ Pb was developed utilizing extraction of triisooctylamine (TIOA)/xylenein HCl+H₂O₂ medium. Polonium in the form of PoCl ₆ ²– was extracted into TIOA phase and ²¹⁰Pb remains in the aqueous phase. Lead-²¹⁰ was determined by -countingof its granddaughter, ²¹⁰ Po ingrown from ²¹⁰ Pb forsome period of time. Distribution of ²¹⁰ Po and ²¹⁰Pb in TIOA and aqueous phases was investigated in various concentrations ofHCl media. Hydrogen peroxide was used to further decompose organic matterand to remove sulfur to prevent its deposition on the silver disc. The improvedprocedure resulted in a good chemical yield (80–95%) and a good á-resolution.     

A rapid enrichment method for the analysis of traces of metals in aqueous solutions

Summary For the determination of traces of heavy metals e. g. from distilled water, drinking water or waste water generally a suitable pretreatment of the samples is necessary. For this reason an enrichment method was developed which makes it possible to precipitate several metals together with carrier elements from aqueous solutions. To carry out the method, 10 to 500 ml of the sample are mixed with 1 ml of a diluted nitric acid to produce a weak acid starting state for the diverse samples. After addition of a reduction solution and the collector solution the metals are precipitated at a constant pH between 5.0 to 5.5 with diethylammonium-N,N-diethyldithio-carbamate. The precipitate can be collected by filtration on a membrane filter. It forms a thin layer on the membrane filter and adheres without any auxiliary products for a long time. The time required for the complete process is less than 15 minutes if the starting volume was about 100 ml. A special equipment is not necessary. In the determination of traces of metals from organic substances a special rapid decomposition method with the decomposition device BIOKLAV^® was developed. By this method it is possible to convert the organic matter into an aqueous solution without addition of any chemicals. The BIOKLAV is a cylindrical pressure vessel with a safety rapid lock. A 20 g sample of organic material, e. g. meat or similar foodstuff, with a water content of 70–80% is pre-dried in the closed vessel and thereafter burnt in oxygen with elevated pressure. After this procedure all traces of metals present in the starting sample are contained in an aqueous solution consisting on the condensed water from drying and the burning products of the organic matter. The time required for the complete process is less than 30 min. From the obtained solution traces of metals are to enrich by precipitation with carbamate. The determination of the traces of metals is possible by a suitable method of analysis like atomic absorption, ICP or X-ray fluorescence. In various water samples, like drinking water and waste water, traces of Cr, Ni, Fe, Cu, Zn, Cd, Pb, As, Hg and Se in amounts of 5–100g were determined. The recovery rate was 80–90%. In organic substances Hg, Cd, Pb and As in amounts ranging from 50–250 ng/g resp. in amounts of 1–5g were detected with recoveries of more than 80%.

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Ein schnelles Anreicherungsverfahren zur Bestimmung von Schwermetallspuren in wärigen Lösungen

Zusammenfassung Zur Bestimmung von Schwermetallspuren z. B. in destilliertem Wasser, Trinkwasser oder Abwasser ist im allgemeinen eine geeignete Probenvorbereitung erforderlich. Für diesen Zweck wurde ein Anreicherungsverfahren ausgearbeitet, um gleichzeitig mehrere Metalle zusammen mit Spurenfänger-elementen aus wäßrigen Lösungen ausfällen zu können. Danach werden 10–500 ml Probenlösung mit 1 ml verd. Salpetersäure versetzt, um bei den verschiedenen Proben jeweils einen schwach sauren pH-Wert einzustellen. Anschließend werden eine Reduktionslösung sowie die Spurenfängerlösung zugegeben und mit einer Pufferlösung ein pH von 5,0–5,5 eingestellt. Die gelösten Metallspuren werden mit Diäthylammonium-N,N-diäthyldithio-carbamat ausgefällt. Der Niedersclhlag wird auf einem Membranfilter gesammelt. Man erhält ohne Hilfsmittel einen dünnen elastischen Film, der lange Zeit auf dem Filter haftet. Bei einem Ausgangsvolumen von 100 ml dauert der gesamte Vorgang weniger als 15 min. Für die Bestimmung von Metallspuren in organischen Substanzen wurde ein Schnellaufschlußverfahren mit dem Aufschlußgerät BIOKLAV^® entwickelt. Damit ist es möglich, die organische Matrix ohne Zusatz von Chemikalien in eine wäßrige Lösung zu überführen. Der BIOKLAV ist ein zylindrisches Druckgefäß mit einem Sicherheitsschnellverschluß. 20 g Probenmaterial mit einem Wassergehalt von 70–80%, z. B. Fleisch oder ähnliche Lebensmittel, werden im geschlossenen Gefäß zuerst vorgetrocknet und anschließend in Sauerstoff bei erhöhtem Druck verbrannt. Nach dem Aufschluß befinden sich die zu erfassenden Metallspuren in einer wäßrigen Lösung, die aus dem kondensierten Wasser des Probenmaterials und den Verbrennungsprodukten der organischen Matrix herrührt. Der gesamte Aufschluß dauert weniger als 30 min. Aus der Lösung können die Metallspuren durch Fällung mit Carbamat angereichert werden. Die Bestimmung der Elementspuren erfolgt z. B. mit Atom-Absorptions-Spektrometrie (AAS), Optischer Emissions-spektrometrie mit Plasma-Anregung (ICP) oder Röntgen-Fluoreszenz-Analyse(RFA). In verschiedenen Wasserproben, wie z. B. Trinkwasser und Abwasser wurden Spuren von Cr, Ni, Fe, Cu, Zn, Cd, Pb, Hg und Se in Mengen von 5–100g bestimmt. Die Wiederfindungsrate war 80–90%. In organischen Substanzen wurden Hg, Cd, Pb und As in Massenanteilen von 50–250 ng/g bzw. in Mengen von 1–5g mit einer Wiederfindungsrate von mehr als 80% bestimmt.

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

HPLC separation of heterocyclic beta-diketonates of actinide, lanthanide and transition metals

Liquid-chromatography conditions for the separation of neutral chelates of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with transition metals, lanthanides and actinides have been established. The use of reverse-phase liquid chromatography, instead of ion-exchange, is a novel approach for actinide separation. The high molar absorptivities of the beta-diketonates in the ultraviolet region allow for their detection at the nanogram level. The potential exists, therefore, for the rapid solvent extraction, concentration and determination of traces of actinides and other metals.     

Comparison of silica-based and polymer-based cation exchangers for the ion chromatographic separation of transition metals

Silica gel- and polymer-based exchangers differ not only in the substrate but usually also in the structure of their sulphonic acid exchange group. The performance and chromatographic behaviour of modern macroporous poly(styrene-divinylbenzene) polymers of 5-μm particle size after surface sulphonation were examined. Further, two commercially available silica gel cation exchangers were investigated as references for what is now possible and how the chromatographic performance is influenced by the substrate and the structure of the exchange site. The influence of the capacity of surface-sulphonated exchangers for acid and complexing eluents, which are necessary when transition metals are to be separated, was studied. The interaction of polarizable metal cations with the π-system of the polymer depends on the resin capacity, and a comparable dependence for H⁺ and complexing eluents was found. The distance of the functional group from the core influences the adsorption effects dramatically. Lowering the non-specific interaction increases the chromatographic efficiency rapidly. The performance of silica gel-based exchangers is nearly one order of magnitude better than that of surface-sulphonated exchangers. The selectivity of the exchangers investigated is strongly dependent on the structure of the exchange site and on the resin capacity.     

Neutron activation determination of noble metals in rocks: A rapid radiochemical separation based on tellurium coprecipitation

A procedure is described for the determination of Pd, Au, Ir, and Pt in rocks at the ppb concentration level. After irradiation with thermal neutrons, powdered rock samples are fused with carriers and Na₂O₂−NaOH. The fusion cake is dissolved in dilute HCl, and the activated noble metals and carriers are coprecipitated as a group with Te, using Sn²⁺ as a reductant. Gamma and X-rays are counted on semi-conductor Ge deterctors. Yields are determined by reirradiation. Results are given for several rocks, including U.S.G.S. standards PCC-1 and W-1.     

A rapid fractionation method for heavy metals in soil by continuous-flow sequential extraction assisted by focused microwaves

A microwave-assisted continuous-flow sequential extraction system was developed for rapid fractionation analysis of heavy metals in soil. Insertion of pressure-adjusted air between the extractants provided stable flows of the extractants without mutual mixing and back-pressure influence of a column packed with soil, thereby facilitating reliable continuous-flow extractions. In addition, use of pure water as a pumping solvent removed metal contamination because of direct contact between corrosive extractants and the pump containing metallic materials. Focused microwave irradiation to the soil accelerated the selective extractions of the acid-soluble and reducible fractions of heavy metals in soil in the first and second steps of the sequential extraction conditions, as defined by the Commission of the European Bureau of Reference (BCR). The microwave-assisted continuous-flow extraction provided high correlations in amounts of six heavy metals except Zn in the first step and Cu in the second step extracted from a reference sludge soil, BCR CRM 483, with a conventional batchwise extraction proposed by BCR; continuous-flow extraction assisted by conductive heating provided lower correlations for all the six metals. The proposed method drastically reduced the time required for the sequence extraction to ca. 65 min without losing accuracy and precision of the fractionation analysis of heavy metals in soil, whereas the BCR batchwise method requires ca. 33 h. An erratum to this article can be found at     

Spectrafluorimetric method for the rapid screening of toxic heavy metals in water samples

A fast and inexpensive sensitive screening test for recognising potential wastewater contamination by the presence of highly toxic heavy metals is described. The test is based on the reaction of the toxic heavy metals Hg(II), Cd(II), Pb(II) and Ag(I) with 6-mercaptopurine (6-MP) to produce highly fluorescent complexes.Optimum experimental conditions include a buffer of pH 7.2 (0.1 M citric acid/0.2 M Na₂HPO₄), a chelating reagent concentration of 6×10⁻⁴ M and the addition of 10⁻⁴ M of o-phenanthroline. The fluorescence emitted by the complexes was measured at 380 and 540 nm for excitation and emission wavelengths, respectively.Detection limits of 4, 3, 6 and 3 μg l⁻¹ were achieved for Hg, Cd, Pb and Ag. Relative standard deviation (R.S.D.) were between ±2 and ±6% of the fluorescence signals for five identical samples. Potential interference effects from other heavy metals (Zn, Mn, Co, Fe, Ni and Cu), which could affect the response of the proposed screening test was investigated. Results showed that none of these metals give rise to noticeable fluorescence signals under the above described experimental conditions.Finally, the capability of the proposed heavy metal screening test for the analysis of contaminated water samples is discussed.     

A rapid method for the separation of radium from Tuwa spring waters for determining the activity ratio of223Ra/226Ra

A rapid method for the separation of radium in spring waters of Tuwa, Panchamahal district, Gujarat State, India, containing large amounts of calcium (0.5 g/l) has been developed. It consists of concentrating polyvalent cations from 21 samples using 10 g of carboxylate exchanger, Zeokarb 226 (NH ₄ ⁺ ) and then precipitating radium as sulfate in the presence of 400 μg of barium.     

A rapid method for detection of genetically modified organisms based on magnetic separation and surface-enhanced Raman scattering

In this study, a new method combining magnetic separation (MS) and surface-enhanced Raman scattering (SERS) was developed to detect genetically modified organisms (GMOs). An oligonucleotide probe which is specific for 35 S DNA target was immobilized onto gold coated magnetic nanospheres to form oligonucleotide-coated nanoparticles. A self assembled monolayer was formed on gold nanorods using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) and the second probe of the 35 S DNA target was immobilized on the activated nanorod surfaces. Probes on the nanoparticles were hybridized with the target oligonucleotide. Optimization parameters for hybridization were investigated by high performance liquid chromatography. Optimum hybridization parameters were determined as: 4 μM probe concentration, 20 min immobilization time, 30 min hybridization time, 55 °C hybridization temperature, 750 mM buffer salt concentration and pH: 7.4. Quantification of the target concentration was performed via SERS spectra of DTNB on the nanorods. The correlation between the target concentration and the SERS signal was found to be linear within the range of 25-100 nM. The analyses were performed with only one hybridization step in 40 min. Real sample analysis was conducted using Bt-176 maize sample. The results showed that the developed MS-SERS assay is capable of detecting GMOs in a rapid and selective manner.