Application of mercury isotopes and their production

Mercury isotopes are now broadly applied in various fields of science and technology. They are used in medicine, nuclear physics investigations, RF standards, nuclear gyroscopes, mercury analysing devices etc. One of the most promising applications is the use of weakly enriched (up to 3%) isotope¹⁹⁶Hg in fluorescent lamps for enhancing their light efficiency. Besides, the application of²⁰¹Hg and²⁰²Hg as the target material for the production at low-energy cyclotrons of one of the most consumed²⁰¹Tl isotope in medicine seems to be perspective. Various methods were proposed and examined for the separation of mercury isotopes. There are: electromagnetic, photochemical, centrifugal, laser, photoionizing method etc. But only two of them were effective for the mercury isotope separation: electromagnetic and photochemical ones. This paper presents a review of the experimental results on separation of various mercury isotopes by different methods.     

Biochemical studies of current environmental levels of trace elements: Cyclotron production of radiothallium and its use for metabolic investigations on laboratory animals

Carrier-free^201+202Tl have been produced in the cyclotron by (p, xn) reactions on mercury targets and used as a trcer for thallium in metallobiochemistry of heavy metal pollution. The separation of^201+202Tl radioisotopes from Hg involved a solvent extraction method leading to labelled univalent Tl(I) ions. This radioactive solution was used to prepare different^201+202Tl labelled compounds such as inorganic Tl(III) ions and organic dimethylthallium. Quality controls have been applied directly on the different radioactive solutions immediately before their administrations to rats in order to ensure that thallium had the chemical form expected. A summary of the main results concerning different aspects of the metabolic investigations on rats such as absorption, retention, excretion, transplacental transport and influence of the different chemical forms of thallium on its metabolism is also reported.     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

197Au (α,xn)201−xTl reactions

Excitation functions of (, xn) reactions on¹⁹⁷Au with x5 have been measured in different irradiations from 10 to 55 MeV bombarding energy, by Ge intrinsic spectroscopy of the residual activity of stacked foils. Absolute cross sections for the formation of^{200,199,198,197,196 m}Tl are reported. Isomeric ratios for products^198mTl and^198gTl were also determined.This work has been sponsored by the Subsecretaría de Ciencia y Tecnología, Argentina.     

Distribution of137Cs,40K,238U and232Th in soils from Northern Venezuela

More than one hundred undisturbed soil samples from Northern Venezuela and the islands of Margarita and Los Roques have been analyzed for¹³⁷Cs,⁴⁰K,²³⁸U and²³²Th by -ray spectroscopy. The specimens were taken from between 5–10 cm below the earth's surface. Thus, they are valid not only for the¹³⁷Cs deposition studies but also for the estimation of the natural -ray dose from primordial radionuclides that form the terrestrial component. The concentration of⁴⁰K was directly determined from its 1461 keV -ray, while those of¹³⁷Cs,²³⁸U and²³²Th were performed using a -ray from one of their daughter radionuclides: the 661 keV -ray of^137mBa for¹³⁷Cs, the 1760 keV -ray of²¹⁴Bi for²³⁸U and the 2620 keV -ray of²⁰⁸Tl for²³²Th. Finally, the concentration values were compared with those of global estimates.     

Aktivierungsanalytische Bestimmung von Cadmium, Quecksilber, Thallium und Wismut in Gesteinen

Zusammenfassung An einer Reihe von U.S. Geological Survey Standardgesteinen und hochreinen Quarzproben wurden die Elemente Cd, Hg, Tl und Bi durch Neutronenaktivierungsanalyse quantitativ bestimmt. Die Abtrennung dieser Elemente von der Matrixaktivität erfolgte durch Ionenaustausch. Cd und Hg wurden so weit gereinigt, als es die -Spektrometrie mit Ge(Li)-Halbleiterdetektoren erforderte. Die -Strahler ²⁰⁴Tl und ²¹⁰Bi wurden radiochemisch rein abgetrennt. Bei einer Bestrahlungszeit von 3 Tagen und einem thermischen Neutronenfluß von 6 · 10¹³ cm^–2 · sec^–1 lagen die erzielten Nachweisgrenzen bei 0,1 ppb für Hg und Tl bzw. bei 1 ppb für Cd und Bi.

---

Determination of cadmium, mercury, thallium and bismuth in terrestrial rocks by neutron activation analysis

In a series of U.S. Geological Survey standard rocks and high purity quartzes the trace elements Cd, Hg, Tl and Bi were determinated by thermal neutron activation analysis. The bulk activity of the samples was removed by ion exchange. Cd and Hg were purified as far as necessary for Ge(Li)--spectrometry. The -emitters ²⁰⁴Tl and ²¹⁰Bi were separated in radiochemical purity. For a 3 days irradiation at a thermal neutron flux of 6×10¹³cm^–2 ×sec^–1 the detection limits were 0.1 ppb for Hg and Tl, and 1 ppb for Cd and Bi.

---

---

Die Untersuchung wurde am Institut für Radiochemie der Kernforschungsanlage Jülich durchgeführt. Herrn Prof. Dr. Stöcklin und den Mitarbeitern des Instituts, insbesondere Fräulein Dr. Bell, sei an dieser Stelle für die großzügige Unterstützung und Bereitstellung der Arbeitsmöglichkeiten gedankt.

---

Herrn Prof. Dr. Wedepohl danke ich für die Stellung des interessanten Themas und Überlassung des Probenmaterials. Fräulein K. Horstmann vom Isotopenlabor des Geochemischen Instituts unterstützte mich bei der radiochemischen Aufbereitung, Herr Fait vom Zentralen Isotopenlabor der Universität Göttingen war mir bei der Messung der low-level--Präparate behilflich. Die Deutsche Forschungsgemeinschaft hat die Arbeiten durch eine Sachbeihilfe gefördert.     

Stripping voltammetric determination of trace amounts of mercury using a carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone

A carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone was used for the voltammetric determination of mercury(II). Mercury was preconcentrated onto the surface of the modified electrode only by the complexing effect of the modifier without application of potential (i.e. in open-circuit conditions). After exchange of the medium, the accumulated amount of mercury(II) was determined by differential pulse anodic stripping voltammetry. The response depended on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 0.1 g 1^–1 Hg(II) for a preconcentration time of 15 min. Preconcentration for suitable times yielded a linear calibration graph from 0.5 to 6000 g 1^–1 Hg(II). For multiple determinations (5 runs), the relative standard deviation was 5% for a concentration of 100 g 1^–1 Hg(II). The proposed procedure was used to determine trace mercury in plant and sewage sludge samples with good results.On leave from Hainan University, Hainan Peoples Republic of China     

Excitation characteristics of elements above Z=30 with57Co,67Ga,75Se,99mTc,111In,125I and201Tl implant sources

Radioactive implant induced X-ray emission (RIXE) spectrometry was examined by mixing a sample in solution with a radioisotope. The radioisotopes of⁵⁷Co,⁶⁷Ga,⁷⁵Se,^99mTc,¹¹¹In,¹²⁵I and²⁰¹Tl were used as implant X-ray excitation sources. Copper, strontium, iodine, barium, lead and uranium solutions were used as samples to be analyzed. K X-ray for all samples and L X-rays for lead and uranium samples were measured with a pure Ge detector. The excitation characteristics of each radioisotope are discussed using the effective excitation efficiency (eff) defined by the equation eff=N_c/(N_aN_d), where N_c is the number of counts in the X-ray peaks, N_a is the number of atoms of interest in the sample, and N_d is the total number of decays of radioisotope for the counting interval.     

Mikrobestimmung von Bromid (Chlorid) durch radioaktive Extraktion

Zusammenfassung Quecksilber(II)-bromid und -chlorid lassen sich durch Extraktion mit Diäthyläther von Quecksilber(II)-ionen trennen. Die Bromid oder Chlorid enthaltende Lösung wird mit einem Überschuß einer mit²⁰³Hg markierten Quecksilbernitratlösung versetzt, dann die entstandenen Halogenidkomplexe mit Äther extrahiert und die- Aktivität der ätherischen Phase gemessen. Die Methode eignet sich zur Bromidbestimmung erheblich besser als zur Chloridbestimmung.

---

Summary Mercury(II) bromide and chloride can be separated from mercury(II) ions by extraction with diethyl ether. The solution containing bromide or chloride is treated with an excess of a mercury nitrate solution labelled with²⁰³Hg; the resulting halogenide complex is extracted into ether and the-activity of the ether phase is measured. The method is much better suited for determining bromide than chloride.

---

---

Wir danken Herrn Prof.L. Erdey für die Ermöglichung unserer Versuche.     

19F and199Hg NMR spectra of certain fluorine-containing arylmercury derivatives of acetylenes

Conclusions ¹⁹F and¹⁹⁹Hg NMR have been used to investigate the comparative influence of electronic effects of the substituents on the shielding of¹⁹F and¹⁹⁹Hg nuclei in ArHgC-CC₆H₄F-4 and 4-FC₆H₄HgC=CR. It has been found that the shielding of the fluorine decreases and the shielding of the mercury increases with increasing electron-acceptor properties of the Ar or R, or when the change is made from toluene to pyridine. The¹⁹F and¹⁹⁹Hg chemical shifts correlate well with the and ⁰ Hammett constants.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1524–1529, July, 1985.     

Low level determination of thallium in biological and environmental reference materials by RNAA using several counting methods

A new RNAA procedure was developed capable of low level determination of thallium in biological and environmental samples. After high fluence neutron irradiation in a nuclear reactor, wet ashing of samples and T1(I) separation by solvent extraction with sodium diethyldithiocarbamate at pH 13, several types of counting were employed to compare their detection limits and to utilize the self-validation principle of NAA. The following measurement modes were used: High efficiency counting of -rays of²⁰²T1 and Hg X-rays produced on decay of²⁰⁴T1 using a well-type HPGe detector, combined ^– ray and ^–-counting of²⁰⁴T1 with the aid of a HPGe planar detector, and liquid scintillation counting and counting of Cerenkov radiation of ^–-particles of²⁰⁴T1. The lowest detection limit of 0.034 ng of T1 was achieved on liquid scintillation counting of²⁰⁴T1. The method was applied for the analysis of biological NIST SRMs 1515, 1573a, 1577b and environmental NIST SRM 1633a. Good agreement was found between the thallium certified value in SRM 1633a and values determined in this work by all counting modes. For SRM 1573a, results in agreement were obtained by two counting modes, while counting of Hg X-rays of²⁰⁴T1 was only used for SRMs 1515 and 1577b.     

Solubility and activity coefficient of thallium (I) chloride in the system TlCl+HCl+NaCl+H2O at 25°C

The solubility of thallium (I) chloride has been studied in aqueous mixtures of HCl and NaCl at 25°C at ionic strengths ranging from 0.10 to 3.20 mol-kg^–1. Activity coefficients were derived and fitted to Pitzer's equations. This required values of the single-electrolyte parameters, ⁰, ¹ and C for TlCl. Since these are not available in the literature, owing to the low solubility of TlCl in water, a method has been devised for evaluating these parameters. These were then used to determine the mixing parameters, and , for the system. Consideration of the higher-order limiting law for symmetrical mixing did not improve the accuracy of the fit. The success with which the ion-interaction theory in its simplest form has been able to model the present system to such a high ionic strength shows that it is not necessary to treat ion association in the system explicitly in terms of an ion association equilibrium constant.     

Aluminum-26: A nuclide for all seasons

The long-lived²⁶Al was discovered in a search for a tracer isotope of the last element for which at least one was available, but it has tumed out to have a number of other scientific applications in addition. Discussed will be: discovery and properties of²⁶Al;²⁶Al as a -ray standard; cosmic-ray-induced²⁶Al in meteorites, lunar matter, and terrestrial materials; extinct natural radioactivity of²⁶Al in meteorites and live²⁶Al in the early Solar System; 1.81-MeV -radiation from²⁶Al in interstellar space; and²⁶Al as a tracer isotope, especially in biology and medicine. Some of these applications are possible because of non-destructive low-level -ray spectrometry, and some because of accelerator mass spectrometry of extremely small amounts of the nuclide.     

Determination of239,240Pu and241Am in environmental samples

An accurate and reliable method has been developed and routinely carried out for the sequential determination of^239,240Pu and²⁴¹Am in environmental samples. After suitable pretreatment.^239,240Pu and²⁴¹Am are separated from other elements by means of the anion exchange resin method. Americium-241 is purified by coprecipitation with calcium oxalate and then ion exchanged in mixed media of the mineral acid-methanol. In the analysis,²⁴²Pu (or²³⁶Pu) and²⁴⁴Cm are used as chemical yield monitors. The recoveries of the yield monitors in the analyses of some kinds of environmental samples were 7080% for plutonium and 7686% for curium. The concentration of^239,240Pu in the coastal sea water were 7.022 Bq/l and that of²⁴¹Am was 1.26.3 Bq/l. The mean concentrations of^239,240Pu in the edible parts of the marine products ranged from 0.22 to 7.4 mBq/kg · fresh and those of²⁴¹Am ranged from 0.11 to 2.6 mBq/kg · fresh.     

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Electrospray ionization mass spectrometry (ESI-MS) coupled to a microreactor is an excellent tool for the investigation of reactions in solution. Here, we report the first results of our investigations into preparatively interesting electron-transfer-initiated chain reactions in solution which proceed via radical cations as reactive intermediates. The tris(p-bromophenyl)aminium hexachloroantimonate (1)-mediated [2+2] cycloaddition of trans-anethole (2) to give 1,2-bis(4-methoxyphenyl)-3,4-dimethylcyclobutane (3) was investigated. The reaction proceeds as a radical cation chain reaction via transient intermediates 2 ⁺ and 3 ⁺ that could be detected and characterized unambiguously directly in the reacting solution by ESI-MS/MS. The identity of the intermediates was confirmed by comparison with authentic MS/MS spectra of 2 ⁺ and 3 ⁺ obtained by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). In addition, substrate and product can be monitored easily in the reacting solution by APCI-MS.Part of this work was presented at the 36th Conference of the German Society for Mass Spectrometry (DGMS).     

Preparation and characterization of theβ-cyclodextrin inclusion complex with phenylpropiolic acid

The preparation of a 1:1 complex involving-cyclodextrin (-CD) and phenylpropiolic acid (PPA) is reported. The new inclusion complex of-CD has been characterized on the basis of its chemical analysis, thermal behavior, infrared spectrum, X-ray powder pattern and¹³C-NMR spectrum in DMSO solution.     

Separation of the radioelements210Pb−210Bi−210Po by spontaneous deposition onto noble metals and verification by Cherenkov and liquid scintillation counting

A method for the separation of²¹⁰Pb,²¹⁰Bi and²¹⁰Po using spontaneous deposition has been developed. The²¹⁰Bi and²¹⁰Po are simultaneously removed by deposition onto nickel foil (copper and tin could also be used but less effectively) while the²¹⁰Po is separated from²¹⁰Bi, after dissolution of the nickel foil, by deposition onto silver foil. The effectiveness of each separation was evaluated by adding aliquot portions of each solution to a cocktail and counting with a liquid scintillation counter. Water was used as the medium to observe the Cherenkov count of the sample solution.     

Quantitative determination of chloride by means of flow injection analysis with spectrophotometric detection in the UV/VIS range

Chloride is determined indirectly by Spectrophotometric flow injection analysis. Two systems are compared, both based on the principle of ion exchange of easily detectable anions versus chloride from suitable mercury salts. The first method is based on the exchange of chloride with chloranilate which is detected at 332 nm or at 306 nm in neutral or in acidic medium respectively. In the second case, chloride reacts with Hg(SCN)₂. The liberated thiocyanate forms a strongly coloured complex with Fe(III) in acidic solution with an absorption maximum at 460 nm. Both methods have a detection limit of about 5 mol Cl^–/l (175 ng/ml). In the case of the thiocyanate method, the relative standard deviation is about 2% (7 measurements) in the range of 5 to 150 mol/l and decreases significantly to a value of approximately 0.2% at higher concentrations; for the chloranilate method it is 10% for lower and about 1% for higher concentrations respectively.     

Production of96Tc and95mTc via the93Nb(α, xn) Reactions

Relatively longer liver technetium tracers such as^95mTc (61 d) are useful for the development, evaluation and comparison of new technetium complexes for eventual development of^99mTc radiopharmaceuticals. The feasibility of producing⁹⁶Tc (4.35 d) and^95mTc (61 d) was studied by the alpha bombardment of pure Nb targets (⁹³Nb-100%).⁹⁶Tc was obtained in a yield of 30 Ci/Ah using 16 MeV alphas, but it contained significant activity of⁹⁵Tc (20 h) Relatively pure⁹⁶Tc and^95mTc was produced in yields of 18 Ci/Ah and about 1 Ci/Ah respectively with alphas of suitable energy and after allowing for suitable cooling periods after the end of bombardment (EOB).     

The simultaneous determination of the emanation fractions of radon and thoron

A procedure first described by O. Hahn in 1935 has been adapted to the measurement of the probability of escape of radon and thoron//the emanation fraction/ in soils and rocks through application of the germanium counter. Measurement of the regrowth of the²¹⁴Pb, Bi,²¹²Pb, Bi and²⁰⁸Tl following emanation loss permits the simultaneous determination of the two emanation fractions.