Determination of radium isotopes in mine waters through alpha- and beta-activities measured by liquid scintillation spectrometry

This paper presents a method for the determination of radium isotopes in mineralised mine waters, based on the separation of alpha- and beta-intensities measured in the precipitate by a liquid scintillation spectrometer in two time intervals (1 day and 7 days) after radium precipitation. The count rates of -particles give not only the concentration of alpha emitters (²²⁶Ra and²²⁴Ra), but also make possible to find the -counting efficiency of the system and through that-to determine the concentration of the -emitting radium isotope (²²⁸Ra) with higher accuracy. An improved chemical procedure was elaborated. By this method radium isotopes in different water samples were determined, in wide range of concentrations, from about 0.06 Bq/dm³ in potable water to more than 100 Bq/dm³ in some mine brines. As an example some analytical results are given. The detection limit, defined as three standard deviations, is-for both radium isotopes –0.03 Bq/dm³ (for intial volume of water sample equal to about 1 dm³ and for counting time of each measurement not longer than 1 hour).     

Determination of natural radioactivity in public drinking water quality assessment

The determination of ₉₀Sr and the gross particleactivity originating from radium isotopes was performed on water samples atvarious stages of treatment taken from water treatment plants before distributionto the consumers.     

Comparative study of measured and critically evaluated resonance integral to thermal cross-section ratios. Part II

The present paper deals with the experimental determination and the critical evaluation of Q_o, the ratio of the resonance integral (I_o) to the 2200 m.s^–1 cross-section (_o) for 57 analytically interesting (n, ) reactions, including a revision and updating of formerly published results for 13 isotopes. Full account is given for deviations from the ideal epithermal neutron flux distribution. The Budapest-Gent cooperative determinations, yielding parallel but independent results, lead to recommended Q_o-values with an average uncertainty as low as 3%. Finally, with the aid of independently evaluated or measured _o-data, a list of recommended I_o-values is given.     

Methodological advances for measuring low-level radium isotopes in seawater

A new approach for quantifying radium isotopes in seawater was developed in advance of the international GEOTRACES program, which has the goal of identifying processes and quantifying fluxes that control the distribution of trace elements and isotopes (TEIs) in the ocean. High-resolution water column samples were collected via a commercially available in situ pump modified to accept multiple filter media including a manganese-oxide (MnO₂) impregnated acrylic cartridge for extracting dissolved radionuclides from seawater. The modifications mitigated prefilter clogging and allowed for up to 1,800 L filtrations in 4 h of pumping. Different MnO₂ cartridge preparation methods were investigated to achieve maximum radium (Ra) extraction efficiency under high sample flow rates. Full-ocean depth profiles were measured for short-lived radium isotopes (²²³Ra and ²²⁴Ra) in shipboard laboratories using a delayed coincidence alpha scintillation counter (RaDeCC). Samples were reanalyzed 4 weeks and 2 months after collection for ²²⁸Th and ²²⁷Ac to correct for supported ²²⁴Ra and ²²³Ra, respectively. Finally, the cartridges were measured on a gamma-ray spectrometer for the long-lived radium isotopes (²²⁶Ra and ²²⁸Ra). Parallel 20 L samples at each pumping depth were collected from Niskin bottles and analyzed via alpha scintillation for ²²⁶Ra to determine radium extraction efficiencies for the cartridges. These modified methods will allow for increased sample throughput, and hence higher spatial resolution for radium isotopes in the ocean. Such resolution will greatly improve the determination of oceanic vertical and horizontal mixing rates over small and large scales, which in turn can be used to calculate fluxes of TEIs into the ocean.     

Determination of the half-lives of transactinium isotopes by relative activity method

Relative activity method offers the potentiality of providing half-life values over a wide range in a short time for different -emitting transactinium isotopes. The method involves the preparation of a synthetic mixture using another isotope of the same element followed by the determination of atom ratio and -activity ratio by thermal ionization mass spectrometry and -spectrometry, respectively. A double dilution technique is described which helps in maintaining the atom ratios as well as -activity ratios close to unity so that these could be determined with high precision and accuracy. Results obtained on the half-lives of²³²U,²³⁸Pu,²⁴²Pu and²⁴³Am using double dilution technique in relative activity method are summarized. Requirements, advantages and applications of this technique for determining the half-lives of other transactinium isotopes are presented.     

Preliminary application of low-background gamma-spectrometry to volcanic ground water

To enrich cosmogenic ⁷Be and ²²Na, artificial ¹³⁷Cs and natural radium isotopes, three chemical methods were applied to large volumes (100–300 l) of ground water from Daisen Volcano, Japan. The co-precipitation method using BaSO₄, Fe(OH)₃ and AMP, yielded ⁷Be, ¹³⁷Cs and radium isotope levels of nearly 100%. An ordinary ion-exchange column method, selectively recovered ²²Na (77%) through two continuous column operations. ⁴⁰K was satisfactorily removed in both, the co-precipitation and column methods. In addition, the simple batch method was suitable for rapid treatment even on the slope of a volcano without sacrificing yields. Low-background γ-spectrometry combined with these chemical treatments enabled the determination of extremely low-levels of ⁷Be, ²²Na, ¹³⁷Cs and radium isotopes (0.01–4 mBq/l) in ground water samples. The measurement of these nuclides of Daisen ground water provide new information on the flow system of volcanic water, including residence time, the mixing of precipitation, and the aquifer’s environment.     

Indikation der Sulfat-F?llungstitration mit adsorptionspolarisierten Elektroden

Summary The indication of the sulphate precipitation-titration using adsorption-polarized electrodes (APE) has been maximized. Large differences in quality of the two electrode surfaces produce broad signals. Suitable preparation of the electrode leads to less defective surfaces. Sharp signals result when the platinum black is electrodeposited at 1.4 V followed by oxidation under the same conditions. Addition of lead-, copper- and mercury-salts to the plating solution increases the surface of the deposits, whereas deposits containing Fe are smoother and lead to sharp peaks.Adsorption as well as coprecipitation of oxoanions cause interference. SeO ₄ ^2– and VO ₃ ^– does not interfere with the determination up to a molar ratio of sulphate to oxoanion of 7.51 and 51 resp., whereas a molar ratio up to 25:1 of CrO ₄ ^2– , MoO ₄ ^2– , WO ₄ ^2– and AsO ₃ sulphate can be tolerated. The influence of IOO ₄ ^2– is negligible. Furthermore, the determination of MoO ₄ ^2– and WO ₄ ^2– was found to be possible by titration using APE-indication.     

Measurement of103mRh produced by the103Rh/γ, γ′ /103mRh reaction with liquid scintillation counting

A liquid scintillation counting technique was applied to measure the isotope^103mRh /half life = 56.12 min/ which is difficult to detect because its -ray is of low energy and low emission probability. Tris-/2,4-pentanedionato/ rhodium /III/ /Rh/ acac/₃/ was irradiated with bremsstrahlung of accelerated 3.2 MeV electrons by LINAC. The method has given a reliable calibration curve for the determination of^103mRh radioactivity below Rh/acac/₃ concentrations of 2 mM. The integrated cross section of¹⁰³Rh/,/^103mRh determined by this method was found to be 6.8±3.4 b MeV at 3.2 MeV.     

On the Applicability of Duolite GT-73 to Column Preconcentration of Gold and Palladium Prior to Determination by Inductively Coupled Plasma Atomic Emission Spectrometry

The preconcentration of Au and Pd on Duolite GT-73 chelating resin with the thiol functional group was investigated prior to determination of these noble metals by means of inductively coupled plasma atomic emission spectrometry. It was found that Au^III and Pd^II were retained on the resin along with other concomitant metals (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) from different HCl-containing media. A two-step elution procedure was developed for the release of the noble metals. First 4.0molL^–1 HNO₃ solution was used to elute the base metals. The recovery of Au and Pd was performed afterwards using 0.50molL^–1 solution of (NH₂)₂CS. Retrieval of Au and Pd retained on Duolite GT-73 was also carried out by decomposition of the resin in the open vessel system using H₂SO₄ with H₂O₂. The detection limits of Au and Pd evaluated for the devised protocol, with a preconcentration factor of 50, were 0.085µgL^–1 and 0.28µgL^–1, respectively. The proposed method was applied to the determination of Au and Pd in spiked electrolytic bath samples.     

Reactions of superoxide anion radical with antioxidants and their use in voltammetry

Kinetic parameters were calculated for the electrochemical reduction of oxygen at a glassy-carbon electrode with the generation of superoxide radical anions in a 0.05 M solution of (C₂H₅)₄NI in dimethylformamide in the presence of fat-soluble antioxidants, retinol and -tocopherol. A procedure based on the protonation of the radical anion with antioxidant molecules is proposed for the voltammetric determination of antioxidants to determine milligram amounts of retinol and -tocopherol in model solutions (RSD = 1–2%). The calibration graphs for retinol and -tocopherol are linear in the concentration ranges 9.7 × 10^–5–2.3 × 10^–3 and 6.2 × 10^–4–3.1 × 10^–3 M, respectively. The detection limits for retinol and -tocopherol are 4.8 × 10^–5 and 4.1 × 10 ^–4 M, respectively. The procedure was applied to the determination of the active component (retinol and -tocopherol) in pharmaceuticals.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 56–59.Original Russian Text Copyright © 2005 by Ziyatdinova, Gilmetdinova, Budnikov.     

Flotation-spectrophotometric determination of ruthenium in the Ru(IV)-chloride-rhodamine 6G-toluene system

Summary Flotation-Spectrophotometric Determination of Ruthenium in the Ru(lV)-Chloride-Rhodamine 6G-Toluene System The reduction of RuO₄ in hydrochloric acid has been examined. A sensitive flotation-spectrophotometric method of the determination of ruthenium based on the ion associate formed by the anionic chloride complex of ruthenium RuCl₆ ^2– with the basic dye Rhodamine 6G (R6G) has been developed. The solution of the ion associate obeys Beer's law up to the concentration of 0.25g Ru/ml. The ion associate precipitates when the aqueous solution is shaken with toluene. The separated compound is dissolved in acetone. The molar absorptivity () at 530 nm is 5.1×10⁵ 1·mole^–1-cm^–1. The relative standard deviation is 3–7%. The mole ratio of RuR6G in the complex is 15. Osmium reacts similarly. The determination of ruthenium can be selective after the preliminary separation of osmium as OsO₄. The method was applied to the determination of microgram amounts of ruthenium in crucible platinum.     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

Determination of234U/238U and235U/238U ratios from commercially available uranium compounds by α-spectrometry

The²³⁴U/²³⁸U and²³⁵U/²³⁸U ratios from uranium compounds by -spectrometry technique have been obtained. Ten commercially available uranium reagents were analyzed. The well-separated peaks corresponding to uranium isotopes are evident, providing an energy spectrum of the -particles of uranium isotopes. It was found that some commerical uranium salts were depleted in²³⁴U and²³⁵U.     

Simultaneous determination of pentachlorophenol and carbaryl in water

Summary A rapid method for the simultaneous determination of pentachlorophenol (PCP) and Carbaryl in water is described. A 1 liter water sample is extracted with hexane after acidification with concentrated H₂SO₄. After evaporation to a small volume, the extract is analyzed by gas chromatography-mass spectrometry, operating in the selected ion monitoring mode. Estimated detection limits are 0.08 g L^–1 for PCP and 0.11 g L^–1 for Carbaryl, with recoveries of 96% for PCP and 97% for Carbaryl.     

Synthesis,chemical, and electrochemical characterization of the [Ag13{μ3-Fe(CO)4}] n− (n = 3, 4, 5) cluster anions: X-Ray structural determination of [N(PPh3)2]3 [Ag12(μ12-Ag){μ3Fe(CO)4}8]1

The oxidation of the [Fe(CO)₄]^2– dianion with Ag⁺ salts occurs through a particularinner-sphere mechanism, which involves an intermediate cascade of silver clusters stabilized by Fe(CO)₄ ligands. The last detectable Ag-Fe cluster of the sequence is the [Ag₁₃{-Fe(CO)₄}₈]^3– trianion, which has been selectively obtained by using ca. 1.7 equivalents of Ag⁺ per mole of [Fe(CO)₄]^2–. The [Ag₁₃{-Fe(CO)₄}₈]^3–- trianion has been isolated in a crystalline state with several quaternary cations, and has been characterized by X-ray diffraction studies of its bis(triphenylphosphine)iminium salt. [N(PPh₃)₂]₃ [Ag₁₃{ ₃-Fe(CO)₄}₈]·2(CH₃)₂CO, monoclinic, space group P2₁ (No.4),a = 16.284(2) Å,b =18.767(5) Å,c = 25.905(4) Å, = 90.46(1)°,V = 7916(3) ų,Z = 2,R = 0.0324. The molecular structure of the anion consists of a centered cuboctahedron of silver atoms with the triangular faces capped by Fe(CO)₄ units. Chemical reduction of ( Ag₁₃{ ₃-Fe(CO)₄}₈]^3– affords the corresponding [Ag₁₃{ ₃-Fe(CO)₄)₈]^4–, which in turn gives [Ag₁₃{ ₃-Fe(CO)₄)₈]^5– and [Ag₆{ ₃-Fe(CO)₄}₄]^– upon further reduction. Electrochemical investigations confirm the reversibility of the [Ag₁₃{ ₃-Fe(CO)₄}₈]^3–/4– redox change. Furthermore, in spite of some electrode poisoning effects, evidence of the existence of the [Ag₁₃{ ₃-Fe(CO)₄}₈]^5– pentaanion was obtained. The yet structurally uncharacterized [Ag₆{ ₃-Fe(CO)₄)₄]^2– dianion is quantitatively obtained by reaction of [Fe(CO)₄]^2– with ca. 1.5 equivalents of Ag⁺ or by addition of one equivalent of Ag⁺ to solutions of the [Ag₅{Fe(CO)₄}₄]^3– trianion. All attempts to isolate its quaternary salts as crystalline materials failed owing to formation of amorphous insoluble precipitates. The above series of ₃-Fe(CO)₄ octa-capped cuboctahedral Ag₁₃ clusters can be envisioned as the Ag⁺ . Ag and Ag^– cryptates of the [Ag₁₂{}₃-Fe(CO)₄}₈]^4– cryptand. respectively.Dedicated to Prof L. F. Dahl on his 65th birthday.     

Determination of 241Pu in marine samples using co-precipitation with rare earth fluoride and liquid scintillation spectrometry

²⁴¹Pu was measured in reference materials and marine samples using a novel method based on rare earth fluoride co-precipitation followed by liquid scintillation spectrometry (LSS). Disc sources used for -spectrometry of ²³⁸Pu and ^239+240Pu were leached with concentrated nitric acid before neodymium fluoride co-precipitation to scavenge plutonium in the lower oxidation states was carried out. After the determination of the chemical recovery by -spectrometry, the precipitate was recovered in a H₃BO₃/HNO₃ based dissolver and mixed with Packard Insta-Gel^Ò Plus cocktail before LSS. Reasonable agreement has been obtained between the results obtained using this methods and the data obtained by direct disc analysis by LSS and ICP-MS. The ²⁴¹Pu/^239+240Pu ratios were coherent with the expected origin of the Pu contaminant in the marine environment showing the validity of the method.This revised version was published online in November 2005 with corrections to the Cover Date.     

Heats of solution of 1∶1 electrolytes in 1-propanol,and derived enthalpies of transfer from water

Heats of solution of 13 11 electrolytes in 1-propanol have been determined calorimetrically at various electrolyte concentrations, and extrapolated to zero concentration to give H _s ^o values for these electrolytes. Together with literature data on three additional 11 electrolytes, these measurements yield a self-consistent set of single-ion enthalpies of transfer from water to 1-propanol. Values are tabulated for 10 univalent cations and five univalent anions. It is shown that the H _t ^o (Ph ₄ As⁺)=H _t ^o (Ph ₄ B^–) assumption yields chemically reasonable single-ion values. Using this assumption, it may be deduced that all the univalent ions studied have about the same enthalpy in 1-propanol as in methanol.     

Precipitation separation of lead and calcium,strontium, barium from acidic solutions using crown ether and tungstosilicic acid

It was found that lead reacts with 18-crown-6 (L) and tungstosilicic acid (H₄A) in acidic solutions and a compound with low solubility is formed what was confirmed by radiometric titration methods. Coprecipitation of complexion cation of PbL²⁺ with similar complexion cations of calcium, strontium and barium was studied. Formation of low soluble salts was utilized for separation of Pb from Ca, Sr and Ba from 1 mol·dm^–3 HNO₃. The ratio of Pb/Ca, Pb/Sr and Pb/Ba in the precipitation or separation factors S_pb/M undoubted depends on the ratio of the stability constants of lead and metals with 18C6 (_Pb/_M), what can be used for determination of more precise constant stability _M.     

Electrochemical Properties and Analytical Applications of Keggin-type Phosphomolybdic Anions in Electrostatically Linked 2-Aminoethanethiol Self-Assembled Monolayers

A composite film containing a heteropolyanion was prepared on a 2-aminoethanethiol (AT) self-assembled monolayer film-modified gold electrode by attaching the Keggin-type phosphomolybdic anion. The surface structures and electrochemical properties of the composite films were characterized by using ATR-FTIR, AC impedance, cyclic voltammetry and chronocoulometry. FTIR studies indicated that there was some electrostatic interaction between Pmo₁₂O₄₂^7– and surface NH₃⁺. Three reversible redox couples were observed in 1.0molL^–1 H₂SO₄ in the potential range of 0–0.7V for the composite film modified electrode, which were attributed to two-electron and two-proton electrochemical processes of PMo₁₂O₄₂^7–. The diffusion coefficient is determined to be 2.04×10^–7cm²s^–1. The composite film shows good catalytic activities for the reduction of nitrite (NO₂^–) in acidic solution and the catalytic mechanisms are described. The modified electrode provides a linear response for NO₂^– in the concentration range of 1.0×10^–4 to 1.0×10^–7molL^–1 by differential pulse adsorptive stripping voltammetry with a correlation coefficient of 0.9965. The detection limit (three times the signal blank/slope) was 2.0×10^–8molL^–1. The modified electrode was used for the determination of NO₂^– in wastewater.     

Infrarot-spektralphotometrische Bestimmung der ?freien? Silanolgruppen in pyrogenen Kiesels?uren

Zusammenfassung Die technischen Eigenschaften pyrogener Kieselsäuren werden entscheidend vom Gehalt an »freien« Silanolgruppen mitbestimmt. Die IR-Absorption dieser Gruppen in CCl₄ gehört zu einer Bande bei 3700 cm^–1. Es wurde festgestellt, daß die maximale Extinktion in CCl₄ unter bestimmten Bedingungen unabhängig von der Anzahl ebenfalls vorhandener »gebundener« Silanolgruppen (max. Extinktion bei etwa 3350–3450 cm^–1) sowie auch weitgehend unabhängig vom Wassergehalt (Feuchtigkeit) ist. Diese Tatsache wurde zur Ausarbeitung eines Routineverfahrens benutzt.

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Infrared-spectrophotometric determination of free silanol groups in pyrogenic silicic acids

Summary The technical properties of pyrogenic silicic acids are decisively co-determined by their content of so-called feee silanol groups. Their infrared absorption in a CCl₄ suspension belongs to a band at about 3,700cm^–1. It has been found that under certain conditions their maximum absorbance in CCl₄ is independent of the number of so-called bonded silanol groups (maximum absorption at about 3,350–3,450cm^–1), additionally existing in all commercial pyrogenic silicic acids, and also in wide ranges of the water content (humidity). This fact has been used as a basis for a quantitative routine determination of free silanol groups.

Zum Gedenken an Heinz Dannenberg