Polarographic determination of microgram amounts of thorium(IV)

Summary Among various salt solutions tested 0.01 N LiNO₃ proved to be most suitable as supporting electrolyte for the polarographic determination of microgram amounts of thorium. Well-developed, maxima-free and reproducible waves were obtained for a Th(IV) concentration range of 1.4–23 g/ml. The minimum detectable limit of the element was 0.8 g/ml. No relationship has been found between Th(IV) and H⁺-ion concentration.

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Polarographische Bestimmung von Mikrogramm-Mengen Thorium(IV)

Zusammenfassung Von verschiedenen untersuchten Salzlösungen hat sich als Grundelektrolyt 0,01 N LiNO₃-Lösung als am günstigsten erwiesen. Es wurden damit gut ausgebildete, maxima-freie und reproduzierbare Stufen für einen Konzentrationsbereich von 1,4–23 g Th(IV)/ml erhalten. Die Nachweisgrenze betrug 0,8 g Th(IV) in 1 ml Lösung. Es wurde kein Zusammenhang zwischen Thoriumkonzentration und H⁺-Ionenkonzentration nachgewiesen.

     

Determination of free formaldehyde in nonwovens in the presence of glyoxalic acid and aldehydes

Summary A method for the determination of free formaldehyde in nonwovens in the presence of interfering components is described.After RP-HPLC separation the water extracted formaldehyde reacts with acetylacetone in a knitted open tube reactor to form a lutidine derivative which is measured, even at low concentrations, by the UV detector. The minimum detectable concentration is 25 g/kg.     

Modeling of Low Concentrations of Reactive Species in Kinetic Monte Carlo Simulations

A new method for determination of contributions of species present in low concentration in kinetic Monte Carlo (MC) simulations of chemical processes is proposed. It allows, for instance, to calculate of exact concentrations when species being of interest appear in MC experiments only for short time intervals. The method is based on monitoring of the cumulative life‐time of the investigated species under consideration as a function of the reaction time and subsequent differentiation of the resulting curve. It is especially useful for determination of distributions of low‐concentration active propagation species in radical polymerizations, both free and controlled ones. The method enables to reduce significantly a simulation scale required for determination of the concentrations of investigated species.

     

Determination of Promedol (Trimeperidine) and Ketamine in Blood Using Gas Chromatography–Mass Spectrometry

A procedure was developed for the gas-chromatographic determination of promedol (trimeperidine) and ketamine in whole blood with mass-selective detection. The detection limit for trimeperidine and ketamine in blood is 0.05 g/mL. The analytical range is 0.1–5.0 g/mL. The maximum within-series errors in the determination of the studied compounds are no higher than 14.1% for concentrations of 0.10 g/mL and 7.47% for concentrations of 1.0 g/mL. The maximum between-series relative errors are 5.75% for concentrations of 0.10 g/mL and 2.7% for concentrations of 1.0 g/mL. The procedure can be used in toxicological and clinical analyses.     

A new spark source mass spectrometric technique for the analysis of sub-ng amounts of trace elements

Summary Spark source mass spectrometric tip-top-technique (TTT) is a new method for the analysis of sub-ng amounts of chemically separated trace elements in geological material. Besides its application to dissolved samples, TTT differs from conventional spark source mass spectrometry in reduction of measuring time (few minutes), photoplate background, and interferences by isobars and cluster-ions, resulting in enhanced sensitivities. Detection limits range from about 5 to 20 pg for the rare earth elements, U and Th, and from about 10 to 100 pg for noble metals. Precisions and accuracies of 1 to 5% are gained for trace elements abundances about 1 ng.A potential and especially useful application of TTT is the analysis of rocks available only in very small sample sizes and/or with very low concentration levels of trace elements. An additional application is the determination of osmium isotopes in geological material.

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Neues funkenmassenspektrometrisches Verfahren für die Analyse von sub-ng-Mengen von Spurenelementen

     

Formation of monodisperse poly(1-methacryloxybenzotriazole) particles by radiation-induced dispersion polymerization

Radiation-induced dispersion polymerization of 1-methacryloxybenzotriazole (MABt) in ethyl propionate starts as homogeneous mixture and the resulting polymer precipitates as spherical particles. Formation, size, and shape of polymer particles are strongly dependent on the initial monomer concentration. Three regions can be distinguished: formation of deformed particles at concentrations of 15 w/v-% MABt; formation of spherical particles at concentrations from 18 to 35 w/v-% MABt; no precipitation of polymer at concentrations of 40 w/v-% MABt. The spherical particles at 20 w/v-% MABt had a diameter of 0.54 ± 0.31 m for 3 kGy irradiation and 2.93±0.68 m for 30 kGy. The number distribution of the microspheres shows that the spherical particles with small sizes formed at low irradiation dose (low conversion) disappears with increasing irradiation dose because of multi-coating by newly produced polymer.     

Neutron activation analysis of thorium after separation of233Th by isotopic ion exchange

The procedure for thorium determination in ammonium diuranate (ADU) and rocks, by neutron activation analysis after chemical separation of²³³Th, is presented. The separation of²³³Th from the interfering radioisotopes is based on the retention of²³³Th by a resin saturated with thorium (isotopic exchange) and on the elution of the interfering radioisotopes by a dilute solution of thorium in 0.5M HCl (ion exchange). The determination limit of thorium in rocks and ADU was found to be 0.56 and 9.3 g, respectively, when a 20% relative standard deviation was assumed as acceptable. The highest value obtained for the determination limit of thorium in uranium compounds, on account of the²³⁴Th activity present, is discussed.From a thesis submitted by C. S. Munita to the Instituto de Pesquisas Energéticas e Nucleares (CNEN/SP) University of São Paulo, in partial fulfillment for a Doctor of Science's Degree. Work supported by the Brazilian Atomic Energy Commission.     

Extraction-spectrophotometric determination of uranium by Arsenazo III encapsulated in liquid membrane

Uranium is extracted by a water-in-oil emulsion consisted from 0.01M 8-hydroxyquinoline /HOx/ in cyclohexane and aqueous solution or Arsenazo III and glycine. Analyzed solution is adjusted to 0.02M 1,2-diaminocyclohexane-N,N,N,N-tetraacetic acid /DCTA/ and pH 7.5±0.1. Preconcentration factor of about 400 can be achieved and when the uranium concentration in the outer solution is above 5 g.dm^–3 /5 ppb/ its spectrophotometric determination in the inner solution of the double emulsion system is possible. Thorium practically does not interfere at the ratio Th:U=20:1.Dedicated to Prof. V.F. Nefedov on the occasion of his 70th birthday     

Thallium determination in biological materials by radiochemical neutron activation analysis

Summary The determination of thallium in biological materials sometimes cause problems because of the low concentrations of this toxic element. In the present work a method is described which optimizes the parameters affecting the specificity and sensitivity of the radiochemical NAA of thallium in biological samples. High thermal neutron flux, complete decomposition of the organic matter by pressurized digestion, TlI precipitations, liquid extraction of HTlBr₄ and La(OH)₃ scavenging purification are the steps leading to the final homogeneous preparation of Tl₂CrO₄ for -activity measurement. The method was applied to various materials as bovine liver, bone and nails. Good agreement was found between certified and determined thallium concentrations of the reference material CRM 176. The chemical yield comes to about 80%, with low deviations. The sensitivity of the method is about 10^–3 g/g, the standard deviations being in the range of 3.6% (CRM 176), 14% (bovine liver), and 17% (bone). Detailed working instructions are given.     

Spectroscopic and Potentiometric Investigation of a Diprotic Acid: An Experimental Approach to Understanding Alpha Functions

A laboratory experiment suitable for second- or higher-year chemistry students uses thymol blue, an organic dye, for investigating the fraction of each colored species present as a function of pH. Visible color changes in the vivid, highly absorbing dye permit students to see relative amounts of acid, base, and ampholyte species during the titration, while potentiometric measurement of pH and spectroscopic determination of concentrations permit quantitation of the species present. A standard Beers law calibration curve is constructed for known concentrations of the pure forms of each species at a pH where that species is present as nearly 100% of the total analytical concentration of the dye. Using the molar absorptivities of the three species computed from the calibration curves, simultaneous determination of concentration by species is performed on a set of solutions having constant total concentration of dye such that each solution represents one point in the range pH 0 to pH 13. A mathematical software application is used to solve the simultaneous equations and determine the fraction of each species present. Students then use a spreadsheet application to plot the fractions as functions of pH (the alpha functions). The significance of the isosbestic points in the spectra is also explored.     

Kinetic Determination of Microquantities of Rutin by Perturbation of the Bray-Liebhafsky Oscillatory Reaction in an Open System

A kinetic method is described for the microquantitative (microconcentration/microvolume) determination of rutin based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory reaction being in a non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor. The response of the matrix system to perturbations by different concentrations of rutin ethanolic solutions is followed by a Pt-electrode. In the concentration range between 7.8×10^–8moldm^–3 and 9.1×10^–6mol dm^–3, we found a linear dependence of the maximal potential shift, E_m, on the logarithm of the rutin concentrations. The unknown concentrations can be determined from the calibration curve up to an accuracy of ±5%. The detection limit is 3.6×10^–8mol dm^–3. The amount of required sample can be as small as 10µL.     

N,N,N′,N′-tetrabutylsuccinylamide as a new extractant in n-dodecane for extraction of uranium(VI) and thorium(IV) ions

N,N,N,N-tetrabutylsuccinylamide (TBSA) was synthesized, characterised and used for the extraction of U(VI) and Th(IV) from nitric acid solutions into n-dodecane. Extraction distribution coefficients of U(VI) and Th(IV) as a function of aqueous nitric acid concentration, extractant concentration and temperature have been measured and found that n-dodecane as diluent was superior to 50% 1,2,4-trimethyl benzene (TMB) and 50% kerosene, (OK) system for extraction of U(VI) and Th(IV). The compositions of extracted species, equilibrium constants and enthalpies of extraction reactions have also been calculated. The formation of the 121 complex of uranyl(II) ion or the 141 complex of thorium(IV) ion, nitrate ion and TBSA and extracted species was further confirmed by the IR spectra of saturated extract of U(IV) and Th(IV).     

Uranium and thorium determination in Brazilian coals by epithermal neutron activation analysis

An experimental technique has been developed to determine impurities in coal. Uranium was determined by counting the²³⁹Np 106.1 keV -ray with a LEPS detector and thorium by counting the²³³Pa 311.8 keV -ray with a Ge(Li) detector. Seventeen coal samples were analyzed with an average precision of 3% and a quantitative determination limit of 0.153 g/g for uranium and 0.078 g/g for thorium. The technique allows determinations of up to twenty elements besides U and Th and can be applied in routine analysis.     

Estimation of natural thorium in low level effluents from processing plants

This is a report of simple estimations of natural thorium in low level effluents generated during the reprocessing of irradiated Th/ThO₂ rods for the recovery of²³³U. The method involved co-precipitation of thorium with ceric iodate at pH 1.29±0.01 and subsequent photometric determination. Conditions were optimised to eliminate the interferences of other ions present in the effluent. Approximately 15 mg each of phosphate, fluoride, and sulphate, 10 mg of iron, and 300 g zirconium did not interfere in the estimation of 2–5 g Th/100 ml of the effluent. Average thorium recovery was around 101.9%±2.6% when nearly 10 g of thorium were spiked.     

A comparative study on the nitrate determination in airborne dust

Summary Two analytical methods for determination of nitrate in airborne dust samples — spectrophotometry and direct potentiometry with ionselective electrodes — are compared. Different aerosol samples collected by an impaction cascade device and a high-volume filter sampler and model powdered dust samples were analysed. It was shown that direct potentiometry is quite satisfactory for nitrate determination irrespective of collecting technique if the known addiMikrochim. Acta 1977 II-6 tion procedure is used. The spectrophotometric determination of impaction-collected aerosol samples suffers from interference by the copper foil used for collection. The advantage of the spectrophotometric method is that concentrations as low as 0.25g/ml can be determined reliably. The advantage of potentiometry is that it gives a simple analytical technique for samples containing down to 1 ppm NO₃ ^– and it can readily be automated.

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Zusammenfassung Zur Bestimmung von Nitrat in Staubproben wurden die UV-Spektrophotometrie und die Direkt-Potentiometrie mit ionenselektiven Elektroden verglichen. Die Untersuchung erfolgte an standardisierten Staubproben und an Proben, die mit High Volume Filter Samplern (Sartorius) und mit Kaskadenimpaktoren gesammelt worden waren. Die Direktpotentiometrie konnte bei alien mit verschiedenen Methoden gesammelten Stauben erfolgreich mit einem Standardadditionsverfahren eingeScizt werden. Die UV-spektrophotometrische Methode konnte bei den Impaktorproben nicht eingeScizt werden, da die Sammlung auf Kupferfolien erfolgte und Kupfer die Bestimmung stört. Der Vorteil der UV-Spektrophotometrie liegt in der Bestimmung sehr kleiner Nitratmengen (bis 0,25g/ml). Der Vorteil der ionenselektiven Elektroden liegt hingegen in der einfachen analytischen Vorgangsweise bei Proben bis zu 1 ppm Nitrat.

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On leave from Faculty of Chemistry, University of Sofia, Sofia, Bulgaria.     

Improvement for α-energy resolution in determination of low level plutonium by liquid scintillation counting

An improvement of -energy resolution for determining low level plutonium has been investigated using combined solvent extraction-low level liquid scintillation counter. In the present work, -energy resolution of 270–290 keV for liquid scintillation spectra of²³⁶Pu and²³⁹Pu is attained. Thus the simultaneous determination of low level plutonium with -liquid scintillation spectrometry may be practized.     

Certification of a new NIST fly ash standard reference material

In June 1993 the National Institute of Standards and Technology (NIST) released the third version of Constituent Elements in Coal Fly Ash Standard Reference Material (SRM 1633b). This material is intended for quality assurance purposes in evaluating the analytical methods used for the determination of constituent elements in coal fly ash or in materials with similar matrices. It has been certified for 23 major, minor and trace elements using ten different analytical techniques. For an element to be certified in a NIST SRM, its concentration is usually determined by at least two independent analytical techniques. The concentrations of additional 24 elements are provided for information only purposes in the new fly ash. Current plans are to certify the concentrations of a number of rare earths upon completion of additional analytical work now in progress. Homogeneity testing was accomplished using instrumental neutron activation analysis and X-ray fluorescence. This presentation summarizes the preparation of this new material and the analytical results used for certification.     

Simultaneous determination of uranium(VI) and thorium(IV) with carminic acid by derivative spectrophotometry

The reactions of uranium(VI) and thorium(IV) ions with carminic acid have been investigated. These ions react with carminic acid in neutral medium, forming colored complexes. The dark purple or red wine complexes show a high absorption in the visible region (597 nm U(VI) and 616 nm Th(IV)). Chemical variables that affect the reaction have been optimized. The spectral overlapping of the color of complexes has been resolved by first-derivative spectrophotometry. The simultaneous determination of uranium(VI) and thorium(IV) mixtures is accomplished by taking the derivative signal (zero crossing) at 597 nm for U(VI) determination and at 616 nm for Th(IV) determination, respectively. The method has been applied to Tyuyamonite ore, containing in the matrix both ions.     

Concentration of232Th,230Th and228Th in various tissues of Japanese subjects

The concentration of²³²Th,²³⁰Th and²²⁸Th in various human tissues of Japanese subjects obtained at autopsies are reported. The tissue samples were weighed, spiked with²³⁴Th tracer and ashed by acid. The solution was dried on a hot-plate. Separation of thorium radionuclides was accomplished through cation-exchange resin chromatography and electrodeposition. The concentrations of thorium isotopes were measured by -spectrometry. Thorium-232 and²³⁰Th concentrations were found to be highest in lung, followed by bone. The maximum concentration of²²⁸Th was in bone. The lowest concentrations of thorium isotopes were in muscle.     

Voltammetric method for the determination of Zn, Cd, Pb, Cu and Ni in interstitial water

To determine heavy metals in interstitial water from Baltic sea sediments a sampling method with subsequent voltammetric determination is described. Copper, lead, zinc and cadmium are determined in the UV-digested samples of interstitial water by differential pulse anodic stripping voltammetry while nickel is determined by adsorption voltammetry. The determination of five metals in one sample in a wide concentrations range is possible using a low cost apparatus. The profiles of the metal concentrations in interstitial water of subsequent layers of sediments, sampled from Puck Bay, Gdask Bay, the Bornholm area and the Supsk area are presented.