Determination of microamounts strontium by substoichiometric isotope dilution analysis

The isotope dilution with substoichiometric separation for the determination of strontium has been investigated. Strontium can be extracted with a substoichiometric amount of bis-1,2-dicarbollylcobaltate in nitrobenzene in the presence of 15-crown-5. It has been found, that Li⁺, Mg²⁺, Ca²⁺ and Fe³⁺ do not interfere in the strontium determination but the high extraction of K⁺, Na⁺ and NH₄ ⁺ ions results in marked influence.     

Determination of microamounts of barium by isotope dilution analysis with substoichiometric separation

In an open neutron reflection setup there are some basic design parameters that have an important influence on the value of the sensitivity. The effects of variations of such parameters in the sensitivity (S) were calculated applying the Monte Carlo N-particle transport code system MCNP-4A.     

Determination of caesium microamounts by isotope dilution with substoichiometric separation

Selectivity of isotope dilution analysis with substoichiometric separation for caesium determination has been investigated. Caesium can be extracted with a substoichiometric amounts of bis 1,2-dicarbollylcobaltate in nitrobenzene in the presence of dibenzo-18-crown-6. The method is selective. Other metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺, Fe³⁺, Al³⁺) do not interfere.     

Determination of lead in rocks by radiometric isotope dilution and substoichiometric extraction

A rapid procedure is described for the determination of lead in rocks by an isotope-dilution substoichiometric method. After the sample has been digested with acid in the presence of ²¹⁰Pb tracer, the lead is separated by dithizone extractions. After the lead has been back-extracted into aqueous solution, it is reacted with a substoichiometric amount of EDTA. Excess of unreacted lead is removed by extraction with dithizone in carbon tetrachloride, and the specific activity of the aqueous complex is determined by counting ²¹⁰Pb. The standard deviation of the method is less than 10 % for replicate determinations of lead in several U.S. Geological Survey standard rocks. The agreement with literature values indicates that the method is accurate.     

Determination of zinc in environmental water by displacement substoichiometric isotope dilution analysis /DSIDA/

Trace amounts of Zn /ng.ml^–1/ were determined using a displacement reaction of /Zn²⁺/ org from the dithizone organic phase into the aqueous phase, with a substoichiometric amount of /Hg²⁺/ aq. The results were compared with direct substoichiometric IDA. Absorption spectrophotometry was used as a reference analysis.     

The determination of zinc by substoichiometric isotope dilution

Recently, R??I?KA et al. proposed a determination of zinc in highly pure germanium dioxide by a substoichiometric extraction technique. In the present work, the effects on the substoichiometric extraction of equilibrium time, pH and interfering ions were investigated by radioactive tracer techniques and spectrophotometric measurements. The sensitivity of the procedure is limited by the blanks and the addition of oxalate ions can give rise to inaccurate results. The specific activity of ⁶⁵Zn was also determined by substoichiometric extraction.     

Determination of magnesium at trace levels by isotope dilution

A mass spectrometric method for the isotopic analysis of magnesium and its determination at low concentrations in the presence of an excess of other elements is described. The lowest level at which magnesium was determined was 1 ppm with a precision and error +/- 1%.     

Determination of lead in biological and environmental samples by203Pb isotope dilution substoichiometric method

A procedure for the determination of lead in various biological and environmental samples by²⁰³Pb radioisotope dilution substoichiometric method is presented. The accuracy of the method by comparison with the literature values of reference materials appears to be good. The standard deviation of the method is less than 10%, and detection limit is about 0.1 g of lead.     

Determination of trace elements in various materials by activation analysis

Recent works on the trace analysis of various materials by activation analysis are summarized. INAA and IPAA are applied for the multielement determination of various standard reference materials and electronic materials. As an example, the analytical results of pepperbush and fluoride glass are shown. In activation analysis using chemical separation, the destructive neutron activation analysis coupled with isotope addition technique is presented and applied to the determination of trace impurities in indium phosphide. Selective substoichiometry and substoichiometric separagtions of some elements are also introduced.     

Determination of iron in silicate rocks by substoichiometric radioisotope dilution analysis

Iron is determined in rocks by an isotope dilution method involving dissolution with hydro fluoric acid, extraction of iron(III) chloride into isopropyl methyl ketone, stripping with dilute nitric acid, and substoichiometric separation of the Fe-EDTA complex on a cation-exchange column. The precision and accuracy are 1.5% relative or better, as indicated by analyses of some U.S. Geological Survey standard rocks.     

Coprecipitation as a means of separation in substoichiometric isotope dilution analysis

Coprecipitation is proposed as a means of obtaining the necessary separation in substoichiometric isotope dilution analysis. It is shown with examples that by applying coprecipitation for separation and by using complexometric and oxidimetric or reductometric reactions as the substoichiometric reaction, a wide field of complexometric determinations of metal ions (e.g., with EDTA) and many types of redox determinations open up for further investigations. The method is simple, not time-consuming and offers many possibilities owing to the freedom to select a suitable precipitate.     

Coprecipitation as a means of separation in substoichiometric isotope dilution analysis

Chromium has been determined by isotope dilution in artificial standards and in standard alloys using the substoichiometric principle. As a substoichiometric reaction the reduction of Cr(VI) to Cr(III) was used, followed by separation of these species by coprecipitation of the trivalent chromium on a Ti(OH)₄ precipitate. For amounts smaller than 1 μg the standard method had to be modified owing to spontaneous reduction of hexavalent chromium in the solution. Interferences from other metals, if they occur, can be easily overcome. The method is simple and inexpensive.     

Comparison of the sub- and super-equivalence and substoichiometric methods of isotope dilution analysis for the determination of a trace amount of antimony

The sub- and super-equivalence methods of isotope dilution analysis (SSE-IDA) have been compared with substoichiometric isotope dilution analysis (Subst-IDA) for the determination of a trace amount of antimony by means of a redox reaction. For this comparison, the difference between the amount separated and the theoretical value was determined under various conditions. Under conditions in which the substoichiometric reaction and separation gave unsatisfactory results, accurate determination could still be performed by SSE-IDA. The reason for this is discussed.     

Determination of cadmium by sub- and super-equivalence isotope dilution analysis

Trace amounts of cadmium were determined by sub- and super-equivalence isotope dilution analysis in model solutions and water samples. Cd/II/ was labelled with¹⁰⁹Cd and was extracted in CHCl₃ as dithiozonate. AAS was chosen as reference analysis.     

Determination of thallium by isotopic dilution method using substoichiometric displacement

A new analytical procedure for the determination of thallium in a wide concentration range has been developed. The method of direct isotopic dilution (IDA) using carrier-free²⁰²Tl and the formerly developed procedure of substoichiometric displacement have been used for the determination of thallium content in various types of analyzed samples e.g. minerals, sediments, ion-exchangers, hydrothermal waters, etc. in the concentration range from several percent to 10^?4%, or subsequently down to 0.01 μg/ml in waters. The results obtained are compared with those of emission spectrometry and activation analysis using (γ, n) reaction. A good agreement was found.     

Determination of trace elements in biological materials by instrumental epithermal neutron activation analysis

The use of reactor epithermal neutrons in instrumental activation analysis is described for the determination of trace elements via long-lived isotopes. A boron carbide filter is used. Results of analyses of human erythrocytes, plasma, urine and some biological reference materials are given to demonstrate the applicability of the method to biological samples. Bromine, iron, cesium, rubidium, selenium and zinc and cobalt are determined. The method provides accuracy and reliability similar to conventional thermal neutron activation but is faster. Limits of detection attainable with the two techniques are compared.     

Determination of strontium in biological materials by charged-particle activation analysis using the stable isotope dilution method

In order to apply the stable-isotope dilution method to charged-particle activation analysis, determination of strontium in biological materials has been studied by proton activation using isotopically enriched⁸⁶Sr as a spike. To avoid thermal decomposition of biological materials due to the low penetrating power of proton beam, and to eliminate interfering nuclear reactions due to the matrix elements, strontium in the sample and/or isotopic mixture as a comparator was separated chemically together with most of calcium before bombardment, and the fraction isolated was converted to a silica-gel pellet as a most suitable physical and chemical form for bombardment. By processing as above, it was demonstrated that the strontium contents in the biological materials can be determined accurately, precisely and easily. Through a series of experiments, the method was also proved to be applicable for charged-particle activation analysis.