Substoichiometric determination of uranium in phosphate rock

The substoichiometric isotope dilution analysis for U(VI) in a synergic extraction system of an excess amount of a chelating agent HHFA and a substoichiometric amount of neutral ligand TOPO has been developed. A constant but substoichiometric amout of U(VI) can be precisely extracted, and U down to ppm levels can be accurately determined by the present method. This method was applied to the analysis of a phosphate rock.     

Substoichiometric isotope dilution analysis of calcium in biological materials

A substoichiometric isotope dilution analysis was developed for the determination of calcium in biological materials. A⁴⁷Ca tracer was produced by the photonuclear reaction and purified by a chromatographic technique on a zeolite column. The appropriate conditions and the reproducibility of the substoichiometric extraction system of TTA-TBP were examined. The present method was applied for NBS-SRM's Spinach and Pine needle, and very good results with high accuracy and precision were demonstrated.     

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.     

Substoichiometric determination of zinc with potassium ethyl xanthate

A rapid radiochemical method has been designed for the determination of microgram quantities of zinc, based on the substoichiometric isotope dilution, using potassium ethyl xanthate as the extraction reagent. pH 5.5 in acetate buffers and chloroform as the extractant were found to be suitable for quantitative substoichiometric extraction. The influence of the diverse ions on the extraction was studied. The zinc contents of a medicinal preparation and biological samples were determined by the present method.     

Substoichiometric radioactivation analysis for ytterbium

The substoichiometric separation of Yb(III) can be achieved by the extraction of a substoichiometric amount of thenoyltrifluoroacetone and an excess amount of phenanthroline in benzene. The appropriate pH range for the substoichiometric extraction is 6–8. The reproducibility of the substoichiometric extraction of Yb(III) is very good as RSD 1%. As an example, Yb in a manganese nodule is determined by the substoichiometry combined with the radioactivation analysis. The content of Yb is 17.63±0.23 g/g. The present procedure can be applied to the determination of other rare earth elements.     

Substoichiometric isotope dilution analysis for uranium by synergic extraction

Substoichiometric extraction of uranyl ion in a synergic system of a chelating reagent and a neutral ligand is described. The system is based on a substoichiometric amount of 2-thenoyltrifluoroacetone (TTA) and an excess of tributylphosphate (TBP); this is compared with a system involving a substoichiometric amount of trioctylphosphine oxide and an excess of TTA. The reproducibility of the substoichiometric extraction is 0.46 or 0.62%, respectively. The former method is superior because extraction of uranyl ion with TBP alone is negligible. The method is applicable to > ca. 10 μg of uranium.     

Substoichiometric separation and determination of trace metals

Substoichiometric methods are eminently suitable for the determination of many elements. As a new application of substoichiometry, a substoichiometric speciation of the element in different chemical states is proposed. Substoichiometric speciation of As(III) and As(V) is demonstrated as an example. This is based on a highly selective substoichiometric extraction of As(III) with thionalide and As(V) with tetraphenylarsonium chloride in the presence of an excess amount of pyrogallol. Coexistence of other diverse arsenic species including methylarsenic compounds does not give any interference to the selective determination of As(III) and As(V). For substoichiometric radioactivation, a novel application of the synergistic extraction system in a combination of a substoichiometric amount of thenoyltrifluoroacetone with an excess amount of phenanthroline is demonstrated for Yb as an example. Substoichiometric speciation based on the selective speration and an application of synergistic extraction to substoichiometric separation have additional possibilities in substoichiometry.     

A new principle of activation-analysis separations-X Substoichiometric determination of traces of gallium

A rapid method for the substoichiometric determination of gallium by neutron-activation analysis has been developed. After irradiation and dissolution of the test sample, gallium carrier is added and two preliminary separation steps are performed: the extraction into chloroform of cupferrates from 7N sulphuric acid and of diethyldithiocarbamates from 2-3N sulphuric acid. The pH of the remaining aqueous phase is then adjusted to 5.5, the solution extracted with a substoichiometric amount of 8-hydroxyquinoline in chloroform and the activity of the gallium hydroxyquinolate extract measured. A simultaneously irradiated gallium standard is treated in exactly the same way. From the activities of these two substoichiometric extracts the amount of gallium originally present in the test sample can be calculated. The method has been applied to the determination of 10(-6) to 10(-3)% of gallium in metallic aluminium and transistor-grade silicon.     

Substoichiometric liquid-liquid extraction and determination of vanadium based on the synergic effect of thenolytrifluoroacetone and trioctylphosphine oxide

Vanadium(IV) is extracted synergically with thenoyltrifluoroacetone (HTTA) and trioctylphosphine oxide (TOPO) in cyclohexane as the mixed ligand complex, VO(TTA)₂TOPO. The synergic extraction constant is 10^5.06. The system can be used for the substoichiometric extraction of vanadium(IV); vanadium(IV) is extracted at pH 4.0–5.0 with a substoichiometric amount of HTTA in the presence of an excess of TOPO. The substoichiometric process combined with isotope dilution was successfully applied to the determination of vanadium(IV) in NBS-1633 coal fly ash; the value found was 222.5 ± 3.5 μg g^?1. The method is shown to be accurate and precise.     

Substoichiometric Isotope Dilution Analysis for the Determination of Iron in Biological Materials and Comparison with Substoichiometric Isotope Dilution Mass Spectrometry

Substoichiometric isotope dilution analysis for the determination of trace iron has been studied by using synergistic extraction of iron(III) with a substoichiometric amount of 4-isopropyltropolone (Hipt) in the presence of an excess of 3,5-dichlorophenol (DCP) in heptane. Optimum conditions for the substoichiometric extraction of iron(III) in g to sub-g levels were examined and the high selectivity for iron(III) toward various metal ions encountered in the analysis of biological materials was confirmed. The present method was applied to a biological reference material (NIES, CRM No.9, sargasso) without any pre-separation and was successfully evaluated. Furthermore, substoichiometric stable isotope dilution mass spectrometry using the present extraction method was also used with the above sample. Applicability and practicability was compared for both substoichiometric methods.     

Substoichiometric extraction of phosphorus

A study of the substoichiometric extraction of phosphorus is described. Phosphorus was extracted in the form of ternary compounds such as ammonium phosphomolybdate, 8-hydroxyquinolinium phosphomolybdate, tetraphenylarsonium phosphomolybdate and tri-n-octylamine phosphomolybdate. Consequently, phosphorus was extracted substoichiometrically by the addition of a substoichiometric amount of molybdenum for all four phosphomolybdate compounds. On the other hand, phosphorus could be separated substoichiometrically with a substoichiometric amount of tetraphenylarsonium chloride or tri-n-octylamine. Stoichiometric ratios of these ternary compounds obtained substoichiometrically were 1∶12∶3 for phosphorus, molybdenum and organic reagent. Applicability of these compounds to phosphorus determination was also discussed.     

The application of substoichiometric radioisotopic dilution principles to controlled-potential coulometry and solvent extraction

Radioisotope dilution principles are applied to controlled-potential electrolysis and solvent extraction with dithizone for the determination of trace amounts of cadmium. A method was developed to verify whether or not the substoichiometric principle was obeyed. If the substoichiometric principle was not obeyed, analysis was still possible by means of calibration curves. In order to obtain independent verification of the series controlled-potential method and to establish a means of comparison with the radioisotope dilution technique a current integration procedure was also employed. A microtechnique was used to extend the sensitivity of the solvent extraction system for cadmium. Standard zinc spelter and high-purity zinc were analyzed for cadmium after separation by a method of standard addition.     

Simulataneous substoichiometric determination of europium and terbium with diethylenetriaminepentaacetic acid and 2-thenoyltrifluoroacetone

The simultaneous substoichiometric separation of europium and terbium is presented and its application to the determination of these elements with DTPA and HTTA is developed. Experimental results for the simultaneous substoichiometric separation are in good agreement with the theoretical results introduced by the principle. Europium and terbium in orchard leaves are determined by simultaneous substoichiometric neutron activation. The analytical values are 23±1.1 ppb for europium, and 17±1.2 ppb for terbium.     

Substoichiometric speciation for inorganic arsenic and methylated arsenic and its application to samples of marine organisms

A substoichiometric isotope-dilution method is described for the determination of monomethylarsonate, MeAs(V), and dimethylarsinate, Me₂As(V). After the separation of MeAs(V) and Me₂As(V) by extraction as their iodides into benzene, these methylated arsenic species are complexed with a substoichiometric amount of diethyldithiocarbamate in benzene, and the uncomplexed methylarsenic species are removed. The relative standard deviations for the substoichiometric extraction of MeAs(V) and Me₂As(V) are 0.55% and 1.1%, respectively. This substoichiometric speciation of methylated arsenic together with an earlier substoichiometric method for speciation of inorganic arsenic species was applied to the speciation of arsenic in an acid-digested solution of a macro-algae sample. It was demonstrated that almost all the arsenic in this solution was Me₂As(V) even after the digestion with nitric acid.     

Simultaneous multielement determination of rare earth elements by substoichiometric activation analysis

This paper presents simultaneous substoichiometric separation of four rare earth elements; samarium, europium, terbium and ytterbium. The elements are separated simultaneously and substoichiometrically by forming their complexanates with substoichiometric DTPA and extracting their unreacted parts with HTTA. Application to the determination of these elements by substoichiometric neutron activation is also presented.     

Substoichiometric exchange extraction of tantalum and gold with tetraphenylarsonium

The conditions for substoichiometric exchange extraction in the system have been investigated in order to establish the feasibility of substoichiometric separation of tantalum and its determination by activation.     

Replacement substoichiometry and its application in activation analysis

A new method based on the substoichiometry principle has been developed. Instead of substoichiometric amounts of chelating agent, substoichiometric amounts of aqueous solution of a competing metal are used. Theoretical relationships have been derived for this method of substoichiometric replacement. Possibilities for its application are discussed.     

Substoichiometry for multielement separation by metal chelate extraction and its application in activation analysis

The method of substoichiometric separation is completed for radioactivity measurements using special nuclear measurement methods in a way that along with the substoichiometric extraction of a given metal the simultaneous quantitative separation of other metals can also be effected. Some general relationships have been derived for the substoichiometric multielement separation of MA _m -type metal chelates. Particularly, the primary dithizonates of silver and copper(II) have been studied, and the application of the method is demonstrated by the separation of silver and copper from cobalt.     

Substoichiometric extraction and quantification of cobalt with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates

A rapid and sensitive substoichiometric radiochemical procedure has been developed for the extraction of cobalt with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates. The relative extractabilities of the cobalt-xanthate complexes into chloroform and carbon tetrachloride were studied. Substoichiometric quantification methods were developed in each case and utilised to determine the cobalt content present in standard solutions as well as biological samples.     

Substoichiometric determination of trace impurities in zinc selenide

Determination of trace impurities in zinc selenide was carried out by substoichiometric neutron activation analysis. Trace impurities were separated from matrix elements by suitable procedures and determined by substoichiometric methods, i.e., Au was extracted with rhodamine-B, Ag and Cu with dithizone, Cr with sodium diethyldithiocarbamate, Co with 1-nitroso-2-naphthol, and Sb with cupferron. Two sorts of zinc selenide single crystals were supplied for analysis and the following values were obtained as impurity concentration; Au 0.36, 0.076 ppb, Ag 42, 32 ppb, Cr. 1.8, 0.63 ppm, Co 0.16, 0.0079 ppm, Sb 8.5, 5.9 ppb and Cu 1.4, 0.44 ppm. The behavior of copper by heat-treatment of zinc selenide was also studied by means of substoichiometric isotope dilution analysis.