Search Results

You are looking at 1 - 10 of 228 items for :

  • All content x
Clear All

and complexing agents. Their effect on central nervous system and on redox process on human body as well as their catalytic property toward enzyme activation and inhibition has also been reported [ 13 , 14 ]. Owing to properties of ligands antimony

Restricted access

Abstract  

In recent years, environmental concerns regarding antimony have grown considerably due to anthropogenic processes that have resulted in increasing concentration of Sb in the environment, and also because of its impacts and possible adverse effects to living organisms. Several techniques have been used, to obtain reliable results for Sb, since Sb is present at low level concentration, requiring analytical instrumentation with low detection limits. The neutron activation analysis (NAA) technique has a high metrological level for the determination of several elements in different matrices. However, Sb determination in environmental and biological samples presents some analytical difficulties due to its low concentrations and gamma ray spectrum interferences. The objective of this research was to study on Sb determination in environmental reference materials by NAA. Ten environmental reference materials were selected and analyzed using long period irradiation at IEA-R1 research nuclear reactor. The induced gamma activities of 122Sb and 124Sb were measured. Relative errors of the results demonstrated that the accuracy depends mainly on Sb radioisotope measured, the decay time for counting and the sample composition.

Restricted access

Abstract  

The analysis of antimony in soil is an important component in the assessment of environmental risk associated with the discharge of munitions at small arms ranges. Proficiency testing samples associated with accreditation to the ISO 17025 standard have been examined for their antimony content using Instrument Neutron Activation Analysis (INAA) and using microwave assisted in situ hydrofluoric acid or nitric acid digestion, or nitrate ashing, followed by ICP-MS analysis. Data are compared with the proficiency testing criteria associated with accreditation and with consensus data. All three techniques afford data which are consistent with accredited analyses. However, the antimony concentrations obtained are method dependant, and generally as follows; INAA > in situ HF > nitrate ashing > nitric acid. In situ HF data and nitrate ashing data are systematically higher and lower than consensus values, respectively, but within the acceptable accreditation range. INAA is the only technique which affords a concentration for antimony in the certified reference material PACS-2 (10.0 ± 0.1 μg g−1) which is not statistically different from its certified value (11.3 ± 1.3 μg g−1).

Restricted access

Abstract  

A radioanalytical method based on substoichiometric principles has been developed for the extraction and determination of antimony/III/ with 1-/2-pyridylazo/-2-naphthol /PAN/. Antimony/III/ forms a red complex with PAN in the presence of I or Br, which is extractable into benzene from sulphuric acid media.

Restricted access

Abstract  

A vitreous form of antimony orthophosphate has been obtained using antimony polyphosphate as a precursor. Morphologically, it is composed of small uniform grains having ellipsoidal shapes. Prolonged thermal treatment leads to the transformation into a crystalline variety. According to TG curves, both forms start to evaporate at 920°C without decomposition. Melting point of crystalline SbPO4 has been determined to be 877°C. Thermomechanical study reveals plastic behavior due to the capacity to flow under shearing stress. Ceramics formation in the system Sb2O3-SbPO4 is discussed. The presence of glass domains in this system has not been confirmed.

Restricted access

Abstract  

Two antimonic acid samples were prepared and designated as hydrolyzed (H-SbA) and refluxed (R-SbA) antimonic acids. Their structure and ion exchange behavior towards Na+ as a simple ion is investigated. R-SbA samples showed higher degree of crystallinity and slightly higher ion exchange capacity than the other sample although it had slightly lower water content. Thermal treatment of both samples showed an increase in their ion exchange capacity on heating up to 200 °C. On further heating up to 400 °C the capacity is appreciably decreased. Equilibria measurements of both samples in dilute solutions showed almost an ideal ion exchange behavior. The obtained data are discussed in detail.

Restricted access

Abstract  

The uptake of fission products 137Cs, 85Sr, 57Co, onto an antimony silicate, and its Na, K, Ca ion-exchanged forms have been studied. Distribution coefficients have been determined as a function of the concentrations of sodium, potassium and calcium nitrate solutions (0.01, 0.1 and 1M). Plots of log distribution coefficients against concentrations enabled the elucidation of exchange mechanisms in some cases. Potassium had the least, and calcium the most effect on isotope uptake when present as macro ions. The presence of sodium promoted hydrolysis that also affected the exchange selectivity.

Restricted access

Abstract  

The redox titration of antimony(III), labeled with125Sb(III), by potassium iodate was radiometrically investigated using the burette method and the standard series method. The stoichiometry of the redox process was determined. The redox valence (the number of equivalents per mol) of potassium iodate for the oxidation of antimony(III) to antimony(V) was found to be 6, differing from the results obtained using the usual visual indicator method, where the value was shown to be 4. This disagreement in the equivalents of potassium iodate for the oxidation of antimony(III) is discussed.

Restricted access

Abstract  

Antimony has been determined in a number of nonmetallic dental materials currently used for tooth restoration. The method applied was instrumental neutron activation analysis. The concentration of antimony in some of the brands tested was found to be as high as 900 fold that in the normal hard dental tissues.

Restricted access

Abstract  

A rapid and sensitive substoichiometric radiochemical method has been developed for the determination of microgram amounts of antimony employing potassium ethylxanthate as a reagent and chloroform as an extractant from sulfuric acid medium. The effect of associated ions on the extraction was studied. The method developed was successfully applied to determine the antimony content in standard solutions and synthetic mixture with an average error ±2.07%

Restricted access