Showing papers on "Antimony published in 1997"

The determination of metals (antimony, bismuth, lead, cadmium, mercury, palladium, platinum, tellurium, thallium, tin and tungsten) in urine samples by inductively coupled plasma-mass spectrometry

Abstract: Objective: An analytical method has been established to determine the concentration of antimony (Sb), bismuth (Bi), lead (Pb), cadmium (Cd), mercury (Hg), palladium (Pd), platinum (Pt), tellurium (Te), tin (Sn), thallium (Tl) and tungsten (W) in urine. The aim was to develop a method which is equally suitable for the determination of environmentally as well as occupationally caused metal excretion. Methods: Inductively coupled plasma-mass spectroscopy (ICP-MS) was used for the determination of metals. Calibration was done using aqueous solutions and standard addition respectively. Results: Urine samples of 14 persons occupationally non-exposed to metals were analysed. With the exception of Pt and Bi all the metals were found in these urine samples. The detection limits for these metals lie between 5 and 50 ng/l. Conclusions: For some metals, which are important from an occupational as well as an environmental viewpoint, ICP-MS is more sensitive than atomic absorption spectrometry (AAS). ICP-MS, moreover, is welcome as a reference method for AAS with the additional advantage of multi-element measurement.

Analysis of Antimony Doping in Tin Oxide Thin Films Obtained by the Sol-Gel Method

Abstract: The antimony doping in SnO2 thin films prepared by the sol-gel dip-coating method has been studied using two characterization techniques. In order to determine the actual doping level directly in the deposited layers, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) have been used. We found that this doping level is systematically lower than expected from the starting solutions composition, and that two oxidation states are present: Sb3+ and Sb5+. As the antimony content increases, there is a competition between Sb5+ and Sb3+ species. The SnO2: Sb thin films have also been observed by transmission electron microscopy (TEM), showing that the measured mean size of crystallites decreases as the Sb content increases in the oxide. No precipitates of either Sn or Sb oxides (other than SnO2) could be detected.

Controls of mineral parageneses in the system Fe-Sb-S-O

Abstract: With few exceptions, the world's antimony resources are derived from hypogene deposits of stibnite which form mainly at temperatures between 150 degrees and 300 degrees C. In this paper, we investigate the stability relationships and solubility of minerals in the system Fe-Sb-S-O, in order to understand why stibnite is so dominant and to explain the distribution of the other minerals in hypogene antimony ore deposits. Textural relationships, chemographic analysis, and thermodynamic data are used to develop calibrated petrogenetic grids for this system. These grids indicate that stibnite is the stable antimony phase for a wide range of physicochemical conditions encountered in nature.At temperatures >350 degrees C typical crustal fluids require concentrations of thousands of parts per million Sb (an unlikely occurrence) in order to saturate with stibnite, whereas at temperatures <250 degrees C stibnite may precipitate from fluids containing as little as 1 ppm Sb. This observation, and the fact that stibnite deposits commonly have complex parageneses in which stibnite is relatively late, suggests that decreasing temperature may be an important control of mineralization. Many stibnite deposits, however, have relatively simple parageneses, and a significant proportion of these is hosted by black shales. It is thus possible that, in many cases, reduction was the principal cause of mineralization. This is consistent with the finding that antimony mineral solubility decreases precipitously with f (sub O 2 ) across the kermesite-stibnite boundary for a wide range of pH (< or = neutrality). Other stibnite deposits with relatively simple parageneses (including some of the world's largest deposits) have formed from solutions which apparently equilibrated with limestone and only became saturated with stibnite when they encountered shale. Intense pyritization is an important feature of some of these deposits. At the near-neutral pH conditions and high Sigma a s implied by equilibration with limestone and pyritization, respectively, Sb is transported largely as the species HSb 2 S (super -) 4 , and stibnite deposition is favored by decreasing pH and/or a (sub H 2 S) , both of which are predicted consequences of pyritization.Gudmundite and native antimony only display the ranges of solubility required to form economic deposits at f (sub O 2 ) , pH, and Sigma a s conditions that rarely occur in nature; these minerals are most effectively deposited by decreasing f (sub O 2 ) . Berthierite is only stable over extremely narrow intervals of f (sub O 2 ) , and f (sub S 2 ) , which probably explains why it is seldom found in large concentrations. Hypogene kermesite is also uncommon for similar reasons. At low temperature it replaces stibnite as the stable phase over a broad range of f (sub O 2 ) -pH conditions and consequently is a common supergene mineral. Senarmontite stability is restricted to extremely high f (sub O 2 ) conditions where its solubility is too high to permit hypogene saturation, except at extraordinarily high Sb concentrations such as might occur during remobilization of preexisting antimony mineralization.The common occurrence of high concentrations of gold in stibnite deposits and vice versa may reflect the fact that at pH conditions coinciding with the H 2 S-HS predominance boundary and f (sub O 2 ) conditions marginally below the sulfate predominance field, both Au and Sb can be transported in appreciable concentrations as bisulfide complexes. Deposition of native gold and stibnite is favored by decreasing pH, with or without reduction. It is probably no coincidence that deposits enriched in Sb and Au occur in settings which would have been capable of providing the relatively alkaline conditions necessary for transport of these metals and are hosted by rocks which were potentially able to cause the acidification needed to induce stibnite-gold mineral precipitation.

Comparative and environmental genotoxicity of antimony and arsenic.

Abstract: Antimony and arsenic compounds are known to have a genotoxic potential. Soil contamination with these elements can be due to the presence of natural ore sources of fahlore (gray copper). As a result, human and animal populations may be highly exposed. The sister chromatid exchange (SCE) test is an adequate tool for the sensitive detection of antimony and arsenic genotoxicity. We used this assay to investigate the coergism of the two elements in vitro to gain data for the assessment of a putative risk from coexposure. The combinative effect of antimony and arsenic in the SCE test appeared subadditive. Additionally, the SCE served to determine the genotoxic potential in extracts of contaminated fahlore soil samples gained under mildly acidic conditions. The genotoxicity observed was very low because antimony and arsenic predominated in the pentavalent, non-genotoxic state, but, the partial antagonism observed in the in vitro experiments could be an additional explanation for the low genotoxicity.

The properties of antimony-doped tin oxide thin films from the sol-gel process

Abstract: Antimony-doped tin oxide thin films have a range of technical applications as conductive coatings, and sol-gel processing seems to offer a number of advantages over other coating techniques. In this study, the sol was prepared from stannic chloride and antimony chloride in alcohol. Films were achieved either from spin-coating of colloidal gel suspensions or from spray-coating of suspensions of sol-gel-derived powder. Both coating methods result in thin films with similar visible light transmission (transmission >80%)and sheet resistance (~5×10 7 Ω/□). However, the surface of the spin-coated films is much more smooth than that of spray-coated films, whilst the spray-coated films contain large particulates, which came from agglomerates in the powder suspensions. Antimony doping of the tin oxide produces a number of effects: it accelerates the gelation, reduces the particle size and the degree of crystallinity of the gel, and decreases the resistance of the powder and films. However, increase of antimony doping from 2.6 to 5.2 mol% does not further decrease the resistance.

Development of a Multi-element Hydride Generation–Inductively Coupled Plasma Mass Spectrometry Procedure for the Simultaneous Determination of Arsenic, Antimony and Selenium in Waters

Abstract: A multi-element hydride generation–inductively coupled plasma mass spectrometry (HG–ICP-MS) method for the simultaneous determination of arsenic, antimony and selenium in water matrices has been developed. The method involves an off-line pre-reduction procedure for the reduction of Se VI to Se IV by HCl, combined with an on-line reduction of As V and Sb V to the trivalent state with thiourea and generation of the hydrides. Analytical characteristics include detection limits of 0.08 ng g -1 As, 0.06 ng g -1 Sb and 0.10 ng g -1 Se, linearity of four orders of magnitude and short and long term reproducibility of between 8 and 12%. Results from four reference water samples for As, Sb and Se showed data which were all within 10% of the target values. Interferences were minimal for As and Sb, whereas Cu 2+ , and to a lesser extent Ni 2+ and Cd 2+ , caused signal suppression effects on Se. Advantages over an alternative, single element, HG–AFS technique include speed of analysis (by a factor of two) and elimination of the conflicting chemistry requirements, traditionally found with sequential single element hydride generation methods.

Antimony and Bismuth Oxide Clusters: Growth and Decomposition of New Magic Number Clusters

Abstract: A series of new “magic number” metal oxide clusters are described for the group V metals antimony and bismuth. Specific nonstatistical stoichiometries of MxOy cation and anion clusters are formed preferentially in the gas phase when oxidized metal is vaporized or when metal is vaporized and combined with gas phase oxygen (e.g., Bi7O10+, Bi9O14+). Essentially the same stoichiometries are seen for antimony and bismuth analogues. The species produced in cluster growth are also produced preferentially by photodissociation of larger clusters. Localized covalent bonding schemes are suggested for these clusters, and polyhedral cage structures are proposed. The stoichiometries observed require a 3+ metal oxidation state in the small clusters, which shifts over to one or more 5+ metal atoms in larger clusters.

The effects of 4-ethylpyridine and 2-cyanopyridine on zinc electrowinning from acidic sulfate solutions

Abstract: The effects of 4-ethylpyridine and 2-cyanopyridine on the electrowinning of zinc in the presence and absence of antimony have been studied The results are compared with those of a common industrial additive, gum arabic Addition of either compound reduced current efficiency, increased power consumption and lowered the surface quality of electrodeposited zinc Both the additives showed similar polarization behaviour to gum arabic Addition of 004mgdm−3 antimony increased current efficiency, reduced power consumption and altered the surface morphology and crystallographic orientations Combinations of antimony with 4-ethylpyridine resulted in very good current efficiencies, and zinc morphology and quality

Bioaccumulation of Antimony by Chlorella vulgaris and the Association Mode of Antimony in the Cell

Abstract: The bioaccumulation and excretion of antimony by the freshwater alga Chlorella vulgaris, which had been isolated from an arsenic-polluted environment, are described. When this alga was cultured in a medium containing 50 μg cm−3 of antimony(III) for 14 days, it was found that Chlorella vulgaris bioaccumulated antimony at concentrations up to 12 000 μg Sb g−1 dry wt after six days' incubation. The antimony concentration in Chlorella vulgaris decreased from 2570 to 1610 μg Sb g−1 dry wt after the cells were transferred to an antimony-free medium. We found that the excreted antimony consists of 40% antimony(V) and 60% antimony(III). This means that the highly toxic antimony(III) was converted to the less toxic antimony (V) by the living organism. Antimony accumulated in living Chlorella vulgaris cells was solvent-fractionated with chloroform/methanol (2:1), and the extract residue was fractionated with 1% sodium dodecyl sulfate (SDS). Gel-filtration chromatography of the solubilized part showed that antimony was combined with proteins whose molecular weight was around 4×104 in the antimony-accumulated living cells. © 1997 by John Wiley & Sons, Ltd.

Analysis of geological materials for bismuth, antimony, selenium and tellurium by continuous flow hydride generation inductively coupled plasma mass spectrometry. Part 1. Mutual hydride interferences

Abstract: A study was made of mutual interferences in the determination of Bi, Sb, Se and Te by hydride generation inductively coupled plasma mass spectrometry (HG-ICP-MS). The design of the study was based upon the valency states in which these elements would occur following two acid digestion procedures commonly used for geological materials (aqua regia and HF-HClO 4 -HNO 3 -HCl), that is, as Bi III , Sb V , Se IV and Te IV . Arsenic in its two valency states (III and V) was also examined as a potential interferent but Ge, Sn and Pb were not, as formation of their hydrides at the concentration of HCI used (2-4 M) would be negligible. Interferents were investigated at concentrations up to 2000 μg l -1 while the analyte concentration was held at 0.2 μg l -1 . AS V and Se IV severely suppressed the signal for Te in both 2 and 4 M HCl, though less so in the stronger acid medium. These interferences were negated by reduction of As V to the non-interfering state As III and Se IV to Se O by addition of KI and ascorbic acid at a final strength of 0.005%. The preferred acid medium was selected as 4 M HCI for two reasons: interferences were reduced; and wash-out time between samples was shorter (i.e., decreased memory effect). Mutual interferences of possible concern comprise the effect of: 2500-fold excess of Bi on the measurement of Te; a 5000-fold excess of Te on Bi; a 2500-fold excess of Bi on Sb; and a 5000-fold excess of Bi on Se. However, these relative abundances in geological materials (rocks, sediments, soils, vegetation) would be extraordinary and hence implementation of the recommended scheme should produce analysis for Bi, Sb, Se and Te by HG-ICP-MS that is free of mutual interference.

An improved method for the simultaneous determination of Sb, As, Bi, Ge, Se, and Te by hydride generation ICP-AES : Application to environmental samples

Abstract: A method is described for the simultaneous determination of antimony, arsenic, bismuth, germanium, selenium, and telluriun, which combines an inductively coupled plasma-atomic emission detection system with a continuous-flow hydride generation technique (HG-ICP). Compromise conditions are established. The sample, in 6 mol/L hydrochloric acid, is mixed with a 0.5% (m/v) sodium tetrahydroborate solution, and a 7.5% (m/v) potassium iodide solution before being pumped to a gas/liquid separator from which the gaseous hydride is transported to the plasma by an argon flow. Detection limits of 0.3, 1.3, 0.7, 3.9, 0.6, and 6.5 μg/L. were obtained for antimony, arsenic, bismuth, germanium, selenium, and tellurium, respectively. These values represent improvements above and beyond those commonly found in the literature for most ele-ments for simultaneous analysis using one set of instrumental parameters. The method is applied to a series of sediment samples and validated for As, Sb, and Se in marine and estuarine reference materials.

Recovering Bi and Sb from Electrolyte in Copper Electrorefining

Abstract: The separation of antimony and bismuth in copper electrorefining is somewhat difficult and costly. An ion-exchange technique for the removal of the metals from the electrolyte has been practiced recently, although the metals recovered require further processing. Sumitomo Metal Mining has developed a process to recover antimony and bismuth directly from the eluant by an electrowinning process using a mixture of sulfuric acid and sodium chloride as an eluant for the desorption from the resin. The content of bismuth in the antimony metal recovered by this process was less than 0.2%, while the content of antimony in the bismuth metal was less than 0.4%.

New square-pyramidal organoantimony(V) compounds; crystalstructures of (biphenyl-2,2′-diyl)phenylantimony(V)dibromide, dichloride and diisothiocyanate,Sb(2,2′-C12H8)PhX2(X = Br, Cl or NCS), and of octahedralSbPh(o-O2C6Cl4)Cl2·OEt2

Abstract: Oxidative addition between (biphenyl-2,2′-diyl)phenylantimony(III), Sb(2,2′-C 12 H 8 )Ph 1 and Br 2 or SO 2 Cl 2 gave Sb(2,2′-C 12 H 8 )PhBr 2 2 and Sb(2,2′-C 12 H 8 )PhCl 2 3, respectively, while the corresponding fluoride Sb(2,2′-C 12 H 8 )PhF 2 4 and the thiocyanate Sb(2,2′-C 12 H 8 )Ph(NCS) 2 5 were obtained by metathesis reactions between 3 and KF and KSCN, respectively Compounds 2 and 3 are isostructural but, in contrast to the closely related SbPh 3 X 2 species, individual molecules have square-pyramidal geometry Again in contrast to SbPh 3 X 2 compounds, secondary antimony–halogen interactions trans to the apical carbon atom lead to solid-state dimers, implying Lewis acidity at antimony Antimony in the thiocyanate 5 showed similar square-pyramidal geometry with N-bonded thiocyanate groups but bridging by one thiocyanate again gives dimers in the solid Oxidative addition between SbPhCl 2 and tetrachloro-ortho-benzoquinone in ether solution gave the tetrachlorocatechol analogue of 3 as a six-co-ordinate ether solvate, SbPh(o-O 2 C 6 Cl 4 )·OEt 2 6 If the weak bond to ether is ignored, antimony again has square-pyramidal geometry but formation of the adduct again points to antimony Lewis acidity A non-solvated substituted catecholate, SbPh(o-O 2 C 6 H 2 Bu t 2 -3,5)Cl 2 8, was also synthesized but crystals suitable for X-ray diffraction could not be obtained