Adsorption of Antimony on Sediments from Typical Water Systems in China: A Comparison of Sb(III) and Sb(V) Pattern

The present work investigated the adsorption of Sb(III) and Sb(V) on five sediment samples (Pearl River, Yangtze River, Yellow River, Yongding River, and Liao River) from typical water systems in China and the adsorption of Sb(V) on Pearl River sediment with different organic carbon (OC) fractions using batch experiments. In order to assess the contributions of sedimentary organic components to the overall adsorption of pentavalent Sb on sediments, one sediment sample was treated by commonly used chemical and physical methods to remove different organic components. Experimental data of Sb(III) and Sb(V) adsorption on five sediments were successfully modeled using the Freundlich (r² > 0.96) isotherm. In general, the sediments with high Fe and Al oxide contents and total organic carbon (TOC) had higher Sb(III) and Sb(V) adsorption than the sediments containing small amounts of Fe and Al oxides and TOC. Dissolved organic carbon (DOC) in sediment promoted the adsorption of Sb(V), and humin fractions and black carbon-like material in sediment had a high affinity for Sb(V).     

Speciation of antimony in natural waters : the determination of Sb(III) and Sb(V) by continuous flow hydride generation-atomic absorption spectrometry

Abstract

A new procedure for the speciation of dissolved antimony is described. This makes use of complexation with citrate to prevent, preferentially, the formation of hydride from Sb(V) and allow the selective determination of Sb(III) to be made by continuous flow hydride generation - atomic absorption spectrometry. When the citric acid (12% m/V) is replaced by potassium iodide (3% m/V), total antimony is determined and the concentration of Sb(V) can be obtained by difference. The determination of the antimony species is dominated in this new procedure by the complexation of Sb(V) with citrate and the effect of pH is limited to a minor, re-inforcing role. This permits acidification to be made with hydrochloric acid. The principal interfering species in the determination of total antimony and Sb(III) is Fe³⁺, with Fe²⁺, Cu²⁺ and Ni²⁺ showing lesser effects on Sb(III). The technique is applied successfully to synthetic mixtures and to natural waters from the environment of a disused antimony mine.

The characteristic concentration obtained for antimony was 0.7 ng mL^–1 and the detection limit 1 ng mL^–1.     

Thiol-induced reduction of antimony(V) into antimony(III): A comparative study with trypanothione, cysteinyl-glycine, cysteine and glutathione

Gluthathione (GSH) has been previously shown to promote the reduction of pentavalent antimony (Sb(V)) into the more toxic trivalent antimony (Sb(III)) in the antimonial drug, meglumine antimonate. However, this reaction occurred at acidic pH (pH 5) but not at the pH of the cytosol (pH 7.2) in which GSH is encountered. The aim of the present study was to further characterize the reaction between thiols and antimonial drugs, addressing the following aspects: (i) the reducing activity of cysteine (Cys) and cysteinyl-glycine (Cys-Gly), expected to be the predominant thiols in the acidic compartiments of mammalian cells; (ii) the reducing activity of trypanothione (T(SH)₂), the main intracelular thiol in Leishmania parasites; (iii) the influence of the state of complexation of Sb(V) on the rate of Sb(V) reduction. We report here that Cys, Cys-Gly and T(SH)₂ did promote the reduction of Sb(V) into Sb(III) at 37 °C. Strikingly, the initial rates of reduction of Sb(V) were much greater in the presence of Cys-Gly, Cys and T(SH)₂ than in the presence of GSH. These reactions occurred at both pH 5 and pH 7 but were favored at acidic pH. Moreover, our data shows that Sb(V) is reduced more slowly in the form of meglumine antimonate than in its non-complexed form, indicating that the complexation of Sb(V) tends to slow down the rate of its reduction. In conclusion, our data supports the hypothesis that Sb(V) is reduced in vivo by T(SH)₂ within Leishmania parasites and by Cys or Cys-Gly within the acidic compartments of mammalian cells.     

Reduction of Sb(V) in a Human Macrophage Cell Line Measured by HPLC-ICP-MS

Drugs based on pentavalent antimony are first-line treatment of the parasite disease leishmaniasis. It is generally believed that Sb(V) acts as a prodrug, which is activated by reduction to Sb(III); however, the site of reduction is not known. It has been hypothesised that the reduction takes place in the parasites' host cells, the macrophages. In this study, the human macrophage cell line Mono Mac 6 was exposed to Sb(V) in form of the drug sodium stibogluconate (Pentostam?). Cell extracts were analysed for Sb species by high-performance liquid chromatography with inductively coupled plasma-mass spectrometry detection. We found that Sb(V) is actually reduced to Sb(III) in the macrophages; up to 23% of the intracellular Sb was found as Sb(III). Transfer of the cells to Sb-free medium rapidly decreased their Sb(V) and Sb(III) content. Induction of the cell's production of reactive oxygen species did not have any marked effect on the intracellular amounts of Sb(III).     

Antimony-Oxidizing Bacteria Isolated from Antimony-Contaminated Sediment – A Phylogenetic Study

Twelve antimony-resistant bacteria were isolated from sediment collected in the vicinity of an antimony oxide-producing factory in Korea. Eight of these strains were heterotrophic Sb(III)-oxidizing bacteria. Phylogenetic study showed that the Sb(III)-oxidizing bacteria fell within two subdivisions of Proteobacteria. Cupriavidus sp. NL4 and Comamonas sp. NL11 belong to the subdivision β-Proteobacteria. Acinetobacter sp. NL1, Acinetobacter sp. NL12, Pseudomonas sp. NL2, Pseudomonas sp. NL5, Pseudomonas sp. NL6, and Pseudomonas sp. NL10 are the members of the γ-subdivision of the Proteobacteria. Among them, Cupriavidus sp. NL4 completely oxidized 100 μmoles of Sb(III) per liter of medium in 500 h, while the other strains were not able to oxidize all of the Sb(III) in the medium, even with longer incubation. The results imply that diverse bacterial lineages are able to detoxify sites polluted with Sb(III) by oxidizing it to Sb(V), and to contribute to antimony cycling in natural environments.     

微生物氧化As(III)和Sb(III)的研究进展

砷(Arsenic,As)和锑(Antimony,Sb)属于同族元素,具有相似的化学性质,是公认的有毒类金属(metalloid),广泛存在于自然界中。随着人类的发展,环境中砷和锑的污染日益严重,类金属污染环境的修复已经刻不容缓。现已表明,自然界中的微生物在砷和锑的生物地球化学循环中发挥着重要的作用,尤其是微生物的氧化作用,可以将毒性较强的亚砷酸盐[Arsenite,As(III)]和亚锑酸盐[Antimonite,Sb(III)]氧化为毒性较低的砷酸盐[Arsenate,As(V)]和锑酸盐[Antimonate,Sb(V)],被认为是一种潜在的类金属污染环境修复方法。本文就国内外对As(III)氧化菌和Sb(III)氧化菌的多样性、As(III)和Sb(III)微生物氧化调控机制和应用的研究进展进行总结,旨在为深入了解和探索微生物介导的砷和锑生物地球化学循环及污染环境的微生物修复提供参考。     

Interaction of antimony tartrate with the tripeptide glutathione implication for its mode of action.

The tripeptide glutathione (gamma-L-Glu-L-Cys-Gly, GSH) is thought to play an important role in the biological processing of antimony drugs. We have studied the complexation of the antileishmanial drug potassium antimony(III) tartrate to GSH in both aqueous solution and intact red blood cells by NMR spectroscopy and electrospray ionization mass spectrometry. The deprotonated thiol group of the cysteine residue is shown to be the only binding site for Sb(III), and a complex with the stoichiometry [Sb(GS)3] is formed. The stability constant for [Sb(GS)3] was determined to be log K 25 (I = 0.1 M, 298 K) based on a competition reaction between tartrate and GSH at different pH* values. In spite of being highly thermodynamically stable, the complex is kinetically labile. The rate of exchange of GSH between its free and Sb-bound form is pH-dependent, ranging from slow exchange on the 1H-NMR timescale at low pH (2 s-1 at pH 3.2) to relatively rapid exchange at biological pH (> 440 s-1). Such facile exchange may be important in the transport of Sb(III) in various biofluids and tissues in vivo. Our spin-echo 1H-NMR data show that Sb(III) rapidly entered red blood cell walls and was complexed by intracellular glutathione.     

Cellular adsorption and absorption of antimony (III) by Mycobacterium smegmatis

Adsorption studies of Sb (III) as the antimonyl (125Sb) tartrate complex using acidified, non-proliferative suspensions of Mycobacterium smegmatis show that the uptake of Sb by the biomass increases with the external concentration of antimony ([Sb]) and decreases, at given concentration, with increasing pH. Measurements of Sb uptake in the cells under growth conditions in liquid culture indicate that the cellular concentration factor of antimony is of the order of 10 when the concentration of antimony in the medium is 10 microM, i.e., close to the minimum inhibitory concentration.     

Use of cloud-point preconcentration for spectrophotometric determination of trace amounts of antimony in biological and environmental samples

This work presents a cloud-point extraction process using the micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological and environmental samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and 3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 4.5. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal reaction conditions and extraction were studied, and the analytical characteristics of the method (e.g., limits of detection and quantification, linear range, preconcentration, improvement factors) were obtained. Linearity for Sb(III) was obeyed in the range of 0.2–20 ng ml⁻¹. The detection and quantification limits for the determination of Sb(III) were 0.055 and 0.185 ng ml⁻¹, respectively. The method has a lower detection limit and wider linear range, inexpensive instrument, and low cost, and is more sensitive compared with most other methods. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma, urine, biological, and water samples.     

Accumulation and mobilization of arsenate by Fe(III) polyions trapped in a Ca-polygalacturonate network

The role of Fe(III) stored at the soil–root interface in the accumulation of arsenate and the influence of citric acid on the As(V) mobility were investigated by using Ca-polygalacturonate networks (PGA). The results indicate that in the 2.5–6.2 pH range Fe(III) interacts with As(V) leading to the sorption of As(V) on Fe(III) precipitates or Fe–As coprecipitates. The FT-IR analysis of these precipitates evidenced that the interaction produces Fe(III)–As(V) inner-sphere complexes with either monodentate or bidentate binuclear attachment of As(V) depending on pH.In the 3.0–6.0 pH range, As(V) diffuses freely through the polysaccharidic matrix that was found to exert a negligible reducing action towards As(V). At pH 6.0 citric acid is able to mobilize arsenate from the As–Fe–PGA network through the complexation of the Fe(III) polyions that leads to the release of As(V).     

As(III) and Sb(III) uptake by GlpF and efflux by ArsB in Escherichia coli

The toxicity of the metalloids arsenic and antimony is related to uptake, whereas detoxification requires efflux. In this report we show that uptake of the trivalent inorganic forms of arsenic and antimony into cells of Escherichia coli is facilitated by the aquaglyceroporin channel GlpF and that transport of Sb(III) is catalyzed by the ArsB carrier protein; everted membrane vesicles accumulated Sb(III) with energy supplied by NADH oxidation, reflecting efflux from intact cells. Dissipation of either the membrane potential or the pH gradient did not prevent Sb(III) uptake, whereas dissipation of both completely uncoupled the carrier protein, suggesting that transport is coupled to either the electrical or the chemical component of the electrochemical proton gradient. Reciprocally, Sb(III) transport via ArsB dissipated both the pH gradient and the membrane potential. These results strongly indicate that ArsB is an antiporter that catalyzes metalloid-proton exchange. Unexpectedly, As(III) inhibited ArsB-mediated Sb(III) uptake, whereas Sb(III) stimulated ArsB-mediated As(III) transport. We propose that the actual substrate of ArsB is a polymer of (AsO)(n), (SbO)(n), or a co-polymer of the two metalloids.     

Syntheses, crystal structures and antimicrobial activities of 6-coordinate antimony(III) complexes with tridentate 2-acetylpyridine thiosemicarbazone, bis(thiosemicarbazone) and semicarbazone ligands

Five novel antimony(III) complexes with the mono- and bis(thiosemicarbazone) ligands of 2N1S or 4N2S donor atoms, N'-[1-(2-pyridyl)ethylidene]morpholine-4-carbothiohydrazide (Hmtsc, L1) and bis[N'-[1-(2-pyridyl)ethylidene]]-1,4-piperazinedicarbothiohydrazide (H(2)ptsc, L7), and the tridentate semicarbazone ligand of 2N1O donor atoms, 2-acetylpyridine semicarbazone (Hasc, L2b), were prepared by reactions of SbCl(3) or SbBr(3), and characterized by elemental analysis, TG/DTA, FT-IR and (1)H NMR spectroscopy. The crystal and molecular structures of five antimony(III) complexes were determined by single-crystal X-ray structure analysis. The neutral, 6-coordinate antimony(III) complexes ([Sb(mtsc)Cl(2)] 1, [Sb(mtsc)Br(2)] 2, [Sb(asc)Cl(2)] 3 and [Sb(asc)Br(2)] 4) are depicted with one electron pair (5s(2)) of the antimony(III) atom, deprotonated forms of multidentate thiosemicarbazone or semicarbazone ligands, and two monodentate halogen ligands, respectively. In the dimer complex 5 ([Sb(2)(ptsc)Cl(4)]) with the ligand in which two tridentate thiosemicarbazone moieties are connected by the piperazine moiety, each antimony(III) was also described as a neutral 6-coordinate structure. These antimony(III) complexes were thermally stable around 200 degrees C. Water-soluble antimony(III) complexes 1 and 2 showed moderate antimicrobial activities against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and -negative bacteria (Escherichia coli and Pseudomonas aeruginosa), yeasts (Candida albicans and Saccharomyces cerevisiae) and molds (Aspergillus niger and Penicillium citrinum). Complex 5 showed moderate antimicrobial activities against four bacteria, and two molds, while the ligand itself showed only modest antimicrobial activities against selected bacteria (B. subtilis, E. coli and S. aureus). The molecular structures and antimicrobial activities of antimony(III) complexes were compared with those of bismuth(III) complexes in the same 15 group in the periodic table.     

Determination of antimony in natural waters by preconcentration on a chelating sorbent followed by instrumental neutron activation analysis

Antimony was preconcentrated from natural waters on thionalide-loaded acrylic polymer (Bio-Beads SM-7) from 0.5 m HCl solution. Prior to the preconcentration, Sb(V) was reduced to Sb(III) with potassium iodide. The antimony retained on the resin was determined by neutron activation and γ-spectrometric measurement of¹²²Sb (564 keV). The lower limit of detection was 0.023 μg/L for a 100-mL sample.     

Leishmania major LmACR2 is a pentavalent antimony reductase that confers sensitivity to the drug pentostam

Arsenicals and antimonials are first line drugs for the treatment of trypanosomal and leishmanial diseases. To create the active form of the drug, Sb(V) must be reduced to Sb(III). Because arsenic and antimony are related metalloids, and arsenical resistant Leishmania strains are frequently cross-resistant to antimonials, we considered the possibility that Sb(V) is reduced by a leishmanial As(V) reductase. The sequence for the arsenate reductase of Saccharomyces cerevisiae, ScAcr2p, was used to clone the gene for a homologue, LmACR2, from Leishmania major. LmACR2 was able to complement the arsenate-sensitive phenotype of an arsC deletion strain of Escherichia coli or an ScACR2 deletion strain of Saccharomyces cerevisiae. Transfection of Leishmania infantum with LmACR2 augmented Pentostam sensitivity in intracellular amastigotes. LmACR2 was purified and shown to reduce both As(V) and Sb(V). This is the first report of an enzyme that confers Pentostam sensitivity in intracellular amastigotes of Leishmania. We propose that LmACR2 is responsible for reduction of the pentavalent antimony in Pentostam to the active trivalent form of the drug in Leishmania.     

Influence of pH, salinity, and organic matter on the adsorption of enteric viruses to estuarine sediment.

This study was designed to determine the degree of adsorption of enteric viruses to marine sediment and factors controlling this association. Adsorption and elution characteristics of several enteroviruses and one rotavirus to estuarine sediments were studied under varying conditions of pH, salinity, and presence of soluble organics. Greater than 99% of the added poliovirus type 1 (LSc), coxsackievirus type B3 (Nancy), echovirus type 7 (Wallace), and rotavirus (SA-11) adsorbed to sediment. Echovirus 1 (Farouk) and a recent isolate typed as coxsackievirus B4 adsorbed significantly less than poliovirus 1 under similar conditions of varying salinity and pH. The presence of soluble organic matter, in the form of secondary sewage effluent or humic acid, did not affect these patterns of adsorption. Only echovirus 1 (Farouk) desorbed when the pH or salinity was altered and then only to a small extent. Three recent isolates of echovirus 1 and echovirus 29 (strain JV-10) also demonstrated varying amounts of adsorption to sediment. These data indicate that enteric viruses can become readily associated with sediment in the estuarine environment and that this association may play a major role in their hydrotransportation and survival.     

Genotoxicity of beryllium, gallium and antimony in short-term assays.

The genotoxicity of beryllium, gallium and antimony compounds was studied with the rec, Salmonella mutagenicity and SCE assays. In the rec assay, all the salts of the metals, BeCl2, Be(NO3)2, GaCl3, Ga(NO3)3, SbCl3, SbCl5, and an oxide, Sb2O3, had DNA-damaging activity. None of the compounds was mutagenic to Salmonella. In the SCE assays using V79 cells, 2 antimony(III) compounds, SbCl3 and Sb2O3, and 2 beryllium compounds, BeCl2 and Be(NO3)2, induced SCEs significantly. Sb2O3, slightly soluble in water, was positive in both the rec assay and the SCE assay at very low doses.     

Role of residual Sb(III) in meglumine antimoniate cytotoxicity and MRP1-mediated resistance

Despite the clinical use of pentavalent antimonials for more than half a century, their metabolism in mammals and mechanisms of action and toxicity remain poorly understood. It has been proposed that the more active and toxic trivalent antimony form Sb(III) plays a critical role in their antileishmanial activity and toxicity. The aim of this work was to investigate the role of residual Sb(III) both in the antileishmanial/antitumoral activities of the pentavalent meglumine antimoniate and in the MRP1 (multidrug resistance-associated protein 1)-mediated resistance to this drug. Samples of meglumine antimoniate differing in their amount of residual Sb(III) (meglumine antimoniate synthesized either from SbCl₅ or from KSb(OH)₆ as well as commercially-available meglumine antimoniate) were evaluated in vitro and in vivo on Leishmania amazonensis infections, as well as for their cytotoxicity to normal and MRP1-overexpressing GLC4 cell lines. Although in vitro the two most effective drugs contained the highest levels of Sb(III), no correlation was found in vivo between the antileishmanial activity of meglumine antimoniate and its residual Sb(III) content, suggesting that residual Sb(III) contributes only marginally to the drug antileishmanial activity. On the other hand, the GLC4 cells growth inhibition data strongly suggests a marked contribution of residual Sb(III). Additionally, the potassium salt of antimoniate (non-complexed form of Sb(V)) was found to be more cytotoxic than meglumine antimoniate. Although MRP1-overexpressing GLC4 cells showed a marked resistance to trivalent antimonials, cross-resistance to meglumine antimoniate was observed only for the products that contained relatively high levels of Sb(III) (at least 0.03% by weight), suggesting that MRP1 mediates resistance to Sb(III) but not to Sb(V). In conclusion, our data strongly suggest that residual Sb(III) in pentavalent antimonial drugs does not contribute significantly to their antileishmanial activity, but is responsible for their cytotoxic activity against mammalian cells and the MRP1-mediated resistance to these drugs.     

Biosorption of Arsenic from Contaminated Water onto Solid Psidium guajava Leaf Surface: Equilibrium,Kinetics, Thermodynamics,and Desorption Study

A batch study on the removal of As(III) and As(V) ions from contaminated water by biosorption using powdered Psidium guajava (Guava) leaf as biosorbent was carried out in the present work. FT-IR (Fourier transform infrared) and SEM (scanning electron microscopy) were used to characterize the surface of the biosorbent. The effect of sorption parameters such as pH, temperature (T _c), adsorbent dose (D _c), and contact time (t _c) were studied. At optimum treatment conditions, the maximum uptake of 1.06 mg of As(III) per gram and 2.39 mg of As(V) per gram onto the surface of biosorbent were obtained. Langmuir and Freundlich isotherm models were examined for sorption equilibrium at various temperatures. The sorption isotherm was favorable with the Freundlich model with the experimental data. Furthermore, higher uptake kinetics was tested for the pseudo-first-order and pseudo-second-order models. The pseudo-second-order model appeared to be the more suitable model to describe arsenic biosorption. ΔG ₀ values were negative at all temperatures, confirming the feasible and spontaneous nature of the biosorption process. Solvent desorption studies help in understanding the mechanism of the adsorption process and also to check the stability of the loaded/spent adsorbents. HCl was found to show maximum effectiveness in the desorption of both As(III) and As(V) with the comparison of other solvents.