Selenious Acid Research Articles

Probing the Influence of Acidity and Temperature to Th(IV) on Hydrolysis, Nucleation, and Structural Topology.

Systematic control of the molar ratio between thorium hydroxides and selenic acid and their reaction temperature under hydrothermal conditions results in four novel thorium-based selenate complexes, namely, [Th8O4(OH)8(SeO4)6(H2O)16]·(SeO4)2·13H2O (Th-1), [Th8O4(OH)8(SeO4)8(H2O)13]·7H2O (Th-2), Th(OH)2(SeO4)H2O (Th-3), and Th3(SeO4)6(H2O)6·2.5H2O (Th-4), as well as the thorium mixed selenite selenate compound Th(SeO3)(SeO4) (Th-5). Smaller [H2SeO4]/[Th(IV)] ratio or lower temperature give rise to the formation of octameric [Th8(μ3-O)4(μ2-OH)8]16+ cores in Th-1/Th-2 and infinite [Th(μ2-OH)2H2O]2+ chains in Th-3, respectively. Increasing the [H2SeO4]/[Th(IV)] ratio or elevating the temperature generates a microporous (11.3 Å voids) open-framework Th-4, a monomeric thorium species without oxo/hydroxyl ligands, and a three-dimensional thorium structure Th-5. Formation of these compounds suggests that variables including acidity and temperature play a critical role in the hydrolysis and oligomerization of ThIV ions. Increasing acidity limits the deprotonation of water molecules and formation of nucleophilic hydroxo/oxo-aquo Th species, and high temperature appears to suppress the olation/oxolation hydrolysis reactions, which in both ways limit the formation of the thorium oligomers.

Crystal structure, vibrational spectra and DFT studies of hydrogen bonded 1,2,4–triazolium hydrogenselenate

The new hydrogen bonded molecular complex 1,2,4–triazolium hydrogenselenate (THS) is prepared by the reaction of 1H–1,2,4–triazole and selenic acid. This complex is stabilised by N–H⋯O and C–H⋯O hydrogen bonding and electrostatic attractive forces between 1H and 1,2,4–triazolium cations and hydrogen selenate anions. The XRD studies revealed that intermolecular proton transfer occur from selenic acid to 1H–1,2,4–triazole molecule, results in the formation of 1,2,4–triazolium hydrogenselenate which contains 1,2,4–triazolium cations and hydrogenselenate anions. The molecular structure of THS crystal has also been optimised by using Density Functional Theory (DFT) using B3LYP/cc–pVTZ and B3LYP/6–311++G** methods in order to find the whole characteristics of the molecular complex. The theoretical structural parameters such as bond length, bond angle and dihedral angle determined by DFT methods are well agreed with the XRD parameters. The atomic charges and thermodynamic properties are also calculated and analysed. The energies of frontier molecular orbitals HOMO, LUMO, HOMO–1, LUMO+1 and LUMO–HUMO energy gap are calculated to understand the kinetic stability and chemical reactivity of the molecular complex. The natural bond orbital analysis (NBO) has been performed in order to study the intramolecular bonding interactions and delocalisation of electrons. These intra molecular charge transfer may induce biological activities such as antimicrobials, antiinflammatory, antifungal etc. The complete vibrational assignments of THS have been performed by using FT–IR and FT–Raman spectra.

Influence of selenous acid microadditive on electrochemical formation of CdS thin films

Electrodeposition of CdS in the presence of H2SeO3 microadditive at 50°C in an aqueous solution was studied. Addition of H2SeO3 affects the growth of CdS thin films and improves structure ordering, coverage, and stoichiometry. The effect of H2SeO3 is advantageous as allows simultaneously improve the coverage and decrease the thickness of the CdS film during the electrodeposition process. Elemental Se detected in the as-deposited CdS films can be easily removed by a vacuum thermal treatment. The reported approach allows the electrodeposition of uniform polycrystalline photosensitive CdS thin films at reduced temperature. The optimal concentration of the microadditive at given conditions is reported.

Influence of selenium supplementation on patients with inflammation: A pilot double blind randomized study.

Theaim of the study was to analyze the effect of selenium supplementation on patients with inflammation receiving PN. This double-blind randomized study included 20 hospitalized patients experiencing an inflammatory process while being fed by PN, who were monitored in three stages: first 72h (0), day 7 (1), and day 14 (2) of PN. The supplemented patients group (G+S) received 60μg/d (0.75μmol) of selenium as selenious acid which was added to the PN bag. The nonsupplemented group (G-S) did not receive selenium. The concentration range of 84 to 100μg/L (1.07-1.27μmol/L) was used as a reference of plasma selenium. The study included 20 patients (8G+S and 12 G-S) mainly diagnosed with cancer and/or sepsis. Most of them were hospitalized in the intensive care unit and were receiving PN for clinical reasons. Plasma selenium was greater in the G+S than in the G-S (P=0.05) in two stages (0 and 1). Since the start of assessment, C-reactive protein (CRP) levels were elevated; however, there was no statistical difference in CRP values between groups (P > 0.05). There was no significant change of glutathione peroxidase over time or between groups (P>0.05). The selenium concentration was greater in the G+S than in the G-S, acting independently from CRP behavior. However, supplementation was not enough to reach the reference values.

An experimental study about the presence of selenium in inorganic gunshot residues (GSR)

Gunshot residues (GSR) are produced by the discharge of firearms, and often provide very important information in criminal investigations in cases involving the use of guns. Elemental analysis, performed by a Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDS), is the most discriminating method for characterizing inorganic GSR particles, and forensic procedures based on SEM-EDS are followed worldwide. The SWGGSR “Guide for Primer Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-ray Spectrometry 11-29-11” refers to “Gun bluing” but Se (and also Cr) is not included among those elements whose presence is allowed in particles which are “characteristic of GSR”, neither according to the SWGGSR guide itself nor the current relevant ASTM “Standard guide for gunshot residue analysis by scanning electron microscopy/energy dispersive X-ray spectroscopy” E1588-16.Whenever unusual elements are found in alleged GSR particles, a “case by case” approach is recommended, and suitable research and documentation is required.In the present paper the authors show evidences of the presence of selenium in lead, barium and antimony (characteristic of) GSR particles detected in casework by laboratories placed both in Europe (Italy and The Netherlands) and in Australia. Firearm bluing products containing selenious acid has been experimentally proven to be a reasonable source for selenium in inorganic GSR particles. For the first time, a case-by-case approach is adopted to support fruitful interpretation of GSR particles containing selenium.

Features of Porous Anodic Alumina Growth in Galvanostatic Regime in Selenic Acid Based Electrolyte

The features of porous anodic Al2O3 formation process in galvanostatic regime in selenic acid based electrolyte under a range of anodization conditions were investigated. The growth process kinetics of porous anodic Al2O3 was characterized by chronopotentiometric curves. The effect of electrolyte concentration, current density and anodization duration on the oxide porous structure ordering was studied by scanning electron microscopy. Approximate regions of self-ordered porous Al2O3 formation process conditions were estimated. It was found that anodization parameters, at which self-ordered porous structure formation is observed, correspond to the conditions of equilibrium of oxidation and etching rates. It is shown that deviations from these conditions lead to the disordering of the porous structure.

Hematuria, an unusual systemic toxicity, in formic acid ingestion: a case report

Abstract Background Acid ingestion can cause severe injuries of the upper gastrointestinal tract and the respiratory tract. Besides hydrofluoric acid and selenious acid, systemic toxicities of acid ingestion can occasionally occur. However, hematuria is a rare systemic toxicity reported in caustic poisoning. Objectives To describe a case of a one-year-old girl who accidentally ingested liquid formic acid. Methods This patient had severe local corrosive effects including a compromised upper respiratory tract and developed gross hematuria during the hospital admission. Results Hematuria could be a consequence of acid ingestion. Conclusions Significant hematuria can be a systemic effect of acid ingestion, but in this case was self-limiting

Selenium uptake through cystine transporter mediated by glutathione conjugation.

Selenium (Se) is an essential trace element and is regarded as a protective agent against cancer. In particular, antioxidant effects of selenoenzymes contribute to cancer prevention. Se can also produce reactive oxygen species and, thereby, exert cancer-selective cytotoxicity. Selenodiglutathione (SDG) is a primary Se metabolite conjugated to two glutathione (GSH) moieties. SDG increases intracellular Se accumulation and is more toxic than selenous acid (H2SeO3), but the mechanisms for importing Se compounds into cells are not fully understood. Here, we propose a novel mechanism for importing Se, in the form of SDG. Cellular intake of Se compounds was assessed based on Se accumulation, as detected by ICP-MS. SDG incorporation was decreased in the presence of thiols (GSH, cysteine or their oxidized forms, GSSG and cystine), whereas H2SeO3 uptake was increased by addition of GSH or cysteine. Cellular SDG uptake was decreased by pretreatment with specific inhibitors against gamma-glutamyl transpeptidase (GGT) or the cystine/glutamate antiporter (system xc-). Furthermore, siRNA against xCT, which is the light chain component of system xc-, significantly decreased SDG incorporation. These data suggest an involvement of SDG in Se incorporation, with SDG processed at the cell surface by GGT, leading to formation of selenodicysteine which, in turn, is likely to be imported via xCT. Because GGT and xCT are highly expressed in cancer cells, these mechanisms mediated by the cystine transporter might underlie the cancer-selective toxicity of Se. In addition, the system described in our study appears to represent a physiological transport mechanism for the essential element Se.

Structure, vibrations and quantum chemical investigations of hydrogen bonded complex of bis(1–hydroxy–2–methylpropan–2–aminium)selenate

The hydrogen bonded molecular complex bis(1–hydroxy–2–methylpropan–2–aminium)selenate (C8H24N2O6Se) has been prepared by the reaction of 2–amino–2–methyl propanol and selenic acid. The X–ray diffraction analysis revealed that the intermolecular proton transfer from selenic acid (SeO4H2) to 2–amino–2–methylpropanol results in the formation of bis(1–hydroxy–2–methylpropan–2–aminium)selenate (HMPAS) salt and the fragments are connected through H–bonding and ion pairing. The N–H⋯O and O–H⋯O interactions between 2–amino–2–methylpropanol and selenic acid determine the supramolecular arrangement in three–dimensional space. The salt crystallises in the space group P121/n1 of monoclinic system. The complete vibrational assignments of HMPAS have been performed by FTIR and FT–Raman spectroscopy. The experimental data are correlated with the structural properties namely the energy, thermodynamic parameters, atomic charges, hybridization concepts and vibrational frequencies determined by quantum chemical studies performed with B3LYP method using 6–311++G*, 6–31+G* and 6–31G** basis sets.

Vibrational spectroscopic and crystallographic study of the novel guanylurea salts with sulphuric and selenic acids

The family of known guanylurea(1+) sulphates was extended for two novel triclinic (space group P-1) members - bis(guanylurea(1+)) sulphate dihydrate and tetrakis(guanylurea(1+)) bis(hydrogen sulphate) sulphate. Additionally, the monoclinic (space group P21/n) guanylurea(1+) hydrogen selenate was also isolated and characterised. Besides of X-ray diffraction study these novel guanylurea chalcogenates were studied by the methods of vibrational spectroscopy. The study of thermal behaviour of the prepared salts revealed reversible λ-shaped anomaly for tetrakis(guanylurea(1+)) bis(hydrogen sulphate) sulphate at 354 K. This effect was studied in detail by the combination of DSC and temperature-dependent IR and Raman spectroscopies.

The Apical Localization of Na+, K+-ATPase in Cultured Human Retinal Pigment Epithelial Cells Depends on Expression of the β2 Subunit.

Na+, K+-ATPase, or the Na+ pump, is a key component in the maintenance of the epithelial phenotype. In most epithelia, the pump is located in the basolateral domain. Studies from our laboratory have shown that the β1 subunit of Na+, K+-ATPase plays an important role in this mechanism because homotypic β1-β1 interactions between neighboring cells stabilize the pump in the lateral membrane. However, in the retinal pigment epithelium (RPE), the Na+ pump is located in the apical domain. The mechanism of polarization in this epithelium is unclear. We hypothesized that the apical polarization of the pump in RPE cells depends on the expression of its β2 subunit. ARPE-19 cells cultured for up to 8 weeks on inserts did not polarize, and Na+, K+-ATPase was expressed in the basolateral membrane. In the presence of insulin, transferrin and selenic acid (ITS), ARPE-19 cells cultured for 4 weeks acquired an RPE phenotype, and the Na+ pump was visible in the apical domain. Under these conditions, Western blot analysis was employed to detect the β2 isoform and immunofluorescence analysis revealed an apparent apical distribution of the β2 subunit. qPCR results showed a time-dependent increase in the level of β2 isoform mRNA, suggesting regulation at the transcriptional level. Moreover, silencing the expression of the β2 isoform in ARPE-19 cells resulted in a decrease in the apical localization of the pump, as assessed by the mislocalization of the α2 subunit in that domain. Our results demonstrate that the apical polarization of Na+, K+-ATPase in RPE cells depends on the expression of the β2 subunit.

Mixed Uranyl Sulfate–Selenates: Evolution of Structural Topology and Complexity vs Chemical Composition

Phase formation in the aqueous system of uranyl nitrate, potassium hydroxide, and variable amounts of sulfuric and selenic acids has been investigated. Four different types of crystalline phases with variable S and Se contents were isolated and characterized using single-crystal X-ray diffraction (XRD) and IR spectroscopy. Topological analysis and information-based complexity calculations demonstrated the following: (a) the absence of a continuous solid solution in the system, (b) the absence of isotypic sulfate and selenate phases, and (c) the discovery of two layered topologies unprecedented among inorganic oxysalts.

In situ diselenide-crosslinked polymeric micelles for ROS-mediated anticancer drug delivery.

Stimuli-responsive micelles have emerged as the drug carrier for cancer therapy since they can exclusively release the drug via their structural changes in response to the specific stimuli of the target site. Herein, we developed the in situ diselenide-crosslinked micelles (DCMs), which are responsive to the abnormal ROS levels of tumoral region, as anticancer drug carriers. The DCMs were spontaneously derived from selenol-bearing triblock copolymers consisting of polyethylene glycol (PEG) and polypeptide derivatives. During micelle formation, doxorubicine (DOX) was effectively encapsulated in the hydrophobic core, and diselenide crosslinks were formed in the shell. The DCMs maintained their structural integrity, at least for 6 days in physiological conditions, even in the presence of destabilizing agents. However, ROS-rich conditions triggered rapid release of DOX from the DOX-encapsulating DCMs (DOX-DCMs) because the hydrophobic diselenide bond was cleaved into hydrophilic selenic acid derivatives. Interestingly, after their systemic administration into the tumor-bearing mice, DOX-DCMs delivered significantly more drug to tumors (1.69-fold and 3.73-fold higher amount compared with their non-crosslinked counterparts and free drug, respectively) and effectively suppressed tumor growth. Overall, our data indicate that DCMs have great potential as drug carriers for anticancer therapy.

Europium(III) Catalysis for Reduction of Thionine Dye by Selenous Acid in Aqueous Sulfuric Acid Solutions: A Kinetic and Mechanistic Approach

ABSTRACTThe catalytic effect of europium(III) on the reduction of thionine dye (Th) by selenous acid has been studied by spectrophotometry in aqueous sulfuric acid solutions at a constant ionic strength of 3.0 mol dm−3 and at different temperatures (283–313 K). A first‐order dependence with respect to both [Th] and [EuIII] was obtained, whereas the orders with respect to [SeIV] and [H+] were less than unity. Variation of ionic strength and dielectric constant of the reaction media did not affect the reaction rates. Probable mechanistic schemes for thionine reductions in both the absence and presence of europium(III) catalyst were proposed. The rate laws associated with the reaction mechanisms were derived, and the reaction constants were calculated. The activation parameters of the rate constants of the slow steps of both uncatalyzed and catalyzed reactions along with thermodynamic quantities of the equilibrium constants are computed and discussed.

Electrodeposition of cadmium selenide

In the present work the process of electrochemical synthesis of cadmium selenide from sulphate solutions has been examined. Electrode reactions taking place at co-deposition of cadmium and selenium were tested with the use of cyclic voltammetry. Two mechanisms of co-deposition of cadmium and selenium were suggested. Within the range of more positive potentials, the following two reactions take place: reduction of selenious acid to selenium, and then underpotential deposition of cadmium on selenium. The second mechanism proceeds within the potentials range below −0.4V vs. SCE and relies on simultaneous reduction of ions of cadmium and selenious acid in a six-electron process. Next, the influence of selenious acid concentration and potential on the Cd–Se coatings deposition process on copper sheets was examined. The coatings were analysed with X-ray spectrofluorometry, electron scanning microscopy and X-ray diffraction. It was demonstrated that it is possible to obtain coatings stoichiometry corresponding to CdSe compound of hexagonal structure from sulphate electrolyte.

Sol–gel synthesis of composite powders in the TiO2–TeO2–SeO2 system

The aim of this paper is to study the gel formation tendency in the TiO2–TeO2–SeO2 system. Telluric acid (H6TeO6), selenous acid (H2SeO3) and titanium butoxide were used as precursors dissolved in ethylene glycol. Transparent monolithic and bright yellow colored gels are situated between 40–100 mol% TiO2, up to 20 mol% SeO2 and 65 mol% TeO2. The phase transformations of the as-prepared gels heat-treated up to 700 °C are investigated by XRD. The chemical states of C, Ti, Se and Te are characterized by means of XPS. Organic and OH groups participate in the amorphous organic–inorganic structure up to 250–300 °C. The structure of the inorganic amorphous phases above 300 °C consists of SeO3, TiO6 and TeOn structural units. The UV–Vis spectra of the binary and three-component gels exhibited a redshift of the cutoff in comparison with those of Ti butoxide gel due to the presence of selenium and tellurium units. Gel formation region in the ternary TiO2–TeO2–SeO2 system

Synthetic, structural, and computational investigations of N-alkyl benzo-2,1,3-selenadiazolium iodides and their supramolecular aggregates.

Despite their versatility, the application of telluradiazoles as supramolecular building blocks is considerably constrained by their sensitivity to moisture. Albeit more robust, their selenium analogues form weaker supramolecular interactions. These, however, are enhanced when one nitrogen atom is bonded to an alkyl group. Here we investigate general methods for the synthesis of such derivatives. Methyl, iso-propyl and tert-butyl benzo-2,1,3-selenadiazolium cations were prepared by direct alkylation or cyclo-condensation of the alkyl-phenylenediamine with selenous acid. While the former reaction only proceeds with the primary and tertiary alkyl iodides, the latter is very efficient. Difficulties reported in earlier literature are attributable to the formation of adducts of benzoselenadiazole with its alkylated cations and side reactions initiated by aerobic oxidation of iodide. However, the cations themselves are resilient to oxidation and stable in acidic to neutral aqueous medium. X-ray crystallography was used in the identification and characterization of the following compounds: [C6H4N2(R)Se](+)X(-), (R = CH(CH3)2, C(CH3)3; X = I(-), I3(-)], [C6H4N2(CH3)Se](+)I(-), and [C6H4N2Se][C6H4N2(CH3)Se]2I2. Formation of SeN secondary bonding interactions (chalcogen bonds) was only observed in the last structure as anion binding to selenium is a strong competitor. The relative strengths of those forces and the structural preferences they enforce were assessed with DFT-D3 calculations supplemented by AIM analysis of the electron density.

Ab initio molecular dynamics investigation of structural, dynamic and spectroscopic aspects of Se(vi) species in the aqueous environment.

Microscopic investigation of solvation of selenic acid (H2SeO4) in the aqueous environment has been carried out using the Car-Parrinello molecular dynamics simulation technique. The species deprotonates to HSeO4(-) in a few picoseconds owing to its low pKa1 value of -3.0. A dynamic equilibrium between HSeO4(-) and SeO4(2-), is observed in qualitative agreement with the reported pKa2 value of 1.70. The governing deprotonation mechanism and the structural and dynamic evolutions of the system, particularly the nature of hydrogen bonding, their strengths and lifetimes are investigated comprehensively. A comparison of the vibrational spectra of the species recorded in the gas phase and in the aqueous environment provides further insights on the nature of the interaction between the solute species and water. The results are in good agreement with the available experimental data and other recent computational studies.

Characterisation of 1,3-diammonium propylselenate monohydrate by XRD, FT-IR, FT-Raman, DSC and DFT studies

The crystals of 1,3-diammonium propylselenate monohydrate (DAPS) were prepared and characterised X–ray diffraction (XRD), FT-IR, FT-Raman spectroscopy, and DFT/B3LYP methods. It comprises protonated propyl ammonium moieties (diammonium propyl cations), selenate anions and water molecule which are held together by a number of hydrogen bonds and form infinite chains. The XRD data confirm the transfer of two protons from selenic acid to 1,3-diaminopropane molecule. The DAPS complex is stabilised by the presence of O–H···O and N–H···O hydrogen bonds and the electrostatic interactions as well. The N···O and O···O bond distances are 2.82–2.91 and 2.77 Å, respectively. The FT–IR and FT–Raman spectra of 1,3-diammonium propyl selenate monohydrate are recorded and the complete vibrational assignments have been discussed. The geometry is optimised by B3LYP method using 6–311G, 6–311+G and 6–311+G* basis sets and the energy, structural parameters, vibrational frequencies, IR and Raman intensities are determined. Differential scanning colorimetry (DSC) data were also presented to analyse the possibility of the phase transition. Complete natural bonding orbital (NBO) analysis is carried out to analyse the intramolecular electronic interactions and their stabilisation energies. The electrostatic potential of the complex lies in the range +1.902e × 10−2 to −1.902e × 10−2. The limits of total electron density of the complex is +8.43e × 10−2 to −8.43e × 10−2.

Decomposition of six common selenium species found in animal tissues using microwave digestion with nitric acid and ICP-MS

In this paper we report the decomposition of common selenium species (selenocysteine, selenomethionine, trimethylselenonium ion, selenosugar-1, methyl-2-acetamido-2-deoxy-1-seleno-β-d-glucopyranoside, selenosugar-2, methyl-2-acetamido-2-deoxy-1-seleno-β-d-galactopyranoside and selenosugar-3, methyl-2-amino-2-deoxy-1-seleno-β-d-galactopyranoside) expected to be found in animal tissues and urine using microwave digestion with nitric acid and ICP-MS. Complete decomposition of selenocystine to selenious acid was achieved, selenomethionine and the two selenosugars, were partially degraded to selenious acid and methylseleninic acid while trimethylselenonium ion was not degraded at all. Hydride generation techniques that rely on selenium to be in an inorganic form would have underestimated total selenium in extracts given that these species have different reactivities with borohydride. As trimethylselenonium ion is not degraded, this may lead to the formation of volatile dimethyselenide or dimethyldiselenide during hydride generation and an overestimation of selenium concentration.