Excess Selenium Research Articles

Metal and metalloid levels in blood of semipalmated sandpipers (Calidris pusilla) from Brazil, Suriname, and Delaware Bay: Sentinels of exposure to themselves, their prey, and predators that eat them

Identifying animals as sentinels for humans and other animal species is an excellent method for understanding exposure to environmental contamination at different times and places. Shorebirds are useful sentinels because they have a world-wide distribution, eat a range of prey, and are eaten by a range of other species, including humans. We collected blood from semipalmated sandpipers (Calidris pusilla) wintering in northern (Suriname N = 71) and northeastern (Brazil N = 61) South America to examine levels of heavy metals and metalloids (arsenic, selenium), and compare them to blood levels in sandpipers at a heavily used stopover site in New Jersey (N = 30; Delaware Bay, NJ). Since blood represents relatively recent exposure, it can provide information on where and when the birds were exposed. Levels were highest in Brazil for arsenic and particularly selenium; highest in Suriname for cadmium and lead; and highest in New Jersey for chromium. Samples from Brazil and Suriname presented higher levels of mercury than did those from New Jersey. There were no geographic differences for cobalt. Levels of all metals were generally within an order of magnitude. The significant geographic difference for selenium was interesting because it is regulated in the body. Selenium levels in the NJ sample were directly proportional to levels found in their principle food at this migration stopover site (eggs of horseshoe crab, Limulus polyphemus). Mean selenium level was almost an order of magnitude higher in the semipalmated sandpiper blood samples from Brazil (mean of 27,500 µg/L= ppb) compared to the other sampling locations (mean > 5330 µg/L). This is a toxic level and cause for concern and further investigation, alerting us to look for other evidence of excess selenium exposure. Otherwise the levels of other metals are generally not high enough to cause harm to the sandpipers themselves or to predators that eat them. We discuss the implications for these birds and their exposure to contaminants at different stopover sites.

Non-stoichiometric grain-growth in ZnSe ceramics for χ(2) interaction

Random quasi-phase-matching is a nonlinear scheme for three-wave mixing in transparent ceramics of non-centrosymmetric cubic materials. This process is controlled by the grain-size distribution of the ceramic and the nonlinear conversion efficiency is maximized when the average grain-size matches the coherence length. In this work, solid-state grain-coarsening is used to fabricate ZnSe ceramics with a desired grain-size. The effect of heat-treatment atmospheres (excess selenium vapor, zinc vapor or vacuum) on the grain-size distribution is investigated at 850°C and 1000°C and as a function of the heat-treatment time. The effect of these grain-size distributions on the efficiency of second-harmonic generation process by random quasi-phase-matching is analyzed theoretically.

Effect of dietary organic selenium on survival, growth, antioxidation, immunity and gene expressions of selenoproteins in abalone Haliotis discus hannai

No studies have been focused on the inclusion of organic selenium in formulated feed of abalone when organic minerals are accepted by aquaculture feed industry. This experiment evaluated the effect of organic selenium on the growth, antioxidation, immunity and gene expressions of selenoproteins in abalone. Graded levels of organic selenium were included to the basal diet at 0.00, 0.15, 0.30 and 0.60 ppm providing 157.83, 322.51, 437.59 and 596.59 ug/kg of selenium in the diet. Accordingly, the diets were named as Se-0.00, Se-0.15, Se-0.30 and Se-0.60 respectively. Results had shown that survival rate, weight gain rate and shell length increase rate were lowest for Se-0.60 group (p < 0.05). The concentration of selenium in the whole body generally increased with increasing level of dietary organic selenium (p < 0.05). The enzyme activities related to antioxidation increased initially with low levels of dietary selenium and decreased with higher levels, with the highest value in Se-0.30 group (p < 0.05). The enzyme activities of immunity increased with the addition of dietary selenium. With the increase of dietary selenium, Myostain expression decreased initially and increased afterwards, with lowest value for Se-0.30 group (p < 0.05). However, the expressions of other genes related to growth, antioxidation and selenoproteins firstly increased and then decreased, with the highest value recorded for Se-0.15 group. In conclusion, the inclusion rate of 0.15 – 0.30 ppm Se in diet could promote growth, antioxidation, immunity and gene expressions of selenoproteins in abalone; however, excess selenium with 0.60 ppm inclusion lever in diet had toxic effects.

Expression Profiles of Selenium-Related Genes in Human Chondrocytes Exposed to T-2 Toxin and Deoxynivalenol.

The combination of excess mycotoxin exposure and selenium deficiency has been widely considered as a cause of Kashin-Beck disease (KBD). The present study aimed to investigate the expression profiles of selenium-related genes in human chondrocytes after exposure to T-2 toxin and deoxynivalenol (DON) and to preliminarily identify the potential biological functions of the identified genes. Gene expression profiling was performed on human chondrocytes treated with 0.01μg/ml T-2 toxin and 1.0μg/ml DON by using Affymetrix Human Gene Arrays. The 1660 selenium-related genes were derived from the Comparative Toxicogenomics Database. Gene-term enrichment analysis was conducted by the DAVID gene annotation tool. Our results showed that 69 and 191 selenium-related genes were differentially expressed after T-2 toxin and DON treatment, respectively. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these identified genes were involved in various biological functions, such as the GO terms in response to oxidative stress, cell cycle arrest, and apoptotic process and the KEGG metabolic, FoxO signaling, and p53 signaling pathways. Our results may help explain the mechanisms of interaction between mycotoxins and selenium following human chondrocyte damage and reveal the potential roles of environmental risk factors in cartilage lesions during KBD development.

Fabrication of stoichiometric oriented Ag2Se thin film by laser ablation

The fabrication of Ag2Se thin films attracts interest due to the unique magnetoresistive and electrical properties of this compound. The laser ablation is one of the most convenient methods of thin films producing. However, all previous authors reported an excess of metallic silver in Ag2Se films deposited by laser ablation. The reasons for this deviation from the stoichiometric composition have not been identified. We have shown that an excess of silver arises due to the selenium evaporation from the surface of large particles in a laser plume. The addition of a 20 at. % excess of selenium to the ablation target enabled us to fabricate stoichiometric and perfectly oriented film of silver selenide.

Titanium Dichalcogenides as Nanoreactors for Magnetic High-Anisotropy Phases.

Composite single crystals consisting of nanoscaled Fe3Se4 inclusions encapsulated into the interlayer space of TiSe2 matrix were obtained by the decay of homogeneous Fe0.5TiSe2 intercalation compound. These composites have a high magnetic anisotropy due to the coherent bond between inclusions and the host lattice of TiSe2. The influence of selenium pressure over the composite surface on the composition of the inclusions is studied, and the possibility of controlling their content is demonstrated. The thermodynamic stability of the composite with a small excess of selenium in comparison with the stoichiometric material is established based on theoretical calculations. The estimated energy of the chemical bond between components of the composite is close to the van der Waals bond energy. A method to control the orientation and defects within the inclusions in the host lattice is proposed.

Cytokinin is involved in TPS22-mediated selenium tolerance in Arabidopsis thaliana.

Excess selenium (Se) is toxic to plants, but relatively little is known about the regulatory mechanism of plant Se tolerance. This study explored the role of the TPS22 gene in Se tolerance in Arabidopsis thaliana. Arabidopsis wild type and XVE mutant seeds were grown on half-strength MS media containing Na2SeO3 for screening of the Se-tolerant mutant tps22. The XVE T-DNA-tagged genomic sequence in tps22 was identified by TAIL-PCR. The TPS22 gene was transformed into the mutant tps22 and wild type plants using the flower infiltration method. Wild type, tps22 mutant and transgenic seedlings were cultivated on vertical plates for phenotype analysis, physiological index measurement and gene expression analysis. We identified an Arabidopsis Se-tolerant mutant tps22 from the XVE pool lines, and cloned the gene which encodes the terpenoid synthase (TPS22). TPS22 was downregulated by Se stress, and loss-of-function of TPS22 resulted in decreased Se accumulation and enhanced Se tolerance; by contrast, overexpression of TPS22 showed similar traits to the wild type under Se stress. Further analysis revealed that TPS22 mediated Se tolerance through reduction of Se uptake and activation of metabolism detoxification, which decreased transcription of high-affinity transporters PHT1;1, PHT1;8 and PHT1;9 and significantly increased transcription of selenocysteine methyltransferase (SMT), respectively. Moreover, loss-of-function of TPS22 resulted in reduced cytokinin level and repression of cytokinin signalling components AHK3 and AHK4, and upregulation of ARR3, ARR15 and ARR16. Exogenous cytokinin increased transcription of PHT1;1, PHT2;1 and SMT and decreased Se tolerance of the tps22 mutant. In addition, enhanced Se resistance of the tps22 mutant was associated with glutathione (GSH). Se stress downregulated TPS22, which reduced endogenous cytokinin level, and then affected the key factors of Se uptake and metabolism detoxification. This cascade of events resulted in reduced Se accumulation and enhanced Se tolerance.

The role of selenium in insulin resistance

In recent years, there has been growing interest in clarifying the pathogenesis of some chronic diseases, such as obesity and type 2 diabetes mellitus. Metabolic alterations in these diseases are characterized by chronic hyperglycemia and insulin resistance. Studies have demonstrated the participation of minerals in the pathogenesis of insulin resistance, more specifically their involvement in the synthesis and regulation of insulin. Selenium is an anti-inflammatory and antioxidant micronutrient that is essential for the activity of selenoproteins. Two selenoproteins (glutathione peroxidase and selenoprotein P) are known to be involved in the insulin signaling pathway. The aim of this review is to provide an update on the role of selenium in insulin resistance mechanisms. Evidence shows that adequate concentrations of selenium play a key role in the secretion and action of insulin, but an excess of selenium in the body is associated with the pathogenesis of insulin resistance and the development of diabetes mellitus.

Heart failure, micronutrient profile, and its connection with thyroid dysfunction and nutritional status

Heart failure (HF) is a growing public health issue; its risk factors include inappropriate dietary intake of microelements such as iodine, selenium, zinc and iron, which may lead to thyroid dysfunction. This study aimed to assess the correlation among the functional class stages of patients with HF, iodine, selenium, iron and zinc levels with the presence of thyroid dysfunction. One hundred nine patients from the HF outpatient clinic of the Clinics Hospital of Ribeirão Preto whose blood and urine were collected for micronutrient analysis and laboratory tests were selected. The subjects' weight and height were also measured to calculate their BMI. First, a descriptive analysis of the data was made into tables, and then statistical analyses were done at a 5% significance level (p<0.05). Most patients whose data was analysed were elderly and overweight. Excess ioduria, serum selenium and zinc, erythrocyte zinc and deficiency in serum iron and erythrocyte selenium were observed. The prevalence of thyroid dysfunction was 8.3%. Multivariate logistic regression verified that thyroid dysfunction increases the chance of classification in functional class III or IV (p=0.015; OR=8.72) by 8.7 times; each year of age increases the chance by 4.6% of classification in functional class III or IV (p=0.008; odds ratio [OR]=1.05), and each unit of BMI increases the chance of classification in functional class III or IV by 9.2% (p=0.028; OR=1.09). Patients with HF were deficient in serum iron and erythrocyte selenium. No connection was found between hypothyroidism and mineral deficiency, which seems to be related more to the severity of the disease than to the micronutrient nutritional profile.

Selenolanthionine is the major water-soluble selenium compound in the selenium tolerant plant Cardamine violifolia

BackgroundSelenium hyperaccumulation in plants often involves the synthesis of non-proteinaceous methylated selenoamino acids serving for the elimination of excess selenium from plant metabolism to protect plant homeostasis. MethodsOur study aimed at the identification of the main selenium species of the selenium hyperaccumulator plant Cardamine violifolia (Brassicaceae) that grows in the wild in the seleniferous region of Enshi, China. A sample of this plant (3.7 g Se kg−1 d.w.) was prepared with several extraction methods and the extracted selenium species were identified and quantified with liquid chromatography mass spectrometry set-ups. ResultsThe Cardamine violifolia sample did not contain in considerable amount any of the organic selenium species that are often formed in hyperaccumulator plants; the inorganic selenium content (mostly as elemental selenium) accounted only for <20% of total Se. The most abundant selenium compound, accounting for about 40% of total Se was proved to be selenolanthionine, a selenium species that has never been unambiguously identified before from any selenium containing sample. The identification process was completed with chemical synthesis too. The molar ratio of lanthionine:selenolanthionine in the water extract was ca. 1:8. ConclusionsFinding selenolanthionine as the main organic selenium species in a plant possibly unearths a new way of selenium tolerance. This article is part of a Special Issue entitled Selenium research in biochemistry and biophysics - 200 year anniversary issue, edited by Dr. Elias Arnér and Dr. Regina Brigelius-Flohe.

Crystal Structure of Binuclear Cobalt Complexes [(Cp′′′Co)2(μ2-η1:η2-S2)2] and [(Cp′′′Co)2(μ2-η1:η2-Se2)2

Binuclear cobalt complexes [(Cp′′′Co)2(μ2-η1:η2-S2)2] (1) (Cp′′′ = η5-1,2,4-tris(tert-butyl)cyclopentadienide) and [(Cp′′′Co)2(μ2-η1:η2-Se2)2] (2) are obtained by the interaction of [(Cp′′′Co)2(μ-η4:η4-C7H8)] with excess sulfur or selenium respectively. The structures of the complexes are determined by single crystal X-ray diffraction.

Monomeric and Oligomeric Metal Selenide Complexes from Structural Transformation of the Tetraselenotungstate Anion

Treatment of W(CO)6 with Na2Sex (x = 2–4) at 90 °C, prepared from heating selenium powder and sodium in DMF solution, afforded (Et4N)2[WSe4] (1) in a relatively high yield. Interaction of 1 with one equiv. [Me3NCH2Ph]Br in MeCN gave a cation exchanging product (Et4N)(Me3Ph2CH2N)[WSe4] (2) in a quantitative yield. Reaction of 1 with excess grey selenium in DMF produced monomeric polyselenide complex (Et4N)2[WO(Se4)2] (3). Treatment of 1 with equal equiv. anhydrous FeCl2 and excess PPh3 in DMF gave a dimeric complex (Fe(DMF)6)[W2Se4(μ-Se)2] (4). Similar reaction using MnCl2·4H2O salt easily gave rise to isolation of a trimeric complex (Mn(DMF)6)[WO(DMF)(μ-WSe4)2] (5). Reaction of 1 with anhydrous ZnCl2 in a mixed DMF/MeCN at 40 °C afforded a mixed-metal selenide complex (Et4N)2[Zn(μ-WSe4)2] (6). All complexes are well characterized by electronic, infrared, mass and NMR spectroscopies in this paper, and the solid-state structures of complexes 1–6 have been also established by X-ray crystallography. Interactions of tetraselenotungstate anion [WSe4]2− and first-row transition metal ions (Fe2+, Mn2+ and Zn2+) in the heating dimethylformide resulted in isolation of monomeric and oligomeric metal selenide complexes (Fe(DMF)6)[W2Se4(μ-Se)2] (Mn(DMF)6)[WO(DMF)(μ-WSe4)2] and (Et4N)2[Zn(μ-WSe4)2].

Concentrations of Trace Elements in Hemodialysis Patients: A Prospective Cohort Study

Low concentrations and excessive concentrations of trace elements have been commonly reported in hemodialysis patients, but available studies have several important limitations. Random sample of patients drawn from a prospective cohort. 198 incident hemodialysis patients treated in 3 Canadian centers. We used mass spectrometry to measure plasma concentrations of the 25 elements at baseline, 6 months, 1 year, and 2 years following enrollment in the cohort. We focused on low concentrations of zinc, selenium, and manganese and excessive concentrations of lead, arsenic, and mercury; low and excessive concentrations of the other 19 trace elements were treated as exploratory analyses. Low and excessive concentrations were based on the 5th and 95th percentile plasma concentrations from healthy reference populations. At all 4 occasions, low zinc, selenium, and manganese concentrations were uncommon in study participants (≤5.1%,≤1.8%, and≤0.9% for zinc, selenium, and manganese, respectively) and a substantial proportion of participants had concentrations that exceeded the 95th percentile (≥65.2%,≥74.2%, and≥19.7%, respectively). Almost all participants had plasma lead concentrations above the 95th percentile at all time points. The proportion of participants with plasma arsenic concentrations exceeding the 95th percentile was relatively constant over time (9.1%-9.8%); the proportion with plasma mercury concentrations that exceeded the 95th percentile varied between 15.2% and 29.3%. Low arsenic, platinum, tungsten, and beryllium concentrations were common (>50%), as were excessive cobalt, manganese, zinc, vanadium, cadmium, selenium, barium, antimony, nickel, molybdenum, lead, and chromium concentrations. There was no evidence that low zinc, selenium, or manganese concentrations exist in most contemporary Canadian hemodialysis patients. Some patients have excessive plasma arsenic and mercury concentrations, and excessive lead concentrations were common. These findings require further investigation.

Long-Term Excessive Selenium Supplementation Induces Hypertension in Rats.

Selenium (Se) is an essential trace element involved in several biological pathways, naturally found in rocks, soils, and food. Even though the daily requirement of Se is achieved through a balanced diet, the use of Se supplements has been frequent. Due to the risk of toxic effects of having Se in excess, supplementation is still under debate. The aim was to evaluate the effects of long-term Se supplementation upon systolic blood pressure (SBP) and redox status of rats exposed to sodium selenite. Male Wistar rats were exposed to 2 and 6mg/L of sodium selenite in drinking water for 85days. SBP and body weight were evaluated weekly; oxidative stress biomarkers were measured in blood or plasma; and Se levels were assessed in blood, plasma, kidney, and liver. Se supplementation (2 and 6mg/L) induced significant increase in the SBP in rats from the 42nd day until the end of the study. This increase on SBP was not associated with significant changes in oxidative stress biomarkers. A significant increase in Se levels was found in whole blood, kidney, and liver from both groups of rats receiving Se supplementation when compared to control. Although the exact mechanisms underlying this augment in SBP are not clear, they are potentially related to other Se biological routes besides the synthesis of selenoproteins, such as GSH-Px. Due to the negative effects upon blood pressure, precautionary measures are advised, since the selling of supplements does not require a medical prescription.

Taming Silicon Congeners of CO and CO2 : Synthesis of Monomeric SiII and SiIV Chalcogenide Complexes.

The synthesis of the unprecedented monomeric SiII selenide complex (bis-NHC)Si=Se→GaCl3 2 (bis-NHC=bis-N heterocyclic carbene, H2 C[{NC(H)=C(H)N(Dipp)}C:]2 , Dipp=2,6-iPr2 C6 H3 ), bearing the elusive SiSe ligand as a heavy CO homologue by the reaction of the silylone-GaCl3 adduct (bis-NHC)Si→GaCl3 1 with elemental selenium in acetonitrile, is reported. The similar conversion of 1 with excess selenium conducted in THF afforded the SiSe2 complex (bis-NHC)Si(=Se)Se→GaCl3 3. Remarkably, the reaction of 1 with Te=P(nBu)3 as a gentle Te transfer reagent led to the isolation of the monomeric SiTe2 complex (bis-NHC)SiTe2 4, the first structurally characterized Lewis acid free heavy CO2 homologue complex. The isolated compounds 2, 3, and 4 have been fully characterized, including single-crystal X-ray diffraction analyses. Their electronic structures and spectroscopic data have also been studied by quantum-chemical calculations.

Taming Silicon Congeners of CO and CO2: Synthesis of Monomeric SiII and SiIV Chalcogenide Complexes

AbstractThe synthesis of the unprecedented monomeric SiII selenide complex (bis‐NHC)Si=Se→GaCl3 2 (bis‐NHC=bis‐N heterocyclic carbene, H2C[{NC(H)=C(H)N(Dipp)}C:]2, Dipp=2,6‐iPr2C6H3), bearing the elusive SiSe ligand as a heavy CO homologue by the reaction of the silylone–GaCl3 adduct (bis‐NHC)Si→GaCl3 1 with elemental selenium in acetonitrile, is reported. The similar conversion of 1 with excess selenium conducted in THF afforded the SiSe2 complex (bis‐NHC)Si(=Se)Se→GaCl3 3. Remarkably, the reaction of 1 with Te=P(nBu)3 as a gentle Te transfer reagent led to the isolation of the monomeric SiTe2 complex (bis‐NHC)SiTe2 4, the first structurally characterized Lewis acid free heavy CO2 homologue complex. The isolated compounds 2, 3, and 4 have been fully characterized, including single‐crystal X‐ray diffraction analyses. Their electronic structures and spectroscopic data have also been studied by quantum‐chemical calculations.

Dietary excess selenium regulates the transcription of pancreatic selenoproteome in chicken

BackgroundRecently, numerous studies have found high Selenium (Se) influences the pancreas in mammals. However, little is known about the influence of high Se in the pancreatic tissue in avian.ObjectiveWe attempted to characterize the relationship between dietary Se, the selenoprotein, and the pancreas in chicken. This project will provide certain help for poultry farming and provide a reference for medicine.Methods1‐day‐old chickens received different quantities of dietary Se (0.15 mg, 3.0 mg, or 5.0 mg Se/kg of diet) for 8 weeks. Blood samples were analyzed immediately for glucose content at 2nd, 4th, 6th, and 8th week. The pancreas tissue was collected and examined for the activity of selenoenzymes (GPX, TrxR), and antioxidant related factors (T‐AOC, MDA, GSH) and mRNA expression of the transcriptome of selenoproteins at 4th and 8th week.ResultsIn the 5.0 mg Se/kg group, a significant increase (P&lt;0.05) in blood glucose was observed. Dietary excess Se influenced on four antioxidant factors, such as T‐AOC, H2O2, MDA, and CAT. From these data, we observed that excess Se induces decreased antioxidant capacity of pancreatic tissue. At super‐nutritional Se (3.0 mg/kg), most selenoproteins were up‐regulated in chicken pancreatic, but Gpx3, Sepp2, and Selu was only down‐regulated.ConclusionDietary Se level can inluence the pancreatic antioxidant capacity by regulating the activity and transcription of selenoenzymes. These results indicate that excess Se induces pancreatic dysfunction through selenoproteins. Dietary Se status stabilizes pancreatic normal physiology function via regulation of the selenoprotemic transcriptions. We hypothesize that hierarchy of regulated the transcriptions of selenoproteome makes an important roles of renal Se metabolism and transport in avian.Support or Funding InformationChina New Century Excellent Talents in University (No. NECT‐1207‐02), National Natural Science Foundation of China (No. 31572586) and Academic Backbone Project of Northeast Agricultural University (No. 15XG16).

Plasmon-electron dynamics at the Au/InSe and Y/InSe interfaces designed as dual gigahertz-terahertz filters

In this work, the X-ray diffraction, the Scanning electron microscopy, the energy dispersive X-ray, the Raman, The UV–vis light and the impedance spectral techniques are employed to explore the structural, vibrational, optical and electrical properties of the Au/InSe and Y/InSe thin film interfaces. It was shown that with its amorphous nature of crystallization, the InSe thin films exhibited n-type conductivity due to the 3% excess selenium. For this form of InSe, the only active Raman spectral line is 121 (cm−1). In addition to the design of the energy band diagram, the analysis the dielectric spectra and the optical conductivities were possible in the frequency range of 270–1000THz. The modeling of the optical conductivities of the Au, Y, Au/InSe and Y/InSe with the help of Lorentz approach for optical conduction, assured that the conduction is dominated by the resonant plasmon-electron interactions at the metals and metals/semiconductors interfaces. It also allowed tabulating the necessary parameters for possible applications in terahertz technology. These parameters are the electron effective masses, the free electron densities, the electron bounded plasmon frequencies, the electron scattering times, the reduced resonant frequencies and the drift mobilities. On the other hand, the impedance spectral analysis of the Y/InSe/Au interfaces in the frequency range of 0.01–1.80GHz, revealed negative capacitance effect associated with band filter features that exhibit maximum transition line at 1.17GHz. This value nominates the interface as a member of filter classes in the gigahertz technology.

Influence of temperature on the magnetic behavior of the Sb35.75Mn1.43Se62.82 compound

Polycrystalline Mn-doped Sb2Se3 was synthesized by using the conventional solid-state reaction method. Structural, optical, and magnetic properties of the prepared material in a fine-powder form were investigated. The elemental analysis of the prepared sample has led to the chemical formula Sb35.75Mn1.43Se62.82 indicating a nearly stoichiometric composition with a slight excess of Se. X-ray diffraction (XRD) studies revealed the presence of a predominant orthorhombic-type structure phase, the same as that of Sb2Se3, and an excess of selenium as a minor secondary phase. The optical absorption of the indicated sample was determined from the room temperature optical diffuse reflection data in the spectral range 400-2000 nm. The analysis of the optical absorption spectra revealed direct fundamental transition with an energy gap value of 1.18 eV. A symmetrical signal of the electron spin resonance (ESR) was obtained for the prepared ingot powder. The ESR spectrum reveals the Lorentzian shape of a broad single peak due to the Mn2+ - Mn2+ interaction with a Lande g-factor value of 2.00523. Magnetic properties such as magnetization $M_{\mathrm s}$ , coercivity $ H_{\mathrm ci}$ were affected by temperature under an applied magnetic field ranging from -20 to 20 kOe. $ M_{\mathrm s}$ and $ H_{\mathrm ci}$ have values ranging from 0.1899 to 0.1226 emu/g and from 1.583 to 0.580 kOe, respectively with increasing temperature from 100 to 300 K. A positive shift of the hysteresis loops along the field axis was observed.

Spectrophotometric Determination of Selenium Through Triiodide Anion.

Selenium is a chemical element found in the human body that plays a crucial role in its regulation. Depending on the concentration, it may have beneficial or have toxic effects. Selenium is incorporated as selenocysteine amino acid residue in selenoproteins which play an important role in many biological functions: anti-oxidant defense, regulation of the immune function and of the inflammatory response, metabolism of thyroid hormones, functioning of the central nervous system, biosynthesis of DNA and RNA, fertility, and reproduction. Excess selenium, altough less common than selenium deficiency, has equally important negative effects. Given the importance of selenium quantification in various samples, the study proposes a simple and direct spectrophotometric determination of selenium using triiodide anions. The method is based on the oxidation of iodide in acidic medium by selenium (IV) contained in the sample, to form elemental iodine which, in turn, reacts with the excess iodide to form the triiodide anions, the most stable soluble species in aqueous solution. Triiodide is colored from yellow to brown, depending on the concentration. The coloured compound has maximum absorbance at specific wavelengths and thus, the stage of interaction with a chromogenic agent is eliminated. Due to the sensitivity of the reaction, the detection limit of triiodide, and therefore selenium, is extended toward lower values. The optimal conditions for the measurements were established: λ = 290 nm, pH = 1.0 - 1.5, reaction time = 15 minutes. Two areas of selenium detection were determined from the samples: 0.025 - 0.100 ppm, and 0.1 - 4.0 ppm. The detection limit of selenium was lowered at 0.100 ppm and even at 0.025 ppm, which significantly improves the sensitivity of the determination. Types of samples were specified which are suitable for analysis using the proposed method and explained why, in case of biological fluids, it must be used only accompanied by an adequate digestion method of the samples. Selenium can be measured by direct spectrophotometric determination of the triiodide anion resulting from the oxidation of iodide by selenium (IV) compounds from the sample. In this regard, a simple, direct, and sensitive determination method of selenium from the samples by UV-Vis spectrophotometry, without the use of chromogenic agents has been optimized.