RESUMO
Seleno-polysaccharides have become a major topic for research owing to their high anti-oxidative capacity and immune-enhancing activities. In this study, galactomannan (GM) was isolated from Sesbania cannabina, and next modified using HNO3-Na2SeO3 method to obtain six varieties of seleno-galactomannans (SeGMs). FT-IR and GPC results showed the changes in chemical structure of SeGMs, indicating successful combination of selenium and GM. By measuring superoxide dismutase and malondialdehyde, the SeGMs showed a stronger protective effect against H2O2-induced oxidative damage in vitro than unmodified GM using macrophage RAW264.7 cell as a model, and the effect of SeGMs-14 was prominent. However, the selenylation modification did not show any obvious effect on the immunomodulatory activity of GM, as determined by the index of tumor necrosis factor-α, interleukin-6, and interleukin-1ß. Overall, the prepared SeGMs from galactomannan could potentially serve as a dietary supplement of Se or an organic antioxidant.
Assuntos
Macrófagos/efeitos dos fármacos , Mananas/farmacologia , Compostos de Selênio/farmacologia , Sesbania/química , Animais , Antioxidantes/fisiologia , Galactose/análogos & derivados , Peróxido de Hidrogênio/toxicidade , Imunidade/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/fisiologia , Mananas/isolamento & purificação , Camundongos , Oxirredução/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Células RAW 264.7 , Compostos de Selênio/isolamento & purificaçãoRESUMO
The fungi Aureobasidium pullulans, Mortierella humilis, Trichoderma harzianum and Phoma glomerata were used to investigate the formation of selenium- and tellurium-containing nanoparticles during growth on selenium- and tellurium-containing media. Most organisms were able to grow on both selenium- and tellurium-containing media at concentrations of 1 mM resulting in extensive precipitation of elemental selenium and tellurium on fungal surfaces as observed by the red and black colour changes. Red or black deposits were confirmed as elemental selenium and tellurium, respectively. Selenium oxide and tellurium oxide were also found after growth of Trichoderma harzianum with 1 mM selenite and tellurite as well as the formation of elemental selenium and tellurium. The hyphal matrix provided nucleation sites for metalloid deposition with extracellular protein and extracellular polymeric substances localizing the resultant Se or Te nanoparticles. These findings are relevant to remedial treatments for selenium and tellurium and to novel approaches for selenium and tellurium biorecovery.
Assuntos
Fungos/metabolismo , Nanopartículas/microbiologia , Selênio/metabolismo , Telúrio/metabolismo , Biodegradação Ambiental , Fungos/classificação , Fungos/crescimento & desenvolvimento , Nanopartículas/química , Oxirredução , Compostos de Selênio/isolamento & purificação , Compostos de Selênio/metabolismo , Telúrio/isolamento & purificaçãoRESUMO
An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.
Assuntos
Técnicas Biossensoriais/métodos , Compostos de Cádmio/isolamento & purificação , DNA/química , Técnicas Eletroquímicas , Compostos de Selênio/isolamento & purificação , Compostos de Cádmio/toxicidade , Ouro/química , Limite de Detecção , Hibridização de Ácido Nucleico/genética , Pontos Quânticos/química , Compostos de Selênio/toxicidade , Estreptavidina/químicaRESUMO
Selenium (Se) exposure poses potential risks to wildlife at the Salton Sea. Our previous research suggests Chlorella sp. be highly efficient at absorbing and volatilizing Se. In developing an algal treatment system for Se removal, this study further evaluated the performance under the conditions to be encountered in the field using Chlorella pyrenoidosa and Chlorella vulgaris. The results show the algal Se removal efficiency was little affected by photoperiod, yet volatilization became relatively greater in dark/light cycles over a longer term. The rates of Se absorption and volatilization by C. vulgaris were 88% and 77% more, respectively, in the DI water, while C. pyrenoidosa acted oppositely, indicating C. vulgaris will perform better in Se removal if nutrient levels are reduced in advance. The presence of sulfate reduced biomass Se, especially through volatilization, by 8% for C. vulgaris, lessening potential ecotoxicity. Finally, C. vulgaris released biomass Se back to the water column under hypersaline conditions, leading to a 6% increase in water Se concentrations. These results suggest C. vulgaris be the best alga for the treatment of Se laden river water in the Salton Sea area, yet a filtering system is required to prevent Se containing algae from entering food chains.
Assuntos
Chlorella vulgaris/metabolismo , Alimentos/efeitos adversos , Fotoperíodo , Salinidade , Compostos de Selênio/isolamento & purificação , Sulfatos/farmacologia , Poluentes Químicos da Água/isolamento & purificação , Biodegradação Ambiental , Biomassa , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Humanos , Compostos de Selênio/metabolismo , Volatilização , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodosRESUMO
A model small-scale field experiment was set up to investigate selenium (Se) uptake by four different varieties of broccoli plants, as well as the effect of Se foliar application on the uptake of essential elements for plants calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P), sulfur (S), and zinc (Zn). Foliar application of sodium selenate (Na2SeO4) was carried out at two rates (25 and 50 g Se/ha), and an untreated control variant was included. Analyses of individual parts of broccoli were performed, whereby it was found that Se in the plant accumulates mainly in the flower heads and slightly less in the leaves, stems, and roots, regardless of the Se rate and broccoli variety. In most cases, there was a statistically significant increase of Se content in all parts of the plant, while there was no confirmed systematic influence of the addition of Se on the changing intake of other monitored elements. Selenization of broccoli leads to an effective increase in the Se content at a rate of 25 g/ha, whereas the higher rate did not result in a substantial increase of Se content compared to the lower rate in all varieties. Therefore, the rate of 25 g/ha can be recommended as effective to produce broccoli with an increased Se content suitable for consumption. Moreover, Se application resulted in an adequate increase of the main organic compounds of Se, such as selenocystine (SeCys2), selenomethionine (SeMet), and Se-methylselenocysteine (Se-MeSeCys).
Assuntos
Brassica/metabolismo , Cistina/análogos & derivados , Compostos Organosselênicos/isolamento & purificação , Compostos de Selênio/metabolismo , Selenocisteína/análogos & derivados , Selenometionina/metabolismo , Transporte Biológico , Brassica/efeitos dos fármacos , Cátions Bivalentes/metabolismo , Cátions Monovalentes/metabolismo , Cistina/isolamento & purificação , Cistina/metabolismo , Flores/efeitos dos fármacos , Flores/metabolismo , Compostos Organosselênicos/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Caules de Planta/efeitos dos fármacos , Caules de Planta/metabolismo , Compostos de Selênio/isolamento & purificação , Compostos de Selênio/farmacologia , Selenocisteína/isolamento & purificação , Selenocisteína/metabolismo , Selenometionina/isolamento & purificação , Espectrofotometria AtômicaRESUMO
A preconcentration system has been developed to determine inorganic selenium species. Selenium was retained by a column filled with polyvinyl chloride (PVC) with lanthanum hydroxide co-precipitation. Speciation was achieved by selective photoreduction previous Se preconcentration. The retention pH was optimized at 10.0. Two multivariate calibrations and a central composite design were employed for optimization of the system. Sample, reagents and acid flow rates are significant variables affecting the system. Employing HG-ICP-OES as detection, the optimized system reached a detection limit of 0.03µg/L, and an enhancement factor of 14875 (25 for preconcentration system, 595 for hydride generation). To verify the method' accuracy, two certified reference materials, BCR® 414 Plankton & IRMM-804 Rice Flour, were analysed. The system was applied to inorganic selenium speciation in several Argentinean beverages to estimate their selenium contribution to diet.
Assuntos
Bebidas/análise , Espectrometria de Massas/métodos , Compostos de Selênio/análise , Compostos de Selênio/isolamento & purificação , Extração em Fase Sólida/métodos , Argentina , Calibragem , Limite de Detecção , Selênio/análiseRESUMO
Solidified floating organic drop microextraction was combined with electrothermal vapourisation inductively coupled plasma mass spectrometry for Se species in Se-rich tea leaves and tea infusion, including total, suspended, soluble, organic and inorganic Se as well as Se(IV) and Se(VI). Ammonium pyrrolidinedithiocarbamate was used as both chelating reagent and chemical modifier in this study. Se(IV) and Se(VI) were separated at pH range of 2.0-5.0. An enrichment factor of 500 was obtained for Se(IV) from this method. Under the optimum conditions, the detection limits for Se(IV) and Se(VI) were 0.19 and 0.26pgmL(-1), respectively. The relative standard deviations were less than 5.5% (c=0.1ngmL(-1), n=9). This method was applied for Se species, its content and distribution in Se-rich tea leaves and tea infusion with satisfactory results. The recoveries of spike experiments are in the range of 92.2-106%. A certified reference material of tea leaves was analyzed by this method, and the results were in agreement with certified values.
Assuntos
Camellia sinensis/química , Espectrometria de Massas/métodos , Compostos de Selênio/química , Compostos de Selênio/isolamento & purificação , Microextração em Fase Sólida/métodos , Chá/química , Folhas de Planta/química , VolatilizaçãoRESUMO
Cadmium sulfide (CdS) nanoparticles (NPs) were synthesized by using banana peel extract as a convenient, non-toxic, eco-friendly 'green' capping agent. Cadmium nitrate and sodium sulfide are main reagents. A variety of CdS NPs are prepared through changing reaction conditions (banana extracts, the amount of banana peel extract, solution pH, concentration and reactive temperature). The prepared CdS colloid displays strong fluorescence spectrum. X-ray diffraction analysis demonstrates the successful formation of CdS NPs. Fourier transform infra-red (FTIR) spectrogram indicates the involvement of carboxyl, amine and hydroxyl groups in the formation of CdS NPs. Transmission electron microscope (TEM) result reveals that the average size of the NPs is around 1.48 nm.
Assuntos
Produtos Biológicos/química , Compostos de Cádmio/química , Musa/metabolismo , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Extratos Vegetais/química , Compostos de Selênio/química , Produtos Biológicos/isolamento & purificação , Compostos de Cádmio/isolamento & purificação , Teste de Materiais , Tamanho da Partícula , Extratos Vegetais/isolamento & purificação , Compostos de Selênio/isolamento & purificaçãoRESUMO
Selenium (Se) species, Se-methyl-seleno-cysteine (MeSeCys), seleno-cystine (SeCys2), seleno-methionine (SeMet), selenite (SeO3(2-)) and selenate (SeO4(2-)), in the three main anatomical tissues of bay scallops (Argopecten irradians), the adductor muscle, the mantle and the visceral mass, were completely released by enzymatic hydrolysis and detected by high performance liquid chromatography (HPLC) in combination with inductively coupled plasma mass spectrometry (ICP-MS). For the thorough hydrolysis of the proteins to free the Se species, bay scallop tissues were pre-treated (pre-hydrolyzed) with papain in a 1molL(-1) sodium bicarbonate solution containing 5mmolL(-1) sodium thiosulfate at 30-40°C for 24h, then hydrolyzed by the combination of Flavourzyme(®) 500 L, carboxypeptidase Y and trypsin (3+1+1) at 45°C, at a constant pH of 8.00 for 6h. Under the optimized conditions, the quantification limits of MeSeCys, SeCys2, SeMet, SeO3(2-) and SeO4(2-) were 0.69, 0.48, 0.93 0.53 and 1.22µgL(-1), respectively (equivalent to 0.14, 0.097, 0.19, 0.11 and 0.24µgg(-1) for real samples). The working curves in the concentration ranges of 2 to 500µgL(-1) were linear with all the RSD (n=5) smaller than 15% and regression coefficients greater than 0.999. The recoveries of the species for spiked samples at 4µgg(-1) (equivalent to 20µgL(-1) in the final hydrolyzates) levels all exceeded 90%. The developed method was validated by the determination of SeMet in SELM-1, a Se enriched yeast certified reference material (CRM). Selenate was the only absent species, whereas the other four species did exist in bay scallops.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Pectinidae/química , Compostos de Selênio/isolamento & purificação , Selênio/isolamento & purificação , Animais , Aspergillus oryzae/enzimologia , Cisteína/análogos & derivados , Cisteína/química , Metionina/química , Pectinidae/metabolismo , Selênio/química , Selênio/metabolismo , Compostos de Selênio/química , Compostos de Selênio/metabolismoRESUMO
HPLC-ICP-MS based on ion-paired reversed phase chromatography for the selenium speciation using the mixture of 1-butanesulfonic acid (BA) and trifluoroacetic acid (TFA) as the mixed ion-pairing reagents was developed and applied to selenium-enriched pakchoi (Brassica chinensis Jusl var parachinensis (Bailey) Tsen & Lee). Several conditions of ion-paired reversed phase HPLC-ICP-MS, such as pH of the mobile phase, concentration of ion pairing reagents, types and length of analytical column, and flow rate of the mobile phase, were optimised for five selenium species; selenate (Se(VI)), Selenite (se(IV)), selenocysteine (SeC), Se-methylselenocysteine (SeMC) and selenomethionine (SeM). The results showed that the optimum conditions for pH, BA and TFA condition, type of separating column and flow rate, were 4.5, 8mM, 4mM, C18 (250 mm length × 4.6mm I.D) and 1.2 mL min(-1), respectively. These conditions archived separation of the organic selenium species. The limits of detection (LOD) and quantitation (LOQ) of each selenium species were lower than 5 and 16 ng Se mL(-1), respectively. Furthermore, the recoveries of most selenium species were good, except for SeC. In this research, selenium-enriched pakchoi was cultivated by supplementing inorganic selenium from selenate into sand. The result showed that inorganic selenium, SeMC, SeM and several unknown species were found in selenium-enriched pakchoi sprouts by using the proposed method. Thereby, the biotransformation of selenate in pakchoi was similar to other Brassicaceae plants such as kale and broccoli.
Assuntos
Brassica/química , Espectrometria de Massas , Compostos de Selênio/química , Ácidos Alcanossulfônicos/química , Brassica/metabolismo , Cromatografia Líquida de Alta Pressão , Cromatografia de Fase Reversa , Concentração de Íons de Hidrogênio , Extratos Vegetais/química , Ácido Selênico/análise , Ácido Selênico/isolamento & purificação , Ácido Selenioso/análise , Ácido Selenioso/isolamento & purificação , Compostos de Selênio/análise , Compostos de Selênio/isolamento & purificação , Selenocisteína/análogos & derivados , Selenocisteína/análise , Selenocisteína/isolamento & purificação , Selenometionina/análise , Selenometionina/isolamento & purificaçãoRESUMO
BACKGROUND: Selenium (Se) is an essential dietary mineral and Radix puerariae (RP) (the dried root of Pueraria lobata Willd.) is a botanical supplement widely used as a nutraceutical. Food enriched with Se provides a feasible and economic approach for production of organic Se compounds. However, little is known about Se-enriched RP and the structure of Se-containing polysaccharides and proteins derived from Se-enriched RP. RESULTS: The organic form of Se accounted for 82.42% of total content. Purification by DEAE-52 and Sephadex G-100 column chromatography yielded three single fractions--RP-SeP-11, RP-SeP-22 and RP-SeP-33--with Se contents of 0.9562 × 10⻳, 0.6113 × 10⻳ and 0.3827 × 10⻳ g kg⻹, respectively. RP-SeP-11 (3.5 kDa) was made of glucose, RP-SeP-22 (19.6 kDa) was composed of xylose and glucose, and RP-SeP-33 (97.9 kDa) was made up galactose, mannose and glucose. Two Se-containing proteins were obtained with Se content of 3.175 × 10⻳ and 4.328 × 10⻳ g kg⻹, respectively. One appeared as three subunits with molecular masses of 43.0, 29.0 and 17.8 kDa while the other appeared as two subunits with molecular masses of 43.0 and 26.3 kDa. CONCLUSION: The results provide a basis for promoting the utilisation of RP resources enriched with Se as a promising tool for the food industry and are significant for its contribution to Se biochemistry in plants.
Assuntos
Dieta , Alimentos Fortificados , Proteínas de Plantas/química , Polissacarídeos/química , Pueraria/química , Compostos de Selênio/química , Selênio/análise , Humanos , Peso Molecular , Monossacarídeos/análise , Proteínas de Plantas/isolamento & purificação , Raízes de Plantas/química , Polissacarídeos/isolamento & purificação , Subunidades Proteicas , Compostos de Selênio/isolamento & purificaçãoRESUMO
The removal of aqueous Se(VI) from a simulated groundwater by granular iron (GI), organic carbon (OC), and a mixture of these reactive materials (GI-OC) was evaluated in laboratory batch experiments. The experiments were performed under anoxic conditions to simulate subsurface treatment. A total reaction time of 120 h (5 d) was chosen to investigate the rapid changes in speciation occurring over reaction times that are reasonable for permeable reactive barrier (PRB) systems. After 120 h, concentrations of Se decreased by >90% in the GI system, 15% in the OC system and 35% in the GI-OC mixture. Analysis of the materials after contact with Se using synchrotron-radiation based X-ray absorption spectroscopy (XAS) indicated the presence of Se(IV) and Se(0) on the margins of GI grains after 6h with evidence of SeO and SeSe bonding, whereas Se(VI) was not observed. After 72 h, Se(0) was the only form of Se present in the GI experiments. In the OC batches, the XAS analysis indicated binding consistent with sorption of aqueous Se(VI) onto the OC with only minor reduction to Se(IV) and Se(0) after 120 h. Selenium XAS spectra collected for the GI-OC mixture were consistent with spectra for Se(IV) and Se(0) on both the margins of GI grains and OC particles, suggesting that the presence of dissolved Fe may have mediated the reduction of sorbed Se(VI). The results suggest that the application of granular Fe is effective at inducing aqueous Se removal in anoxic conditions through reductive precipitation processes.
Assuntos
Recuperação e Remediação Ambiental/métodos , Água Subterrânea/análise , Ferro/química , Compostos de Selênio/isolamento & purificação , Solo/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Precipitação Química , Água Subterrânea/química , Água Subterrânea/normas , Oxigênio/química , Projetos de Pesquisa , Compostos de Selênio/química , Solubilidade , Propriedades de Superfície , Poluentes Químicos da Água/química , Madeira/química , Espectroscopia por Absorção de Raios XRESUMO
The isotope (79)Se may be of great concern with regard to the safe disposal of nuclear wastes in deep geological repositories due to its long half-life and potential mobility in the geosphere. The Se mobility is controlled by the oxidation state: the oxidized species (Se(IV)) and (Se(VI)) are highly mobile, whereas the reduced species (Se(0) and Se(-II)) form low soluble solids. The mobility of this trace pollutant can be greatly reduced by interacting with the various barriers of the repository. Numerous studies report on the oxidized species retention by mineral phases, but only very scarce studies report on the selenide (Se(-II)) retention. In the present study, the selenide retention by coprecipitation with and by adsorption on mackinawite (FeS) was investigated. XRD and SEM analyses of the samples reveal no significant influence of Se on the mackinawite precipitate morphology and structure. Samples from coprecipitation and from adsorption are characterized at the molecular scale by a multi-edge X-ray absorption spectroscopy (XAS) investigation. In the coprecipitation experiment, all elements (S, Fe, and Se) are in a low ionic oxidation state and the EXAFS data strongly point to selenium located in a mackinawite-like sulfide environment. By contacting selenide ions with FeS in suspension, part of Se is located in an environment similar to that found in the coprecipitation experiment. The explanation is a dynamical dissolution-recrystallization mechanism of the highly reactive mackinawite. This is the first experimental study to report on selenide incorporation in iron monosulfide by a multi-edge XAS approach.
Assuntos
Compostos Ferrosos/química , Compostos de Selênio/isolamento & purificação , Selênio/isolamento & purificação , Adsorção , Precipitação Química , Modelos Moleculares , Selênio/química , Compostos de Selênio/química , Espectroscopia por Absorção de Raios X , Difração de Raios XRESUMO
Fish are selenium rich foodstuffs and a major selenium source for the Japanese population. Niboshi is processed from Japanese anchovy (Engraulis japonicus) and commonly used to prepare soup stock for Japanese dishes. In this study, we characterized selenium species in the Niboshi extract by ultrafiltration, ion-exchange chromatography and mass spectrometry. Selenium species in the Niboshi were more extractable by polar solvents (water and ethanol) than an apolar one (hexane) along with amino acids and proteinous species. Selenium in the water-extract from the Niboshi was mostly ascribed to organoselenium compounds with a molecular mass less than 5 kDa. Although selenoamino acids and selenoproteins and their fragments were involved in the extract, a large portion of the selenium species appeared to be low-molecular-mass organoselenium compounds other than selenoamino acids and their derivatives. Ion-exchange chromatographic separations revealed that most of the selenium species in the extract possess anionic and/or amphoteric characteristics. One of these selenium species from the Niboshi extract was detected at m/z 577 for 80Se by mass spectrometry subsequent to ion-pair extraction.
Assuntos
Compostos Organosselênicos/química , Selênio/química , Animais , Cromatografia por Troca Iônica/métodos , Peixes , Espectrometria de Massas/métodos , Peso Molecular , Compostos Organosselênicos/isolamento & purificação , Selênio/isolamento & purificação , Compostos de Selênio/química , Compostos de Selênio/isolamento & purificação , Selenoproteínas/química , Solventes/química , Ultrafiltração/métodosRESUMO
A non-chromatographic separation and preconcentration method for Se species determination based on the use of an on-line ionic liquid (IL) dispersive microextraction system coupled to electrothermal atomic absorption spectrometry (ETAAS) is proposed. Retention and separation of the IL phase was achieved with a Florisil(®)-packed microcolumn after dispersive liquid-liquid microextraction (DLLME) with tetradecyl(trihexyl)phosphonium chloride IL (CYPHOS(®) IL 101). Selenite [Se(IV)] species was selectively separated by forming Se-ammonium pyrrolidine dithiocarbamate (Se-APDC) complex followed by extraction with CYPHOS(®) IL 101. The methodology was highly selective towards Se(IV), while selenate [Se(VI)] was reduced and then indirectly determined. Several factors influencing the efficiency of the preconcentration technique, such as APDC concentration, sample volume, extractant phase volume, type of eluent, elution flow rate, etc., have been investigated in detail. The limit of detection (LOD) was 15 ng L(-1) and the relative standard deviation (RSD) for 10 replicates at 0.5 µg L(-1) Se concentration was 5.1%, calculated with peak heights. The calibration graph was linear and a correlation coefficient of 0.9993 was achieved. The method was successfully employed for Se speciation studies in garlic extracts and water samples.
Assuntos
Alho/química , Líquidos Iônicos/química , Microextração em Fase Líquida/métodos , Compostos de Selênio/análise , Compostos de Selênio/isolamento & purificação , Espectrofotometria Atômica/métodos , Água/química , Ácido Clorídrico/química , Indicadores e Reagentes/química , Sistemas On-Line , Compostos Organofosforados/química , Pirrolidinas/química , Tiocarbamatos/químicaRESUMO
An analytical method for selenium species of selenate (SeVI), selenite (SeIV), selenomethionine (SeMet), selenocystine (SeCys2 ) and selenoethionine (SeEt) was established using high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A Hamilton PRP X-100 reversed-phase anion exchange column (250 mm x 4.6 mm, 5 microm) with a 5 mmol/L citric acid buffer solution (pH 4.5, adjusted with 20% (v/ v) ammonia) as mobile phase was used for separation, and ICP-MS was used for detection. The five species were completely separated within 21 min. All the linear correlation coefficients of the five selenium species were greater than 0.999 5, and the detection limits of SeVI, SeIV, SeMet, SeCys2, SeEt were 0.4, 0.4, 5.6, 0.9 and 1.2 microg/L, respectively. The extraction procedure was studied for fresh mushroom and pork samples. For water-soluble selenium compounds, citric acid was a good extraction solution, and the recoveries were around 100% for inorganic selenium and in the range of 85.0% - 95.3% for SeMet; but worse for SeCys2 and SeEt. As for the proteinase K, the recoveries of SeCys2 and SeEt were raised to the range of 79.9% -91.5%. The method has the advantages of simple operation and good accuracy, and can be used for the quantitative determination of the five selenium species in food.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Análise de Alimentos/métodos , Espectrometria de Massas/métodos , Compostos Organosselênicos/isolamento & purificação , Compostos de Selênio/isolamento & purificação , Selênio/química , Agaricales/química , Animais , Cromatografia por Troca Iônica/métodos , Carne/análise , Compostos Organosselênicos/química , Selênio/análise , Compostos de Selênio/química , SuínosRESUMO
Room-temperature ionic liquids (RTILs) improved reversed-phase high performance liquid chromatography (RP-HPLC) on-line combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for selenium speciation. The different parameters affecting the retention behaviors of six target selenium species especially the effect of RTILs as mobile phase additives have been studied, it was found that the mobile phase consisting of 0.4% (v/v) 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 0.4% (v/v) 1-butyl-2,3-dimethylimidazolium tetrafluroborate ([BMMIM]BF(4)) and 99.2% (v/v) water has effectively improved the peak profile and six target selenium species including Na(2)SeO(3) (Se(IV)), Na(2)SeO(4) (Se(VI)), L-selenocystine (SeCys(2)), D,L-selenomethionine (SeMet), Se-methylseleno-l-cysteine (MeSeCys), seleno-D,L-ethionine (SeEt) were separated in 8 min. In order to validate the accuracy of the method, a Certified Reference Material of SELM-1 yeast sample was analyzed and the results obtained were in good agreement with the certified values. The developed method was also successfully applied to the speciation of selenium in Se-enriched yeasts and clover. For fresh Se-enriched yeast cells, it was found that the spiked SeCys(2) in living yeast cells could be transformed into SeMet. Compared with other ion-pair RP-HPLC-ICP-MS approaches for selenium speciation, the proposed method possessed the advantages including ability to regulate the retention time of the target selenium species by selecting the suitable RTILs and their concentration, simplicity, rapidness and low injection volume, thus providing wide potential applications for elemental speciation in biological systems.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Líquidos Iônicos/química , Espectrometria de Massas/métodos , Sistemas On-Line , Selênio/análise , Selênio/química , Biotransformação , Cromatografia Líquida de Alta Pressão/normas , Cromatografia de Fase Reversa/normas , Concentração de Íons de Hidrogênio , Imidazóis/química , Indicadores e Reagentes/química , Cinética , Espectrometria de Massas/normas , Medicago/química , Metanol/química , Padrões de Referência , Reprodutibilidade dos Testes , Selênio/isolamento & purificação , Selênio/metabolismo , Compostos de Selênio/análise , Compostos de Selênio/química , Compostos de Selênio/isolamento & purificação , Temperatura , Leveduras/metabolismoRESUMO
This work investigates for the first time the potential of mixed-mode (anion-exchange with reversed-phase) high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the simultaneous retention and selective separation of a range of inorganic and organically-bound selenium (Se) species. Baseline separation and detection of selenocystine (SeCys(2)), Se-methyl-selenocysteine (SeMC), selenomethionine (SeMet), methylseleninic acid (MSA), selenite, gamma-glutamyl-methyl-selenocysteine (gamma-glutamyl-SeMC), and selenate in a Se standard mixture by mixed-mode HPLC-ICP-MS was achieved by switching between two citrate mobile phases of different pH and ionic strength within a single chromatographic run of 20 min. Limits of detection obtained for these Se species ranged from 80 ng kg(-1) (for SeMC) to 123 ng kg(-1) (for selenate). Using this approach as developed for selenium speciation, an adequate separation of inorganic and organic As compounds was also achieved. These include arsenite, arsenate, arsenobetaine (AsB) and dimethylarsenic acid (DMA), which may coexist with Se species in biological samples. Application of the newly proposed methodology to the investigation of the elemental species distribution in watercress (used as the model sample) after enzymatic hydrolysis or leaching in water by accelerated solvent extraction (ASE) was addressed. Only SeMet, SeMC and selenate could be tentatively identified in watercress extracts by mixed-mode HPLC-ICP-MS and retention time matching with standards. Recoveries (n=3) of these Se species from samples spiked with standards averaged 102% (for SeMC), 94.9% (for SeMet) and 98.3% (for selenate). Verification of the presence of SeMet and SeMC in an enzymatic watercress extract was achieved by on-line HPLC-ESI MS/MS in selected reaction monitoring (SRM) mode.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Compostos Organosselênicos/isolamento & purificação , Compostos de Selênio/isolamento & purificação , Espectrometria de Massas em Tandem/métodos , Brassicaceae/química , Brassicaceae/metabolismo , Cisteína/análogos & derivados , Metionina/análogos & derivados , Compostos Organosselênicos/química , Extratos Vegetais/química , Reprodutibilidade dos Testes , Compostos de Selênio/química , Sensibilidade e EspecificidadeRESUMO
Removal of selenate ion from the liquid phase by hydroxysulfate green rust (GR(SO4)) was investigated in the pH range from 7.5 to 10.0. Batch tests showed that the total selenium concentration decreased more rapidly with increasing pH. However, the amount of selenium removed from the liquid phase increased as the pH decreased. X-ray absorption spectrometric analysis demonstrated that the Se(VI) in the selenate ion was reduced to elemental selenium Se(0) at pH 9.0, whereas the existence of small amount of intermediate Se(IV) was detected at pH 7.5. Comparing the mass balance of the amount of consumed ferrous iron in GR(SO4), [DeltaFe(II)], and the amount of Se(VI) removed from the liquid phase, [DeltaSe(VI)], [DeltaFe(II)] is approximately six times larger than [DeltaSe(VI)] in mol units. This is also indirect but convincing evidence that the oxidation of Fe(II) in GR(SO4) leads to the simultaneous reduction of Se(VI) to Se(0). Powder X-ray diffraction analysis showed that the end product of GR(SO4) depends on the pH: magnetite for pH>9.0, goethite for pH<8.0, and their mixture at pH 8.5. These results indicate that the solution pH has a significant effect on the reaction path of selenate removal by GR(SO4).
Assuntos
Compostos Férricos/química , Óxido Ferroso-Férrico/química , Compostos Ferrosos/química , Compostos de Selênio/química , Compostos de Selênio/isolamento & purificação , Sulfatos/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Absorção , Precipitação Química , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Transmissão , Oxirredução , Ácido Selênico , Selênio/química , Análise Espectral , Difração de Raios X , Raios XRESUMO
The aim of this work was to study selenium (Se) speciation in the potato ( Solanum tuberosum L.) cultivar Desiree, enriched in Se by foliar spraying with a water solution containing 10 mg of Se/L in the form of sodium selenate. Four combinations of treatments were used: well-watered plants with and without Se foliar spraying and drought-exposed plants with and without Se foliar spraying. Water-soluble Se compounds were extracted from potato tubers by water or enzymatic hydrolysis with the enzyme protease XIV, amylase, or a combination of protease XIV and amylase. Extraction was performed using incubation at a constant temperature and stirring (37 degrees C at 200 rpm) or by ultrasound-assisted extraction (300 W), using different extraction times. Separation of soluble Se species (SeCys2, SeMet, SeMeSeCys, selenite, and selenate) was achieved by ion-exchange chromatography, and detection was performed by inductively coupled plasma-mass spectrometry (ICP-MS). Results showed that the concentration of selenate extracted was independent of the enzymatic extraction technique (approximately 98 ng/g for drought-exposed and 308 ng/g for well-watered potato tubers), whereas the extraction yield of SeMet changed with the protocol used (10-36%). Selenate and SeMet were the main soluble Se species (representing 51-68% of total Se) in potato tubers, regardless of the growth conditions.