Speciation of inorganic selenium using capillary electrophoresis–inductively coupled plasma-atomic emission spectrometry with on-line hydride generation

Cu(II) detection by a fluorometric probe based on thiazoline-amidoquinoline derivative and its application to water and food samples

Two novel fluorescent probes for Cu2+ detection have been developed based on thiazoline-quinoline conjugates bearing a 4-ethynyl-N,N-dimethylaniline unit (QT1 and QT2). QT2 exhibits instantaneous fluorescence quenching of Cu2+ with an emissive change from bright orange to arctic blue under UV light irradiation (365 nm). The plots of I0/I against Cu2+ concentrations show a good linear relationship that ranges from 0 to 50 µM with a coefficient of determination (R2) = 0.9906 and a limit of detection (LOD) of 76 nM, which is considered low (4.84 ppb). A 1:1 complexation between QT2 and Cu2+ was confirmed by UV-Vis titration, ESI-MS, and SC-XRD. The QT2·Cu2+ complex was dissociated by the addition of EDTA. The fluorescence quenching mechanism involves the ligand-to-metal charge transfer (LMCT) of a paramagnetic Cu2+ complex. The QT2 probe on a paper-based strip was used to determine the amount of Cu2+ in water and food samples (shiitake mushrooms and oysters).

Turning gray selenium into a nanoaccelerator of tissue regeneration by PEG modification

Selenium (Se) is an essential trace element involved in nearly all human physiological processes but suffers from a narrow margin between benefit and toxicity. The nanoform of selenium has been proven shown to be more bioavailable and less toxic, yet significant challenges remain regarding the efficient and feasible synthesis of biologically active nanoselenium. In addition, although nanoselenium has shown a variety of biological activities, more interesting nanoselenium features are expected. In this work, hydrosoluble nanoselenium termed Nano-Se in the zero oxidation state was synthesized between gray Se and PEG. A zebrafish screen was carried out in zebrafish larvae cocultured with Nano-Se. Excitingly, Nano-Se promoted the action of the FGFR, Wnt, and VEGF signaling pathways, which play crucial roles in tissue regeneration. As expected, Nano-Se not only achieved the regeneration of zebrafish tail fins and mouse skin but also promoted the repair of skin in diabetic mice while maintaining a profitable safe profile. In brief, the Nano-Se reported here provided an efficient and feasible method for bioactive nanoselenium synthesis and not only expanded the application of nanoselenium to regenerative medicine but also likely reinvigorated efforts for discovering more peculiarunique biofunctions of nanoselenium in a great variety of human diseases.

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It was found that selenium nanoparticles through FGFR、Wnt、VEGFR signal pathway to promote tissue regeneration;

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Development a new water-soluble, bio-compatible, zero oxidation state Nano-Se;

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Development a new efficient and safe nano-biologic agent for promoting tissue regeneration.

Speciation of inorganic selenium in natural water by in situ solid-phase extraction using functionalized silica

Functionalized adsorbents with poly-(4,9-dioxododecane-1,12-guanidine) (SiO₂-PDDG) and mercaptophenyl groups (MPhS) were used for the separation of Se(VI) and Se(IV) for the first time. Fixation of PDDG was characterized by capillary electrophoresis and TGA/DSC. The quantitative extraction of Se(VI) proceeded due to anion exchange at pH 3-7. The adsorption capacity of SiO₂-PDDG for Se(VI) was 28 μmol g^-1. Silicas with mercaptophenyl groups were used for the extraction of Se(IV) from solutions in the range of 2 M HCl - pH 6.5. The adsorption capacity of MPhS was 35 μmol g^-1. A system of columns containing synthesized adsorbents was proposed for the separation of Se(VI) and Se(IV) and their subsequent determination by ICP-MS. Optimal parameters of adsorption include a flow rate of 1 mL min^-1, pH of 5, and sample volume of 200 mL. Se(IV) was desorbed with 5 mL of 0.25 M 2,3-dimercapto-1-propanesulphonic acid and Se(VI) with 5 mL of 1 M HNO₃. The preconcentration factor was 40. The limits of detection (3s) were 0.75 and 1.25 ng L^-1 for Se(VI) and Se(IV), respectively. The proposed method (SPE-ICPMS) was used to determine selenium species in natural water and certified reference materials. The separation was carried out directly at the sampling site.

Determining selenium speciation by graphite furnace atomic absorption spectrometry

A straightforward method for measuring two aquatic inorganic species of selenium, selenate, Se(VI), and selenite, Se(IV), was developed in this study. Selenium toxicity and bioaccumulation in food chain are strongly dependent on its speciation. Therefore, it is important to measure selenium species as part of any selenium risk assessment practice. In this method, total selenium was first measured using graphite furnace atomic absorption spectrometry, and then, chemical procedures in the literature were used to reduce selenite, Se(IV), to hydrogen selenide (H₂Se). Total selenium of the same solution was measured again with the analytical instrument after stripping H₂Se from the solution. The difference of total selenium measured gave Se(IV) concentration. The two main species in natural waters are Se(VI) and Se(IV). Therefore, it can be assumed that after removing Se(IV) from the solution, the remaining total selenium is Se(VI). The two inorganic selenium species of (IV) and (VI) in purified waters and synthetic irrigation waters both spiked with Se(VI) and Se(IV) were determined using this method. Recovery of spiked samples in diluted synthetic irrigation water was 97% for Se(VI) and 99% for Se(IV). Detection limits of the method were 0.32 µg L^-1 for Se(VI) and 0.11 µg L^-1 for Se(IV). The advantages of the method developed in this study are that it employs a straightforward simple chemical reaction combined with acidification and stripping, requires only one instrument (graphite furnace atomic absorption spectrometry), and does not require extensive sample pretreatment.

Environmental Impacts of Selenium Contamination: A Review on Current-Issues and Remediation Strategies in an Aqueous System

In both aquatic and terrestrial environment, selenium contamination may exist at concentrations above the micronutrient limit. Since there is such a narrow bandwidth between which selenium concentration is acceptable, the health of the public may be at risk of selenium toxicity once the concentration increases beyond a threshold. Selenium contamination in an aqueous environment can occur due to anthropogenic activities and/or from natural sources. This study presents a review of the forms of selenium, inorganic and organic selenium contamination, mobilization, analytical methods for various forms of selenium and remediation strategies. The review also provides recent advances in removal methods for selenium from water including bioremediation, precipitation, coagulation, electrocoagulation, adsorption, nano-zerovalent iron, iron co-precipitation and other methods. A review of selenomethionine and selenocysteine removal strategy from industrial wastewaters is presented. Selenium resource recovery from copper ore processing has been discussed. Various analytical methods used for selenium and heavy metal analysis were compared. Importantly, existing knowledge gaps were identified and prospective areas for further research were recommended.

Speciation and Determination of Selenium Oxyanions at the Drinking Water Pollution Concentration Levels

The research on selenium presence in water resources has revealed the need to determine the respective aquatic species. As selenium oxyanions SeO32− (SeIV) and SeO42− (SeVI) predominate in natural waters, their determination is essential, mainly due to different ecotoxicity properties, as well as to different removal options from relevant-polluted waters. This study focuses on the SeO32−/SeO42− speciation/separation and determination through the selective adsorption of SeO32− only onto specific iron oxy-hydroxides (FeOOHs). For this purpose, the laboratory prepared FeOOHs examined along with the commercially available relevant material (Bayoxide), which was found to present optimum results for the speciation of selenium oxyanions, at the low concentration range 10–100 μg/L, using a dose of 0.5 g/L of adsorbent and gently stirring for 30 min at the usually encountered pH value of 7.3 ± 0.2. Moreover, the relevant experiments showed that the other major ions Cl−, HCO3−, NO3−, SO42−, Ca2+, Mg2+, Na+, possibly found in most natural waters at the concentration range 0–200 mg/L, as well as silicon, total organic carbon (TOC) of natural organic matter (NOM) and iron at the concentration range 0–50 mg/L, 0–5 mg/L and 0–1 mg/L, respectively, did not interfere with the selective adsorption of Se(IV). Furthermore, the most important advantage of this selective speciation method is its implementation/combination with all commonly applied analytical methods for the determination of total selenium.

Monitoring and analysis of selenium as an emerging contaminant in mining industry: A critical review

Selenium is an indispensable trace element for humans, however, its release at high concentrations becomes a major concern for terrestrial and aquatic ecosystems due to its bioaccumulation potential. Mining and metal-mineral processing are among the main sources of selenium released into the environment. Excessive levels of selenium may induce toxicity in human as selenosis, in grazing animals as alkali disease and in aquatic organisms as larval and developmental deformities and mortality. Due to the introduction of new policies for Se monitoring in the mining industry mainly setting the guidelines for selenium level in freshwaters as recommended by the Canadian Council of Ministers of Environment and Environment and climate change Canada, an improved understanding of Se occurrence, mobility, bioavailability and treatment technologies for efficient removal is timely and required. In this context, this review updated the understanding of mining-related selenium occurrence in surface water, soil and plant, with a focus on its mobility and bioavailability. Selenium uptake, translocation, accumulation, and metabolism in plants are further presented. Selenium monitoring and treatment is the key to adopt the corrective measures to mitigate highly contaminated effluent and to minimize the associated adverse health effects. Future research directions and recommendations for selenium analysis and treatment processes are also discussed.

Simple Fluorescence Turn-On Chemosensor for Selective Detection of Ba2+ Ion and Its Live Cell Imaging

A phenoxazine-based fluorescence chemosensor 4PB [(4-(tert-butyl)-N-(4-((4-((5-oxo-5H-benzo[a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)benzamide)] was designed and synthesized by a simple synthetic methods. The 4PB fluorescence chemosensor selectively detects Ba²⁺ in the existence of other alkaline metal ions. In addition, 4PB showed high selectivity and sensitivity for Ba²⁺ detection. The detection limit of 4PB was 0.282 μM and the binding constant was 1.0 × 10⁶ M^-1 in CH₃CN/H₂O (97.5:2.5 v/v, HEPES = 1.25 mM, pH 7.3) medium. This chemosensor functioned through the intramolecular charge transfer (ICT) mechanism, which was further confirmed by DFT studies. Live cell imaging in MCF-7 cells confirmed the cell permeability of 4PB and its capability for specific detection of Ba²⁺ in living cells.

Application of enzymatic probe sonication for selenium speciation in animal feeds

Enzymatic probe sonication (EPS) was investigated as a novel and alternative technology for the extraction of five Se species SeCys₂, MeSeCys, Se (IV), SeMet and Se (VI) from animal feeds. The critical parameters of EPS such as enzyme types, ultrasonic power, sample/enzyme ratio, extraction time and temperature were carefully optimized. Under current conditions, one sample can be extracted in 60s, in contrast to several hours required by the conventional enzymatic methods Moreover, the extraction is performed in pure water, no further temperature control or pH adjustment is needed, and therefore the risk of species interconvertion is drastically reduced or inhibited. The Se species were separated and quantitatively determined by high-performance liquid chromatography-hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS), which allows the separation of organic and inorganic Se species in a single chromatographic run. The newly developed method was successfully applied to the determination of Se species in 18 feed samples collected from markets and local farms. Concerning the feed samples studied, the results of this work suggest that stricter measures should be taken to control the Se-enriched feed supplements in terms of Se species.

A "turn-on" fluorescent chemosensor for aluminum ion and cell imaging application

A simple and efficient fluorescent chemosensor for Al(3+) is reported in the paper. The chemosensor is obtained by dehydration reaction of 2-hydroxy-1-naphthaldehyde and 2-aminophenol. The chemosensor has high selectivity and sensitivity for Al(3+) and displays fluorescence "off-on" switch signal. The detection limit of the chemosensor for Al(3+) can reach 1.0×10(-7) M in DMSO/H2O (1:9, v/v) solution. The mass spectra and Job's plot analysis confirm the 1:1 stoichiometry between chemosensor and Al(3+). Potential utilization of the probe as an intracellular sensor of Al(3+) in human cancer (HiSa) cells is also examined by confocal fluorescence microscopy.

Selenium contaminated waters: An overview of analytical methods, treatment options and recent advances in sorption methods

Selenium is an essential trace element for many organisms, including humans, but it is bioaccumulative and toxic at higher than homeostatic levels. Both selenium deficiency and toxicity are problems around the world. Mines, coal-fired power plants, oil refineries and agriculture are important examples of anthropogenic sources, generating contaminated waters and wastewaters. For reasons of human health and ecotoxicity, selenium concentration has to be controlled in drinking-water and in wastewater, as it is a potential pollutant of water bodies. This review article provides firstly a general overview about selenium distribution, sources, chemistry, toxicity and environmental impact. Analytical techniques used for Se determination and speciation and water and wastewater treatment options are reviewed. In particular, published works on adsorption as a treatment method for Se removal from aqueous solutions are critically analyzed. Recent published literature has given particular attention to the development and search for effective adsorbents, including low-cost alternative materials. Published works mostly consist in exploratory findings and laboratory-scale experiments. Binary metal oxides and LDHs (layered double hydroxides) have presented excellent adsorption capacities for selenium species. Unconventional sorbents (algae, agricultural wastes and other biomaterials), in raw or modified forms, have also led to very interesting results with the advantage of their availability and low-cost. Some directions to be considered in future works are also suggested.

Sensitive, selective analysis of selenium oxoanions using microchip electrophoresis with contact conductivity detection

The common selenium oxoanions selenite (SeO3(2-)) and selenate (SeO4(2-)) are toxic at intake levels slightly below 1 mg day(-1). These anions are currently monitored by a variety of traditional analytical techniques that are time-consuming, expensive, require large sample volumes, and/or lack portability. To address the need for a fast and inexpensive analysis of selenium oxoanions, we present the first microchip capillary zone electrophoresis (MCE) separation targeting these species in the presence of chloride, sulfate, nitrate, nitrite, chlorate, sulfamate, methanesulfonate, and fluoride, which can be simultaneously monitored. The chemistry was designed to give high selectivity in nonideal matrices. Interference from common weak acids is avoided by operating near pH 4. Separation resolution from chloride was enhanced to improve tolerance of high-salinity matrices. As a result, selenate can be quantified in the presence of up to 1.5 mM NaCl, and selenite analysis is even more robust against chloride. Using contact conductivity detection, detection limits for samples with conductivity equal to the background electrolyte are 53 nM (4.2 ppb Se) and 380 nM (30 ppb) for selenate and selenite, respectively. Analysis time, including injection, is ∼2 min. The MCE method was validated against ion chromatography (IC) using spiked samples of dilute BBL broth and slightly outperformed the IC in accuracy while requiring <10% of the analysis time. The applicability of the technique to real samples was shown by monitoring the consumption of selenite by bacteria incubated in LB broth.

Synthesis of cross-linked chitosan and application to adsorption and speciation of Se (VI) and Se (IV) in environmental water samples by inductively coupled plasma optical emission spectrometry

A new type of cross-linked chitosan was synthesized with Diethylene Triamine (DCCTS). The adsorption of Se (VI) on DCCTS was studied. The effect factors on adsorption and the adsorption mechanism were considered. The results indicated that the DCCTS could concentrate and separate Se (IV) at pH = 3.6; the maximum adsorption efficiency was 94%, the adsorption equilibrium time was 30 min; the maximum adsorption capacity was 42.7 mg/g; the adsorption fitted Langmuir equation. A novel method for speciation of Se (VI) and Se (IV) in environmental water samples has been developed using DCCTS as adsorbent and ICP–OES as determination means. The detection limit of this method was 12 ng/L, the relatively standard deviation was 4.5% and the recovery was 99%~104%.

Selenium speciation in flue desulfurization residues

Flue gas from coal combustion contains significant amounts of volatile selenium (Se). The capture of Se in the flue gas desulfurization (FGD) scrubber unit has resulted in a generation of metal-laden residues. It is important to determine Se speciation to understand the environmental impact of its disposal. A simple method has been developed for selective inorganic Se(IV), Se(VI) and organic Se determination in the liquid-phase FGD residues by hydride generation atomic fluorescence spectrometry (AFS). It has been determined that Se(IV), Se(VI) and organic Se can be accurately determined with detection limits (DL) of 0.05, 0.06 and 0.06 microg/L, respectively. The accuracy of the proposed method was evaluated by analyzing the certified reference material, NIST CRM 1632c, and also by analyzing spiked tap-water samples. Analysis indicates that the concentration of Se is high in FGD liquid residues and primarily exists in a reduced state as selenite (Se(IV)). The toxicity of Se(IV) is the strongest of all Se species. Flue gas desulfurization residues pose a serious environmental risk.

Development of a simple and fast voltammetric procedure for determination of trace quantity of Se(IV) in natural lake and river water samples

A simple and fast cathodic stripping voltammetric procedure for determination of trace quantity of Se(IV) in natural samples containing high concentrations of surfactants and humic substances was developed. The procedure exploiting selenium accumulation (from sample solution spiked with 0.1 mol L(-1) HClO(4) and 4 x 10(-4)mol L(-1) Cu(NO(3))(2)) as Cu(2)Se was employed as the initial method. The deposited Cu(2)Se was stripped by differential pulse cathodic potential scan. The interference from dissolved organic matter such as surfactants and humic substances was eliminated by adding Amberlite XAD-7 resin to the voltammetric cell. The whole procedure was applied to a single cell, which allows one to monitor the voltammetric scan. Optimum conditions for removing the surfactants and humic substances due to their adsorption on XAD-7 resin were evaluated. The method was tested on synthetic samples spiked with surfactants and humic substances. The calibration graph for Se(IV) under optimized conditions following the accumulation of 30s was linear in the range from 2 x 10(-9) to 2 x 10(-7)mol L(-1) and was found to obey the equation y=0.74x-0.61, where y and x are the peak current (nA) and Se(IV) concentration (nmol L(-1)), respectively. The linear correlation coefficient was r=0.9993. The relative standard deviation for determination of Se(IV) at the concentration of 1 x 10(-8)mol L(-1) was 3.7% (n=5). The detection limit estimated from three times the standard deviation for low Se(IV) concentration and accumulation time of 30s was about 7.8 x 10(-10)mol L(-1). The presented procedure was successfully applied to selenium determination in TMRAIN-95 certified reference material and to real samples including spiked lake and river waters for selenium speciation.