Selenium Species Research Articles

Selenium species transforming along soil-plant continuum and their beneficial roles for horticultural crops.

Selenium (Se) acquirement from daily diet can help reduce the risk of many diseases. The edible parts of crop plants are the main source of dietary Se, while the Se content in crops is determined by Se bioavailability in soil. We summarize recent research on the biogeochemical cycle of Se driven by specific microorganisms and emphasize the oxidizing process in the Se cycle. Moreover, we discuss how plant root exudates and rhizosphere microorganisms affect soil Se availability. Finally, we cover beneficial microorganisms, including endophytes, that promote crop quality and improve crop tolerance to environmental stresses. Se availability to plants depends on the balance between adsorption and desorption, reduction, methylation and oxidation, which are determined by interactions among soil properties, microbial communities and plants. Reduction and methylation processes governed by bacteria or fungi lead to declined Se availability, while Se oxidation regulated by Se-oxidizing microorganisms increases Se availability to plants. Despite a much lower rate of Se oxidization compared to reduction and methylation, the potential roles of microbial communities in increasing Se bioavailability are probably largely underestimated. Enhancing Se oxidation and Se desorption are crucial for the promotion of Se bioavailability and uptake, particularly in Se-deficient soils. Beneficial roles of Se are reported in terms of improved crop growth and quality, and enhanced protection against fungal diseases and abiotic stress through improved photosynthetic traits, increased sugar and amino acid contents, and promoted defense systems. Understanding Se transformation along the plant-soil continuum is crucial for agricultural production and even for human health.

Determination of selenium nanoparticles in fermented dairy products

A single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) method with improved sensitivity for determination of selenium nanoparticles (SeNPs) in lactic acid bacteria, bifidobacteria, and yeast was developed. The carbon-induced signal enhancement using 1% (v/v) methanol for preparation of sample dispersion led to decreasing detection limits from 61 nm to 47 nm in comparison to pure aqueous dispersion. Accuracy of SeNPs' size and number concentration determination were tested by adding artificially prepared SeNPs to the cells dispersion. While the found size of the SeNPs corresponded to original value, the number concentration recovery ranged from 46 to 102%. The repeatability of SeNPs size measurement was 0.6–15% and of number concentration determination 2.5–54%. The spherical and ovoid shaped SeNPs with average diameter in range of 60–261 nm and number concentration of 2.4 × 109–1.6 × 1011 mL−1 located both extracellularly and intracellularly was found by transmission electron microscopy and sp-ICP-MS in cell cultures growing in medium containing 10 mg L−1 of sodium selenite. Bio-synthesized SeNPs were stable for one week in aqueous dispersion and their stability was prolonged to one month by addition of hydrochloric acid (pH = 1.5). Moreover, the possibility of analyzing SeNPs in enzymatic extracts intended for speciation analysis of organic selenium species was proven to be suitable also for SeNPs characterization. Thus, a way to share sample preparation procedure with different types of analyses was demonstrated.

Understanding soil selenium accumulation and bioavailability through size resolved and elemental characterization of soil extracts

Dietary deficiency of selenium is a global health threat related to low selenium concentrations in crops. Despite the chemical similarity of selenium to the two more abundantly studied elements sulfur and arsenic, the understanding of its accumulation in soils and availability for plants is limited. The lack of understanding of soil selenium cycling is largely due to the unavailability of methods to characterize selenium species in soils, especially the organic ones. Here we develop a size-resolved multi-elemental method using liquid chromatography and elemental mass spectrometry, which enables an advanced characterization of selenium, sulfur, and arsenic species in soil extracts. We apply the analytical approach to soils sampled along the Kohala rainfall gradient on Big Island (Hawaii), which cover a large range of organic carbon and (oxy)hydroxides contents. Similarly to sulfur but contrarily to arsenic, a large fraction of selenium is found associated with organic matter in these soils. However, while sulfur and arsenic are predominantly found as oxyanions in water extracts, selenium mainly exists as small hydrophilic organic compounds. Combining Kohala soil speciation data with concentrations in parent rock and plants further suggests that selenium association with organic matter limits its mobility in soils and availability for plants.

Speciation Analysis of Selenium Nanoparticles and Inorganic Selenium Species by Dual-Cloud Point Extraction and ICP-MS Determination.

Application of selenium nanoparticle (SeNP)-based fertilizers results in the release of SeNPs to aquatic systems, where SeNPs may transform into inorganic selenite (Se(IV)) and selenate (Se(VI)) with higher toxicity. However, methods for the speciation analysis of different Se species are lacking, hindering the accurate assessment of the risks of SeNPs. Herein, for the first time, a Triton X-45 (TX-45)-based dual-cloud point extraction (CPE) method was established for the selective determination of SeNPs, Se(IV), and Se(VI) in water. TX-45 can adsorb on the surface of SeNPs and facilitate the extraction of SeNPs into the lower TX-45-rich phase in the first CPE, while Se(VI) and Se(IV) retain in the upper aqueous phase. In the second CPE, Se(IV) can selectively associate with diethyldithiocarbamate and be concentrated in the TX-45-rich phase, whereas Se(VI) remains in the upper phase. Different Se species can be isolated and then quantified by ICP-MS. The presence of coexisting ions and dissolved organic matter (0-30 mg C/L) did not interfere with extraction and separation. The feasibility of the presented method was confirmed by the analysis of natural water samples, with a detection limit of 0.03 μg/L and recoveries in the ranges of 61.1-104, 65.5-113, and 80.3-131% for SeNPs, Se(IV), and Se(VI), respectively. This study aims to provide an effective method to track the fate and transformation of SeNPs in aquatic systems and further contribute to estimating the potential risks of SeNPs to environmental organisms and human bodies.

The Role of Selenium and Hydrocarbons in Au-Ag Ore Formation in the Rodnikovoe Low-Sulfidation (LS) Epithermal Deposit, Kamchatka Peninsula, Russia

Gold-silver mineralization in the Rodnikovoe LS epithermal deposit is characterized by selenium speciation. Two main alternating ore assemblages have been identified: silver-aguilarite-acanthite and gold-uytenbogaardtite-acanthite. The former mineral association is intergrown with secondary silver (Ag0.77–0.91), whereas the latter assemblage is closely associated with high-grade gold (Au0.63–0.67). However, both are dominated by Ag0.49–0.56Au0.44–0.51 alloys. The geochemical evolution of the ore-forming system developed in the direction: Fe → Cu; Ag → Au; S → Se; As → Sb. Organic compounds (1 relative %) of both biogenic and thermogenic origin were found in fluid inclusions. These molecules participated in the formation of Ag,Au-complexes and transported noble metals along with selenium. Hydrothermal fluids are characterized by fSe2/fS2 ratios < 1, conditions such that the deposition of selenide minerals is inhibited, except for the naumannite and acanthite series. These conditions allow active entry of selenium into sulfosalts (the selenium substitutes for sulfur).

Mechanisms of changing speciation and bioavailability of selenium in agricultural mollisols of northern cold regions

The distribution, speciation, and bioavailability of selenium (Se) - an essential micronutrient for human beings - in agricultural soils influence the resource recovery of agricultural benefits and the sustainable use of Se in agroecosystems. Quantitative understanding in this regard however remains limited in the world's mollisol agroecosystems, despite their critical importance in securing global food supply. Herein, a systematic investigation of Se in the river sediment-irrigation water-mollisols-rhizosphere-rice seeds continuum, at the core zone of the northern mollisol regions, was conducted to elucidate the hydrological-hydrogeochemical processes and mechanisms responsible for the distribution and bioavailability of Se. The content of total Se in the mollisols ranged between 0.12 and 0.54 mg/kg with an average of 0.31 mg/kg. At the riverside flood plains, humic-acid bound Se accounted on average for 39 % of total Se. This pool of Se can be transformed to water-soluble and ion-exchangeable Se(VI), supporting a higher potential of Se bioavailability at riparian agricultural mollisols. For mollisol lands far from the river channels, the topography affects the speciation and partitioning of Se presumably through regulating water retention and organic matter transport. Moreover, altering pH and redox conditions in response to irrigation with the river water may boost Se bioavailability in weakly acidic and high Eh mollisols. It can be in part ascribed to the transformation of organic-bound Se along with infiltrated oxygenated water that leads to the increase of water-soluble and ion-exchangeable Se. These findings reinforce that hydrological-hydrogeochemical perturbations due to irrigation with surface water need to be assessed carefully in the management of Se resources in the mollisol agroecosystems.

Draft Genome Sequence of Stutzerimonas stutzeri NT-I, Which Reduces Selenium Oxyanions into Elemental Selenium and Volatile Selenium Species.

Stutzerimonas stutzeri strain NT-I effectively reduces selenate and selenite into elemental selenium and volatile selenium species. It is thus a promising biological agent for treatment of selenium-contaminated wastewater. We here report the draft genome sequence of this strain.

Trichloroisocyanuric Acid (TCCA): A Suitable Reagent for the Synthesis of Selanyl‐benzo[b]chalcogenophenes

AbstractA new approach for the synthesis of 3‐organoselanyl‐benzo[b]chalcogenophenes promoted by trichloroisocyanuric acid is reported. The reaction was carried out with electrophilic selenium species which were generated in situ by the reaction between trichloroisocyanuric acid and diorganyl diselenides using ethanol as solvent. The developed method uses mild reaction conditions and was efficient for the synthesis of different 3‐organoselanyl‐benzo[b]chalcogenophenes in a good to excellent yields. Analysis of 77Se NMR spectroscopy indicates that the electrophilic PhSeCl was formed in situ and a plausible reaction mechanism was proposed.

A reliable method of high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry for determining selenoamino acids in selenoproteins from Lactococcus lactis

A reliable method for simultaneous determination of four organic selenium species by HPLC-ICP-MS was developed and implemented in determining organic selenoamino acids (Se-AAs) in selenoproteins from Lactococcus lactis (L. lactis) NZ9000. The method consisted of liberating Se-AAs from selenoproteins using ultrasound-assisted protease hydrolysis, and quantitatively detecting Se-AA speciations by HPLC-ICP-MS. After optimizations of proteolysis conditions, chromatographic conditions and determination conditions, the established method could efficiently separate the four Se-AAs, including SeCys, SeCys2, SeMeCys and SeMet within 10 min. It presented high sensitivity with the limits of detection and quantitation in the range of 0.197∼0.240 μg∙L−1 and 0.788∼0.960 μg∙L−1, respectively, good repeatability with a relative standard deviation (RSD) of less than 5%, and good recovery in the desired floating range of 90%∼105%, verifying the good accuracy. The method successfully detected four selenium species in the purified glutathione peroxidase (LlGPx) overexpressed in L. lactis NZ9000, SeCys (0.9716∼1.6784 μg∙g−1), SeCys2 (1.0695∼1.2124 μg∙g−1), SeMeCys (0.7288∼0.7984 μg∙g−1) and SeMet (1.0058∼1.9571 μg∙g−1), accounting for up to 80.14% of total selenium. There was no difference of order of magnitude in the four Se-AAs, indirectly indicating the random incorporation of selenium into selenoprotein LlGPx in L. lactis NZ9000. This work throws new light on the identification and biosynthesis of organic selenium species in selenoproteins and selenium-riched organisms like L. lactis.

Organic selenium compounds determination in the complex matrix by the 1H-77Se HMBC method

The development of the organic Selenium (Se) speciation assay to evaluate Se-enriched yeasts (SeYs) with high selectivity and good sensitivity is highly desired. We investigated contents of three organic Se compounds with a proton-detected 1H-77Se multiple-bond correlation (1H-77Se HMBC) method in a complex yeast matrix. The method showed quantitative correlation peaks resulting by the long-range coupling (nJ(77Se,1H), n = 2, 3) between 1H and 77Se atoms. Broadband excitation and homonuclear coupling evolution suppression can be achieved by utilizing the shaped pulse in the 77Se dimension and the constant time period, respectively. Several NMR methods were compared to improve performances of the 1H-77Se HMBC method in sensitivity. The limit of quantifications (LOQs) were 0.10, 0.11, and 0.15 mmol/L for SeMet, MeSeCys and SeCys2, respectively. Furthermore, the method can greatly raise the resolution without any separation technique compared to other one- and two-dimensional NMR and chromatographic method. The validation of the methodology showed satisfactory specificity, accuracy, precision, and linearity. The method was suitable for routine analysis, quality control and market supervision of Se species in the enriched-Se yeast.

Expansion of the Conceptual Model for the Accumulation of Selenium in Lentic Food Chains to Include Redox-Controlled Generation and Diffusion of Selenite and Dissolved Organo-Selenium Compounds.

The controls governing the availability of reduced selenium (Se) species, namely selenite (Se[IV]) and dissolved organo-Se (DOSe), to primary producers at the sediment-water interface in depositional environments (i.e., lentic systems) were assessed through consideration of theoretical principles and field data. Selenite is generated in suboxic sediment porewater via the microbially mediated reduction of selenate (Se[IV]) and/or reductive dissolution of Se-bearing iron oxides. Field data for lentic environments demonstrate that the production of DOSe in sediment porewaters can also be redox- and depth-dependent. In this manner, the remobilization depths of Se(IV) and DOSe in depositional environments are dependent on the vertical redox gradient (dEh/dz), where deeper depths of remobilization are observed in less reducing sedimentary environments (lower dEh/dz). In turn, remobilization depth has a direct bearing on the concentration of dissolved Se(IV) and DOSe that may be realized at the sediment-water interface because the depth of reaction governs the diffusive path length, concentration gradient, and rate of diffusional transport toward the sediment-water interface. The principles that link sediment redox gradients, depth of remobilization, diffusive transport processes, and concentration of reduced Se species at the sediment-water interface have a direct bearing on the potential for Se uptake by primary producers in lentic food chains (e.g., phytoplankton, biofilms, bacteria). Overall, these processes complement the current conceptual "benthic detrital food chain" model that describes the accumulation of Se in lentic systems. Environ Toxicol Chem 2022;41:2859-2869. © 2022 SETAC.

Salsola soda as selenium biofortification crop under high saline and boron growing conditions.

In California, there is a shortage of good quality water available for irrigated agriculture due to severe drought. Consequently, saline groundwaters and drainage waters containing natural-occurring selenium (Se) and boron (B) salts are being considered as alternative sources of water for irrigation on salt and B tolerant crops like the edible halophyte-agretti (Salsola soda L.). In this multi-year field study, we evaluated agretti grown as a Se-biofortification crop in typical saline/B-laden soils (10 dS m−1 and 12 mg B/L) and irrigated with saline (3–8 dS m−1) and low-saline water (<1 d/S m) containing B (3–6 mg B/L) and Se (0.02–0.25 mg Se/L) at different evaporation transpiration (Eto) rates (100, 75, and 50 %, respectively). During the four-year study, fresh biomass yields ranged from 1 to 3 kg/m2 and were generally highest with irrigation at 100 % Eto with either saline or low-saline water. Tissue Se concentrations ranged from 2 to 3.2 mg Se / kg DW and 0.4–0.5 mg Se/kg DW with saline and low-saline irrigation, respectively. Selenium speciation in plant tissue showed the following: selenomethionine (SeMet) > selenate (SeO4) > methylselenocysteine (MeSeCys), irrespective of any treatment (i.e., year of planting, saline or low saline irrigation, rate of water application, direct seeding or transplanted). Agretti did not exhibit any toxicity symptoms as indicated by changes in total phenolic concentrations. Total phenolics ranged from 180 to 257 GAE/L and showed no significant differences among all treatments, although they were generally higher at the lowest water treatment (50% Eto). In regard to toxic ion accumulation, agretti tolerated excessive sodium (Na) and boron (B) and tissue concentrations ranging from 5.5 to 8.8% Na and 60 to 235 mg B/kg DW, respectively. Results from this multi-year study have identified a unique Se-biofortification strategy for producing Se-enriched agretti using saline, B- and Se-laden soil and irrigating with saline and low-saline water, respectively. Successful production of this crop may promote Se- biofortification strategies in poor quality regions where natural- occurring Se is present in soils and in waters used for irrigation.

Exceptional removal and immobilization of selenium species by bimetal-organic frameworks

Binary metallic organic frameworks can always play excellent functions for pollutants removal. One binary MOFs, UiO-66(Fe/Zr)), was newly synthesized and applied to remove aquatic selenite (SeIV) and selenate (SeVI). The adsorption behaviors and mechanisms were investigated using batch experiments, spectroscopic analyses, and theoretical calculations (DFT). The characterization results showed that the material inherited the topological structure of UiO-66 and excellent thermal stability. The large specific surface area (467.52 m2/g) and uniform mesoporous structures of the synthesized MOFs resulted in fast adsorption efficiency and high adsorption capacity for selenium species. The adsorbent kept high adsorption efficiency in a wide pH range from 2 to 11 with good anti-interference ability. The maximum adsorption capacity for Se(IV) and Se(VI) reached as high as 196 mg/g at pH 3 and 258 mg/g at pH 5, respectively. The process was conformed to fit pseudo-second-order kinetics and Langmuir isotherm, and could be explained by the formation of Fe/Zr-O-Se bond on the material surface, which was interpreted by the results of XPS, FTIR and DFT calculation. The regeneration and TCLP experiments demonstrated that UiO-66(Fe/Zr) could be regenerated for five cycles without obvious decrease of efficiencies, and the leaching rate of the adsorbed Se(IV) and Se(VI) in the spent adsorbent were only 4.8% and 2.3%. More than 99% of original Se(IV) and Se(VI) in the lake and tap water samples (1.0 mg/L of Se) could be removed in 2.0 h.

Association between selenium species and hippocampal volume in subjects with mild cognitive impairment

Association between selenium species and hippocampal volume in subjects with mild cognitive impairment

Soil and foliar selenium application: Impact on accumulation, speciation, and bioaccessibility of selenium in wheat (Triticum aestivum L.).

A comprehensive study in selenium (Se) biofortification of staple food is vital for the prevention of Se-deficiency-related diseases in human beings. Thus, the roles of exogenous Se species, application methods and rates, and wheat growth stages were investigated on Se accumulation in different parts of wheat plant, and on Se speciation and bioaccessibility in whole wheat and white all-purpose flours. Soil Se application at 2 mg kg–1 increased grains yield by 6% compared to control (no Se), while no significant effects on yield were observed with foliar Se treatments. Foliar and soil Se application of either selenate or selenite significantly increased the Se content in different parts of wheat, while selenate had higher bioavailability than selenite in the soil. Regardless of Se application methods, the Se content of the first node was always higher than the first internode. Selenomethionine (SeMet; 87–96%) and selenocystine (SeCys2; 4–13%) were the main Se species identified in grains of wheat. The percentage of SeMet increased by 6% in soil with applied selenite and selenate treatments at 0.5 mg kg–1 and decreased by 12% compared with soil applied selenite and selenate at 2 mg kg–1, respectively. In addition, flour processing resulted in losses of Se; the losses were 12–68% in white all-purpose flour compared with whole wheat flour. The Se bioaccessibility in whole wheat and white all-purpose flours for all Se treatments ranged from 6 to 38%. In summary, foliar application of 5 mg L–1 Se(IV) produced wheat grains that when grounds into whole wheat flour, was the most efficient strategy in producing Se-biofortified wheat. This study provides an important reference for the future development of high-quality and efficient Se-enriched wheat and wheat flour processing.

FeSe/FeSe2 Heterostructure as a Low‐Cost and High‐Performance Electrocatalyst for Oxygen Evolution Reaction

AbstractA key consensus of implementing large‐scale water splitting is developing highly efficient, durable, and earth‐abundant electrocatalysts for oxygen evolution reaction (OER). In recent years, the Fe‐based materials used in OER have attracted researchers’ great attention around the globe, and Fe has been identified as the OER active sites. In this study, we firstly synthesized the coral‐like FeSe/FeSe2 heterostructure catalyst via a one‐pot solvothermal method. We demonstrated that different components of FeSe/FeSe2 heterostructure can facilitate the electron transfer process of the system, where a high Fe charge state promotes OER performance, rendering the coral‐like FeSe/FeSe2 heterostructure to be more promising Fe‐based electrocatalyst for oxygen evolution reaction in alkaline. As expected, the as‐prepared FeSe/FeSe2 heterostructure with highly charged iron and negatively charged selenium species exhibited better OER performance and needed only an overpotential of 309 mV to achieve an anodic current density of 10 mA cm−2. In addition, the catalyst had quick kinetics and good durability in alkaline medium. The present study would open up a potential avenue for the development of highly active non‐noble‐metal electrocatalysts.

Speciation of Selenium in Selenium-Enriched Foods by High-Performance Liquid Chromatography-Inductively Coupled Plasma-Tandem Mass Spectrometry

Herein, a method was established for the speciation of six selenium species by high performance liquid chromatography-inductively coupled plasma-tandem mass spectrometry (HPLC-ICP-MS/MS). The factors affecting separation were carefully investigated, including ionic strength, pH, and methanol content. Six species of selenium could be completely separated within 20 min, under the mobile phase of 25 mM citric acid in pH = 4.0 containing 2% methanol. The detection limits of selenite (Se(IV)), selenate (Se(VI)), selenomethionine (SeMet), selenocystine (SeCys2), methylselenocysteine (MeSeCys), and selenoethionine (SeEt) were 0.04, 0.02, 0.05, 0.02, 0.03, and 0.15 ng mL−1, respectively. To verify the practicality of this method, the analysis of selenium-enriched foods such as selenium-enriched spring water, selenium-enriched salts, and selenium-enriched tea were conducted, and recovery of 93.7–105% was achieved with RSD &lt; 5%, revealing the high practical utility of the proposed method.

Reactive sulfur and selenium species in the regulation of bone homeostasis.

Reactive oxygen species (ROS) are important modulators of physiological signaling and play important roles in bone tissue regulation. Both reactive sulfur species (RSS) and reactive selenium species (RSeS) are involved in ROS signaling, and recent work suggests RSS and RSeS involvement in the regulation of bone homeostasis. For example, RSS can promote osteogenic differentiation and decrease osteoclast activity and differentiation, and the antioxidant activity of RSeS play crucial roles in balancing bone remodeling. Here, we outline current research progress on the application of RSS and RSeS in bone disease and regeneration. Focusing on these investigations, we highlight different methods, tools, and sources of RSS and RSeS, and we also highlight future opportunities for delivery of RSS and RSeS in biological environments relating to bone.

Desorption characteristics of selenium and tellurium thin films

The temperature-dependent desorption behavior of selenium and tellurium is investigated using a heated quartz crystal microbalance. Prior to heating the quartz crystal microbalance, selenium and tellurium films with varying thickness were deposited using thermal effusion cells in a molecular beam epitaxy system for subsequent determination of temperature-dependent mass loss of the deposited films. The desorption rate for tellurium was found to exhibit one sharp peak around 190 °C, indicating the loss of the entire film irrespective of film thickness within a temperature window of 20 °C, which was completely evaporated at 200 °C. Similar experiments for selenium revealed that the thermal desorption took place via a two-stage process with a smaller portion of the material desorbing within an even narrower temperature window of 5 °C at a much lower peak temperature of 65 °C, while most selenium desorbed within a temperature range of 10 °C around 90 °C. This two-stage behavior indicated the presence of at least two chemically distinct selenium species or binding states. The direct and quantitative determination of the chalcogen desorption process provides important insights into the kinetics of chalcogenide-based film growth and is in addition of applied benefit to the research community in the area of Se/Te capping and decapping of air sensitive materials as it provides temperature ranges and rates at which full desorption is achieved. Our work furthermore points toward the need for a more detailed understanding of the chemical composition state of atomic and molecular beams supplied from thermal evaporation sources during growth.

Multi-commutated flow system for inorganic selenium speciation in infusion tea samples by chemical vapor generation atomic fluorescence spectrometry

This work proposes an automated strategy for the inorganic selenium speciation in infusion tea samples, employing an MSFIA-CVG-AFS system and sodium tetrahydroborate for chemical vapor generation. The selenium total is determined after an online prereduction step of selenium (VI) to selenium (IV) in alkaline media, using a UV reactor with a 15 W Hg lamp. Selenium (IV) is quantified directly on the sample, and selenium (VI) is determined by the difference between the total selenium and selenium (IV) concentrations. The optimization of the chemical parameters: hydrochloric acid – hydrobromide acid solution concentration, potassium iodide concentration, sodium hydroxide concentration, and sodium tetrahydroborate concentration was performed using a (24−1) two-level fractional factorial design. The validation parameters were determined for total selenium and selenium (IV), and the results found were: limits of detection and quantification of 0.05 and 0.18 μg L−1, respectively; a linear range of 0.18–5.0 μg L−1, precision expressed as the relative standard deviation of 2.1% for a sample number of 10, for both analytes. The system allows the speciation analysis with an injection throughput of 15 injections per hour. This analytical method was applied for inorganic selenium speciation in nine infusions of tea samples purchased commercially in supermarkets in Palma de Mallorca City, Spain. The concentrations of selenium (IV) and total selenium varied from 0.2 to 0.6 μg L−1 and 0.4–2.0 μg L−1, respectively. The accuracy method was evaluated using spike tests, and the recoveries achieved varied from 91 to 111%.