Total content of As,Sb, Se,Te and Bi in Spanish vegetables,cereals and pulses and estimation of the contribution of these foods to the Mediterranean daily intake of trace elements

As, Sb, Se, Te and Bi were quantified in vegetables, pulses and cereals, in order to increase the available information on the presence of these elements in the Mediterranean daily intake. Samples were dry ashed and the ashes dissolved with diluted HCl. Hydride generation atomic fluorescence spectrometry was used for quantification. Limits of detection (LOD) ranged from 0.2 to 1.7 ng g⁻¹ and the accuracy was assessed by the analysis of three certified reference materials, Rice Flour (NIST 1568a), Tomato Leaves (NIST 1573) and Cabbage (IAEA 359). Good concordance between results found and certified values were always observed. As, Sb, Se, Te and Bi levels varied in samples analysed from values under the LOD till 1001, 47, 270, 104 and 48 ng g⁻¹, respectively.     

Selenium species in leaves of chicory,dandelion, lamb’s lettuce and parsley

Lamb’s lettuce, dandelion, parsley and four cultivars of chicory were cultivated aeroponically for 41 days with nutrient solution containing 7  mg Se/L in the form of Na₂SeO₄. Se compounds were determined by high performance liquid chromatography–ultraviolet treatment–hydride generation atomic fluorescence spectrometry (HPLC–UV–HG-AFS) in the green parts of the selected plants. Se species were extracted by water and by enzymatic hydrolysis with Protease XIV. Separation of Se^IV, Se^VI, SeMet, SeMeSeCys and SeCys₂ was made by a combination of anion and cation exchange chromatography in which the columns were connected on-line to a UV–HG-AFS detection system. Se accumulated efficiently in plant leaves up to 480 μg/g dry mass, mostly as Se^VI, i.e. the form of Se in the nutrient solution. Beside inorganic Se, selenomethionine (6–21%), selenomethylselenocysteine (0.5–4.4%) and selenocistine (<DL-0.8%) were determined in the extracts after enzymatic hydrolysis. Some unidentified peaks were also observed in the chromatograms.     

Accumulation and species distribution of selenium in Se-enriched bacterial cells of the Bifidobacterium animalis 01

Bifidobacterium animalis 01 (B. animalis 01) could absorb 16.7–39.6% of inorganic selenium in the medium and transform most of it into organic selenium. Most of the organic selenium (50.7–63.0%) was found in the protein fraction, 9.62–18.7% in the polysaccharide fraction, 0.273–0.754% in the nucleic acid fraction, and 20.8–30.9% in other components. Furthermore, the selenium content of different protein extractions was in the following order: Alkaline-soluble protein-bound Se (46.5–53.4%) > Water-soluble protein-bound Se (27.4–30.8%) > Salt-soluble protein-bound Se (7.79–11.9%) > Alcohol-soluble protein-bound Se (not detected). Additionally, the molecular mass of most proteins or protein subunits containing selenium was about 10–20 kDa. Analysis by LC–MS showed that selenomethionine (SeMet) is the major selenocompound in protein.     

Determination of 5 natural selenium species in selenium-enriched bamboo shoots using LC-ICP-MS

A method for simultaneous determination of the selenium species methylselenocysteine (MeSeCys), selenocysteine (SeCys₂), selenite (SeIV), selenomethionine (SeMet), and selenates (SeVI) in natural selenium-enriched bamboo shoots was developed. Samples were extracted using sonication with a solution of pepsin. Different selenium species were separated using an anion exchange column with isocratic elution and a citric acid mobile phase at pH 4.7. Separated selenium species were detected as ⁸⁰Se using inductively coupled plasma mass spectrometry (ICPMS) in dynamic reaction cell (DRC) gas mode. The method achieved acceptable quantitative recoveries of 73.9 to 113.4% with relative standard deviations of <5%. The limits of detection were 1, 2, 2, 3, and 3 μg/kg (fresh weight) for SeCys₂, Se, MeSeCys, SeMet, and Se, respectively. The method was simple, rapid, accurate, and useful for determination of selenium species in natural selenium enriched bamboo shoots.     

Fast determination of arsenic,selenium, nickel and vanadium in fish and shellfish by electrothermal atomic absorption spectrometry following ultrasound-assisted extraction

Ultrasound-assisted extraction of As, Se, Ni and V from fish and shellfish has been applied as a fast and reliable sample pre-treatment method for accurate determination of the four elements by electrothermal atomic absorption spectrometry with Zeeman (As, Se) or Deuterium (Ni, V) background correction. A multivariate optimization approach has been employed for establishing the effect of variables influencing the extraction process. Under suitable conditions, quantitative extractions occurred from a 10 mass sample (particle size <100 μm) suspended in 1.5 mL of acidic extractant (0.5 or 3% v/v HNO₃) and subjected to high intensity ultrasound (50% amplitude; 3 min). The method was successfully validated against the following certified reference materials: NRCC-DORM-2 dogfish muscle, NRCC-DOLT-2 dogfish liver, NRCC-TORT-2 lobster hepatopancreas, NIST-SRM 1566b oyster tissue and BCR 627 tuna fish. The following seafood samples were analyzed: hake (Merluccius merluccius), sole (Solea solea), clam (Venerupis rhomboides), prawn (Panaeus kerathurus), cuttlefish (Sepia officinalis), shrimp (Palaemon elegans), razor shell (Ensis ensis), cockle (Cardium edule), Mussel (Mytilus galloprovincialis), edible crab (Cancer pagurus), meagrin (Lepidorhombus whiffiagonis). The concentration ranges (μg/g, dry weight) for the elements determined were as follows: As (12.6–190), Se (0.73–2.34), Ni (2.94–46) and V (0.82–5.14). The detection limits (LODs), defined as 3s/m (s being the standard deviation of 10 blank and m the slope of the calibration graph), in dry tissue were 0.6, 0.3, 0.2 and 0.4 μg/g for As, Se, Ni and V, respectively. Between-batch precision was expressed as relative standard deviation from three separate extractions was in the range 3–10%.     

Chemical characterisation and speciation of organic selenium in cultivated selenium-enriched Agaricus bisporus

The selenium concentration in Agaricus bisporus cultivated in growth compost irrigated with sodium selenite solution increased by 28- and 43-fold compared to the control mushroom irrigated solely with water. Selenium contents of mushroom proteins increased from 13.8 to 60.1 and 14.1 to 137 μg Se/g in caps and stalks from control and selenised mushrooms, respectively. Selenocystine (SeCys; detected as [SeCys]₂ dimer), selenomethionine (SeMet), and methyl-selenocysteine (MeSeCys) were separated, identified and quantified by liquid chromatography–electrospray ionisation-mass spectrometry from water solubilised and acetone precipitated proteins, and significant increases were observed for the selenised mushrooms. The maximum selenoamino acids concentration in caps and stalks of control/selenised mushrooms was 4.16/9.65 μg/g dried weight (DW) for SeCys, 0.08/0.58 μg/g DW for SeMet, and 0.031/0.10 μg/g DW for MeSeCys, respectively. The most notable result was the much higher levels of SeCys accumulated by A. bisporus compared to SeMet and MeSeCys, for both control and selenised A. bisporus.     

Extraction of Se species in buckwheat sprouts grown from seeds soaked in various Se solutions

The transformation of selenium (Se) in buckwheat sprouts grown from seeds soaked in various Se solutions (Se-methionine (10 mg Se L⁻¹), selenate or selenite (5, 10, 20 mg Se L⁻¹)) was investigated. The extraction procedure was optimised by (a) using optimal extraction media (water, phosphate buffer, 0.1, 0.2, 0.3 M HCl, the enzyme protease alone or in combination with cellulase, amylase or lipase), and by (b) optimising the ratio between sample and enzyme. For Se speciation analysis extracts with the highest percentage of soluble Se were analysed, and additionally the stability of the extracts was investigated. The results showed that uptake of Se by sprouts was dependent on the form and concentration of Se in the solution used for soaking. Optimal extraction efficiencies were obtained by hydrolysis with 0.3 M HCl and protease. Selenate (23.7–29.7% from Se(VI) sprouts and in trace amounts from Se(IV) and SeMet sprouts), Se-methionine (2.4–7.9%) and selenite (traces) were detected in all supernatants, regardless of soaking solution.     

Bio-fortification and isotopic labelling of Se metabolites in onions and carrots following foliar application of Se and Se

The aims were to bio-fortify onions by foliar application of selenium (Se) and to intrinsically label bioactive Se-metabolites in onion and carrot by enriched, stable ⁷⁷Se for use in human physiological studies. Onion bulbs and leaves were enriched in Se by repeated foliar spraying of 10 or 100 μg Se ml⁻¹ solutions of sodium selenite (Se(IV)) or sodium selenate (Se(VI)). ICP-MS analysis of onion leaves and bulbs showed that the Se concentration was enhanced by up to a factor of approximately 50 and 200 in bulbs and leaves, respectively. HPLC–ICP-MS analysis of proteolytic plant extracts showed that foliar application of Se(IV) gave rise to bio-synthesis of a higher fraction of the desired organic Se species and was better tolerated by the plants than Se(VI). Based on these findings onions and carrots were bio-fortified by foliar application of a solution of ⁷⁷Se(IV) that was enriched to 99.7% as ⁷⁷Se. The ⁷⁷Se- labelled metabolites in onions were predominantly γ-glutamyl-⁷⁷Se-selenomethyl-selenocysteine (γ-glu-Me⁷⁷SeCys), ⁷⁷Se-methylselenocysteine (Me⁷⁷SeCys) and ⁷⁷Se-selenomethionine (⁷⁷SeMet). Furthermore, we report here for the first time the finding in carrots of the bioactive Me⁷⁷SeCys, the identity of which was verified by HPLC–ESI-MS/MS.     

Enrichment of Pleurotus ostreatus mushrooms with selenium in coffee husks

Pleurotus ostreatus fungus forms an edible mushroom that possesses important nutritional and medicinal properties. Selenium (Se) is essential to human diets and it is in low concentration in the soil, and consequently in food. P. ostreatus was grown in coffee husks enriched with various concentrations of sodium selenite. The biological efficiency of P. ostreatus was affected by the addition of high concentrations of Se. The highest level of Se absorption was obtained by adding 51 mg kg¹ of sodium selenite. The mushrooms from first flush contained more Se than the further flushes. These results demonstrate the great potential of coffee husks in the production of Se-enriched mushrooms and show the ability of this fungus to absorb and biomagnify Se.     

转基因大豆对硒的富集作用和形态分布研究

目的研究转基因大豆对硒的富集作用以及富集前后转基因大豆中硒的形态分布和形态转化。方法 采用电感耦合等离子体质谱分析转基因大豆富集前后硒的总量,采用蛋白酶提取,高效液相色谱-电感耦合等离子体质谱(high performance liquid chromatography-inductively coupled plasma-mass spectrometry,HPLC-ICP-MS)联用技术分析转基因大豆中的硒酸盐(selenate,Se VI)、亚硒酸盐(selenite,Se IV)、硒代蛋氨酸(selenomethionine,Se Met)和硒代胱氨酸(selenocystine,Se Cys)等几种硒化合物。盆栽种植试验研究转基因大豆对硒的富集作用。通过对照试验,考察大豆植株不同部位总硒含量变化和形态分布的转化情况。结果转基因大豆对硒有较好的富集作用,吸收的亚硒酸盐在大豆植株中部分转化成了硒代蛋氨酸和硒代胱氨酸。结论 了解了转基因大豆的形态分布和转化情况,可以更好地评估转基因大豆的食用安全风险并进行生物利用开发。     

HPLC-ICP-MS在线联用分析食品中无机硒和硒氨基酸的形态

以亚硒酸盐（Se（Ⅳ））、硒酸盐（Se（Ⅵ））、硒胱氨酸（Se Cys₂）、硒蛋氨酸（Se Met）、甲基硒代半胱氨酸（Me Se Cys）和硒代乙硫氨酸（Se Et）为硒形态的目标分析物,采用Dionex Ion Pac AS11色谱柱（250 mm×4.0 mm）为分离柱,通过优化流动相的p H、浓度、甲醇含量、流速和色谱柱的柱温等因素对六种目标硒形态分离及不同提取方法对目标分析物提取效率的影响,建立了高效液相色谱-电感耦合等离子体质谱（HPLC-ICP-MS）在线联用同时测定食品中无机硒和硒氨基酸的分析方法。Me Se Cys、Se Met、Se Et、Se（Ⅳ）、Se Cys₂和Se（Ⅵ）的检出限分别为0.25、0.20、0.35、0.15、0.30、0.15μg Se/L;Me Se Cys和Se Cys₂的线性范围为2.0²500μg Se/L,Se（Ⅳ）和Se（Ⅵ）线性范围为1.2¹200μg Se/L,Se Met和Se Et的线性范围分别是1.5¹500μg Se/L和2.2²200μg Se/L,各硒形态的线性相关系数均不少于0.9997。将该方法应用于食品中硒形态的分析,其加标回收的回收率为80.8%¹06.7%,相对标准偏差（RSDs,n=3）为4.7%⁹.6%。方法具有操作简单、方便快速、灵敏度高和环境友好等优点,可满足食品中硒形态定量分析。      

Se improves indole glucosinolate hydrolysis products content, Se-methylselenocysteine content, antioxidant capacity and potential anti-inflammatory properties of sauerkraut

Selenium (Se) has a well-known role in prevention of chronic diseases associated with oxidative stress and inflammation. The objective was to produce Se-enriched sauerkraut and to study the effect of selenite addition on indole glucosinolate hydrolysis products, vitamin C, Se biotransformation and microbial quality. The antioxidant activity of sauerkraut and its ability to inhibit NO production in LPS-induced macrophages were also examined. White cabbage was naturally fermented with 0.3 mg of Na₂SeO₃/kg fresh cabbage (NFSe) or without Se addition (NF). Total Se content reached up to 1.29 μg/g d.m. (0.11 μg/g f.m.). Selenomethylselenocysteine was the major Se form found in NFSe cabbage. Se addition caused a slight reduction of ascorbigen (6%) and vitamin C (5%) contents in sauerkraut (P ? 0.05); however, lactic acid bacteria increased (3%), and the formations of indole-3-carbinol and indole-3-acetonitrile were markedly enhanced (74% and 13%, respectively). NFSe cabbage extracts showed higher (P ? 0.05) antioxidant activity (163 μmol trolox/g d.m.) and inhibition of NO production in LPS-induced macrophages (IC₅₀ = 44.0 μg/ml) than did NF cabbage extracts. Consequently, Se-enriched sauerkraut can be considered as a health-promoting food.     

Selenium concentration in St. John’s wort (Hypericum perforatum L.) herb after foliar spraying of young plants under different UV-B radiation levels

St. John’s wort (Hypericum perforatum L.) was grown under different levels of UV-B radiation, with selenium (10 mg l⁻¹ Se applied by foliar spraying in the form of sodium selenate) or without foliar Se application. The different levels of UV-B radiation comprised an enhanced level simulating 17% ozone depletion, ambient level, and a reduced level of UV-B radiation. The concentration of Se in unsprayed plants was from 20 ng g⁻¹ to 120 ng g⁻¹. The concentration of Se in the organs of plants foliarly sprayed with Se ranged from 1000 ng g⁻¹ to 12,000 ng g⁻¹, the highest concentration being detected in plants grown under reduced levels of UV-B radiation. Foliar application of Se fertiliser is feasible and effective in St. John’s wort and results in Se-enriched nutritional supplements.     

Determination of sub-ng g–1 levels of total inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry after pre-concentration

ABSTRACT

A new and simple ultrasonic-assisted extraction (UAE) procedure was developed for the determination of inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry (HG-AAS). The various analytical variables affecting complex formation and extraction efficiency were investigated and optimised. The method is based on selective complex formation of As(III) and Se(IV) in the presence of excess As(V) and Se(VI) with toluidine red in the presence of tartaric acid at pH 4.5, and then extraction of the resulting condensation products into the micellar phase of non-ionic surfactant, polyethylene glycol dodecyl ether, Brij 35. Under optimised conditions, good linear relationships were obtained in the ranges of 4–225 and 12–400 ng l^–1 with limits of detection of 1.1 and 3.5 ng l^–1 for As(III) and Se(IV), respectively. The repeatability was better than 3.9% for both analytes (n = 10, 25 ng l^–1) while reproducibility ranged from 4.2% to 4.8%. The recoveries of As(III) and Se(IV) spiked at 25–100 ng l^–1 were in the range of 94.2–104.8%. After pre-concentration of a 5.0 ml sample, the sensitivity enhancement factors for As(III) and Se(IV) were 185 and 140, respectively. Accuracy was assessed by analysis of two standard reference materials (SRMs) and spiked recovery experiments. The method was successfully applied to the accurate and reliable determination of total As and total Se by HG-AAS after pre-reduction with a mixture of L-cysteine and tartaric acid. Finally, the method was shown to be rapid and sensitive, with good results for extraction, pre-concentration and determination of total As and Se contents (as As(III) and Se(IV)) from food samples.     

Simultaneous multi-channel hydride generation atomic fluorescence spectrometry determination of arsenic,bismuth, tellurium and selenium in tea leaves

A novel, rapid and sensitive method for the simultaneous multi-channel hydride generation atomic fluorescence spectrometry (HG-AFS) determination of total arsenic (As), total bismuth (Bi), total tellurium (Te) and total selenium (Se) in tea leaves was proposed. The operating parameters of self-made multi-channel HG-AFS were optimised, including negative high voltage of photo multiplier tube (PMT), the flow rates of carrier and shield gas, observation height and lamp currents. The conditions of hydride generation for As, Bi, Te and Se were studied in details. Under optimal conditions, the method detection limits (MDL) for As, Bi, Te and Se in tea leaves were 0.0152 μg g⁻¹, 0.0080 μg g⁻¹, 0.0022 μg g⁻¹ and 0.0068 μg g⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of As, Bi, Te and Se in various tea leaves and the spike recoveries were in the range of 90–103%. The accuracy of method was validated by analysing a tea certified reference material. The obtained values were consistent with the certified ones.     

Speciation of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry after cloud point extraction

A new method was developed for the determination of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry detection after cloud point extraction. Effective separation of organic and inorganic selenium in selenium-enriched rice was achieved by sequentially extracting with water and cyclohexane. Under the optimised conditions, the limit of detection (LOD) was 0.08 μg L⁻¹, the relative standard deviation (RSD) was 2.1% (c = 10.0 μg L⁻¹, n = 11), and the enrichment factor for selenium was 82. Recoveries of inorganic selenium in the selenium-enriched rice samples were between 90.3% and 106.0%. The proposed method was successfully applied for the determination of organic and inorganic selenium as well as total selenium in selenium-enriched rice.     

Tungsten permanent chemical modifier with co-injection of Pd(NO3)2 + Mg(NO3)2 for direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry

A tungsten carbide coating on the integrated platform of a transversely heated graphite atomizer (THGA^®) used together with Pd(NO₃)₂ + Mg(NO₃)₂ as modifier is proposed for the direct determination of lead in vinegar by graphite furnace atomic absorption spectrometry. The optimized heating program (temperature, ramp time, hold time) of atomizer involved drying stage (110 °C, 5 s, 30 s; 130 °C, 5 s, 30 s), pyrolysis stage (1000 °C, 15 s, 30 s), atomization stage (1800 °C, 0 s, 5 s) and clean-out stage (2450 °C, 1 s, 3 s). For 10 μL of vinegar delivered into the atomizer and calibration using working standard solutions (2.5–20.0 μg L⁻¹ Pb) in 0.2% (v/v) HNO₃, analytical curve with good linear correlation (r = 0.9992) was established. The characteristic mass was 40 pg Pb and the lifetime of the tube was around 730 firings. The limit of detection (LOD) was 0.4 μg L⁻¹ and the relative standard deviations (n = 12) were typically <8% for a sample containing 25 μg L⁻¹ Pb. Accuracy of the proposed method was checked after direct analysis of 23 vinegar samples. A paired t-test showed that results were in agreement at 95% confidence level with those obtained for acid-digested vinegar samples. The Pb levels varied from 2.8 to 32.4 μg L⁻¹. Accuracy was also checked by means of addition/recovery tests and recovered values varied from 90% to 110%. Additionally, two certified reference materials were analyzed and results were in agreement with certified values at a 95% confidence level.     

Determination of selenium content in selected Pakistani foods

Owing to increased concern in a number of diseases associated with low-selenium (Se) foods, the estimation of total Se content (TSC) is the focus of research these days. TSC was determined in fruits, vegetables, meat, milk, poultry, fish and cereals. Hydride generation atomic absorption spectrometric method was employed using the wet digestion method. Different certified reference materials were used for the validation of the method. The lowest Se content was found in plant-based foods, whereas the highest was in fish and appreciable in other animal-based foods. The data was compared with TSC data from other countries. TSC in Pakistani foods was comparable with other countries, with few exceptions. This report may serve as a database for TSC in Pakistani foods.     

Uptake of the cyanobacterial toxin cylindrospermopsin in Brassica vegetables

Toxin-producing cyanobacterial species are increasingly being found in freshwater systems. However, literature on the impact of many cyanobacterial toxins on plants is scarce. Cylindrospermosin (CYN), a secondary metabolite of cyanobacteria such as Cylindrospermopsis and Aphanizomenon species, is a potent hepatotoxin and protein synthesis inhibitor. Worryingly, CYN is increasingly found in surface and drinking water worldwide causing human and animal intoxications. Further, exposure of crop plants to CYN by irrigation with contaminated water has already been shown. Therefore, in this study, horticulturally important and highly consumed Brassica species were investigated to determine the level of CYN in the leaves after exposure of the roots to the toxin. Treatment of Brassica oleracea var. sabellica, Brassica juncea, and Sinapis alba under varying experimental conditions showed significant CYN uptake, with CYN levels ranging from 10% to 21% in the leaves compared to the CYN concentration applied to the roots (18–35 μg/l). In seedlings, CYN concentrations of up to 49 μg/g fresh weight were observed. Thus, crop plants irrigated with CYN-containing water may represent a significant source of this toxin within the food chain.