Determination of Inorganic Selenium Species in Dietary Supplements by Hyphenated Analytical System HPLC-HG-AAS

Construction and optimisation of a hyphenated analytical system for high performance liquid chromatography with hydride generation atomic absorption spectrometry detection system are described together with results of its use for investigation of food products. The use of anion-exchange chromatographic column permitted separation of inorganic selenium species Se(IV) and Se(VI) at the limit of detection of 10?ng?mL^?1 for both species. The analytical system was used for determination of selenium species in dietary supplements available on the Polish market. The content of inorganic selenium species was found not to exceed 50% of its total content, and in the majority of products, the dominant species was Se(IV). In the majority of products, the total contents of selenium were close to those declared by the producers.     

Selenium species in buckwheat cultivated with foliar addition of Se(VI) and various levels of UV-B radiation

Common (Fagopyrum esculentum Moench) and tartary (Fagopyrum tataricum Gaertn.) buckwheat was treated by spraying the leaves with a water solution containing 15 mg Se per litre in the form of sodium selenate in the flowering period. The selenium content in all parts of plant was found to be less than 200 ng g⁻¹ in non-treated and in the range 2700–4650 ng g⁻¹ in selenium treated buckwheat. Exposure to UV-B radiation lead to higher Se accumulation in flowers of both Se enriched cultivars. For speciation analysis enzymatic hydrolysis was carried out, separation and detection of selenium species was performed by high performance liquid chromatography–ultraviolet treatment–hydride generation atomic fluorescence spectrometry (HPLC–UV–HG-AFS). In flowers and leaves, on average 11% of the Se content was soluble and in the form of Se(VI), representing between 0.6% (flowers) and 3% (leaves) of the Se content. The remaining soluble non-amino acid organic Se was not detected by HPLC–UV–HG-AFS. In seeds 93% of the selenium content was found in the extracts and the main selenium species was SeMet with 93 ± 5% relative to the selenium content.     

Combined speciation analysis by X-ray absorption near-edge structure spectroscopy, ion chromatography, and solid-phase microextraction gas chromatography-mass spectrometry to evaluate biotreatment of concentrated selenium wastewaters

In this study we evaluate the potential of anaerobic granular sludge as an inoculum for the bioremediation of selenium-contaminated waters using species-specific analytical methods. Solid species formed by microbial reduction were investigated using X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K-edge. Furthermore, dissolved selenium species were specifically determined by ion chromatography (IC) and solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). Least-squares linear combination of the XANES spectra for samples incubated with the highest selenate/selenite concentrations (10(-3) M) show the predominance of elemental selenium and a Se(-I) selenide, such as ferroselite, the thermodynamically most stable iron selenide. In contrast, elemental selenium and Se(-II) selenides are the main species detected at the lower selenate/selenite concentrations. In each repeated fed batch incubation, most aqueous selenite anions were converted into solid selenium species, regardless of the type of electron donor used (acetate or H(2)/CO(2)) and the selenium concentration applied. On the other hand, at higher concentrations of selenate (10(-4) and 10(-3) M), significant amounts of the oxyanion remained unconverted after consecutive incubations. SPME-GC-MS demonstrated selenium alkylation with both electron donors investigated, as dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe). Selenite was even more alkylated in the presence of H(2)/CO(2) (maximum 2156 μg of Se/L of DMSe + DMDSe) as compared to acetate (maximum 50 μg of Se/L). In contrast, selenate was less alkylated using both electron donors (maximum 166 and 3 μg of Se/L, respectively). The high alkylation potential for selenite limits its bioremediation in selenium laden waters involving H(2)/CO(2) as the electron donor despite the fact that nontoxic elemental selenium and thermodynamically stable metal selenide species are formed.     

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。     

Heavy metals in edible mushrooms in Italy

The distribution of arsenic, cadmium, lead, mercury, and selenium was investigated in 1194 samples of 60 species of common, edible mushrooms collected mainly in the province of Reggio Emilia, Italy. The quantitative determination of heavy metals (mg/kg dry weight) was carried out by spectrophotometry, with the exception of Hg, which was determined by atomic absorption spectroscopy.     

Selenium uptake and species distribution in selenium-enriched bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) seeds obtained by two different cultivations

In this work, bean plants were cultivated in two different ways using two modes of selenium supplementation in the form of sodium selenate. Each group consisted of the same four cultivars. Group A plants were grown in soil and twice foliarly sprayed at an interval of 10 days with an aqueous solution of 10 mg Se L⁻¹ at flowering time. Group B plants were hydroponically cultivated after the maternal seeds were soaked in nutrient solution containing the same Se content as used for foliar fertilisation. Bean seeds obtained from group A plants accumulated much more Se (around 2 μg g⁻¹ dry weight) than those seeds obtained from group B plants (around 0.6 μg g⁻¹ dry weight). No differences in Se content within each group were found. After enzyme hydrolysis, 85±7% of soluble selenium was found in group A and 65±2% of soluble Se in group B with respect to the total Se content in seeds. In bean seed supernatants SeMeSeCys, SeMet and two unknown species were found. These four species together represented 79±8 and 53±9% of the Se mass fraction of group A and group B, respectively. No differences in the presence of selenium species were found between the four cultivars and cultivation conditions.     

Current knowledge in species-related bioavailability of selenium in food

Selenium is an essential trace element that has raised interest because of its antioxidant and anticancer properties. The beneficial or toxic effect of Se is not only dose-dependent, but also relates to the chemical form of the element and its bioavailability. In this review, recently published data is summarised concerning both Se speciation and Se relative bioavailability in various foodstuffs. In addition, Se bioavailability is discussed in relation to the species-dependent metabolism in humans. In this way, the understanding of the potential health impact of Se species in commonly consumed food is aimed to be improved. It is strongly suggested on the basis of a higher retention and a lower toxicity, that organic Se (especially SeMet, the major species in food) is more recommendable than inorganic Se in the frame of a balanced diet. Further research is however desirable concerning the characterisation of unidentified Se species and determination of their health effects.     

Selenium content in the pilchard of the Adriatic Sea

The selenium content was determined in the muscle tissue (M. longissimus dorsi) of the pilchard (Clupea pilchardus). The fishes originated from catches at two localities, the mid-and northern Adriatic Sea, during two seasons—spring and autumn. The selenium content was determined by the hydride procedure of atomic absorption spectrophotometry, with the results being expressed as wet weight (ww). Four groups of the analysed samples indicated differences in the selenium content, depending on the location and time (season) of the catch. The highest selenium content was found in the pilchard of the mid-Adriatic Sea in spring (712.7 ±23.7 ng/g wet weight) and the lowest in the pilchard of the northern Adriatic Sea caught in autumn (472.7± 34.7 ng/g ww.). Regardless of seasonal differences and/or geographical aspects, the pilchard of the Adriatic Sea contains on average 580 ng Se/g ww and may be considered a significant source of this essential micronutrient.     

Selenium contents of Portuguese commercial and wild edible mushrooms

The selenium contents of 66 mushroom samples, wild growing or commercially available in Portugal, fresh, canned or dried, were determined. The samples consisted of 18 mushroom species, mainly selected in accordance with their availability and consumer preference. The selenium contents varied considerably between different mushroom species. The highest selenium contents were found in the wild species Boletus aestivalis (48.5 mg/kg dry weight, DW), Boletus pinophilus (19.9 mg/kg DW), Boletus edulis (14.9 mg/kg DW), Boletus aereus (12.3 mg/kg DW), Boletus fragans and Boletus spretus (∼2 mg/kg DW). Other mushrooms having considerable selenium contents included Marasmius oreades (1.5 mg/kg DW), Agaricus bisporus “Portobello” (1.25 mg/kg DW), A. bisporus (1.0 mg/kg DW) and Russula cyanoxantha (0.72 mg/kg DW). The selenium contents of these mushrooms are sufficient to provide nutritionally significant amounts in relation to the total daily intake of selenium. Other edible mushrooms, such as Lentinula edodes, Pleurotus ostreatus, Cantharellus cibarius,Craterellus cornucopioides and Lepista nuda, contained only small amounts of selenium. The importance of these mushrooms as a source of selenium is therefore marginal.     

Detection of irradiation treatment in dried mushrooms by photostimulated luminescence,EPR spectroscopy and thermoluminescence measurements

Detection of the irradiation treatment of nine species of dried mushrooms commercially available employing photostimulated luminescence (PSL), electron paramagnetic resonance spectroscopy (EPR/ESR) and thermoluminescence (TL) is described. PSL is adaptable to six to seven species shortly after irradiation, but the PSL signal decays with storage and may render detection impossible. After 4 months of storage, six species could still be well identified by PSL if the radiation dose was higher than 5 kGy. EPR spectroscopy enabled detection with five to six species, both cellulose and crystalline sugar-like radicals being observed. For some mushrooms, hat or leg parts showed a different response and some lots could not be identified at all. TL - although being more cumbersome - allowed unequivocal identification of all species of investigated mushrooms. It is concluded that dried mushrooms exposed to ionising radiation can be successfully detected by at least one of the analytical methods investigated.     

野生蘑菇中多种元素含量及砷、硒形态分析技术研究

本文首先采用微波消解法对我国不同区域代表性的野生可食用蘑菇进行前处理,再通过电感耦合等离子体光谱和质谱法测定消解液中代表性元素含量并对部分元素进行形态分析。实验结果表明,通过电子耦合等离子体光谱检测常见元素(钾、钙、钠、镁、锌、锰、磷、铁和铜),检测的线性范围均为0～500 μg/mL, 得到的线性方程相关系数均大于0.999,各元素检出限在0.1~7 mg/kg之间;通过电感耦合等离子体光谱和质谱检测重金属元素(硼、铝、钛、钒、铬、钴、镍、砷、硒、锶、钼、镉、锡、锑、钡、汞、铊和铅),检测的线性范围为0~500 μg/mL,得到的线性方程相关系数均大于0.999,各元素检出限在0.0001~2 mg/kg之间;同时,确定了对砷和硒的形态分析前处理和检测方法,并分析无机砷和无机硒的占比,该方法能够满足日常分析检测,并为科学评价野生蘑菇中常见元素含量提供数据参考。     

食物中硒的研究进展

硒是一种人体必需的微量元素,其功效不仅与含量相关,而且与硒形态及其生物有效性相关。本文总结了硒的摄入量标准,论述了不同类型食物中硒总量和硒形态研究进展,以期为开发和利用富硒食物、合理指导硒营养摄入与补充提供参考。     

光谱分析技术在野生食用牛肝菌研究中的应用研究进展

牛肝菌具有重要的食药用和经济价值,是世界性美味野生食用菌。其质量安全可控是保障消费者健康及产业绿色持续发展的基础,建立全面、稳定、系统的质量评价方法有利于强化牛肝菌质量控制,对市场稳定发展具有重要意义。光谱分析技术具有简便、快速、实用性强等特点,能够弥补传统感官评定的缺陷,提高分析准确性,广泛用于牛肝菌品质研究,是评价牛肝菌品质优劣、鉴别真伪以及确保其质量稳定一致的重要技术支撑。本文对近年国内外光谱分析技术在野生食用牛肝菌研究方面的应用现状和进展进行综述,探讨了红外、紫外光谱及多光谱信息融合技术在牛肝菌产地、种类、贮藏年限鉴别评价等方面的应用前景,以期为牛肝菌的深入研究和合理开发利用提供参考。     

Dietary selenium intake influences Cx43 dephosphorylation, TNF-α expression and cardiac remodeling after reperfused infarction

Scope : Post‐infarct left ventricular dysfunction and cardiac remodeling are the primary causes of chronic heart failure in industrialized countries. In the present study, we examined the influence of dietary selenium intake on cardiac remodeling after reperfused myocardial infarction and explored one of the possible mechanisms. Methods and results : Rats were fed a diet containing either 0.05 mg/kg (Low‐Se, group of rats receiving the low‐selenium diet) or 1.50 mg/kg (group of rats receiving the high‐selenium diet) selenium. At the end of the 5th week of the diet, rats were subjected to transient (1 h) coronary ligation followed by 8 days of reperfusion. Infarct size and cardiac passive compliance were increased in the Low‐Se group compared with group of rats receiving the high‐selenium diet. Similarly, indices of cardiac remodeling (thinning index and expansion index) were more altered in Low‐Se hearts. These adverse effects of the Low‐Se diet on cardiac remodeling were accompanied by an increase in cardiac TNF‐α content, a decreased activity of antioxidant seleno‐enzymes and an increase in connexin‐43 dephosphorylation. Conclusion : Dietary selenium intake influences post‐infarct cardiac remodeling even when provided within the range of physiological values. Our data suggest that the cardioprotective effect of selenium might be mediated by a reduced oxidative stress, a lower connexin‐43 dephosphorylation, and a decreased TNF‐α expression.     

Fate of selenium in coal combustion: volatilization and speciation in the flue gas

In light of Title I of the Clean Air Act Amendments of 1990, selenium will most probably be considered for regulation in the electric power industry. This has generated interest for removing this element from fossil-fired flue gas. This study deals with coal combustion: selenium volatilization and its speciation in the cooled flue gas were investigated to better understand its chemical behavior to validate the thermodynamic approach to such complex systems and to begin developing emission control strategies. Se volatility is influenced by several factors such as temperature, residence time, fuel type, particle size, and Se speciation of the fuels, as well as the forms of the Se inthe spiked coal/coke. Spiked coke and coal samples were burned in a thermobalance, and atomic Se and its dioxide were identified in the cooled combustion flue gas by X-ray photoelectron spectroscopy (XPS). A thermodynamic calculation was applied to a complex system including 54 elements and 3,200 species that describes the coal combustion. Several theoretical predictions concerning Se behavior, such as its speciation in flue gas, agreed well with experiments, which supports using thermodynamics for predicting trace element chemistry in combustion systems.     

Selenium speciation in enriched vegetables

The ability of several plants to accumulate and transform inorganic forms of selenium into bioactive organic compounds has important implications for human nutrition and health. Se-enriched Allium group vegetables such as garlic, onion and ramps have been mainly the subject of several studies in the recent years. Apart from the total Se uptake, enrichment treatments normally undergo certain metabolic changes that determine the final product as well as its translocation and accumulation in different plant tissues. For this reason, it is important to find which form of selenium should be used for supplementation to obtain a high content of this element in the final plant. Moreover, its distribution in different parts of plants as well as characterisation and quantification of individual species becomes an issue. This review gives a brief, critical overview of the studies carried out to characterise selenium species produced by different enriched vegetables. The use of different extraction and clean-up methodologies will be discussed in conjunction with different selenium enrichment procedures.     

Selenium speciation studies in Se-enriched chives (Allium schoenoprasum) by HPLC-ICP–MS

In this study, three liquid chromatographic techniques were employed to better understand selenium species distribution in Chives (Allium schoenoprasum) separately grown in three different supplementation media Se(IV), Se(VI), and SeMet. The highest selenium accumulation up to 700 μg Se g⁻¹ was observed in the case of the Se(VI)-enriched samples on the basis of total selenium measurements. Size-exclusion chromatography (SEC-HPLC) was performed for investigation of selenium containing proteins in chives. For speciation of selenium containing amino acids, reversed-phase ion-pairing chromatography (RP-IP-HPLC) and for enantiomeric separations, a crown ether column was used. In all three cases online detection with inductively coupled plasma mass spectrometry was performed for selenium specific detection. Two extractions (perchloric acid–ethanol and enzymatic) were carried out on chive samples. Speciation analysis on the chives grown in three different media revealed that selenium distribution among different forms of amino acids in the sample strongly depends on the type of enrichment employed. Enrichment with Se(VI) leads to accumulation of selenium in inorganic forms, while in case of Se(IV) and SeMet-enriched samples, methyl-selenocysteine and selenocystine were found to be present. Not surprisingly, chiral speciation revealed the presence of the l-enantiomeric forms of selenoamino acids in the sample. The major enantiomer found in the perchloric acid–ethanol extracts was l-MeSeCys, while in the enzymatic extracts l-SeMet was also detected.     

Speciation of selenium in selenium-enriched seeds,buckwheat (<Emphasis Type="Italic">Fagopyrum esculentum</Emphasis> Moench) and quinoa (<Emphasis Type="Italic">Chenopodium quinoa</Emphasis> Willdenow)

Buckwheat (Fagopyrum esculentum Moench) and quinoa (Chenopodium quinoa Willdenow) are widely used as food ingredients. The nutritional characteristics of these plants, i.e., high contents of proteins and amino acids suggest that selenium (Se) is preserved as selenoamino acid derivatives, in particular, selenomethionine (SeMet) in proteins, similar to selenized yeast. Therefore, buckwheat and quinoa are expected to be a good nutritional source of Se. Selenized buckwheat and quinoa were cultivated on Se-fortified soil using sparingly soluble Se salts, such as barium selenate and barium selenite. Se concentration in the edible parts of these plants was determined, and Se extraction efficiency with enzyme or alkali was evaluated. In addition, the chemical species of Se in the low molecular weight fraction of these plants were determined by HPLC-ICP-MS. Total Se concentrations in the edible parts of selenized buckwheat and quinoa were 170.4 ± 2.9 μg/g and 102.7 ± 2.4 μg/g wet weight, respectively. Thus, these selenized seeds were found to be Se accumulators. The results indicate that Se in selenized buckwheat exists mainly as SeMet, while Se in selenized quinoa exists not only as SeMet but also as selenate (Se(VI)) and non-protein forms.     

Speciation of selenium in vitamin tablets using spectrofluorometry following cloud point extraction

Selenium is one of the trace and essential elements for good health but required only in a very narrow range. Hence, determination of selenium in trace level is important. In this work, cloud point extraction (CPE) with non-ionic surfactant Triton X-114 and the fluorometric ligand, 2,3-diaminonaphtalene (DAN) were used for extraction of trace amounts of organic and inorganic selenium species prior to their determination by spectrofluorometry. CPE parameters affecting complexation and phase separation were optimised. The limit of detection calculated by using nine replicate measurements of 0.020 mg/L Se solution after complexing with DAN and 10-fold CPE preconcentration was 2.1 μg/L. Accuracy of the method was checked using EnviroMat Waste Water, EU-L-2 as CRM and result was found to be in good agreement with the certified value. The suggested method can be used for selenium species of selenite, selenate, and total organic selenium at μg/L level.     

分次加硒法培养高富硒量螺旋藻及其对藻体光合色素和蛋白质含量影响的研究

在螺旋藻生长的不同阶段分次添加无机硒(Na2SeO3)进行富硒处理。设置11个实验组,分别从第1天至第10天分次加硒,观察不同硒处理组中螺旋藻对无机硒的富集转化及其光合色素、蛋白质的变化情况。结果表明,在螺旋藻生长的第7、8、9三天分次加硒(实验组7),可获得硒产率1743.06μg/L、有机硒比率为86.85%的高富硒量螺旋藻,与对照相比,其硒含量增加150倍,生物量也明显提高(1.34g/L,对照组为1.18g/L);该实验组藻体中的硒主要分布在水溶性蛋白质中,占总硒含量的60.51%,占有机硒含量的69.67%;螺旋藻主要营养物质藻蓝蛋白(PC)、别藻蓝蛋白(APC)、类叶黄素、β-胡萝卜素含量也有不同程度的增加,表明此富硒方法是螺旋藻高值化处理的有效途径。