硒酵母中有机硒及硒代氨基酸含量的测定方法

报道了人工培养硒酵母中有机硒及硒代胱氨酸（ＳｅＣｙｓ）和硒代蛋氨酸（ＳｅＭｅｔ）含量的测定方法。采用透析处理法使硒酵母中的无机硒和有机硒得以分离,并采用催化分光光度法测定了硒酵母中有机硒的含量;采用氨基酸自动分析仪测定了硒酵母中ＳｅＣｙｓ和ＳｅＭｅｔ的含量。     

反相离子对高效液相色谱-电感耦合等离子体质谱法测定富硒酵母中硒

富硒酵母样品用pH 7.5的Tris-盐酸缓冲溶液经超声破碎提取30min,于提取液中加链霉蛋白酶E在37℃搅拌18h,高速离心分离。取上清液经Millipore Corp超滤膜过滤,滤液中无机硒(Ⅵ及Ⅳ)和有机硒,即硒代半胱氨酸、硒代尿素和硒代蛋氨酸通过Waters Symmetry ShieldRP18色谱柱分离。用不同比例混合的甲醇-七氟丁酸溶液作流动相进行梯度洗脱,用电感耦合等离子体质谱法在线测定洗脱液中各种形态硒的含量。5种形态硒的质量浓度均在100μg·L-1以内呈线性。应用此法分析了富硒酵母样品,结果表明:无机硒占总硒量的1.63%,65%的硒以易被人体吸收的硒代蛋氨酸形式存在。     

大米中硒含量的测定

为使人们更好地控制和调节硒的摄入量,用紫外分光光度法测定了大米中的硒含量。样品通过混酸消化,将有机硒转化成无机硒,酸性条件下,Se(Ⅳ)与邻苯二胺反应,产物在335nm有最大吸收峰。测定结果表明,天津小站米、东北米、丝苗米、泰国香米、富硒米的有机硒含量分别为:0.041、0.046、0.035、0.034、2.021μg/g,有机硒含量占总硒含量的比例分别是89.13%、82.14%、87.50%、80.95%、98.92%。富硒米硒含量及有机硒的比例明显高于其它种类的米。     

控温消解-氢化物发生-原子荧光光谱法测定水中硒形态

取10.00 mL水样,于60～70℃加热蒸发至近干,加入硝酸-高氯酸(1+1)混合酸2.0mL,继续加热至白烟冒尽,加入盐酸2.0 mL,摇匀,加热保持微沸3～5 min,冷却后转移至10mL比色管中,用去离子水定容,使用氢化物发生-原子荧光光谱仪测定总硒的含量。另取10.00mL水样,加入盐酸2.0mL,于60～70℃加热至溶液体积小于5mL,转移至10mL比色管中,用去离子水定容,使用氢化物发生-原子荧光光谱仪测定无机硒(即四价硒和六价硒的总和)的含量。另取水样5.00mL于10mL比色管中,加入盐酸2.0mL,用去离子水定容,使用氢化物发生-原子荧光光谱仪测定四价硒的含量。用总硒含量减去无机硒含量即为有机硒含量,无机硒含量减去四价硒含量即为六价硒含量。在最佳仪器工作条件下,硒的质量浓度在1.00～20.0μg·L~(-1)内与其对应的荧光强度呈线性关系,硒的检出限(3s)和测定下限(10s)分别为0.11,0.36μg·L~(-1)。采用本方法测定某地区水中的总硒、无机硒和四价硒,加标回收率在95.7%～104%之间,相对标准偏差(n=6)在1.9%～3.2%之间。采用本方法测定了不同地区水中的总硒、无机硒和四价硒,利用差减法计算得有机硒和六价硒的含量。     

原子荧光光谱法直接测定二甲基二硒

硒位于第六主族,为准金属元素。在自然界中硒的存在形式按其结合形态分为无机硒和有机硒[1,2]。有机硒较无机硒具有更高的生物活性,因此准确测定各种样品中的有机硒具有重要意义。对于挥发性有机硒,一般采用洗脱富集将其与样品基体分离,采用固相吸附[3,4]或液氮冷阱捕集[5,6],热解析或溶剂萃取后用气相色谱测定[7,8]。这些方法可以提供许多有机硒的信息,但其不足之处是程序较为繁琐。原子荧光光谱分析法(AFS)具有准确度高、灵敏度高、线性范围宽、干扰少等优点,故本文利用AFS的特点及二甲基二硒(DMDSe)的挥发性,在不加任何试剂的条件下,…     

氢化物发生-原子吸收光谱法测定黄芪中硒

黄芪试样经硝酸-过氧化氢消解,用氢化物发生-原子吸收光谱法测定黄芪中总硒、无机硒和有机硒的含量。使用15 g·L^-1硼氢化钾-3 g·L^-1氢氧化钠溶液与溶液中硒离子反应生成氢化物。分析中采用载气流量240 mL·min^-1。硒的质量浓度在60μg·L^-1以内与吸光度呈线性关系,方法的检出限（3σ）为0.21μg·L^-1。应用此法测定黄芪中硒的含量,总硒测定值为105μg·g^-1、硒（Ⅳ）测定值为15μg·g^-1、硒（Ⅵ）测定值为9μg·g^-1、有机硒测定值为81μg·g^-1。黄芪中的硒主要存在形式为有机硒,占总硒含量的77%。     

顺序注射HG-AFS法测定富硒农产品中无机硒和有机硒

本文建立了顺序注射氢化物发生原子荧光法测定硒的分析方法.探讨了富硒农产品中无机硒和有机硒的分离及提取方法.优化了仪器的工作条件,考察了KBH4浓度和酸介质浓度对硒原子荧光强度的影响.方法的线性范围为1～100μg/L,检出限为0.02μg/L,无机硒的回收率为95.0%～104.0%.     

两种干海产品中硒含量的紫外-可见分光光度间接测定

基于Se(IV)与I-的反应建立了紫外-可见分光光度法间接测定干海产品中总硒及无机硒的含量。获得影响分析性能的最佳因素:最大吸收波长516 nm,反应体系中2%KI、6.0 mol·L~(-1)HCl及0.02 mol·L~(-1)EDTA-2Na的加入量分别为0.6 m L、1.0 m L、2.0 m L,室温下反应25 min。25 m L反应液中硒含量(μg)在0.05~14.4范围内与吸光度呈线性:A=-0.0049+0.05176c,r=0.9998,检测限0.01μg/25 m L(3S/k)。成功用于干海产品虾皮及银鱼中总硒及无机硒含量测试。结果表明有机硒含量占总硒67%以上,总硒及无机硒的回收率分别为95.3~99.3%、101.8~108.1%。该法操作简单,抗干扰能力强,具有良好准确度及重现性。     

硒化合物与脂质过氧自由基作用的研究

本文以卵磷脂、亚油酸和脂质体作为生物膜模型, 鼠红细胞膜作为生物膜实例, 通过ESR研究, 观察到包括RSe和RSeSeR在内的硒化合物在模拟的和真实的生物膜体系中对脂质过氧自由基的清除作用, 使得硒作为自由基清除剂的假说在体外模型体系实验中被初步证实, 提示占体内总硒量约2/3的非GSH-Px硒可能是通过直接清除过氧自由基而发挥其生理功能, 研究表明, 其清除作用是针对生物膜磷脂分子上的不饱和脂肪酸过氧自由基, 其作用部位处于膜磷脂双分子层中部疏水区(脂相)中, 在体外实验的清除效果上, 有机硒优于无机硒, 某些有机硒化合物表面出“奇偶规律"。CNDO/2计算表明, 硒化合物清除脂质过氧自由基可能是通过硒中心自由基而起作用的。     

高效液相色谱-电感耦合等离子体质谱分析几种富硒产品的硒总量及其形态

本文采用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)分析了几种富硒产品中硒的总量及其形态。结果表明,四种富硒产品的硒总量均有不同程度增加,富硒大米和富硒茶叶中的硒总量较高,分别为1.300μg/g和0.459μg/g,富硒大米和富硒大葱的富硒倍率相对较高,分别为未富硒产品的24.1和17.8倍。以0.1mol/LHCl辅助超声预处理样品进行富硒螺旋藻和富硒大葱中硒的形态分析,发现富硒大葱中的硒主要为有机态的甲基硒代半胱氨酸(MeSeCys)以及部分硒代蛋氨酸(SeMet),而富硒螺旋藻中的硒大部分为无机硒。说明经根部吸收等富集方式可有效将无机硒转化为有机硒,而某些方式未能完全转化。     

Development of extraction methods for speciation analysis of selenium in aqueous extracts of medicinal plants

Advanced extraction methods have been developed for direct speciation of dissolved inorganic and organic selenium (Se) species in aqueous extracts of medicinal plants (MPs). The inorganic species of Se (SeIV and SeVI) were separated from organic forms by adsorbing inorganic Se on alumina, while the organic Se was not retained. The retained inorganic Se species was eluted with 10 mL 0.2 M HCl. The total inorganic Se species was determined after prereduction of SeVI into SeIV with concentrated HCl. The SeIV in the eluent and total inorganic Se species were then complexed with diethyldithiocarbamate. The resultant complexes were entrapped in the nonionic surfactant Triton X-114. The total Se, organic Se, total inorganic Se, and SeIV species were determined by electrothermal atomic absorption spectrometry with a modifier. The SeVI concentration was obtained by subtracting SeIV from total inorganic Se contents. The main factors affecting the methodologies were investigated in detail. Under the optimized experimental conditions, the LOD for SeIV was 50 microg/L. Among dissolved inorganic and organic Se species in aqueous extracts of MPs, organic Se species were present in the range of 74-84%, SeIV 3.62-7.47%, and SeVI 12.4-18.57% of total Se contents.     

用离子抑制色谱法分析二（2,2,6,6—四甲基—4—哌啶基）马来酸酯合？…

建立了用离子抑制色谱法分析二（２,２,６,６－四甲基－４－哌啶基）马来酸酯合成反应液的方法。平均回收率为９８．８％,相对标准偏差为０．５６％,测量的平均相对偏差不大于５．０％,方法简单,快速,可用于工艺条件的选择和质量检测。     

Selenium speciation in animal tissues after enzymatic digestion by high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry

A procedure is described for the enzymatic digestion of tuna and mussel samples that allows the determination of selenium species by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. The species were extracted by two-step enzymatic hydrolysis with a non-specific protease (subtilisin). The selenium species were separated on a Spherisorb 5 ODS/AMINO column using two different chromatographic conditions, namely phosphate buffers at pH 2.8 and pH 6.0 as mobile phases. The method determines organic (trimethylselenonium, selenocystine, selenomethionine and selenoethionine) and inorganic selenium species (selenite and selenate), but only organic selenium species were found in the samples. The sum of identified selenium species in the sample was about 30% of the total selenium present in the enzymatic extract despite the fact that recoveries of total hydrolysed selenium were 93-102%. Trimethylselenonium ion and selenomethionine were found in both tuna and mussel samples and an unknown selenium species was also found in tuna samples.     

Organic and inorganic selenium speciation in environmental and biological samples by nanometer-sized materials packed dual-column separation/preconcentration on-line coupled with ICP-MS

A novel, fast, and cheap nonchromatographic method for direct speciation of dissolved inorganic and organic selenium species in environmental and biological samples was developed by flow injection (FI) dual-column preconcentration/separation on-line coupled with ICP-MS determination. In the developed technique, the first column packed with nanometer-sized Al(2)O(3) could selectively adsorb the inorganic selenium [Se(IV), Se(VI)], and the retained inorganic selenium could be eluted by 0.2 mol l(-1) NaOH, while the organic Se [selenocystine (SeCys(2)) and selenomethionine (Se-Met)] was not retained. On the other hand, the second column packed with mesoporous TiO(2) chemically modified by dimercaptosuccinic acid (DMSA) could selectively adsorb Se(IV) and SeCys(2) and barely adsorb Se(VI) and Se-Met. When the sample solution was passed through the column 1, separation of inorganic selenium and organic selenium could be achieved first. Then, the effluent from column 1 was successively introduced into the column 2 and the speciation of organic selenium could be attained due to the different adsorption behaviors of Se-Met and SeCys(2) on DMSA modified TiO(2). After that, the eluent from column 1 contained Se(IV), and Se(VI) was adjusted to desired pH and injected into column 2, and the speciation of Se(IV) and Se(VI) could also be realized thanks to their different retention on column 2. The parameters affecting the separation were investigated systematically and the optimal separation conditions were established. The detection limits obtained for Se(IV), Se(VI), Se-Met and SeCys(2) were 45-210 ng l(-1) with precisions of 3.6-9.7%. The proposed method has been successfully applied for the speciation of dissolved inorganic and organic selenium in environmental and biological samples. In order to validate the methodology, the developed method was also applied to the speciation of selenium in certified reference material of SELM-1 yeast, and the determined values were in good agreement with the certified values.     

Biological and chemical investigation of Allium cepa L. response to selenium inorganic compounds

The aim of this study was to evaluate the biological and chemical response of Allium cepa L. exposed to inorganic selenium compounds. Besides the investigation of the total content of selenium as well as its chemical speciation, the Allium test was used to evaluate the growth of onion roots and mitotic activity in the roots’ meristem. The total content of selenium was determined by inductively coupled plasma mass spectrometry (ICP MS). High-performance liquid chromatography (HPLC), coupled to ICP MS, was used for the selenium chemical speciation. Results indicated that A. cepa plants are able to biotransform inorganic selenium compounds into their organic derivatives, e.g., Se-methylselenocysteine from the Se(IV) inorganic precursor. Although the differences in the biotransformation of selenium are due mainly to the oxidation state of selenium, the experiment has also shown a fine effect of counter ions (H⁺, Na⁺, NH₄ ⁺) on the response of plants and on the specific metabolism of selenium.

Molecular emission cavity analysis13-a new flame analytical technique : Part II.The determination of selenium and tellurium

The determination of 0.4–4 μg of selenium by molecular emission cavity analysis is described. Selenium in organic compounds is determined after oxygen flask combustion. Metal ion interferences are eliminated by reduction of selenium to the element, filtration onto a glass-fibre paper, and direct incorporation of the filter into the cavity. Applications to the determination of selenium in inorganic and organic compounds are described. The determination of μg-amounts of tellurium is also outlined.     

Trends in selenium biochemistry

The biochemistry of selenium-containing natural products, including selenoproteins, is reviewed up to May 2002. Particular emphasis is placed on the assimilation of selenium from inorganic and organic selenium sources for selenoprotein synthesis, the catalytic role of selenium in enzymes, and medical implications of an unbalanced selenium supply. The review contains 393 references on key discoveries and recent progress.     

Effect of selenium in organic and inorganic form on liver,kidney, brain and muscle of <Emphasis Type="Italic">Wistar</Emphasis> rats

Selenium is a micronutrient, localized in the active sites of enzymes such as glutathione peroxidase and thioredoxin reductase, and participating together with these enzymes in an antioxidant defence system of organisms against free radicals. Administration of selenium is necessary for maintaining oxidative homeostasis. The present experiment is aimed at investigation of selenium impact on basal metabolic processes and selected antioxidants in a Wistar rat model, fed selenium in organic and inorganic forms. Liver, kidney, brain and muscle were sampled during a month-long feeding with four different doses of selenium (0.075 mg or 1.5 mg of inorganic and/or organic selenium per kg of feed). We found a significant reduction in glutathione level in liver tissue regardless of the form of the administered selenium. On the other hand, selenium caused a decreased glutathione reductase level in the liver and metallothionein level in the liver, kidney and muscle.