原子荧光法测定土壤中的硒

本文应用双道原子荧光光度计测定土壤中的硒。本文对样品的消解方式,仪器工作条件,共存元素的干扰及消除等方面进行探讨。在优化的分析条件下,硒的检出浓度为0.12μg/L,相对标准偏差为4.36%,测定值在标准样品值的不确定度范围内。实验表明,该方法操作简便,有较好的精密度和准确度。     

微波消解-原子荧光光谱法测定中药中的砷和硒

建立了微波消解-原子荧光光谱测定中药中砷和硒含量的方法。该方法测定砷和硒的检出限分别为0.087μg/L和0.123μg/L,荧光强度与砷及硒的质量浓度在0~200μg/L及0~100μg/L范围内呈线性关系。用于中药中砷和硒的测定,相对标准偏差(n=6)均小于3.6%,砷的回收率在95.2%~102.8%之间,硒的回收率在94.5%~104.8%之间。     

应用AFS—930型双道原子荧光光度计联合测定水中的砷和硒

本文采用原子荧光光谱法,研究了联合测定水样中砷和硒的技术。用10%盐酸和1%硫脲-1%抗坏血酸混合试剂处理样品,并以2.0%硼氢化钾和0.5%氢氧化钠为还原剂,在5%的盐酸介质测定砷和硒。砷和硒的检出限分别为:0.20μg/L和0.13μg/L,本方法具有操作简便、快速、基体干扰少、灵敏度高等优点,可用于水样中砷和硒的联合测定。     

原子荧光光谱法测定新疆雪菊中微量硒

原子荧光光谱法测定雪菊中微量硒,对原子荧光光谱法的参考测试条件进行了优化,具有操作简单、快速、灵敏度高等优点,方法检出限为0.3μg/L,相关系数为：0.999971,测定雪菊花中硒的回收率为94-103%,RSD=0.20%,用国家标准物质对结果的准确性进行了验证,测定结果是满意。     

氢化物原子荧光光谱法同时测定生活饮用水中砷和硒

建立了氢化物发生原子荧光光谱法同时测定生活饮用水中砷和硒的方法.测试结果表明砷和硒在质量浓度分别为0.00μg/L~10.00μg/L和0.00μg/L~40.00μg/L范围内呈线性关系,相关系数分别为(砷r=0.9998,硒r=0.9997)。仪器检出限为砷:0.03μg/L硒:0.05μg/L。本方法检出限砷为0.075μg/L;硒为0.125μg/L。水质样品中砷的回收率为92.6%~96.5%,精密度为0.8%~1.4%;硒的回收率为91.2%~97.4%,精密度为1.0%~1.6%。应用本方法测定生活饮用水中的砷和硒方法简便、快速,结果准确可靠,较好地提高了工作效率。     

ICP-MS法同时测定金属包装材料中8种可溶性有害元素

建立了电感耦合等离子体质谱(ICP-MS)法同时测定金属包装材料中砷、钡、镉、铬、铅、锑、硒、汞等8种可溶性有害元素的分析方法,全面考察了消解剂种类及其用量、内标元素的选择及方法的干扰等影响其测量的各种因素,确定了最佳的实验测定条件。方法的检出限为0.03~0.18μg/L,相对标准偏差(RSD)小于5%,加标回收率为87.4%~118.1%。采用该法对金属包装材料实际样品进行了分析,结果表明,此方法简单、准确、重现性好。     

ICP-MS测定食品原料中微量硒

建立基于同位素77Se、乙醇基体改进电感耦合等离子体质谱法(ICP-MS)直接测定食品原料中微量硒的方法。实验以2%(V/V)乙醇作为基体改进剂,采用Y元素作内标补偿基体效应,选择同位素77Se测定样品中的硒,方法检出限为0.87 ng/g,精密度(RSD,n=6)5%,回收率为98.1%~106.0%。该方法具有简便、快速、灵敏、准确、消耗小等优点,可为食品原料中微量硒的测定提供参考。     

双道原子荧光光谱法同时测定土壤中的汞和硒

建立了同时测定土壤中汞和硒的原子荧光光谱法。对试样的预处理和消解方法进行了详述。试样的相对标准偏差Hg为3.60%,回收率在90%~109%之间;Se为4.10%,回收率在92~101%之间。汞和硒的检出限分别为0.051μg.L-1和0.29μg.L-1。本方法操作简便、快速、灵敏度高。     

高效液相色谱-原子荧光光谱法测定茶叶中硒的赋存形态

建立了一种采用高效液相色谱-原子荧光联用仪测定茶叶中硒的赋存形态分析方法。该方法对硒代胱氨酸、亚硒酸根、硒代蛋氨酸、硒酸根4种硒形态的检出限0.096～0.64 ug/L,线性范围达到2个数量级以上,标准曲线可得到良好的线性关系,连继进样7次相对标准偏差RSD均小于4%。加标回收试验显示,该法测量回收率在81.47%～119.30%,具有较高准确度。茶叶3种前处理方式,纯水浸提法和盐酸提取法都没有检验出峰值,甲醇提取法检验总硒含量0.48 mg/kg的茶叶,结果显示硒代蛋氨酸6.25 ug/L,说明两种前处理方式都不适合茶叶硒形态分析,甲醇提取法仅适合于高硒含量样品,最优化的提取方法尚有待进一步研究。     

氢化物发生-原子荧光光谱法测定血清中硒含量研究

采用氢化物发生-原子荧光光谱法测定血清中的硒含量。通过实验确定介质酸浓盐酸溶液的最适宜体积分数为10%,还原剂硼氢化钾溶液的最适宜质量分数为1.5%。采用干法消解、湿法消解、微波消解对样品进行前处理,研究不同的消解方法对硒含量测定的影响,实验结果表明:微波消解法优于其他两种方法,具有污染小、时间短、准确度高的优点。该方法的检出限为0.004μg/L,标准偏差为2.88%,加标回收率在94.5%~102.5%之间。微波消解-原子荧光光谱法可以快速测定大批量血清样品,缩短工时、提高效率,适用于临床检测。     

Inorganic selenium speciation in groundwaters by solid phase extraction on Dowex 1X2

A Dowex 1X2 resin separation technique followed by analysis with atomic absorption spectroscopy was evaluated for the study of inorganic selenium speciation in groundwaters. After Se(IV) and Se(VI) were retained on the resin column, Se(IV) and Se(VI) were eluted out by 0.1 and 1M nitric acid solutions. The method detection limit was 5.6 ng/L for both Se(IV) and Se(VI). Analysis of synthetic solutions consistently yielded more than 90% recovery of these two selenium forms with negligible cross-contamination. The results of spiked well waters show that this method can be applied at ultra-trace level of Se in groundwater and the interference of chloride ion can be neglected. Water samples collected from the monitoring wells in the Science-based Industrial Park, Hsin-Chu, Taiwan, were analyzed. Average dissolved selenium concentrations were 32.1+/-17.6 ng/L. The proportion of Se(VI) to the total dissolved selenium ranged from 47.6 to 61.2% and an average of 53.8% in water samples analyzed.     

Microwave digestion of environmental and natural waters for selenium speciation

A microwave preparation procedure is proposed for selenium speciation in natural and drinking waters. Different chemical reagents were tested, and the conditions for Se speciation were optimized. The effect of the different reagents on various oxidation states of selenium under microwave digestion conditions was investigated. Most of the Se(-II) was converted to selenite when digested with HNO3 and <20% to selenate. The digestion with H2O2/H2SO4 can change most Se species into Se(IV). The concentration of Se(IV) in the samples was then determined by HPLC with a fluorescence detector after derivatization with 2,3-diamino-naphthalene (DAN). The microwave preparation procedure allows Se speciation in water samples. Se(IV) was determined after concentrating the sample under nitrogen protection. The amount of Se(IV) and Se(VI) was measured by adding an equal volume of concentrated hydrochloric acid to water sample to reduce Se(VI) to Se(IV). Then the amount of Se(VI) can be calculated by subtraction. The total selenium can be determined after digestion with H2O2/H2SO4, or after digestion with HNO3 followed by reduction with concentrated hydrochloric acid. Selenium (-II, 0) was calculated by subtracting inorganic Se(IV+VI) from the total. Detection limits of 0.0066 ng and 0.0096 ng Se were obtained for HNO3 and H202/H2SO4 as digestion reagents, respectively. The total Se in the four water samples tested range from 0.20 to 0.90 microg L(-1). Among them the dominant form was Se(VI) with the exception of pond waters where Se(-II) predominated.     

Quantification, localization, and speciation of selenium in seeds of canola and two mustard species compared to seed-meals produced by hydraulic press

Brassica plants accumulate selenium (Se) especially in seeds when grown in soils laden with Se. We report a chemical analysis of Se in Brassica seeds (canola, Indian mustard, and white mustard) and in their hydraulically pressed seed meals, which are used as a Se supplement in livestock animal feeds. Complementary techniques were used to measure total Se concentrations, to map the localization of Se, and to quantify different Se forms. Seeds and hydraulically pressed seed meals contained an average of 1.8 and 2.0 μg Se g(-1) DW, respectively. Selenium was primarily located in cotyledons and roots of seed embryos. Microfocused Se K-edge XANES and bulk XANES showed that seeds contained 90% of Se as C-Se-C forms. Hydraulically pressing seeds for oil caused changes in the forms of Se as follows: 40-55% C-Se-C forms, 33-42% selenocystine, 5-12% selenocysteine, and 11-14% trimethylselenonium ion. Aqueous extracts of seed and seed meals were also analyzed by SAX-HPLC/ICPMS and found to contain mainly the C-Se-C form SeMet, but also another C-Se-C form MeSeCys, which is of dietary pharmacological interest for cancer inhibition. In addition, SAX-HPLC/ICPMS also detected selenocystine and selenocysteine, further confirming the results obtained by XANES analyses.     

Sorption of selenium(IV) and selenium(VI) to mackinawite (FeS): effect of contact time, extent of removal, sorption envelopes

Higher concentrations (127, 253 μM) of Se(IV) at pH 8 were completely removed by 0.5 g/L FeS within 120 min. Removal of Se(VI) by FeS at pH 8 was less extensive than removal of Se(IV). Only 10% of the Se(VI) was removed by 1 g/L FeS within 1h. Removal patterns for Se by FeS depend on pH. Removal patterns of Se at pH 7 and pH 8 were best described by BET models for Se(IV) and Freundlich models for Se(VI), while removal patterns of both at pH 9 and 10 were best described by Langmuir models. Sulfate at 1 and 10 mM had negligible effect on removal of Se(IV) by FeS, while sulfate had little effect on removal of Se(VI) by FeS, but there was some indication that sulfate promoted removal of Se(VI) at intermediate concentrations. The test for the effect of pH on sorption of Se(IV) by FeS showed nearly complete removal at all but the high initial pH. When pH was raised back to initial value, greater removals were observed than initially. Mixtures of Se(VI) and FeS showed moderate removal at low pH, a minimum removal near pH 6 and nearly complete removal at high pH. Very high stability was observed with negligible release as pH decreased.     

Determination of mercury and selenium in herbal medicines and hair by using a nanometer TiO2-coated quartz tube atomizer and hydride generation atomic absorption spectrometry

The nanometer TiO(2) particle was coated onto the inner wall of a T-shaped quartz tube atomizer (QTA) and then was used as a new atomizer (NT-QTA) for the determination of Hg and Se by hydride generation atomic absorption spectrometry (HGAAS). After coating 67.4 mg TiO(2) on a quartz tube, the analytical performance of NT-QTA-HGAAS was compared to conventional QTA-HGAAS and it was improved as follows: (a) the linear range of the calibration curves was expanded from 10.0-80.0 ng mL(-1) to 5.0-150.0 ng mL(-1) for Hg, and from 10.0-70.0 ng mL(-1) to 5.0-100.0 ng mL(-1) for Se; (b) the characteristic concentration of was decreased from 2.8 ng mL(-1)/1% to 1.1 ng mL(-1)/1% for Hg and from 1.2 ng mL(-1)/1% to 0.8 ng mL(-1)/1% for Se; and (c) the interference from the coexistence of As on the determination of Hg and Se could be eliminated. The achieved technique was applied for the determination of Hg and Se in herbal medicines and hair.     

Hazardous concentrations of selenium in soil and groundwater in North-West India

Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 μg L(-1)) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg(-1)) and Barwa (3.1 mg kg(-1)). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO(2) (40-62 wt.%), Al(2)O(3) (9-21 wt.%) and K(2)O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.     

Geochemical modelling of arsenic and selenium leaching in alkaline water treatment sludge from the production of non-ferrous metals

Geochemical modelling of leaching of oxyanion forming elements such as arsenic (As) and selenium (Se) is frequently not successful. A consistent thermodynamic dataset of As and Se was therefore composed, not only including precipitation, but also adsorption and solid solution, and was applied to the pH-dependent leaching behaviour of As and Se in an alkaline residue with a pH 11.1 from the lime treatment of sulphuric acid wastewaters from the production of non-ferrous metals. The As and Se content ranged up to 6.7 wt% and 0.29 wt%, respectively and speciation analysis showed that 96.3% of As occured as arsenate whereas Se speciation comprised 79% selenate and 21.0% selenite. XRD and SEM/EDX analysis showed that arsenate occurred as rauenthalite (Ca(3)(AsO(4))(2).10H(2)O), associated with gypsum, the most important mineral. Arsenate and arsenite concentrations were only slightly below equilibrium with rauenthalite and calciumarsenite (CaHAsO(3)), respectively and consideration of adsorption and solid solution only marginally improved model predictions. Selenate (Se(VI)) and selenite (Se(IV)), on the other hand, were far from equilibrium with their corresponding calcium metalate. The application of solid solutions and adsorption of Se(VI) and Se(IV) oxyanions with gypsum, calcite and ettringite significantly improved model predictions but missing thermodynamic data and especially the lack of a comprehensive model for solid solution and surface exchange with calcite and ettringite still hampered efficient modelling.     

Determination of selenomethionine and selenocysteine in human serum using speciated isotope dilution-capillary HPLC-inductively coupled plasma collision cell mass spectrometry

A method for the accurate determination of selenoamino acids in human serum by HPLC-ICPMS was developed using the species-specific isotope dilution analysis principle. A serum sample was enzymatically digested with a mixture of lipase and protease after derivatization of the selenocysteine residues with iodoacetamide. The selenoamino acid fraction was isolated by size exclusion LC followed by the separation of selenomethionine and the carboxymethylated selenocysteine by capillary HPLC. The isotope-specific determination of 77Se and 80Se was achieved on-line by ICP collision cell MS allowing the removal of polyatomic interferences. Quantification was carried out by isotope dilution using a 77Se-labeled selenomethionine spike and the determination of the 77Se/80Se ratio in the cHPLC selenomethionine peak. The accurately determined selenomethionine was used as an internal standard for the selenocysteine determination from the same chromatogram. The modification of the previously developed cHPLC-ICPMS interface allowed the reduction of the absolute detection limits twice (down to the 75-fg level), which resulted in the lowest ever reported procedural detection limits (below 0.5 ng g(-1) for a 450-mg serum sample). The precision was less than 5% RSD. The method was validated by the mass balance of selenium (amino acid incorporated vs total).