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91.
C.V.S. Ieggli D. Bohrer S. Noremberg P.C. do Nascimento L.M. de Carvalho S.L. Vieira R.N. Reis 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
An oil-in-water formulation has been optimized to determine trace levels of selenium in whole hen eggs by graphite furnace atomic absorption spectrometry. This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures. Graphite furnace atomic absorption spectrometric (GF AAS) measurement was carried out using standard addition calibration and Pd as a modifier. The precision, expressed as relative standard deviation, was better than 5% and the limit of detection was 1 µg L− 1. The validation of the method was performed against a standard reference material Whole Egg Powder (RM 8415), and the measured Se corresponded to 95.2% of the certified value. The method was used for the determination of the Se level in eggs from hens treated with Se dietary supplements. Inorganic and organic Se sources were added to hen feed. The Se content of eggs was higher when hens were fed with organic Se compared to the other treatments. The proposed method, including sample emulsification for subsequent Se determination by GF AAS has proved to be sensitive, reproducible, simple and economical. 相似文献
92.
Aino J. Karhu Juho Jämsä J. Mikko Rautiainen Raija Oilunkaniemi Tristram Chivers Risto S. Laitinen 《无机化学与普通化学杂志》2017,643(7):495-500
The reaction of tBuNH2 with a mixture of SeCl2 and SeOCl2 in a 6:2:1 molar ratio produces the novel selenium‐nitrogen chain ClSeN(tBu)Se(O)Cl ( 4 ), in which the selenium atoms are in two different oxidation states, SeII and SeIV. The crystal structure of 4 is compared with that of the related SeII/SeII system ClSeN(tBu)SeCl ( 1 ) and differences are attributed to hyperconjugative effects. The energetics of the formation of 4 via two different routes are elucidated by PBE0/def2‐TZVPP calculations. 相似文献
93.
Christina M. Gonzalez Jeffrey Hernandez Jason G. Parsons Jorge L. Gardea-Torresdey 《Microchemical Journal》2010,96(2):324-329
Selenium (Se) is naturally occurring in the environment and is an essential nutrient in mammals. However, environmental Se can be increased to toxic levels through different industrial practices. The potential adsorption of the Se oxoanions, selenite and selenate, from aqueous solutions onto nanosynthesized MnFe2O4 was investigated using batch techniques and DRC-ICP-MS spectroscopy. The nanomaterial (NM) was laboratory synthesized through slow titration of a mixture of Fe2+ and Mn2+ ions. X-ray diffraction and Scherrer's equation were used to determine the phase of the material and crystallite size, respectively. The effects of pH, reaction time, competitive anions, and the adsorption capacity of the synthesized NM to bind selenite and selenate were investigated. The Langmuir isotherm was used to determine the binding capacity of the NM. Results showed that the phase of the nanomaterial was similar to Jacobsite with a size of 27.5 nm. Results also showed that the sorption of either 100 ppb of selenite or selenate was pH independent in the pH range 2 to 6 and occurred within 5 min of contact time. The introduction of Cl− and NO3− anions individually added to solution had no significant effect on the sorption of either selenite or selenate. However, it was found that the addition of SO42− had a competitive effect only on the sorption of selenate, first seen at 10 ppm and more pronounced at 100 ppm of SO42−. In the presence of 100 ppm of PO43−, the adsorption of selenate decreased to 87% while selenite sorption decreased to 20%. From the Langmuir isotherm equation it was determined that the nano-Jacobsite had a selenite and selenate binding capacity of 6573.76 and 769.23 mg Se/kg of NM, respectively. 相似文献
94.
Karl O. Christe David A. Dixon Mathias Hopfinger Thomas M. Klapötke Burkhard Krumm 《Journal of fluorine chemistry》2010,131(7):791-422
The [((C6H5)3P)2N]+, [(C6H5)4P]+ and [N(CH3)4]+ salts of SeF5−, SeF62− and SeOF3− and CsSeO2F were prepared and characterized. Crystal structures were obtained for [((C6H5)3P)2N][SeF5] and [((C6H5)3P)2N][SeOF3] CH2Cl2. In contrast to oxygen-bridged dimeric TeOF3−, the SeOF3− anion in [((C6H5)3P)2N][SeOF3] CH2Cl2 is monomeric and represents the first experimentally well determined molecular structure of a monomeric trifluoro-chalcogenite anion. Similarly, [((C6H5)3P)2N][SeF5] represents the first example of a structure containing a well-isolated undistorted SeF5− anion. The NMR and the vibrational spectra and their assignments were re-examined and corrected by comparison with high-level theoretical calculations. Whereas the previously published normal coordinate analysis of SeF5− is correct, that for SeOF3− needs major revision. 相似文献
95.
[CoCl2{N,N′-Te2(NtBu)4}] (1) was obtained in good yields by the reaction of equimolar amounts of (tBu)NTe(μ-NtBu)2TeN(tBu) and CoCl2 in toluene under an argon atmosphere. The crystal structure of 1·CH2Cl2 showed that the dimeric tellurium diimide ligand is N,N′-chelated to cobalt. The related reaction of Se(NtBu)2 and CoCl2 affords a green product tentatively identified as a 1:1 adduct [CoCl2{N,N′-Se(NtBu)2}] (CHN analysis). However, recrystallization from thf produces the ion-separated complex [Co2(μ-Cl)3{N,N′-Se(NtBu)2}2(thf)2][CoCl3{NH2(tBu)}]·1½thf (2·1½thf), in which the monomeric selenium diimide ligand is N,N′-chelated to cobalt in the cation. A pathway for the formation of 2 from [CoCl2{N,N′-Se(NtBu)2}] in thf is proposed. 相似文献
96.
银杏叶中总硒和各种溶解形态硒含量随着季节而变化,实验研究了不同采摘期银杏叶中总硒及不同溶解态硒含量分布.7月、9月和霜降之后采摘的银杏叶总硒的含量分别为1.873,2.136,0.815 mg·kg-1,硒的形态以水溶态硒为主.银杏叶粗多糖含量分布依次为9月>7月>11月.7月份采集的银杏叶中得到粗多糖为棕褐色固体粉末... 相似文献
97.
A simple, reliable, trace determination of selenomethionine (Semet) based on a direct hydride generation atomic absorption spectrometric method was developed using sodium tetrahydroborate (0.3% in 0.2% NaOH) and hydrochloric acid (3 M). The method excluded any chemical pretreatment prior to hydride generation (HG). The optimized HG system was successfully coupled with the HPLC system. The detection limit (3σ of blank; n=5), reproducibility (R.S.D. of three successive analyses/day, performed on three different days), and repeatability (R.S.D. of three successive analyses) of the method were 1.08 ng ml−1, 9.8% for 9.04 ng ml−1 and 2.1–9.5% for 30.0–1.27 ng ml−1 Semet as Se (standards prepared in Milli-Q water). Calibration graph was linear up to 30 ng ml−1. This HPLC-HG-AAS method is very promising and successfully determined Semet (spiked) in human urine. 相似文献
98.
The syntheses of the selenium containing heterocycles dibenzoselenophene ( 1 ≡ biphenSe) and dibenzo[1,2]diselenine ( 2 ≡ biphenSe2) were optimized. The halogenation reactions of 1 and 2 with XeF2, SO2Cl2, Br2 and I2 were performed and the corresponding products characterized. In the case of 1 , the selenium(IV) dihalogenides, biphenSeF2 ( 3 ), biphenSeCl2 ( 4 ), biphenSeBr2 ( 5 ), and the adduct biphenSe·I2 ( 6 ), were isolated and identified. The extremely sensitive selenium(IV) difluoride 3 slowly formed significant amounts of an adduct with HF of the corresponding selenium(IV) oxide biphenSeO·HF ( 3a ) upon storage in glass vessels at low temperatures. In the case of 2 , the selenium(IV) trihalogenides, biphen(SeHal3)2 (Hal = F, Cl, Br), were found to be extremely labile (Hal = F) or not detectable (Hal = Cl, Br). Instead, as decomposition products, the selenium chloride species Se2Cl2, SeCl4 and 1 were detected. In the case of Hal = I, the stable adduct biphenSe2·I2 ( 7 ) was isolated. In addition to characterization by multinuclear NMR spectroscopy, several molecular structures of biphen‐selenium substituted halogenides were determined. 相似文献
99.
23Na NMR方法观察硒缺乏对大白鼠红细胞钠离子浓度的影响 总被引:1,自引:1,他引:0
用无损伤23Na NMR检测技术测定了正常和低硒饲料喂养的大白鼠的红细胞内钠离子浓度.结果表明:(1)缺硒可引起胞内钠离子浓度升高,(2)高钠细胞比正常细胞易溶血,(3)在饲料中补充Na2SeO3后可使胞内钠离子浓度恢复至正常水平,溶血情况也有所改善. 相似文献
100.
单缝石英管火焰原子吸收法测定蒜头、茶叶、大米中微量硒 总被引:9,自引:0,他引:9
本法利用单缝石英管,提高火焰原子吸收法的灵敏度并降低测试成本。方法用于大米、蒜头、茶叶中硒的测定,获得满意的结果。 相似文献