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断续流动注射-催化原子荧光光谱法测定碘 总被引:6,自引:0,他引:6
基于碘对亚砷酸-硫酸铈的催化反应,断续流动进样,用氢化物发生.原子荧光光谱法直接测定As(Ⅲ)的浓度变化,建立了微量碘间接测定的方法。在实验条件下,碘离子的线性范围为0.80μg/L;相对标准偏差为2.3%;检测限为4μg/L.加标回收率为92.5%-98.2%。测定结果与硫氰酸铁-亚硝酸催化动力学法相比具有很好的一致性。 相似文献
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浊点萃取-电热原子吸收光谱法分析铬的形态 总被引:21,自引:0,他引:21
提出了测定铬形态的新方法——浊点萃取-电热原子吸收光谱法(PPE-ETAAS)。该法基于利用非离子表面活性剂Triton X-100的浊点现象,当加热至其浊点时,溶液分为两相,Cr(Ⅲ)与8-羟基喹啉形成的疏水性螯合物进入富胶束相中,从而实现与Cr(Ⅵ)的分离。在本法中,8-羟基喹啉既作为化学分离,富集剂,又作为ETAAS测定中的化学改进剂。对影响浊点萃取分离的主要因素进行了详细的研究。在最优实验条件下,方法测定Cr(Ⅲ)的检出限为0.023μg/L;相对标准偏差为1.1%(C=2.0μg/L,n=6)。本法具有简便、灵敏、富集倍数高和避免使用有机溶剂的优点。 相似文献
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流动注射-荧光法同时测定水中的镍和锌 总被引:7,自引:0,他引:7
研究了用流动注射荧光法测定水中的镍和锌。镍和锌都使新点绿NG(Newport Green^TM)的荧光加强,分别测定时均有良好的线性关系,线性范围10μg/L-200μg/L,检测限分别为8.1μg/L和8.4μg/L;镍与Newport Green^TM反应缓慢,而锌与Newport Green^TM是瞬间反应,因此,记录某一时间点的荧光强度,利用荧光强度的加和性原理,研究了同时测定水体中的镍和锌方法。 相似文献
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断续流动-氢化物发生-原子荧光光谱法测定木材中砷含量 总被引:6,自引:0,他引:6
采用断续流动进样氢化物发生,原子荧光光谱法测定木材中砷含量,确定了仪器的最佳工作条件,考察了酸度、预还原剂和还原剂用量和栽流流速的影响以及共存元素的干扰情况。在选定的测定条件下,砷的检出限为0.5μg/L,相对标准偏差为1.7%,回收率为95.8%~102.0%。 相似文献
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活性氧化铝微柱分离富集-电感耦合等离子体原子发射光谱法在线测定水中铬(Ⅲ)和铬(Ⅵ) 总被引:7,自引:0,他引:7
研究了活性氧化铝对Cr(Ⅲ)和Cr(Ⅵ)分离富集的性能,建立了流动注射(FI)-在线微柱分离富集-电感耦合等离子体原子发射光谱(ICP-AES)法测定水中微量Cr(Ⅲ)和Cr(Ⅵ)的分析方法。优化了流动注射测定的条件,进样频率为60/h;检出限(3σ):Cr(Ⅲ)为0.8μg/L,Cr(Ⅵ)为0.6μg/L;线性范围为5-600μg/L;相对标准偏差小于2.4%;回收率为94.0%-102%。 相似文献
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以N-十二烷基二甲基铵基乙酸为增敏剂催化光度法测定锰 总被引:13,自引:0,他引:13
基于存在增敏剂N-十二烷基二甲基铵基乙酸(DDMAA)和活化剂氨三乙酸,锰(Ⅱ)催化高碘酸钾氧化萘酚绿B的反应,拟定了测定痕量锰的新催化光度法。本法在两性表面活性剂DDMAA存在下,灵敏度提高10.3倍(Mn~(2+)量为0~6.0μg/L)和5.3倍(Mn~(2+)量为6.0~14μg/L),相对标准偏差为0.5%,检出限为5.6×10~(-8)g/L,可用于酒样和谷物制品中锰的测定。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献