原子荧光光谱法测定中药材中砷

试样用硝酸加压消解(测总砷),或用盐酸(1+1)溶液在60℃浸取(测无机砷)。以硫脲溶液作为预还原剂,以硼氢化钾溶液作为还原剂,利用原子荧光光谱法测定中药材中砷的含量。分析中采用载气及屏蔽气的流量依次为400mL·min-1及900mL·min-1。砷(Ⅲ)的荧光强度与其质量浓度在80.0μg·L-1以内呈线性关系,方法的检出限(3s/k)为31ng·L-1。应用此法对中药材样品进行分析,样品中总砷测定值在139～372ng·g-1之间,加标回收率在89.0%～93.3%之间;无机砷测定值在41～103ng·g-1之间,加标回收率在86.0%～92.0%之间。     

氢化物发生-原子荧光光谱法同时测定陈皮中砷和汞

采用微波消解法消解陈皮样品,利用氢化物发生-原子荧光光谱法同时测定陈皮中砷和汞.研究并优化了硼氢化钾的用量、消解介质的酸度、共存离子的干扰和消除等试验条件.荧光强度与砷及汞的质量浓度在20.0μg·L-1及2.00 μg·L-1以内呈线性关系,方法的检出限为0.084μg·L-1(砷)和0.022 μg·L-1(汞).应用此法分析了6个陈皮试样,测定值的相对标准偏差均小于7.0%,以标准加入法做回收率试验,平均回收率分别为93.6%(砷)和90.7%(汞).     

微波消解试样-原子荧光光谱法测定土壤中硒碲

应用HG-AFS法及微波加热试样消解法测定了土壤中硒和碲的含量,对试样消解参数、仪器工作条件及氢化物发生反应条件等作了试验并讨论.该方法测定硒及碲的检出限均为0.01μg·g-1,荧光强度与硒及碲的质量浓度在5～100μg·L-1及0.5～10μg·L-1范围内呈线性关系.应用此方法分析了3个土壤试样,测定值的相对标准偏差(n=6)均小于5%.用标准加入法作了回收试验,硒的回收率在92.0%～102.6%之间,碲的回收率在90.1%～98.8%之间.     

微波消解-原子荧光光谱法测定皮革中砷和汞

建立了皮革中砷和汞的微波消解-原子荧光光谱测定方法。在优化的实验条件下,砷、汞含量分别在0.60～150ng/mL和0.10～20ng/mL范围内线性良好。砷、汞检出限分别为0.22ng/mL和0.04ng/mL。方法测定砷的回收率为96.0%～104%,汞的回收率为95.0%～110%。方法准确、灵敏、快速、可应用于皮革样品中砷和汞的同时测定。     

电感耦合等离子体质谱法测定蒺藜皂苷中有害元素

蒺藜皂苷样品经高压密闭罐消解处理,采用电感耦合等离子体质谱法测定其中铬、锰、镍、镉、钡、铜、锌、砷、硒、汞、铅等11种有害元素的含量。在优化的仪器工作条件下,砷和汞的检出限(3σ)为1×10-4μg.g-1,其余各元素为1×10-5μg.g-1。11种元素的回收率在94.4%～111.8%之间。方法用于茶叶标准物质(GBW 08505)分析,所获得的测定值与标准值相吻合。     

微波消解样品-电感耦合等离子体原子发射光谱法测定铅精矿中铅、砷、镉、汞

采用微波消解样品-电感耦合等离子体原子发射光谱法同时测定铅精矿中主体元素铅及有毒有害元素砷、镉、汞的含量。0.20g试样置于消解罐中,先后加入硝酸9mL、盐酸3mL、氟硼酸2mL及过氧化氢2.5mL,密闭罐盖按设定的微波消解程序进行消解。试验选择铅、砷、镉和汞的分析线分别为220.351,189.042,228.802,184.950nm以消除基体干扰。铅、砷、镉、汞的检出限分别为16.0,2.2,0.4,0.8μg.g-1。方法用于铅精矿标准样品(GBW 07617)和铅精矿实际样品分析,此方法的测定值与认定值及原子吸收光谱法或原子荧光光谱法的测定值相一致。方法的相对标准偏差(n=10)在0.15%～3.9%之间。     

冷原子荧光光谱法测定沉积物中总汞方法的改进

应用国家标准方法(GB/T 22105.1-2008)测定沉积物中总汞量时,对其中的样品消解方法作如下改进:①试样置于盐酸-硝酸(3+1)混合酸中浸泡过夜,次日加水定容为50mL,取其上层清液供冷原子荧光光谱法测定其总汞量;②上述试样溶液如在1～3d内分析毋需加入保护剂及稀释剂,按改进后的方法,总汞的质量浓度在4.00ng.L-1以内与荧光强度呈线性关系,检出限(3S/N)为0.011ng.L-1。用于沉积物中总汞的测定,经t-检验与国家标准方法测定值无显著差异。方法的日内(n=6)和日间(n=5)相对标准偏差分别在1.1%～3.7%和5.9%～7.0%之间。     

微波消解-原子荧光光谱法测定海洋生物体中汞

应用原子荧光光谱法测定海洋生物体中汞的含量。试样用盐酸、硝酸和过氧化氢混合溶液在微波消解仪中消解处理,经试验选定消解程序为:①消解功率1 600 W;②5min升温至120℃,保持5min;③5min升温至160℃,保持10min。分析时仪器工作条件为负高压260V,灯电流为40mA,载气流量为800mL.min-1。汞的质量浓度在0.80μg.L-1以内与相应的荧光强度呈线性关系,方法检出限(3s/k)为0.002mg.kg-1。方法用于测定海洋生物体中汞的含量,测定值的相对标准偏差(n=6)在2.7%～6.0%之间,加标回收率在90%～104%之间。     

微波消解样品-原子荧光光谱法同时测定海苔中砷和汞

采用微波消解技术处理样品,用原子荧光光谱法同时测定海苔中砷和汞.砷和汞的回收率分别为90.0%～97.0%和90.0%～94.0%;砷和汞的检出限(S/N=3)分别为0.10μg·L-1和0.01μg·L-1.     

原子荧光光谱法测定土壤中的砷和汞

采用原子荧光光谱法测定土壤中的砷和汞。样品经微波消解后,采用On-Guard H前处理柱去除消解液中的干扰离子,然后进行测定。在最佳条件下,砷和汞的线性范围为0.50~8.00μg·L-1,检出限(3s/k)分别为0.005,0.002μg·g-1。方法用于分析标准物质,测定值与认定值相符,测定值的相对标准偏差(n=6)小于4%。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

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.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

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.