茜素紫修饰碳糊电极吸附阳极溶出伏安法测定痕量锑的研究

报道了采用茜素紫修饰碳糊电极测定痕量锑的阳极溶出伏安法。在 0 .0 3mol·L- 1邻苯二甲酸氢钾 盐酸缓冲溶液 (pH 2 .4 )中 ,通过开路富集 ,Sb(Ⅲ )与茜素紫形成络合物而富集于电极表面 ,然后交换介质至 0 .6mol·L- 1盐酸中 ,于 - 0 .6 0V还原后再进行阳极化扫描 ,于 - 0 .50V左右获得一灵敏的锑的溶出峰 ,二次导数峰电流与Sb(Ⅲ )的浓度在 4 .1× 10 - 9～ 2 .9× 10 - 7mol·L- 1范围内呈线性关系 ,检出限达 1.6× 10 - 9mol·L- 1。方法应用于水样中锑的测定 ,结果满意     

氢化物发生结合电感耦合等离子体原子发射光谱法测定天然水样中Sb(Ⅲ)和Sb(V)

提出了氢化物发生结合电感耦合等离子体-原子发射光谱法(HG-ICP-AES)测定河水和土壤提取液中Sb(Ⅲ)和Sb(V)的方法,在pH 4.5～5.5的HOAc-NaOAc介质中,Sb(Ⅲ)与NaBH4反应生成SbH3,而Sb(V)不与NaBH4反应,这样可测出Sb(Ⅲ);而在3.0mol·L-1HCl中,用KI还原Sb(V)为Sb(Ⅲ),可测定总锑量.差减法得Sb(V).该方法的Sb(Ⅲ)和总锑检出限分别为0.30和0.63ng·ml-1,河水和土壤提取液的回收率为90%～100%,证明其适用于天然水样中Sb(Ⅲ)和Sb(V)的检测.     

氢化物发生结合电感耦合等离子体原子发射光谱法测定天然水样中Sb（Ⅲ）和Sb（Ⅴ）

提出了氢化物发生结合电感耦合等离子体 原子发射光谱法(HG ICP AES)测定河水和土壤提取液中Sb(Ⅲ)和Sb(Ⅴ)的方法,在pH4.5～5.5的HOAc NaOAc介质中,Sb(Ⅲ)与NaBH4反应生成SbH3,而Sb(Ⅴ)不与NaBH4反应,这样可测出Sb(Ⅲ);而在3.0mol·L-1HCl中,用KI还原Sb(Ⅴ)为Sb(Ⅲ),可测定总锑量。差减法得Sb(Ⅴ)。该方法的Sb(Ⅲ)和总锑检出限分别为0.30和0.63ng·ml-1,河水和土壤提取液的回收率为90%～100%,证明其适用于天然水样中Sb(Ⅲ)和Sb(Ⅴ)的检测。     

锑(Ⅲ)-钛铁试剂-溴化十六烷基三甲胺体系极谱络合吸附波研究

在 0 .0 4mol·L- 1磷酸中 ,锑 (Ⅲ ) 钛铁试剂 (Tiron) 溴化十六烷基三甲胺体系产生灵敏的极谱络合吸附波。峰电位为 - 0 .4 4V(vs .SCE) ,二阶导数峰高与锑 (Ⅲ )浓度在 8.2× 10 - 10 ～ 2 .0× 10 - 6mol·L- 1范围内呈线性关系 ,检出限达 4× 10 - 10 mol·L- 1。研究了极谱波的性质及电极反应机理。方法应用于三氧化二砷及铜合金中微量锑的直接测定 ,结果满意     

氢化物发生-原子吸收光谱法测定锑(Ⅲ)和锑(Ⅴ)

提出在酸性条件下以氟化钠为掩蔽剂测定锑(Ⅲ),在碱性介质中加入氟化钠消除价态的影响测定锑总量,两者相减求出锑(Ⅴ),实现对锑(Ⅲ)和锑(Ⅴ)的分别测定.研究了在酸性介质中测定锑(Ⅲ)及碱性介质中测定锑总量的条件及共存离子的干扰和消除.工作曲线的线性范围为：0～20 μg·L-1锑(Ⅲ);0～80 μg·L-1锑(Ⅴ),相关系数大于0.999,方法的检出限为0.31 μg·L-1锑(Ⅲ),0.69 μg·L-1锑(Ⅴ).对水样和土壤样品进行了测定,相对标准偏差(RSD)小于5%.     

示波极谱法直接快速测定痕量锑的研究

在0.06 mol.L-1硫酸溶液中,Sb(Ⅲ)与焦性没食子酸络合物产生一个灵敏的导数极谱波,峰电位为-0.4 V(vs.SCE),有微量Se(Ⅳ)存在下,灵敏度大为提高,锑浓度在0.03~1.2 mg.L-1范围内峰高与浓度呈线性关系,应用于锌电解液中痕量锑的测定。检出限为0.004 mg.L-1,RSD为1.8%~2.2%,回收率为95.0%~105.0%。     

合金钢中微量锑的富集条件的探讨

锑在钢中的存在形式及作用与砷相似 ,系有害杂质元素 ,因此一般须严格控制其含量甚微(<0 .0 1 % ) [1] ,对于标样的定值 ,常采用 GB2 2 3.47- 95载体沉淀 -钼蓝光度法测定锑的方法 ,对于合金钢的分析 ,该方法在实际应用过程中存在一些问题 ,即沉淀分离不易完全 ,致使结果偏低。本文针对这一问题开展试验 ,进行方法改进 ,结果比较满意。1　试验部分1 .1　主要试剂与仪器亚硫酸钠溶液 :1 0 0 g· L-1酒石酸钠溶液 :2 0 g· L-1抗坏血酸溶液 :90 g· L-1显色剂溶液 :称取磷酸二氢钾 0 .0 55g和钼酸钠(Na2 Mo O4 · 2 H2 O) 3.61 g溶于水中…     

电位溶出法间接测定血清中钙镁

利用钙置换Zn EGTA中锌 ,镁置换Zn EDTA中锌 ,采用计时电位溶出法间接地测定血清中钙镁含量。血清用量仅为 2 0 μl,且不必消化 ,钙的线性范围为 0～ 4 80 μg·L- 1,检出限为 2 μg·L- 1,相关系数为 0 .9976 (n =6 ) ,镁的线性范围为 0～ 2 88μg·L- 1,检出限为 1μg·L- 1,相关系数为0 .9984 (n =6 )。用模拟血清测定钙的平均回收率为 99.4 % ,镁的平均回收率为 10 0 .1%。     

石墨炉原子吸收光谱法测定玻璃器皿浸出的锑量

用乙酸(4+96)浸泡玻璃器皿24 h±10 min,使锑离子从玻璃器皿样品中漫出.用石墨炉原子吸收光谱法测定所得溶液中锑量,测定中加入铜(Ⅱ)离子作基体改进剂并采用氘灯扣背景,在制作工作曲线及空白溶液时采用与试样处理匹配的方法抵消了由乙酸存在而引起的误差.对石墨炉的升温程序,特别是灰化温度和原子化温度做了试验并对相关条件予以优化.结果表明:在所测得的吸光度与锑(Ⅲ)的质量浓度在20μg·L-1以内呈线性关系,方法的检出限(3S/b)为0.483μg·L-1,锑的特征浓度为0.396 pg/1%.用标准加入法做了回收试验,测得回收率在93%～104%之间.     

单扫示波极谱法连续测定水样中锑和锡

在pH 2.1的H_2SO_4-NaOAc介质中,有微量Se(Ⅳ)存在时,Sb(Ⅱ)或Sn(Ⅳ)—草酸铵—α,α′-联吡啶络合物产生灵敏的络合吸附催化波。锑和锡浓度分别在0.5～200ng·ml~(-1)和0.8～250ng·ml~(-1)范围内与峰高呈线性关系。锑和锡的检出限分别为0.2ng·ml~(-1)和0.4ng·ml~(-1)。方法用于水样中痕量锑、锡的连续测定,结果满意。     

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.     

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.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.