铋B-芦丁体系的微分吸附计时电位法研究

提出一种测定痕量铋的微分吸附计时电位法。利用悬汞电极作工作电极 ,置富集电位于 0 .10V ,在0 .0 15mol/LHAc 0 0 0 5mol/LNaAc 7.5× 10 -7mol/L芦丁的底液中 ,测定铋 的线性范围为 1.0× 10 -10 ～7 5× 10 -8mol/L ,检出限为 5× 10 -11mol/L。探讨了影响方法灵敏度的主要因素 ,研究了电极过程。利用此法测定了中草药样品中的铋含量 ,结果满意。     

铋(Ⅲ)-芦丁体系的微分吸附计时电位法研究

提出一种测定痕量铋的微分吸附计时电位法.利用悬汞电极作工作电极,置富集电位于0.10 V,在0.015 mol/L HAc-0.005 mol/L NaAc-7.5×10-7 mol/L芦丁的底液中,测定铋(Ⅲ)的线性范围为1.0×10-10～7.5×10-8 mol/L,检出限为5×10-11 mol/L.探讨了影响方法灵敏度的主要因素,研究了电极过程.利用此法测定了中草药样品中的铋含量,结果满意.     

阿霉素在多壁碳纳米管膜电极上的电化学行为及其分析研究

报道了一种多壁碳纳米管(MWNT)膜电极的制备方法。研究了阿霉素(ADM)在多壁碳纳米管膜电极上的电化学行为。优化了测定阿霉素的各实验参数,实验证实,ADM浓度在2.0×10-8～1.0×10-5mol/L之间其还原峰电流与浓度有良好的线性关系。富集4min后检测,本法的检出限为5.0×10-9mol/L。用此膜电极测定了病人服用阿霉素后尿样中阿霉素的浓度,取得了满意的结果。     

丝氨酸织组膜电极的研究

利用猪肝组织膜配合氨气敏电极,研制了丝氨酸生物催化传感电极。丝氨酸浓度的测定范围为5.1×10~(-5)～3.2×10~(-3)mol/L,检出限为3.1×10~(-5)mol/L。研究和讨论了电极的最佳工作条件,并测定了实验条件下酶催化反应的米氏常数Km。该电极用于合成样品分析,效果满意。     

杯芳烃修饰玻碳电极吸附溶出伏安法测定微量铅

研究了以杯芳烃衍生物修饰玻碳电极,以其吸附溶出伏安法测定微量铅。对富集时间、铅的浓度、支持电解质、样品溶液pH值及部分离子干扰等进行了实验。实验发现以氢氧化钠溶液处理修饰电极可提高测定灵敏度,经过优化处理后,线性范围和检出限分别为5.0×10-7～1.0×10-5mol/L和1.0×10-8mol/L。应用本法对合成水样进行了测定,结果满意。本文还对吸附溶出机理进行了讨论。     

丁二酮肟修饰碳糊电极阳极溶出伏安法测定痕量铋

报道了用丁二酮肟修饰碳糊电极测定微量铋的电分析方法。Bi~(3+)通过与电极表面的丁二酮肟作用而富集在电极表面,同时在-0.40 V(vs.SCE)还原成零价,当电极电势从-0.40 V向0.40 V扫描时,被还原的铋从电极表面溶出,在0.03 V出现一个十分灵敏的阳极溶出峰。优化了各种实验参数,如支持电解质的选择及pH值、丁二酮肟的用量、富集电位及时间等。修饰电极测定铋的线性范围为1×10~(-9)～1×10~(-6)mol/L。富集6 min后检出限可达4×10~(-10)mol/L。该方法简便快速,灵敏度高,分析成本低廉,并成功应用于实际水样中微量铋的测定。     

核黄素的微分脉冲溶出伏安分析

采用循环伏安法和微分脉冲溶出伏安法,对核黄素在裸金电极和巯基化合物分子自组装膜修饰金电极上的电化学行为进行了研究,发现在pH4.8的B-R缓冲溶液中,核黄素在裸金电极和分子自组装膜修饰金电极上均于-0.35V左右产生一对可逆的氧化还原峰。核黄素在裸金电极和谷胱甘肽、三巯基丙酸、二巯基苯丙咪唑分子自组装膜修饰金电极上,其浓度分别在3.0×10-7～2.3×10-4mol/L、1.05×10-6～2.0×10-4mol/L、2.1×10-6～2.08×10-4mol/L、1.05×10-6～2.0×10-4mol/L范围内与微分脉冲伏安峰峰电流之间有良好的线性关系,其相关系数分别为0.9932、0.9909、0.9857、0.9832,核黄素的检出限为2.1×10-7mol/L、5.2×10-7mol/L、8.6×10-7mol/L、5.2×10-7mol/L。对浓度为1.0×10-5mol/L的核黄素进行10次平行测定,所得峰电流的相对标准偏差为2.0%。将该方法用于核黄素片剂和复合维生素B片剂的测定,结果令人满意。     

基于尼古丁对胆碱氧化酶的抑制作用测定尼古丁的研究

基于尼古丁对胆碱氧化酶(CHOD)的抑制作用,将胆碱氧化酶电极用于微量尼古丁的测定。酶电极制作中,先在铂电极表面修饰一层壳聚糖膜,再用戊二醛交联CHOD。采用这种酶固定化方法,电极在4. 0×10-6 ~ 3×10-3 mol/L胆碱的浓度范围呈线性关系。探讨了工作电位、pH、底物浓度等实验条件对酶电极性能及抑制过程中响应电流的影响,测定了电极的重现性、干扰及使用寿命。电极检测尼古丁的线性范围为1. 5×10-5 ~3×10-3 mol/L;检出限为1. 25×10-5 mol/L。将电极用于实际样品烟草中尼古丁回收率的测定,结果良好。     

就地镀铜旋转圆盘玻碳电极上阳极溶出测定砷(Ⅳ)

在铜或硒存在下利用悬汞电极阴极溶出测定砷已见报道,但使用玻碳电极进行砷的测定尚属少见。砷的阳极溶出法因汞电极中汞的氧化干扰而无法进行。本实验采用就地镀铜玻碳电极作工作电极成功地进行砷的阳极溶出法测定。 (一)操作步骤加入适量的砷、铜及硫酸溶液到50ml容量瓶中使砷的最终浓度为1.0×10~(-7)mol/L-9.0×10~(-6)mol/L,铜(Ⅱ)为4.0×10~(-6)mol/L,硫酸为0.6mol/L。将溶液转入石英电解池中,通氮除氧5min,在-0.60V沉     

聚氯乙烯膜普鲁卡因选择电极的研制与应用

研制了一种以普鲁卡因碘化物与碘化铋形成的缔合物为电活性物质的PVC(聚氯乙烯 )膜普鲁卡因选择电极 ,测定了普鲁卡因注射液的含量 ;电极的线性响应范围1.0×10 -1～6.3×10 -5mol/L,级差电位为45mV/pc ,检出限为3.4×10-5 mol/L ;该电极响应迅速 ,测定结果与药典法相符     

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.     

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.     

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.     

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.