聚对氨基苯磺酸修饰电极差分脉冲伏安法测定对乙酰氨基酚

在由pH 7.0的磷酸盐缓冲溶液和2.0×10~(-3)mol·L~(-1)对氨基苯磺酸组成的支持电解质中,以100mV·s~(-1)扫描速率在玻碳电极上先后在电位-1.5～2.5V范围内循环扫描10周、在电位-1.5～1.5V范围内循环扫描15min,制得聚对氨基苯磺酸修饰的玻碳电极。循环伏安法研究发现:对乙酰氨基酚在该修饰电极上出现了一对氧化还原峰,两峰的电位差为30mV;差分脉冲伏安法研究发现:在pH5.9的磷酸盐缓冲溶液中,对乙酰氨基酚在0.295V处出现一良好的氧化峰。且乙酰氨基酚的浓度在2.0×10~(-7)～1.0×10~(-5)mol·L~(-1)范围内与峰电流呈线性关系,检出限(3S/N)为9.0×10~(-8)mol·L~(-1)。据此提出了差分脉冲伏安法测定药片中对乙酰氨基酚的含量,3个样品的测定结果与标示值相符,测得平均回收率为98.6%,相对标准偏差(n=6)均小于3.5%。     

聚对氨基苯磺酸修饰电极差分脉冲伏安法测定多巴胺

采用电化学方法将对氨基苯磺酸聚合在玻碳电极表面制得聚对氨基苯磺酸修饰电极,并用循环伏安法和差分脉冲伏安法研究了多巴胺在该修饰电极上的电化学行为。结果表明:在pH 7.0的磷酸盐缓冲溶液中,多巴胺在0.148 V处出现一良好的氧化峰。多巴胺浓度在4.0×10-7~1.0×10-5mol.L-1范围内与其峰电流呈线性关系,检出限(3S/N)为1.0×10-7mol.L-1。将该法用于针剂中多巴胺的测定,回收率在91.0%~112.0%之间,相对标准偏差(n=5)在2.4%~3.2%之间。     

氨基酸和金属分层修饰电极的制备及对麝香草酚的测定

用循环伏安法制备了不同类型的金属、氨基酸分层修饰电极,用阻抗谱对修饰电极进行了表征,以麝香草酚作为探针,研究了麝香草酚在不同修饰电极上的电化学行为。其中用银和L-苯丙氨酸分层修饰电极测定麝香草酚,峰电流最大。在最佳条件下,麝香草酚在银、L-苯丙氨酸分层修饰电极上产生一个明显的氧化峰,峰电位为:Epa=0.795 V,用循环伏安法进行测定时,峰电流与麝香草酚胺浓度在1.00×10~(-5)~1.00×10~(-3)mol·L~(-1)呈良好的线性关系,检出限为5.0×10~(-6)mol·L~(-1)。用差分脉冲法测定时,峰电流与麝香草酚浓度在7.50×10~(-6)~7.50×10~(-4)mol·L~(-1)呈良好的线性关系,检出限为8.0×10~(-7)mol·L~(-1)。该法用于药品中麝香草酚的测定,结果满意。     

百草枯在氧化石墨烯修饰玻碳电极上的电化学行为及其差分脉冲伏安测定

将氧化石墨烯悬浮液(1g·L~(-1))10μL滴涂于玻碳电极表面,烘干后,在0.10mol·L~(-1)的KH_2PO_4溶液中于-0.9V还原600s制备了氧化石墨烯修饰玻碳电极,用扫描电子显微镜、透射电子显微镜和电化学方法对修饰电极进行了表征。用差分脉冲伏安法研究了百草枯在氧化石墨烯修饰电极上的电化学行为,发现此修饰电极对百草枯的还原有明显的电催化作用。百草枯在pH 7.5的磷酸盐缓冲溶液中,在氧化石墨烯修饰电极上产生催化还原反应,在差分脉冲伏安曲线上先后在-0.6,-0.1V处出现2个还原峰。因后者与底液的还原峰重叠,故测定中采用-0.6V处的还原峰电流为测量值。经试验,百草枯在修饰电极上的富集电位为-0.6V,富集时间为200s,选用的扫描速率为50 mV·s~(-1)。在最佳试验条件下百草枯浓度在9.00×10~(-7)～1.00×10~(-5) mol·L~(-1)和1.00×10~(-5)～5.00×10~(-5) mol·L~(-1)内与其在-0.6V处的还原峰电流呈线性关系,检出限(3s/k)为1.64×10~(-7) mol·L~(-1)。方法应用于农药中百草枯含量的测定,测定值与标示值相符,对土壤样品进行加标回收试验,回收率在89.5%～114%之间。     

基于钯/壳聚糖/氧化还原石墨烯修饰电极的制备 及对利发霉素的检测

制备了钯(Pd)/壳聚糖-还原氧化石墨烯(CS-RGO)修饰电极。采用循环伏安法研究了利发霉素在该修饰电极上的电化学行为,并利用示差脉冲伏安法对其进行测定。在0.1 mol·L~(-1)的磷酸盐缓冲溶液(PBS,pH=7.0)中,利发霉素的氧化峰电流大小与其浓度在1.0×10~(-7)～1.0×10~(-3) mol·L~(-1)浓度范围内成良好的一次线性关系,检出限为7.4×10~(-9) mol·L~(-1)(S/N=3)。此外,该修饰电极具有很好的稳定性和抗干扰能力。     

长春地辛在硫化铜纳米花/石墨烯修饰玻碳电极上的电化学行为

通过改进的Hummers法和溶剂热法分别制备了石墨烯和硫化铜纳米花。采用滴涂法进一步依次将石墨烯和硫化铜纳米花修饰于玻碳电极,制备了硫化铜纳米花/石墨烯修饰玻碳电极(Nanoflower CuS/GR/GCE)。利用循环伏安法和差分脉冲伏安法等研究了长春地辛在该修饰电极的电化学行为。结果表明:长春地辛的浓度在1.0×10~(-8)~1.0×10~(-7) mol·L~(-1),1.0×10~(-7)~1.1×10~(-5) mol·L~(-1)及1.1×10~(-5)~1.0×10-4 mol·L~(-1)内与其对应的峰电流的减小量呈线性关系,检出限(3S/N)为4.9×10~(-9 )mol·L~(-1)。对1.0×10~(-6) mol·L~(-1)长春地辛标准溶液连续测定5次,测定值的相对标准偏差为1.2%。方法用于长春地辛药品样品的分析,加标回收率在97.1%~103%之间。     

对苯二酚在普鲁士蓝/聚对氨基苯磺酸复合膜修饰电极上电化学行为的探究

采用电沉积法制备了普鲁士蓝/聚对氨基苯磺酸(PB/p-ABSA)复合膜修饰电极,并研究了对苯二酚在该电极上的电化学行为。实验发现,对苯二酚在该修饰电极上的氧化还原反应是受扩散控制的两质子两电子转移过程;在1.0×10~(-4)～1.5×10~(-2) mol·L~(-1)的范围内,峰电流与对苯二酚浓度呈良好的线性关系,线性方程为lgI=0.8161lgc+4.0282,R~2=0.9993,检出限为3.0×10~(-5) mol·L~(-1)。结果表明,与裸电极、PB修饰电极相比,PB/p-ABSA复合膜修饰电极对对苯二酚催化效果更佳。采用标准加入法对模拟水样中对苯二酚的含量进行了测定,回收率在95.0%～106.3%之间,表明该法准确度高,可靠性强。     

ZnSe-C60修饰玻碳电极用于测定水中甲萘酚的含量

将C_(60)分散在ZnSe量子点溶液中,将此悬浮液滴涂于玻碳电极表面,自然晾干后制得ZnSe-C_(60)修饰电极,以循环伏安法研究了甲萘酚在此修饰电极上的电化学行为。结果表明:与ZnSe修饰电极和C_(60)修饰电极相比较,甲萘酚在ZnSe-C_(60)修饰电极表面的电化学响应效果最好。以pH 8.0磷酸盐缓冲溶液为底液,在1.0～-1.0V电压范围内,以0.10V·s~(-1)的扫描速率,采用微分脉冲伏安法对甲萘酚进行测定,甲萘酚的浓度在3.0×10~(-6)～1.5×10~(-5) mol·L~(-1)内与其氧化峰电流呈线性关系,检出限(3S/N)为1.0×10~(-6) mol·L~(-1)。方法应用于水样中甲萘酚的测定,结果与标准方法测定值相符,加标回收率在96.5%～104%之间,测定值的相对标准偏差(n=5)在2.3%～4.4%之间。     

三聚氰胺修饰玻碳电极用于溶出伏安法测定水样中痕量银

用电化学沉积法将三聚氰胺修饰在玻碳电极上,应用此三聚氰胺修饰玻碳电极测定银时,试液在pH 4.6的乙酸-乙酸钠缓冲溶液中,在—0.45V处还原60 s,然后在0～+0.6V范围内扫描,使银离子从修饰电极上溶出,实现了水样中银离子的溶出伏安法测定,在+0.27V处可得银离子的氧化峰电位,银的浓度在6.0×10~(-9)～5.0×10~(-7)mol·L~(-1)范围内与其峰电流呈线性关系,检出限(3S/N)为1.0×10~(-9)mol·L~(-1)。方法用于实际水样中痕量银的测定,加标回收率在90.0%～96.0%之间。     

石墨烯修饰的三唑磷分子印迹电化学传感器的制备

采用石墨烯作为电极增敏材料,制备三唑磷(TAP)分子印迹电化学传感器。采用自由基聚合法,在石墨烯修饰电极(GR/GCE)上合成分子印迹聚合物膜(MIP)。利用微分脉冲伏安法、电化学阻抗谱对不同修饰电极进行电化学表征,利用微分脉冲伏安法考察了MIP和非分子印迹聚合物膜(NIP)传感器的电化学性能。在最优实验条件下,TAP浓度在1.0×10~(-7)～2.0×10~(-5)mol·L~(-1)内和MIP膜传感器峰电流呈线性关系,检出限为4.3×10~(-8)mol·L~(-1)(S/N=3)。建立MIP膜传感器的动力学吸附模型,测得结合速率常数k为9.0580 s。     

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%.     

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.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.