纳米氧化铁修饰玻碳电极检测痕量镉离子

制备了一种纳米氧化铁修饰玻碳电极,并研究了镉离子在该修饰电极上的溶出伏安行为。结果表明,纳米氧化铁颗粒能有效促进镉离子的溶出伏安响应。在pH 6.0的磷酸缓冲溶液中,镉离子能有效吸附在纳米氧化铁表面并在-1.0 V时被还原。被还原的镉在正向扫描过程中可以重新氧化,并在-0.85 V处出现一明显的溶出伏安氧化峰。该峰电流随镉离子浓度的增大而增大,可用于对镉离子的检测。在最佳检测条件(pH 6.0,富集时间350 s,富集电位-1.0 V)下,镉离子的响应电流与其浓度在6.0×10-10～1.0×10-8mol/L以及1.0×10-8～1.0×10-5 mol/L范围内呈良好线性,检出限(S/N=3)为1.0×10-10 mol/L。干扰实验结果表明,一些常见的阳离子以及阴离子对镉离子的检测无明显干扰。将该方法用于实际样品的检测,回收率良好。     

差分脉冲溶出伏安法测定陶瓷器皿中铅和镉的溶出率

采用4%的乙酸浸泡陶瓷样品24 h,应用同位镀汞差分脉冲溶出伏安法测定了陶瓷样品中微量重金属铅、镉的溶出量。以0.1 mol/L的硝酸溶液做底液,0.1 mol/L的KCl溶液做支持电解质,2 g/L的Hg2+溶液做镀汞液,测得铅的溶出峰电位为-0.5 V(vsSCE),镉的溶出峰电位为-0.7 V(vsSCE),两者含量在5×10-4～1 mg/L和5×10-4～0.5 mg/L范围内峰电流和其含量呈良好的线性关系,检出限分别为2×10-4和4.3×10-3mg/L。     

聚赖氨酸/多壁碳纳米管修饰电极测定大米中的铅

通过滴涂及电聚合方式分别将多壁碳纳米管和赖氨酸共修饰于玻碳电极上,制备出聚赖氨酸/多壁碳纳米管修饰电极,并建立了阳极溶出伏安法测定铅离子的新方法。采用线性扫描伏安法及循环伏安法研究了铅离子在修饰电极上的电化学行为,并考察了测定底液、底液p H值、富集电位、富集时间等条件的影响。在最佳实验条件下,铅离子的溶出峰电流与其浓度在2.0×10-7~8.0×10-5mol·L-1范围内呈良好的线性关系,检出限为1.0×10-7mol·L-1。利用所制备的修饰电极对大米样品进行加标回收实验,回收率为98%~102%。该方法具有良好的灵敏度和稳定性,已成功应用于大米样品中铅离子的测定。     

茜素红S/多壁碳纳米管修饰碳糊电极阳极溶出伏安法测定痕量铜

制备了茜素红S/多壁碳纳米管修饰碳糊电极,提出了一种灵敏的溶出伏安法测定痕量铜的新方法.在极谱分析仪上采用二阶导数线性扫描伏安法进行分析,在0.1 moL/L的HAc-NaAc缓冲溶液(pH 4.1)中,Cu与修饰电极表面的茜素红S(ARS)形成Cu(Ⅱ)-ARS络合物而富集于电极表面,于-400 mV处还原后,再进行阳极化扫描,于64 mV处获得一灵敏的铜的阳极溶出峰,峰电流与Cu(Ⅱ)浓度在2×10-11 mol/L～6×10-7 mol/L范围内呈良好的线性关系,检出限(S/N=3) 为8.0×10-12 mol/L(富集时间240 s).方法应用于人发中铜含量的测定,回收率为98%～102%.     

碳糊电极阳极吸附伏安法测定洛美沙星

报道了碳糊电极阳极吸附伏安法测定洛美沙星的新方法。在0.096mol L的KHP NaOH(pH5.4)缓冲液中,用碳糊电极为工作电极,在0.3V(vs.SCE)富集一定时间,然后从0.3～1 3V以300mV s扫速线性扫描,记录其在1 02V的二次导数阳极溶出峰。溶出峰电流与洛美沙星浓度在8.0×10-9～8.0×10-8mol L(富集90s)和8.0×10-8～8.0×10-7mol L(富集30s)范围内呈良好的线性关系,相关系数分别为0.9844和0.9967,检出限为9.0×10-10mol L(S N=3)。探讨了洛美沙星在碳糊电极上的伏安性质和电极反应机理,并且成功地应用于人体尿液中洛美沙星的测定,结果与紫外光度法基本吻合。     

聚邻苯三酚修饰电极的制备及其对铜(Ⅱ)的测定

采用电化学方法在pH 7.0磷酸缓冲溶液(PBS)中,将邻苯三酚氧化电聚合制成稳定的水不溶性膜修饰在玻碳电极(GCE)表面,将制得的膜修饰电极(PPG/GCE)在一定电位下选择性预富集铜(Ⅱ),并用差分脉冲溶出伏安法测定。结果表明,该膜修饰电极对铜(Ⅱ)的富集作用明显强于裸玻碳电极。对电聚合条件、富集和溶出介质、还原时间、富集电位等实验参数进行了考察,在优化实验条件下,Cu(Ⅱ)的浓度在5.0×10-8~1.0×10-5mol/L范围内与阳极氧化峰电流呈线性关系,相关系数为0.998 1,检出限为1.0×10-9mol/L。制得的修饰电极具有较高的灵敏度和选择性,可用于实际样品人发的分析,样品的回收率为99%~104%。     

石墨烯修饰电极对维生素B12的电化学响应及其分析应用

应用石墨烯修饰的玻碳电极结合循环伏安法研究了维生素B12在该电极上的电化学行为;用差示脉冲溶出伏安法考察了石墨烯修饰量、缓冲溶液种类、pH、富集电位及富集时间对响应电流的影响。在最佳实验条件下,响应电流与维生素B12的浓度在1.6×10-7~9.5×10-6mol/L范围内有良好的线性相关,检出限为5.9×10-8mol/L。方法可用于药物和人尿样品中维生素B12的检测。     

锆-钙-茜素红异多核配合物在碳纳米管修饰电极上的阴极吸附伏安法行为及分析应用

制备了碳纳米管修饰碳黑微电极,研究了锆-钙-茜素红异多核络合物在该电极上的阴极吸附伏安行为,提出了一种测定痕量锆的新方法.采用二阶导数线性扫描伏安法进行分析.在0.096mol/L乙酸-0.048mol/L邻苯二甲酸氢钾缓冲液(pH=3.8)中,络合物吸附在碳黑微电极表面,于-502mV(vs SCE)处产生1灵敏的溶出峰,峰电流与锆的浓度在6.0×10<-12>～8.0×10-7mol/L范围内呈良好的线性关系,检出限(S/N=3)为4.0×10-12mol/L(富集时间180s).用于岩矿样品中痕量锆的测定,结果满意.     

石墨烯/聚邻苯二胺膜修饰碳糊电极电催化性能的研究

研制了一种新型的石墨烯/聚邻苯二胺膜饰碳糊电极(GR/PPD/CPE)。在NaH2PO4-Na2HPO4缓冲溶液(pH 7.3)中,利用循环伏安法研究了对苯二酚(HQ)和邻苯二酚(CC)在该修饰电极上的电化学行为,利用线性扫描溶出伏安法研究了扫速与峰电流或峰电位的关系,利用微分脉冲溶出伏安法测定了HQ和CC的含量,线性范围分别为6.5×10-7~5.0×10-4mol/L和1.0×10-7~5.0×10-4mol/L,检出限(S/N=3)分别为8.0×10-8mol/L和2.0×10-7mol/L。方法用于自来水样中的HQ和CC的测定,回收率在96.5%~102.5%之间。     

1-(3-硝基苯基)-3-[4-(苯基偶氮)苯基]-三氮烯修饰碳糊电极测定痕量锡

制备了三氮烯修饰碳糊电极(m-NPPAPT/CPE),并研究了Sn(Ⅱ)在该电极上的吸附伏安行为,建立了一种测定痕量锡(Ⅱ)的新方法。采用二阶导数线性扫描溶出伏安法进行分析。结果表明:在1mL 0.5mol/L HCl溶液中,于-1200mV处搅拌富集一定时间,在-1200～-200mV范围内以150mV/s的扫描速度线性扫描,Sn(Ⅱ)吸附在修饰电极表面,于约-476mV(vs SCE)处产生一个灵敏的阳极溶出峰,峰电流比未修饰电极增大约11倍。其峰电流与Sn(Ⅱ)浓度在4.0×10-10～1.0×10-8 mol/L和1.0×10-8～4.0×10-6 mol/L范围内分两段呈良好线性关系,其线性回归方程分别为ip(μA)=1.646C(μmol/L)+2.9566和ip(μA)=52.804C(μmol/L)-0.6402,相关系数分别为0.9973和0.9967;检出限(S/N=3)为2.7×10-10 mol/L(富集时间120s)。本方法操作简便、灵敏度高,应用于罐头食品中锡含量的测定,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.     

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.