半胱胺锌修饰玻碳电极测定饲料添加剂赖氨酸铜螯合物的螯合率

采用半胱胺锌(C2H7NS)3·Zn SO4·Zn Cl2修饰玻碳电极,以差分脉冲伏安法(DPV)在0.1 mol/L的KCl溶液中对游离Cu2+进行了测定。游离Cu2+浓度与氧化峰电流值在0.01~0.5 mmol/L范围内呈良好线性关系,线性回归方程为I=-0.1005c-1.6×10-5,相关系数为R2=98.63,检出限(S/N=3)为0.1μmol/L。通过加标实验验证修饰电极对Cu2+含量测定,回收率为95.1%~102.6%,RSD(n=5)在3%以内。考察了干扰金属离子(M g2+,Mn2+,Zn2+)对电极检测Cu2+无影响,制备的修饰电极对赖氨酸铜螯合物不响应,直接测定赖氨酸铜螯合物螯合率为91.78%和91.93%。     

2,4-二硝基苯酚在类普鲁士蓝修饰电极上的电化学行为及分析应用研究

利用电化学沉积法制备了稀土铕(Ⅲ)离子掺杂的类普鲁士蓝化学修饰电极(Eu-PB/GC/CME),采用循环伏安法(CV)和示差脉冲伏安法(DPV)研究了该修饰电极上2,4二-硝基苯酚的电化学行为。结果表明,该修饰电极与裸电极相比能显著提高2,4二-硝基苯酚的还原峰电流,还原电位降低53 mV,线性范围明显增宽。还讨论了支持电解质种类、酸度、修饰层厚度和扫速等因素对2,4二-硝基苯酚伏安响应的影响。在优化的实验条件下,2,4二-硝基苯酚的示差脉冲峰电流(Epc=-341 mV)与浓度在2.0×10-5~2.0×10-3mol/L和2.0×10-7~8.0×10-6mol/L范围内分别呈良好的线性关系,回归方程为ipc(μA)=9.821×104c(mol/L) 22.142(r=0.9992,n=10)和ipc(μA)=4.2025×105c(mol/L) 0.3720(r=0.9967,n=8),检出限(3σ)为6.0×10-8mol/L。该电极用于模拟废水样中2,4二-硝基苯酚的测定,回收率为97.3%~103.0%,结果令人满意。     

修饰铂电极上Bi(Ш)的示波双电位滴定法

制备了Bi(Ⅲ)修饰铂电极,用循环伏安法表征了Bi(Ⅲ)在电极上的吸附特性,探讨了电极的响应机理。 通过优化实验条件,建立了一种测定Bi(Ⅲ)的示波双电位滴定法。 在0.1 mol/L的硝酸溶液中(pH=1.0),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Bi(Ⅲ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。 Bi(Ⅲ)在1.19×10-4～1.44×10-2 mol/L时,回收率为99.8%～100.1%,检出限(S/N=3)为1.0×10-4 mol/L。 该修饰电极具有良好的稳定性和重现性,在含有1.0×10-2 mol/L Bi(Ⅲ)的溶液中,连续7次测定,所得终点电位值均在100 mV左右,其相对标准偏差(RSD)为0.04%。 应用该方法测定含铋样品,RSD值(n=7)小于0.25%,回收率为99.5%～100.5%,测定结果与指示剂法测定值相符。     

修饰铂电极上Mn(Ⅱ)的示波双电位滴定法测定

制备了Mn(Ⅱ)修饰铂电极,用循环伏安法表征了修饰电极的电化学性能,并对电极响应机理进行了探讨.优化了试验条件,提出了一种新的测定Mn(Ⅱ)的示波双电位滴定法.在1.0 mol/L的六次甲基四胺底液(pH=5.5～6.6)中,用修饰电极作为双指示电极,以EDTA标准溶液滴定Mn(Ⅱ),利用示波器屏幕上荧光点的显著最大位...     

多壁碳纳米管修饰电极检测盐酸氯丙嗪的研究

制备了多壁碳纳米管修饰玻碳电极,采用循环伏安法(CV)研究了盐酸氯丙嗪在修饰电极上的电化学特性,发展了一种新的检测盐酸氯丙嗪的电化学分析方法。在最佳实验条件下,用循环伏安法检测盐酸氯丙嗪,其响应电流与盐酸氯丙嗪的浓度在8.0×10-5~1.0×10-3mol/L范围内有很好的线性关系,线性方程为Ip(A)=0.0106c(mol/L)-8×10-8(R2=0.999,n=6),检出限为6.2×10-6mol/L(S/N=3)。方法可用于盐酸氯丙嗪片的测定。     

银-氨基乙酸复合膜修饰玻碳电极循环伏安法测定苏丹红Ⅲ

制备了银-氨基乙酸复合膜修饰玻碳电极,采用循环伏安法研究了苏丹红Ⅲ在修饰电极上的电化学行为。结果表明:在pH 3.0的磷酸盐缓冲溶液中,苏丹红Ⅲ在修饰电极上呈现一对灵敏的氧化还原峰,提出了用循环伏安法测定苏丹红Ⅲ的方法。苏丹红Ⅲ的浓度在3.0×10-7～4.0×10-5 mol·L-1范围内与还原峰电流呈线性关系,检出限(3S/N)为9.0×10-8 mol·L-1。修饰电极用于调味品中苏丹红Ⅲ的测定,回收率在94.1%～98.5%之间,测定值的相对标准偏差(n=6)在2.2%～4.6%之间。     

盐酸吡哆辛在聚烟酸修饰电极上的电化学行为及测定

采用电聚合方法制备了聚烟酸修饰玻碳电极(PNA/GCE),并利用循环伏安法(CV)和差分脉冲伏安法(DPV)考察了盐酸吡哆辛(VB6)在该修饰电极上的电化学行为。结果表明,VB6在PNA/GCE上的氧化峰电流显著提高,电极反应为扩散控制的一电子两质子反应。利用差分脉冲伏安法对VB6进行测定,线性范围为0.08~400μmol/L,VB6的检出限为0.02μmol/L,测定结果的相对标准偏差为3.1%(n=8),加标回收率为95.8%~103.7%。该方法可用于VB6片中VB6含量的测定。     

盐酸吡哆辛在石墨烯-碳纳米管/聚烟酸复合修饰电极上的电化学行为研究及其测定

通过滴涂和电聚合的方法制备了石墨烯(GN)-多壁碳纳米管(MWCNTs)/聚烟酸(PNA)修饰玻碳电极。利用循环伏安法和差分脉冲伏安法考察了盐酸吡哆辛(VB6)在此修饰电极上的电化学行为和测定方法。结果表明,VB6在此修饰电极上有一明显的不可逆氧化峰(Epa=1.049 V),该电极与GCE、PNA/GCE以及GN/MWCNT/GCE相比,VB6的氧化峰电流显著提高,电极反应为扩散控制的一电子两质子反应。利用差分脉冲伏安法对VB6进行测定,线性范围为0.05~200μmol/L,检出限为0.02μmol/L,相对平均偏差为3.1%(n=8)。本方法可用于测定VB6片和B族维生素片中的VB6含量测定,加标回收率为在96.1%~104.5%之间。     

银掺杂聚L-酪氨酸修饰电极的制备及对尿酸的测定

利用循环伏安法将银和L-酪氨酸聚合修饰在玻碳电极表面,制成银掺杂聚L-酪氨酸(Ag-PLT/GCE)修饰电极,研究了尿酸在该电极上的电化学行为,建立了循环伏安法测定尿酸的新方法。在pH=3.0的磷酸盐缓冲溶液中,扫描速率为100mV/s时,尿酸在该修饰电极上产生一氧化峰,Epa=0.637V(vs.Ag/AgCl)。用循环伏安法进行测定时,峰电流与尿酸浓度在8.0×10-7～1.0×10-5mol/L和1.0×10-5～1.0×10-4mol/L范围内呈良好的线性关系,检出限为3.0×10-7mol/L。方法用于尿样中尿酸的测定,结果满意。     

纳米金修饰玻碳电极对鸟嘌呤的催化氧化

采用电化学沉积法制备了纳米金修饰玻碳电极,并用循环伏安法和电化学阻抗法进行了表征,以此建立了一种直接测定鸟嘌呤的电分析方法。在磷酸盐缓冲溶液(pH 6.0)中,研究了鸟嘌呤在纳米金修饰电极上的电化学行为,实验结果表明,纳米金修饰电极可以增强鸟嘌呤在电极表面的吸附,并加快鸟嘌呤在电极表面的电子传输,使其电化学信号明显增大,检测灵敏度大大提高,该修饰电极对鸟嘌呤表现出良好的电催化性能。在优化实验条件下对鸟嘌呤进行测定,方法的线性范围为8.0×10-7~6.0×10-5mol/L,检出限为1.0×10-8mol/L,在鸟嘌呤浓度为1.0×10-5mol/L时测得RSD(n=10)为2.5%。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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.     

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%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

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.