槲皮素修饰碳糊电极吸附溶出伏安法测定人血清中铜

制作了用槲皮素作修饰剂的修饰碳糊电极 ,利用此电极为工作电极 ,建立了测定痕量铜的新方法。在甲酸钠 -盐酸缓冲溶液 ( p H4.7)中 ,于 0 .2 0 V( vs.SCE下同 )处搅拌富集 ,铜 ( )与碳糊修饰电极表面的槲皮素形成电活性络合物而吸附富集于电极表面 ,于 - 0 .40 V静止还原后 ,阳极化线性扫描 ,在 - 0 .0 3V左右获得一灵敏的二次导数溶出峰。在不同富集时间下 ,其二次导数峰电流与铜 ( )浓度分别在1 .5× 1 0 - 9～ 8.0× 1 0 - 8mol/ L和 1 .5× 1 0 - 8～ 9.0× 1 0 - 7mol/ L两个范围内成良好的线性关系 ,检出限可达 8.0× 1 0 - 10 mol/ L。同时探讨了电极反应机理。方法应用于人血清中痕量铜的测定 ,获得了令人满意的结果     

乙二胺四乙酸二钠/碳糊修饰电极测定银离子

报道EDTA/碳糊修饰电极的制备及对银离子的测定。该电极在硝酸介质中 - 0 .6 0V(vs .Ag/AgCl)电位下富集Ag+ ,在 +0 .0 8V处得到一个灵敏的阳极溶出峰 ,峰电流与Ag+ 浓度在 1.0× 10 -9～ 1.0× 10 -6mol/L范围呈良好线性关系 ,检出限为 6 .8× 10 -10 mol/L。     

碳糊电极吸附溶出伏安法测定游离钙

基于Ca(Ⅱ)-茜素红S(ARS)络合物在碳糊电极上的还原波,建立了吸附溶出伏安测定游离钙的新方法。在1.5×10-2mol/LKOH-2.0×10-5mol/LARS介质中,Ca(Ⅱ)-ARS络合物在碳糊电极上于-0.89V处产生一吸附还原波。当富集电位为.0.1V,富集时间90s,扫描速度为100mV/s时,该络合物单扫描阴极溶出峰的二阶导数峰电流与游离钙离子浓度在3.0×10-8~2.0×10-6mol/L范围内呈线性关系;检出限为9.4×10-9mol/L。在0.2mol/LHCl中清洗2min,该电极重现性良好。该方法可用于血清、牛奶和自来水中游离钙的测定。     

茜素修饰碳糊电极吸附伏安法测定痕量铜

报道了采用茜素修饰碳糊电极测定痕量铜的阳极溶出伏安法。在浓度为0 .1 mol/L 的 HAc- Na Ac缓冲溶液 (p H4.5)中 ,于 +0 .1 0 V处富集 ,- 0 .30 V还原后再进行阳极化扫描 ,于 - 0 .0 5V处获得一灵敏的铜的溶出峰 ,二次导数峰电流与铜浓度在 1 .6× 1 0 -9mol/L～ 4.7× 1 0 -7mol/L范围内呈线性关系 ,检出限达 8.0× 1 0 -10 mol/L。同时 ,对电极反应机理进行了讨论。方法应用于锌合金中铜的测定。     

四羟基蒽醌修饰活性炭碳糊电极阳极溶出法测铜

报道了将四羟基蒽醌吸附在稻壳基活性炭上,用直接混合法制成碳糊化学修饰电极及其在测定Cu(Ⅱ)中的应用。实验确定了阳极溶出法测定Cu(Ⅱ)的最佳操作条件。支持电解质为0.03 mol/L H2SO4,富集电位在-0.8V,该电极对Cu(Ⅱ)在5.0×10-8~1.0×10-2mol/L范围内分段有良好的线性响应;实际样品分析浓度小于1.0×10-2mol/L的均不需要稀释,高浓度的样品可不设富集时间,从-0.8 V处直接做阳极扫描,低浓度的样品则需设相应的富集时间,富集时间300 s时,检出限为5.0×10-9mol/L,Mg2+、Mn2+、A l3+和Fe3+等十余种共存离子基本不干扰。用本法分析人发中的铜与光谱法对照,结果令人满意。     

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。     

基于十六烷基三甲基溴化铵存在下铅、银离子的高灵敏度电化学测定

报道了在适量十六烷基三甲基溴化铵 (CTMAB)存在下 ,高灵敏度测定水体中铅、银离子的化学修饰碳糊电极。在pH 2 .5 0 .1mol LKNO3溶液中 ,铅、银离子在钠型蒙脱石修饰碳糊电极上通过离子交换而富集 ,同时被还原。在阳极扫描过程中 ,分别在 - 0 .5 2V和 0 .2 3V(vs.SCE)处出现灵敏的溶出峰。详细研究了测定水样中铅、银离子的条件 ,如介质的pH、CTMAB用量、修饰剂用量、富集电位和时间等。该修饰电极连续测定铅、银离子的线性范围为 5 .0× 10 - 9mol L～ 1.0× 10 - 7mol L(Pb2 + )和 8.0× 10 - 9mol L～ 1.0× 10 - 7mol L(Ag+ ) ,富集 4min后检出限分别为 1.0× 10 - 1 0 mol L(Pb2 + )和 3.0× 10 - 1 0 (Ag+ )。     

聚L-赖氨酸修饰电极对去甲肾上腺素的电催化氧化

研究了L 赖氨酸在玻碳电极上电化学聚合的条件及修饰电极的电化学特性,发现该聚合膜对去甲肾上腺素(NE)的电氧化有显著的催化作用,在磷酸盐缓冲溶液(pH7)中,恒电位-0.2V富集2.0min后,用方波溶出伏安法对NE进行了测定,线性范围为1.0×10-8～5.0×10-4mol L,检出限(信噪比=3)为8 2×10-10mol L。对1.0×10-7mol LNE平行测定8次相对标准偏差为2 4%。     

多壁碳纳米管修饰电极阳极溶出法测定痕量锌

报道了自制的多壁碳纳米管修饰电极测定锌离子的电分析方法。在浓度0.20mol/L的乙酸钠溶液中,以此修饰电极作为工作电极,以-1.50V为富集电位,150s为富集时间,用方波伏安溶出法(起始电位:-1.5V;终止电位:-0.8V;电位增量:0.01V;振幅:0.05V;频率:5Hz)测定-1.30V处的峰电流,用峰高定量。结果表明,该电极对锌离子吸附的灵敏度较高;当锌离子浓度为1.0×10-6～9.0×10-6mol/L时,线性关系好,相关系数为0.9992;对自来水样本进行了测定,取得了满意的结果,加标回收率在97%～105%之间。     

有序介孔碳-壳聚糖修饰玻碳电极差分脉冲溶出伏安法测定痕量锡(Ⅱ)

将有序介孔碳(OMC)分散于壳聚糖(CTS)溶液,并用于修饰玻碳电极,制成有序介孔碳-壳聚糖修饰玻碳电极(OMC-CTS/GCE),用差分脉冲溶出伏安法研究锡(Ⅱ)在该电极上的溶出伏安特性。实验发现,在1.0mol/L盐酸中,锡(Ⅱ)在-1.2V处被富集在修饰电极表面,在0.0～+1.0V电位范围,以100mV/s的速率扫描,锡(Ⅱ)在+0.35V处产生一灵敏的溶出峰,峰电流与锡(Ⅱ)的浓度在5.0×10-8～1.0×10-5mol/L范围内呈良好的线性关系,检出限(S/N=3)为2.2×10-9 mol/L。方法用于合金中痕量锡(Ⅱ)的测定,结果同火焰原子吸收光谱法(FAAS)测定结果一致。     

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%).     

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.     

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.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

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.