修饰铂电极-示波双电位滴定法测定Zn(Ⅱ)

制备了锌修饰铂电极,建立了一种新的测定Zn(Ⅱ)的示波双电位滴定法。在六次甲基四胺溶液(1.0mol/L)中(pH=5.5),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Zn(Ⅱ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。在3.0×10-4～2.0×10-3mol/L的浓度范围内,Zn(Ⅱ)的回收率为99.9%～100.2%。该修饰电极具有良好的稳定性和重现性,对Zn(Ⅱ,1.0×10-3mol/L)溶液连续11次测定,所得终点电位值均在10.1mV左右,其相对标准偏差(RSD)为0.5%。用来测定含锌的实际样品,其结果与指示剂法测定的值基本一致。     

线扫伏安法同时测定5-羟基色氨酸和色氨酸

研究了色氨酸和5-羟基色氨酸在玻璃碳电极上的电化学行为,研究了不同pH、静置时间、扫描速度以及表面活性剂等的影响,探讨了色氨酸和5-羟基色氨酸在玻璃碳电极上的氧化机理,建立了线扫伏安法同时测定色氨酸和5-羟基色氨酸的方法.实验发现,在含3.33×10-4 mol/L十二烷基磺酸钠的0.1mol/L柠檬酸(pH=4.50)介质中,5-羟基色氨酸和色氨酸分别在 0.675V和 1.070V产生一灵敏的氧化峰.对5-羟基色氨酸,相应的氧化峰的峰高与浓度在2.40×10-5 mol/L～8.00×10-4 mol/L范围内呈良好的线性关系,线性相关系数为0.9994;对色氨酸,其氧化峰的峰高与浓度在2.40×10-5 mol/L～6.40×10-4 mol/L浓度范围内呈良好的线性关系,线性相关系数为0.9929.该方法测量2.00×10-4 mol/L色氨酸和5-羟基色氨酸的相对标准偏差分别为3.2%和3.8%(n=10).     

涂丝Ag-Ag2S电极测定水体中微量氰化物的研究

本文报道了涂丝Ag-Ag2S电极测定水体中微量氰化物(CN-)的分析方法。该方法对现用的Ag(CN)2-指示剂配制方法以及使用浓度作了新的改进,加之成功地在ISAB中引入有机溶剂等,较大程度地提高了测定CN-的灵敏度。该方法测定CN-的线性范围为1.0×10-3～1.0×10-7mol/L,检出限可达4.0×10-8mol/L,标准偏差小于0.015,回收率为99%～104%。本方法与比色法对照,相对误差≤1.3%,结果令人满意。     

流动注射化学发光法测定3种氟喹诺酮类药物

研究发现,氟喹诺酮类药物对可溶性Mn(-甲醛化学发光体系有强烈的增敏作用,结合流动注射技术,建立了3种氟喹诺酮类药物诺氟沙星、氧氟沙星和环丙沙星的流动注射化学发光新方法。在优化的实验条件下(2×10-4molMn(-3%甲醛-3mol/L磷酸),本方法测定诺氟沙星、氧氟沙星和环丙沙星的线性范围分别为1.0×10-7～1.0×10-5mol/L,1.0×10-7～1.0×10-5mol/L和3.0×10-7～5.0×10-5mol/L;检出限分别为3×10-8mol/L,3×10-8mol/L,1×10-7mol/L;相对标准偏差(5.0×10-6mol/L氟喹诺酮类药物,n=11)分别为2.6%,1.6%和2.8%。该方法已用于诺氟沙星胶囊中诺氟沙星的含量测定。     

分光光度法测定饮料中六偏磷酸钠添加剂

在pH 8.6的Tris-HCl缓冲溶液中,六偏磷酸钠使天青B在溶液中发生聚集,溶液由天蓝色逐渐变为紫色,体系的吸光度降低,光散射增强.在优化条件下,在6.0 ×10-7～1.0×10-5 mol/L范围内,天青B在602 nm处的吸光度降低与六偏磷酸钠浓度呈良好的线性关系,检出限(3σ)为 5.3 ×10-7 mol/L.对浓度为5.0×10-6 mol/L的六偏磷酸钠溶液平行测定11次,其相对标准偏差为 2.5%.本方法用于饮料中添加剂六偏磷酸钠含量的分析,平均标准加入回收率为99.5%～112.3%,可实现六偏磷酸钠的可视化半定量检测.     

水中微量芘和荧蒽的胶束增敏荧光分析法同时测定

建立了吐温-20(Tween-20,Tw-20)直接荧光法同时测定水中溶解态芘(pyrene,Py)和荧蒽(fluoranthene,FLuA)的方法.该法测定芘和荧蒽的线性范围分别为1.98×10-10 ～9.88×10-8 mol/L和2.00×10-9 ～7.99×10-7 mol/L,检出限分别为9.88×10-11 mol/L和5.99×10-10 mol/L.方法灵敏,用于自来水、江水样的分析,取得了良好的效果,芘的回收率分别为92%～102%和101%～102%,荧蒽的回收率分别为90%～100%和94%～111%.为预测和治理水污染提供了一种灵敏、快速且简便的测试手段.     

修饰铂电极上Zn(Ⅱ)的示波双电位滴定法

制备了锌修饰铂电极,建立了一种新的测定Zn(Ⅱ)的示波双电位滴定法。在1.0 mol/L的六次甲基四胺溶液中(pH=5.5),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Zn (Ⅱ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。Zn (Ⅱ)在3.0×10-4 ～2.0×10-3 mol/L时,回收率为99.9%～100.2%。该修饰电极具有良好的稳定性和重现性,在含有1.0×10-3 mol/L Zn (Ⅱ)的溶液中,连续11次测定,所得终点电位值均在10.1 mV左右,其相对标准偏差(RSD)0.5%。应用该方法测定含锌样品,测定结果与指示剂法测定值相符。     

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。     

纳米金修饰的碳纤维超微电极在高浓度抗坏血酸体系中选择性测定多巴胺

将柠檬酸三钠与硼氢化钠还原氯金酸制备纳米金颗粒,采用一步恒电位沉积的方法在碳纤维超微电极上沉积纳米金颗粒,并对电极进行电化学表征。分别对100μmol/L DA、1mmol/L AA在该电极上修饰前后的电化学行为进行了研究,结果表明在浓度为1 mmol/L抗坏血酸共存下,DA的浓度(0. 1～10μmol/L)与氧化峰电流成正比,线性回归方程为Ip(μA)=200 c(μmol/L)+2×10~(-4),相关系数R~2=0. 9979,线性范围0. 1～10μmol/L,检出限为1. 28×10~(-2)μmol/L (S/N=3)。方法可用于较高浓度抗坏血酸共存下对多巴胺的选择性测定。     

基于多壁碳纳米管化学修饰电极直接测定饮料中的麦芽酚

采用循环伏安法和示差脉冲伏安法研究了麦芽酚在多壁碳纳米管修饰电极上的电化学行为,建立了一种直接测定饮料样品中麦芽酚含量的电分析测试方法. 在pH=8.5的NH3 ·H2 O-NH4 Cl 缓冲溶液中,麦芽酚在多壁碳纳米管修饰电极上于0.55 V(vs.SCE)产生不可逆的氧化峰. 该修饰电极对麦芽酚的电化学反应具有促进作用,阳极峰电流与溶液中麦芽酚的浓度成正比,线性范围为5.0×10-6～9.0×10-4mol/L,检出下限为2.0×10-6mol/L.对含5.0×10-5mol/L的麦芽酚溶液平行测定10次的相对标准偏差(RSD)为1.1%.多壁碳纳米管修饰电极具有良好的电极稳定性,可用于饮料样品中麦芽酚的直接测定,避免了繁复费时的样品前处理过程. 将该修饰电极用于啤酒、可乐和葡萄酒样品中麦芽酚测定,回收率为98%～103%.     

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.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.