体积排阻高效液相色谱-电感耦合等离子体质谱测定印度芥菜中镉的形态

建立了体积排阻高效液相色谱-电感耦合等离子体质谱法(SEC-HPLC-ICP-MS)测定镉超积累植物印度芥菜中镉的形态分析方法.在镉胁迫下,诱导产生植物螯合肽(PCs).因此,在叶片和根部均检测到植物螯合肽(PC)3-Cd、植物螯合肽(PC)2-Cd、谷胱甘肽(GSH)-Cd,及半胱胺酸(Cys)-Cd 4种形态.研究结果证明,植物螯合肽的合成机制为先形成GSH-Cd而后形成植物螯合肽.在植物不同部位,Cd存在形态不同.叶片中主要以GSH-Cd存在,而在根部主要以PC2-Cd为主,结合不同镉刺激浓度条件下植物体内镉分布规律初步推断:根部PC2-Cd除了自身合成产生外,还有部分为叶部转移.为了防止巯基化合物氧化反应的发生,样品采取液氮保护并于-70 ℃保存,样品分析全流程用氮吹防氧化措施.     

柱前衍生高效液相色谱-荧光检测法测定水稻中7种巯基化合物

建立了水稻中半胱氨酸(Cys)、谷胱甘肽(GSH)和植物螯合肽(phytochelatin, PC:PC₂、PC₃、PC₄、PC₅、PC₆)7种巯基化合物的柱前衍生高效液相色谱-荧光检测分析方法.样品经0.1%三氟乙酸(TFA)(含6.3 mmol/L二乙烯三胺五乙酸(DTPA))超声提取,然后以单溴二胺(mBrB)为衍生剂在pH 8.0的4-羟乙基哌嗪丙磺酸(HEPPS)缓冲溶液中衍生化.采用的色谱分离柱为Agilent Eclipse plus C_l8柱,流动相为0.1%TFA(pH 2.5)和100%乙腈(ACN),梯度洗脱,流速为0.8 mL/min.荧光检测的激发波长和发射波长分别为380 nm和470 nm.结果表明,7种巯基化合物在0.7~100.0 mg/L范围内,峰面积与质量浓度之间的线性关系良好(r²≥0.9991);检出限为0.03~0.20 mg/L;加标回收率为89.26%~99.42%,相对标准偏差为2.05%~5.87%.该方法准确、灵敏度高、重现性好,为水稻中巯基化合物的研究提供了检测手段.     

CL-7301微色谱柱分离铀化合物中痕量镉的方法研究

采用CL-730l树脂微色谱柱研究了铀化合物中基体铀和痕量镉的分离条件,并用在线富集法测定了铀化合物中的痕量镉.通过试验选择0.125mol/L的HI酸介质中,镉的吸附率接近100%,而铀不被吸附,分离效率达到99.9%以上.吸附在柱上的镉用10 g/L EDTA 洗脱,原子吸收光度法测定.利用在线富集技术,镉的检出限降低至2.3μg/L.对八氧化三铀和分析纯醋酸双氧铀样品中痕量镉进行测定,方法精密度为1.5%,加标回收率为96%～98%.     

氢化物发生-原子荧光光谱法测定蔬菜中的镉

研究了以8-羟基喹啉与钴离子作为协同增效剂,氢化物发生-原子荧光光谱测定蔬菜中镉的方法.得到测镉的最佳条件是: 3%HCl 1 mg/L Co2 5 mg/L 8-羟基喹啉体系.本法线性范围0.5～20 μg/L,检出限为0.03 μg/L,RSD为2.5%.本法应用于测定蔬菜中镉的回收率为92%～105%.     

螯合稀土金属标记蛋白质技术的建立与优化

建立了一种基于螯合稀土金属标记蛋白质的技术,优化了影响标记效率的各种条件.在50 mmol/L TEAB缓冲体系(pH 7.5),DTPA与肽段摩尔比为100: 1,常温反应30 min的条件下,DTPA标记完全;在100 mmol/L乙酸铵缓冲液(pH 6.0),稀土金属与DTPA摩尔比为4: 1,37 ℃反应1 h的条件下,稀土金属螯合反应完全.考察了不同稀土金属的螯合效率,发现离子半径最小的Lu螯合效率最高.本方法被成功应用于肽混合物标记.     

三乙烯四胺修饰β-环糊精交联树脂分离富集/原子吸收法测定大米中的铅、镉

该文制备了一种新型吸附材料三乙烯四胺修饰β-环糊精交联树脂(TETA-β-CDP),并对其进行红外光谱表征,优化了该吸附材料对痕量铅、镉的吸附和解析条件,建立了动态条件下同时分离富集/原子吸收光谱测定大米中铅和镉的新方法。在p H 5.5时,样品溶液以1.0 m L/min流速过柱,试液中的Pb2+和Cd2+可被该树脂定量富集,其动态饱和吸附容量分别为22.8,31.3 mg/g,吸附在TETA-β-CDP上的Pb2+和Cd2+可用0.1 mol/L HCl以0.8 m L/min流速完全洗脱。该方法对铅、镉的检出限(3σ,n=11)分别为0.038 mg/L和0.016 mg/L;线性范围分别为0.2~20 mg/L和0.05~2.5 mg/L;相对标准偏差(RSD)分别为2.8%和1.7%;加标回收率分别为97.5%~101.0%和95.0%~102.5%。该方法用于大米样品中痕量铅、镉的测定,结果满意。     

微波消解镉柱还原光度法测定水中总氮

以碱性过硫酸钾为消解液,利用微波快速消解水样,流动注射与镉还原柱相连,分光光度法测定水样中的总氮.在消解升温时间200 s,消解温度125℃,消解时间750 s,还原泵速20 r/min,镉柱装填高度10 cm,pH=8.0～9.0的测定条件下,氮的检出限为0.005 mg/L,线性范围为0～5 mg/L,相对标准偏差...     

柱前衍生化气相色谱法分析豌豆根尖粘液中的多糖

采用三氟乙酸水解豌豆根尖粘液中的多糖,衍生化后用气相色谱分离测定6种单糖.实验表明,根尖粘液用三氟乙酸水解并乙酰化,采用OV-17石英毛细管色谱柱(35 m×0.32 mm, 0.33 μm),利用气相色谱法对6种单糖进行分离测定,6种糖全部达到基线分离,总分析时间为42 min.用保留时间定性,外标法定量.方法线性范围为0.0025～2.5 g/L,各标准曲线相关系数r>0.9991; 检出限0 0216～0.1578 mg/L,加样回收率为96.7%～107.4%.实验结果表明,本方法可有效测定逆境胁迫下植物根尖粘液中的糖类物质.     

氢化物发生-原子荧光法测定纯铜中镉

用717阴离子交换树脂填充柱选择性吸附CdCl42-阴离子,以实现其与大量铜基体的分离。在标准溶液中匹配适当基体浓度并采用氢化物发生-原子荧光法,实现了铜/镉质量比为2000~50000的纯铜中痕量镉的测定。在基体铜的浓度为50mg/L的样品消化液中,镉的检出限为0.2μg/L;精密度为3.0%(n=7,3.0μg/L),镉浓度在1.0~25.0μg/L范围内呈良好线性关系。本法适用于纯铜中痕量镉的测定。     

离子色谱法检测二肌酸苹果酸氯化铋配合物中的氯离子含量

对本课题组制备的二肌酸苹果酸氯化铋配合物进行处理,并用离子色谱方法检测样品中的Cl-含量.方法中通过滴加过氧化氢使配合物中的生物配体分解,经过低温灰化,高温灼烧,然后转移定容,稀释100倍,用离子色谱方法检测.选择的离子色谱检测条件为:使用AS11-HC阴离子分离柱,流动相为20 mmol/L NaOH溶液,25μL进样,抑制电导检测器,检测样品中Cl-的含量.本方法的线性范围1～20 mg/L,检出限为2μg/L,检测配合物中Cl-含量的平均值为14.90%.相对标准偏差为0.13%.方法可用于肽类配合物实际样品分析.     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.