离子交换微柱在线富集-电感耦合等离子体原子发射光谱法测定黄芪中稀土元素

以阳离子交换树脂微柱为柱填充材料,采用电感耦合等离子体原子发射光谱法(ICP-AES)进行检测,研究了三种阳离子树脂在动态条件下对16种稀土离子的交换性能。并确定了最佳交换及洗脱条件。结果表明:005×7树脂的富集效果最好,在4 mL.min-1的进样速度下稀土元素均被定量富集,用4 mol.L-1HCl溶液能迅速地将微柱上稀土离子完全洗脱。富集倍数可达32~42倍,稀土元素的检出限为0.09~2.49μg.L-1,相对标准偏差为1.2%~4.7%(n=6)。方法应用于茶叶标准样品中稀土元素的测定,其测定值与标准值吻合。并对内蒙古产区的黄芪中的稀土元素进行了测定,加标回收率在91%~110%之间。     

阳离子交换树脂分离-分光光度法测定水中痕量铜

采用静态法研究了HD-8阳离子交换树脂对铜的吸附速率、吸附温度和吸附量等性能。试验结果表明:在0.1～0.5mol·L~(-1)盐酸溶液介质中铜的吸附率在95%以上,用3mol·L~(-1)盐酸溶液3mL可将吸附于柱上的铜(Ⅱ)完全洗脱下来。在优化的试验条件下,该HD-8阳离子交换树脂微柱对铜的富集限为2μg/200mL,富集倍数为67倍。在此基础上提出了一种阳离子交换树脂分离分光光度法测定水样中痕量铜的方法。该方法用于测定鄱阳湖水中痕量铜,测得平均回收率为101.5%之间,相对标准偏差(n=5)为1.82%。     

异麦芽低聚糖浆的分离与测定

采用001×7(732)强酸性苯乙烯系阳离子交换树脂色谱分离法对异麦芽低聚糖(IMO)糖浆进行了分离提纯,并用HPLC分析测定其组成。试验表明,当进料量35 mL;操作温度71℃,洗脱速度9 mL.min-1,树脂柱9 mm×4 m,可以有效地去除葡萄糖等成分,提高异麦芽低聚糖的纯度。     

阳离子交换树脂富集-流动注射-冷原子荧光光谱法测定环境水样中痕量汞

提出了用阳离子交换树脂富集环境水样中痕量汞,用流动注射-冷原子荧光光谱法测定其中汞的含量。对阳离子交换柱的制备、富集时间、介质及洗脱剂的酸度等分析条件做了试验并予以优化。汞的质量浓度在40 ng.L-1以内与其荧光强度呈线性关系,方法的检出限(3s)为0.13 ng.L-1。应用此法对环境水样进行分析,并以此样品为基体作回收试验,测得汞的回收率在72.5%~101.3%之间。     

在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收法测定水中痕量镉和铜

应用高效的在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收系统直接测定水中痕量镉和铜 ,试验用内装 2 0 0 mg Amberlite XAD- 4键合的 5-磺酸 - 8-羟基喹啉螯合树脂的锥形柱 ,在 p H6条件下 ,样品流速为 6.0 ml·min-1,90 s装样 ,用 0 .5mol· L-1HCl洗脱 ,分析速度为30样·h-1分别获得 38和 40倍的富集 ,经石英缝管增敏 ,总灵敏度分别提高 1 36和 1 2 0倍 ,检出限为 0 .1和 0 .2μg· L-1。对镉和铜含量分别为 2 .0 ,5.0μg· L-1的水样连续测定 1 1次的相对标准偏差分别为 2 .8%和 3.4% ,可直接测定水体中 μg· L-1级的镉和铜。     

DDTC阴离子交换树脂对痕量铜(Ⅱ)的预浓缩及光度测定

近年来,用强碱性阴离子交换树脂制备螯合型树脂柱已愈益为人们所重视。但均存在柱流速慢(<5mL/min)、洗脱剂用量大、预处理时间长及富集系数小等缺点。曾有人用十八烷基键合玻璃微珠预浓缩并用PADAP分光光度法测定钴。特点是洗脱剂用量少、浓缩倍数高(500倍),但水样需经预处理。我们综合上述两类层析柱优点,将铜试剂(二乙胺二硫代甲酸钠,NaDDTC)中的螯合集团交换在强碱性阴离子树脂上,制备了螯合型树脂柱。初步实验证明,含铜水样流经DDTC阴离子交换树脂柱后形成的中性铜螯合物被键合在树脂上,用氯仿洗脱,可浓缩万倍,水样毋需预处理,检出下限10~(-11)g/mL。     

弱酸阳离子交换纤维柱富集-电感耦合等离子体原子发射光谱法测定水样中的稀土

提出了聚丙烯基弱酸性阳离子交换纤维柱富集痕量稀土元素,1.0 mol/L HCl溶液作为洗脱剂,电感耦合等离子体原子发射光谱法测定水样中稀土元素的方法。在优化的试验条件下,弱酸性阳离子交换纤维对La、Nd、Eu、Gd、Er和Yb的吸附容量分别为86.5,98.2,98.7,99.2,84.9,91.5 mg/g;La、...     

阳离子交换树脂分离电感耦合等离子体质谱法测定空气颗粒物中铂族元素

用Dowex AG50W-X8阳离子交换树脂分离空气颗粒物中Pt、Pd、Rh测定的干扰元素Cu、Ga、Hf、Pb、Rb、Sr、Y.模拟标准液实验确定出Dowex AG50W-X8阳离子交换树脂分离流程的最佳条件:上柱HCl浓度为0.8 mol/L,树脂柱床高为4 cm,洗脱速率为1 mL/min.铂族元素分析的国际标准物质BCR-723对照分析表明,Pt、Pd、Rh的测定值与标准值吻合,干扰元素Cu、Ga、Pb、Rb、Sr、Y的分离效率均大于94%,这表明所建立的Dowex AG50W-X8阳离子交换树脂分离流程是可靠的.     

反相高效液相色谱法测定果汁中的有机酸

介绍了用反相高效液相色谱(RP HPLC)测定果汁中有机酸的方法。应用反相C18色谱柱,5g·L-1磷酸二氢铵(pH3.0)溶液作为流动相,流速为1.0ml·min-1,检测波长为210nm,能将果汁中的8种有机酸一次分离测定,重现性好,回收率为94.0%～115.5%。     

制药废液中氨基酸的分离与测定

为测定维生素 B12 制药厂排出的废液中氨基酸量,先在所取的废液样品中加入乙酸铅使其中蛋白质及其他大分子有机物产生沉淀并用离心法分离.上层澄清液中的氨基酸通过装有强酸性阳离子交换树脂的交换柱(25 cm×2.5 cm)予以分离,用1 mol·L-1 氨水将氨基酸从柱上洗脱.在所得洗脱液中用气相色谱-质谱及傅立叶变换红外光谱法对氨基酸进行定性及定量测定.     

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.     

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.     

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.     

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.