硅藻土负载TODGA分离-电感耦合等离子体质谱法测定氧化铈中氧化钆、氧化铽

建立了硅藻土负载N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)分离柱分离,电感耦合等离子体质谱法(ICP-MS)测定氧化铈中氧化钆、氧化铽含量的方法。试样用50%(体积分数)硝酸溶液和30%过氧化氢溶解,取含氧化铈50 mg的样品溶液导入自制的硅藻土负载TODGA的分离柱(连接一个蠕动泵,用于控制流量),用pH 1.5的硝酸溶液以2.0 mL·min~(-1)流量淋洗分离柱,直至淋洗液中铈的质量浓度小于1 000μg·L~(-1)。用60 mL pH 0.92的盐酸溶液以2.0 mL·min~(-1)流量反洗待测元素钆和铽,弃去前20 mL反洗液,收集后40 mL反洗液并用水稀释至50 mL。在线加入10μg·L~(-1)铯内标溶液,用ICP-MS分析样品溶液中目标物的含量。结果显示,氧化钆、氧化铽的质量浓度均在50.00μg·L~(-1)以内与其对应的待测元素与内标元素强度比值呈线性关系,检出限(3s)分别为0.102,0.049μg·g~(-1)。方法用于实际样品分析,氧化钆和氧化铽的测定值分别为0.73,0.68μg·g~(-1),测定值的相对标准偏差(n=11)为4.8%和5.2%,加标回收率分别为101%和99.0%。     

氢化物发生-原子荧光光谱法测定大蒜中砷和硒

采用氢化物发生-原子荧光光谱法测定大蒜中砷和硒。样品经硝酸和高氯酸消解,在盐酸(5+95)溶液中,加入溶于50g·L~(-1)氢氧化钠溶液的20g·L~(-1)硼氢化钾溶液,使其与溶液中砷及硒离子反应生成氢化物。分析中采用载气流量依次为800mL·min~(-1),600mL·min~(-1),屏蔽气的流量均为1000mL·min~(-1)。试样溶液中加入硫脲-抗坏血酸混合溶液作为还原剂。于仪器中引入试样溶液0.5mL,按选定的工作条件操作。砷及硒的质量浓度分别在0.04～0.40,1.00～10.0μg·L~(-1)范围内与其荧光强度呈线性关系,方法的检出限(3s/k)砷为0.017μg·L~(-1),硒为0.314μg·L~(-1)。分别加入两元素的标准溶液作回收试验,测得砷和硒的回收率分别在95.3%～104.4%和94.7%～105.2%之间。     

电感耦合等离子体质谱法同时测定葡萄中40种痕量元素

葡萄样品用微波消解处理后,采用电感耦合等离子体质谱法测定所得样品溶液中40种元素的含量。使用合适的同位素、内标和干扰校正方程消除了被测元素的干扰。方法的检出限(3s)在0.003 6～0.53μg·L-1之间。方法用于苹果标准物质(GBW 10019)的分析,测定值与认定值相符,相对标准偏差(n=6)在1.6%～8.5%之间。     

电感耦合等离子体质谱法测定纳米铜粉中6种微量元素

纳米铜粉样品(0.5000g)用8mol·L~(-1)硝酸溶液20mL溶解,用水定容至100mL,从上述溶液中分取10.0mL用0.3mol·L~(-1)硝酸溶液定容至50 mL。采用电感耦合等离子体质谱法测定样品溶液中钴、银、锑、锡、钡、铅等6种微量元素。以115In和205 Tl作为内标对测定的基体效应进行了校正,采用测定元素同位素以消除和减少质谱干扰。6种元素的检出限(3s)为0.002~0.074μg·L~(-1)。加标回收率为94.0%~103%,测定值的相对标准偏差(n=11)均小于5.0%。     

微波消解-电感耦合等离子体质谱法测定镍精矿中Ga、Ge、Se、Cd、In、Te、La和Tl

样品经硝酸-盐酸-氢氟酸-过氧化氢(3+1+1+1)混合液微波消解后,加入硝酸(1+1)溶液溶解盐类,定容后供电感耦合等离子体质谱分析。以~(103)Rh和~(232)Th为内标,采用校正方程消除质谱干扰。Se的线性范围为0.500~500.0μg·L~(-1),其他7种元素的线性范围均为0.050~100.0μg·L~(-1),8种元素的检出限(3s)在0.01~0.8 mg·kg~(-1)之间。加标回收率在90.9%~113%之间,测定值的相对标准偏差(n=4)在0.90%~7.7%之间。方法用于测定镍精矿标准物质中Cd,测定值与认定值相符。     

微波消解样品-原子荧光光谱法测定酸菜中砷

称取一定量已切碎、捣碎并混匀的酸菜样品用硝酸及过氧化氢先在90℃水浴中消解约20min,然后将溶液冷却,移入微波消解仪中消解。消解完毕后将溶液冷至室温,移入25mL容量瓶中,加入50g·L~(-1)硫脲-50g·L~(-1)抗坏血酸混合溶液5 mL,加水定容。在所选定的仪器条件下用14g·L~(-1)硼氢化钾溶液作还原剂生成砷的氢化物进行测定。砷的质量浓度在10.00μg·L~(-1)以内与相应的荧光强度值呈线性关系。方法的检出限(3s/k)为0.064μg·L~(-1),测得方法的回收率在89.0%～102.5%之间,测定值的相对标准偏差(n=6)为1.7%。     

氢化物发生-原子荧光光谱法测定低合金钢中微量砷

采用氢化物发生-原子荧光光谱法测定低合金钢中砷的含量。样品经盐酸-硝酸混合酸消解,以盐酸(5+95)溶液为反应介质,15g·L~(-1)硼氢化钾-2g·L~(-1)氢氧化钾的混合溶液为还原剂,采用柠檬酸作为掩蔽剂。砷的质量浓度在60.0μg·L~(-1)以内与荧光强度呈线性关系,方法的检出限(3s/k)为0.023μg·L~(-1)。应用此法对标准钢样进行了分析,测定结果与认定值相符合,可满足钢铁中微量砷(质量分数0.001%～0.04%)的测定要求。     

电感耦合等离子体质谱法测定水溶性原料药中痕量镍

水溶性原料药样品(0.500 0g)经50mL硝酸(2+98)溶液溶解后,采用电感耦合等离子体质谱法测定样品溶液中痕量镍。以铑为内标,采用动能甄别模式,利用动能甄别效应有效去除干扰。镍的线性范围在5.0μg·L~(-1)以内,检出限(3s)为0.002μg·L~(-1)。加标回收率在96.0%~97.0%之间,测定值的相对标准偏差(n=6)小于5.0%。     

微波消解-电感耦合等离子体质谱法同时测定铝土矿中11种金属元素

建立了微波消解-电感耦合等离子体质谱法(ICP-MS)同时测定铝土矿中锂、铬、铜、铁、钛、钾、钠、钙、镁、铅、锌等11种金属元素含量的方法。将铝土矿粉碎、研磨和干燥后,取0.1 g样品,加入3 mL硫酸、1 mL硝酸、2 mL氢氟酸和3 mL盐酸,按升温程序微波消解样品,加40 g·L~(-1)硼酸溶液10 mL,继续在120℃下消解10 min,使消解液变澄清。冷却后取出,180℃加热至近干,用1%(体积分数)硝酸溶液稀释,按照ICP-MS条件测定。通过用10 g·L~(-1)铝基体溶液配制混合标准溶液系列并加入内标元素Sc、Ge、Bi的方法来消除基体干扰,选择合适的待测元素同位素的方法来消除谱线重叠干扰。结果显示:11种元素的质量浓度均在一定范围内与其对应的响应值与内标元素响应值的比值呈线性关系,检出限(3s)为0.011～1.400 mg·kg~(-1)。对实际样品进行加标回收试验,测定值为0.13～72.21 mg·L~(-1),测定值的相对标准偏差(n=6)为0.69%～2.6%,回收率为94.0%～106%;此方法用于分析3种铝土矿成分分析标准物质GBW 07177、GBW 07179、GBW 07180,所得测定值均在认定值要求的范围内。     

浊点萃取-氢化物发生-原子荧光光谱法测定水样中痕量铅

提出了氢化物发生-原子荧光光谱法测定水中痕量铅的方法。以双硫腙为络合剂,在pH 8.0的硼砂溶液中,用非离子表面活性剂Triton X-114浊点萃取样品溶液中痕量铅。选用15.0 g·L~(-1)硼氢化钾溶液作为产生氢化铅的还原剂,氢化物发生反应在盐酸(1+99)介质中进行,铅的质量浓度在0.05～3.2μg·L~(-1)范围内与其相应的荧光强度呈线性关系。方法的检出限(3S/N)为0.016μg·L~(-1)。应用此方法测定了水中铅的含量,测得回收率在96.5%～104.6%之间,相对标准偏差(n=6)均小于5%。     

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.