分光光度法与火焰原子吸收光谱法测定钢中硼的比较

提出了萃取-分光光度法和火焰原子吸收光谱法测定钢中硼的两种方法,比较了两者的线性范围、检出限、样品测定结果等.试验发现:分光光度法和火焰原子吸收光谱法在硼含量分别为0.11～3.2 mg·L-1和0.05～3.24 mg·L-1范围内时,吸光度与其质量浓度呈线性关系,检出限(3S/N)分别为0.033,0.036 mg·L-1.经检验,两种方法的测定结果之间无显著性差异.     

火焰原子吸收光谱法间接测定钢中硼量

在弱酸介质中,硼、苯羟乙酸和[Fe(Phen)3]2+(phen:邻二氮菲)缔合生成具有较大疏水基团的化合物,用1,2-二氯乙烷萃取,再用去离子水反萃取,再用火焰原子吸收光谱法测定水相中铁,由此间接测定硼的含量.硼的质量浓度在0.05～3.24 mg·L-1范围内呈线性,方法检出限(3S/N)为0.036 mg·L-1.应用此方法测定了硼钢标准样品中硼含量,测得结果与已知值相符.     

火焰原子吸收光谱法间接测定白酒中甜蜜素

提出了一种火焰原子吸收光谱法间接测定白酒样品中甜蜜素的测定方法.采用乙醚将甜蜜素从酸化后的白酒样品中提取出,提取液经挥发去除乙醚后加浓硝酸置于100℃水浴中硝化,硝化产生的硫酸根与铬酸钡悬浮液反应生成硫酸钡,通过用火焰原子吸收光谱法测定反应中定量释出的铬酸根间接换算成甜密素含量.甜蜜素的质量浓度在0.35 g·L-1以内与吸光度呈线性关系,其线性回归方程为A=0.301 ρ<,甜>+0.018,检出限(3S/N)为0.02 g·L-1.在0.060,0.250,0.500 g·L-1的标准加入水平下进行了精密度试验,所得相对标准偏差(n=6)分别为8.93%,3.44%,3.63%.加标回收率在86.7%～105.0%之间.     

原子吸收光谱法间接测定食品中甲醛含量

提出了原子吸收光谱法间接测定食品中甲醛含量的方法。甲醛与斐林溶液(含铜离子和酒石酸钾钠的碱性溶液)在沸水浴中反应30min生成氧化亚铜沉淀,或与银氨溶液(含银离子的氨性溶液)在50℃水浴中反应15min生成单质银沉淀。两种沉淀分别用6mol·L-1盐酸溶液和6mol·L-1硝酸溶液溶解,并用原子吸收光谱法测定反应中定量释出的铜量或银量,间接换算成甲醛含量。铜和银的质量浓度分别在7.000,6.000mg·L-1以内与吸光度呈线性关系。在试样溶液中加入1.000mg·L-1铜、银标准溶液并按所述方法进行分析,所得回收率在99.6%～101%之间(Cu)和81.9%～84.2%之间(Ag)。     

功能化温控离子液体萃取-火焰原子吸收光谱法测定痕量镉

采用功能化温控离子液体萃取-火焰原子吸收光谱法测定痕量镉。优化的试验条件如下:1离子液体的用量为0.25g;2溶液的pH为5.81;3离心时间30 min;4反萃取剂为2mol·L-1盐酸溶液5.00 mL;5超声时间为30 min;6反萃取3次。镉的质量浓度在1.20mg·L-1以内与其吸光度呈线性关系,检出限(3s/k)为0.027mg·L-1。方法应用于模拟水样的分析,测定值与参考值相符。加标回收率在102%~110%之间,测定值的相对标准偏差(n=3)均小于1.0%。     

火焰原子吸收光谱法测定钢铁中磷的含量

钢铁样品经盐酸-硝酸(3+1)混合酸溶解后,采用火焰原子吸收光谱法测定样品溶液中磷的含量。磷在适宜的乙炔-空气火焰中可形成PO双原子分子,选择测定波长为327.04nm。磷的质量浓度在1.0g·L-1以内与其吸光度呈线性关系,方法的检出限(3s)为0.001g·L-1。方法应用于钢铁标准物质(YSBC 20310-2002,GBW 01312)的分析,测定值与认定值相符,测定值的相对标准偏差(n=5)小于4%。     

纳米钛酸锶钡粉体吸附富集-火焰原子吸收光谱法测定水样中锰离子

提出了纳米钛酸锶钡粉体吸附富集,火焰原子吸收光谱法测定水中痕量锰的含量。在pH 6的氨性缓冲介质中,采用纳米钛酸锶钡(0.02 g)对水样(10 mL)中的锰离子振荡吸附15 min。优化条件下吸附容量达5.4 mg.g-1。方法检出限(3s/k)为2.1μg.L-1。用0.15 mg.L-1锰(Ⅱ)标准溶液连续测定6次,求得其相对标准偏差(n=6)为3.4%。用于河水和地下水中痕量锰的测定,用标准加入法测得方法的回收率在93.5%~99.7%之间。     

离子交换柱分离-火焰原子吸收光谱法间接测定钢铁中磷

在试样溶解过程中,加入氢氟酸与高氯酸,蒸发使硅以SiF4状态除去,并蒸发至高氯酸冒烟使磷氧化为正磷酸离子(PO43-).分取部分试样溶液,用离子交换分离法将PO43-与大量铁(Ⅲ)及其他共存的阳离子分离.收集淋洗液于容量瓶中,加入已知过量的铅标准溶液使生成磷酸铅沉淀.用火焰原子吸收光谱法测定溶液中过量的铅离子,从而间接求得试样中磷的含量.吸光度与磷的质量浓度在2.0 mg·L-1以内呈线性关系.方法的检出限为5.9/μg·L-1,应用此方法测定了3件标准样品的磷含量,测得结果与证书值相符,分析结果的相对标准偏差(n=11)在1.7%～4.0%之间.     

原子吸收光谱法间接测定葡萄糖注射液中的还原糖

提出了原子吸收光谱法间接测定葡萄糖注射液中还原糖的方法。在pH 9.0～10.0的碱性介质中,铜盐与还原糖反应生成氧化亚铜沉淀,沉淀经离心分离后用硝酸溶解,通过用原子吸收光谱法测定反应中定量析出的铜量,间接换算成还原糖含量。铜的质量浓度在5.0mg·L-1以内与吸光度呈线性关系,方法的检出限(3S/N)为1.0mg·L-1。在0.500,0.750mg·L-1的标准加入水平下于葡萄糖注射液中加入标准溶液并按所述方法进行分析,进行了回收和精密度试验,所得回收率在98.0%～100%之间,相对标准偏差(n=6)小于4.0%。     

火焰原子吸收光谱法测定仿真饰品中铅、镉和钡

提出了火焰原子吸收光谱法测定仿真饰品中的铅、镉和钡的含量。详细叙述了不同材料饰品的前处理方法。在优化的仪器工作条件下,铅、镉和钡的质量浓度分别在0.1～5.0,0.05～1.0,1.0～20 mg·L^-1范围内与吸光度呈线性关系,方法的检出限（3s）依次为0.05,0.006,0.1 mg·L^-1。方法用于测定样品中铅、镉和钡的含量,加标回收率在88.0%～104%之间,测定值的相对标准偏差（n=7）均不大于4%。     

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.