悬浮液进样-石墨炉原子吸收光谱法测定生物样品中微量铬

提出了固体悬浮液进样石墨炉原子吸收光谱法直接测定铬的方法,并对各分析条件进行了优化.采用1.2 g·L-1琼脂溶液为悬浮剂,将样品均匀悬浮于其中,由自动进样器直接将样品悬浮液注入石墨炉中,加入基体改进剂,石墨炉原子吸收光谱法测定生物样品中铬.在优化的试验条件下,方法的检出限(3σ)为0.5 pg·L-1.铬的质量浓度在50 μg·L-1以内呈线性关系,回归方程为A=0.2521 C 0.0311,样品加标回收率为98.6%～103.2%.     

嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法分析痕量铬的形态

研究了嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法对尿中痕量铬的形态分析方法,探讨了嵌段分子筛聚合材料P123-SH吸附铬的原理和最佳条件。在pH 7.0、常温下,Cr3+和Cr(Ⅵ)被很好的分离,且Cr3+可被该材料定量吸附,其吸附容量为6.15 mg/g。吸附的Cr3+可用2 mol/L的HCl洗脱,用石墨炉原子吸收法测定洗脱下来的Cr3+,往溶液中加入0.1%抗坏血酸将Cr(Ⅵ)还原为Cr3+测总铬,Cr(Ⅵ)含量为总铬减去Cr3+,方法测定Cr3+的检出限为0.011μg/L(3σ,n=11),线性范围为0.1～10μg/L,加标回收率在94%～106%之间,对0.50μg/L的Cr3+溶液平行测定7次,RSD为3.6%。方法可应用于生物样品和环境样品中痕量铬的形态分析。     

石墨炉原子吸收法测定动物组织中的微量铬

采用石墨炉原子吸收法测定动物组织中的微量铬,以HNO3-HC lO4为消化剂,消化温度为250℃,消化时间为90 m in。研究了进样酸度和共存离子对测定结果的影响,铬的浓度在10~300 ng/(10 mL)内服从比耳定律,铬的浓度与吸光度的线性相关系数为0.998 4。将该方法用于兔肝脏中铬的测定,测定结果的相对标准偏差为5.0%(n=10),加标回收率为93.8%~95.0%。     

石墨炉原子吸收光谱法测定食品中的铝含量

建立了食品中铝含量的石墨炉原子吸收光谱方法。样品经消化后,在396.2 nm分析波长下,不加基体改进剂,直接用石墨炉原子吸收光谱法测定食品中的铝。线性范围为0～200μg/L,相关系数r=0.9986,测定结果的相对标准偏差(RSD)小于4%。用该方法对有证标准物质进行测定,测定结果与标准值相符合。该法能满足各类食品中铝含量检测的要求。     

正交试验优化石墨炉原子吸收光谱法测定海水中的总铬

建立了测定海水中总铬的石墨炉原子吸收光谱法。利用抗坏血酸作为基体改进剂,针对灰化温度、灰化时间、原子化温度、基体改进剂加入量4种因素,利用正交试验优化了石墨炉原子吸收光谱法测定海水中总铬的实验条件。结果表明:原子化温度对测试过程的影响最大,正交试验的最优测试条件:灰化温度1 300℃,灰化时间20 s,原子化温度2 400℃,抗坏血酸质量分数为5%。在优化条件下,校正曲线的相关系数为0.999 8,测定结果的相对标准偏差为3.80%(n=12),样品加标回收率在98.2%~109.2%之间。该法适用于测试大洋海水中的总铬含量。     

微波消解-石墨炉原子吸收光谱法测定胶囊中的痕量铬

研究了微波消解-石墨炉原子吸收光谱法测定胶囊中痕量铬的方法.选择HNO3作为微波消解的酸,通过干扰试验,发现该方法的选择性满足要求.方法线性关系良好,相关系数r2=0.999 8,检出限为1.7×10-14g,测定结果的相对标准偏差为2.63%(n=7),加标回收率为95.0%～104.0%.方法灵敏度高,重复性好,适...     

平台石墨炉原子吸收法测定血清铬

介绍了用平台石墨炉原子吸收法测定血清铬的方法，详述了测定的实验条件，比较了平台石墨炉原子吸收法与火焰法、普通石墨管石墨炉原子吸收法测定血清铬的差异，提出以硝酸镁为基体改进剂，血清经酸处理后可使测定结果几乎无干扰，并测定７５名健康体检者，其参考范围为０．４７６－０．５９２μｇ／Ｌ。     

平台石墨炉原子吸收法测定血清铬

介绍了用平台石墨炉原子吸收法测定血清铬的方法，详述了测定的实验条件，比较了平台石墨炉原子吸收法与火焰法、普通石墨管石墨炉原子吸收法测定血清铬的差异，提出以硝酸镁为基体改进剂，血清经酸处理后可使测定结果几无干扰，并测定了７５名健康体检者，其参考范围为０．４７６￣０．５９２μｇ／Ｌ。     

微波消解-石墨炉原子吸收光谱法测定纸质食品包装材料中的痕量镉

建立了微波消解–石墨炉原子吸收光谱法测定纸质食品包装材料中痕量镉的检验方法。样品经微波消解后,以硝酸镍为基体改进剂,试验确定了石墨炉原子吸收法测定镉的最佳仪器条件。镉的质量浓度在0～10μg/L与吸收峰面积呈良好的线性关系,线性相关系数r=0.9997,检出限为0.025μg/L。将该法用于纸质食品包装材料中痕量镉的测定,并进行加标回收试验,回收率为96.0%～105.5%,相对标准偏差不大于4.4%(n=10)。     

固体进样石墨炉原子吸收光谱法测定船用燃料油中硅、铝含量

建立了固体进样石墨炉原子吸收光谱法测定船用燃料油中微量硅、铝元素含量的快速检测方法。通过选择谱线和背景校正模式,优化了石墨炉条件;根据待测样品及元素特点优化了升温程序。硅、铝的测定波长分别为251.6,394.4 nm,采用塞曼背景校正,样品无需前处理,直接通过石墨舟进样检测。燃料油中硅、铝元素的检出限分别为0.165,0.126 ng;3个浓度水平下,硅元素平均回收率为88%~92%,铝元素平均回收率为93%~95%,测定结果的相对标准偏差为4.2%~10.7%(n=6)。采用本法对实际燃料油样品进行测定,硅、铝元素的测定结果与IP 501方法测定结果基本一致。该方法取样量少、操作简便、快速,检验结果准确度高、稳定性好,适用于船用燃料油中微量硅、铝元素含量的定量检测。     

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.