双波长分光光度法同时测定溶液中的硝酸根和碘离子

食品和环境样品中往往同时含有硝酸根和碘离子,用紫外分光光度法直接测定硝酸根或碘离子时,二者相互干扰。为此建立了主、次波长分别为220.0、231.5 nm的等吸收点双波长紫外分光光度法测定溶液中的硝酸根和共存的碘离子。当溶液中硝酸根的浓度在0~0.12 mmol/L的范围内,碘离子的浓度在0~0.10 mmol/L的范围内时,主、次波长下的吸光度差值A220-231.5与溶液中硝酸根的浓度 呈良好线性关系,线性方程为A220-231.5 = 2.9958 0.0016（R2 = 0.99994）;其中A220 (NO3-) = 3.6099 0.0084（R2 = 0.99994）,利用吸光度的加和性：A220 (I-) = A220 - A220 (NO3-) = 10.7394 0.0029（R2 = 0.99994）,间接得到碘离子含量 。硝酸根和碘离子的平均相对标准偏差分别为0.6%、0.2%,回收率分别为99.5~102%、99.9~100%。方法简便快捷,可用于溶液中微量硝酸根和碘离子的同时测定。     

顺序注射化学发光联用技术测定食品中的碘

基于酸性溶液中HCHO存在下,KMnO4可氧化I-产生很强的化学发光的原理,建立了一个简单快速测定微量碘的顺序注射化学发光分析方法。I-在3.0×10-8~8.0×10-6mol/L范围内与发光强度呈良好线性关系。对2.0×10-6mol/L I-11次重复测定的相对标准偏差(RSD)为2.6%,方法的检出限(3σ)1.3×10-8mol/L,测定了4种食品中的碘量,回收率为92.8%~107.7%。分析频率为70 h。     

罗丹明6G褪色光度法测定微量铁

在稀硫酸介质中,Fe3+氧化I-成I2,I2与过量的I-结合生成I-3阴离子,I-3阴离子与罗丹明6G形成离子缔合物,导致罗丹明6G吸光度降低.在罗丹明6G的吸收峰526 nm波长下测定时,Fe3+的质量浓度在20～200 μg·L-1范围内,反应体系吸光度的降低值与Fe3+的质量浓度呈线性关系,方法的检出限(3s/k)为16.6 μg·L-1.据此建立了褪色光度法测定Fe3+的方法.用于中草药中微量铁的测定,回收率在96.7%～103.0%之间,相对标准偏差(n=5)在2.2%～4.7%之间.     

反相离子对高效液相色谱法测定微量碘的研究

建立了一种反相离子对高效液相色谱测定微量碘的新方法。采用WatersSpherisorbODS2(5μm ,4.6mmi.d.×250mm)色谱柱 ,以甲醇 -水 (体积比为30∶70)作为流动相 ,四丁基溴化铵 (TBA·Br)作离子对试剂 ,流速为1.0mL/min,在223nm处检测 ,将I- 与在紫外区有吸收的共存离子完全分离。I- 的质量浓度在0.20～180μg/mL范围内 ,峰面积Y与质量浓度X(μg/mL)呈良好的线性关系 ,r=0.9997 ,I -的检出限为53.2μg/L。该方法已用于海水和海带、紫菜等食品中碘含量的测定 ,加标回收率为98%～101 % ,相对标准偏差为1.04 %～3.01 %。     

全自动电位滴定法测定水中氯化物

为了实现快速准确测定水中氯化物含量,建立了一种全自动电位滴定法测定水中氯化物的分析方法,对取样体积进行了优化,结果表明本方法最佳取样体积为50mL。研究了CO32-、S2-、I-、Br-等对氯化物测定结果的影响,并就干扰离子的消除提出了有效的方法,水样中加入1 ml （2+98）硝酸溶液可消除S2-、CO32-的干扰,当水样中I-、Br-浓度高于5mg/L时仪器可自动校正并扣除干扰。本方法检出限为0.19mg/L,大大低于水质 氯化物的测定 硝酸银滴定法GB 11896-89中规定的10 mg/L的要求,该方法测定地表水、地下水和工业废水实际样品,精密度为1.9%～2.3%,加标回收率为91.9%～99.0%。采用全自动电位滴定法测定水中氯化物,方法检出限低、精密度和正确度良好。本方法的建立为复杂环境水样中氯化物的准确测定提供了有益的技术支撑。     

流动注射化学发光法测定废水中Mn(Ⅱ)

鲁米诺与K2S2O8在碱性介质中能产生稳定的化学发光信号,Mn2+对鲁米诺过硫酸钾体系的化学发光产生微弱的抑制作用,而Ag+能增强Mn2+对发光体系的抑制作用,据此建立测定了废水中微量Mn2+的流动注射化学发光分析方法。Mn2+的浓度在1.0×10-10～1.0×10-7mol/L范围内与相对发光强度(ΔI)呈良好的线性关系,检出限为1.0×10-12mol/L;对1.0×10-7mol/LMn2+进行11次平行测定,其相对标准偏差RSD为1.3%。方法已用于测定废水中Mn2+的含量。     

氧弹燃烧-离子色谱法测定电子产品连接线中的卤素

建立了氧弹燃烧法处理电子产品连接线,离子色谱测定样品中卤素的分析方法。选用TSK-gelSuperIC-AZ阴离子分析柱,以NaHCO3(7.5mmol/L)+Na2CO3(1.1mmol/L)为流动相等度洗脱,抑制电导检测。结果表明,该条件下F-浓度在0.02～2mg/L,Cl-和Br-浓度在0.05～5mg/L范围内峰面积与浓度的线性关系良好(r>0.999),实际样品中卤素回收率为90.52%～97.24%,样品测定结果相对标准偏差均为0.73%～2.01%(n=5)。应用氧弹燃烧-离子色谱法测定电子产品连接线中的卤素离子,方法简便、快捷,测定结果准确。     

纳米银掺杂炭气凝胶修饰电极对卤素离子的电化学响应

首次以新型的纳米银掺杂炭气凝胶为材料,制备了一种新型纳米银炭电极,并考察了该电极对卤素离子的电化学响应。在0.1 mol/L的KNO3中,用微分脉冲伏安法对含Cl-的溶液以及卤素离子共存时的溶液进行测定,结果表明:峰电流与Cl-浓度呈线性关系,线性范围为2.0×10-7-4.2×10-5mol/L;检出限为1.2×10-8mol/L。此外响应电流与Cl-、Br-、I-3种离子的总浓度在6.0×10-7-1.2×10-5mol/L范围内呈线性关系。结果表明,纳米银掺杂炭气凝胶修饰电极可望用于痕量卤素离子的测定。     

银催化甲醛前行动力波的研究

实验发现 ,在银微盘电极上 ,于HAc NaAc的甲醛溶液中 ,加入少量I-或Br-,循环伏安扫描电位在0 .2～ -0 .8V时 ,就会出现灵敏的甲醛还原峰。机理探讨表明 :在阳极化过程中 ,Ag+ 与I-或Br-生成AgI或AgBr;在较低电位负向扫描时 ,阴极溶出Ag+ ,新产生的活性Ag+ 于电极表面催化了甲二醇脱水为甲醛。采用示差脉冲溶出伏安法 ,峰电流与甲醛的浓度在 5 .0× 1 0 -7～ 2 .0× 1 0 -5mol/L范围内呈较好的线性关系 ;检出限为 5 .0× 1 0 -7mol/L ;对 2 .0× 1 0 -6mol/L甲醛测定 5次 ,相对标准偏差为 3 .0 %。可用于直接电化学方法测定痕量甲醛。     

离子色谱法同时测定化妆品中的铵和6种烷基胺

建立同时测定化妆品中铵和6种烷基胺的离子色谱(IC)分析方法。优化了色谱条件和样品前处理方法,样品经100 mmol/L乙酸-20%(v/v)乙腈溶液浸提,固相萃取(SPE)柱去除阴离子、中和氢离子后进样测定。考察了提取溶液的pH、有机溶剂和共存离子对测定结果的影响。分析方法的线性范围为0.3～15 mg/L,检出限为2.1～7.9 mg/kg,定量限为7～26 mg/kg。采用建立的分析方法测定了清洗、柔肤、祛斑、防晒、烫发、染发和育发类化妆品的加标回收率的范围在80.2%～109.2%之间,相对标准偏差(RSD)的范围为0.5%～3.1%。方法选择性好,灵敏度高,抗干扰强,用于实际样品测定结果准确。     

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.