偏最小二乘-分光光度法同时测定芦丁与槲皮素的方法研究

芦丁和槲皮素在紫外区的最大吸收波长接近,吸收光谱严重重叠,普通光度法分析难以实现两者的直接测定.该文通过测定以1∶4甲醇-水为溶剂的芦丁、槲皮素标准混合溶液在200～500 nm波长范围的吸收光谱,采用偏最小二乘法(PLS法)建立校正模型,对样品中的芦丁和槲皮素的含量进行预测,建立了偏最小二乘-分光光度法同时测定芦丁和...     

偏最小二乘-分光光度法同时测定钢样中铬、锰

在石亢_磷混合酸介质中,钢铁样品中铬和锰在银离子存在下用过硫酸铵溶液分别氧化至六价和七价,用分光光度法同时测定样品中铬和锰的含量.在380～600 nm波长范围,每间隔10 nm测定一次吸光度.借计算机及Matlab语言编写程序,对所得吸光度数据用偏最小二乘计算法处理并获得结果.     

人工神经网络紫外光度法同时测定甲基苯甲醛的三种同分异构体及其与偏最小二乘法的比较

同分异构体的同时测定一直是分析化学领域的热点和难点问题,本文将化学计量学中的多元校正方法,如偏最小二乘法和人工神经网络法与紫外分光光度法相结合,同时测定了紫外吸收光谱严重重叠的甲基苯甲醛的三种同分异构体混合体系中各组分的含量。确定了测定的最佳波长范围为230～304 nm;测得48个混合标样的吸光度值用于建立模型,其中,邻、间、对甲基苯甲醛的浓度范围分别为6.0～15.0、7.0～16.0和8.0～19.0 μg·mL-1。7个模拟样品作为监测集用于检验所建立模型的预测性能。本文还讨论了三种组分浓度比例对所建立模型预测性能的影响并确定了可以准确测定的浓度比例范围。所建立的方法用于模拟样品的测定,其回收率在84.00%与109.60%之间。与偏最小二乘法的测定结果比较,经成对t检验表明,两种方法对邻、间甲基苯甲醛测定结果无显著性差异;而对甲基苯甲醛的测定,人工神经网络法的测定结果优于偏最小二乘法。     

改进的多波长K系数-分光光度法同时测定食品中锌和铅

报道了对多波长K系数-分光光度法同时测定食品中锌及铅的改进方法.采用5-Br-PADAP作为显色剂,Triton X-100作为增溶剂,在pH 9.2的氨性缓冲溶液中进行锌(Ⅱ)及铅(Ⅱ)与5-Br-PADAP的显色反应,采用不加显色剂的空白溶液作为参比溶液,除了显色剂在测量波长区间的吸收所引起的误差.测定锌(Ⅱ)时,选用的波长为558 nm,参比波长为572 nm及446 nm;测定铅(Ⅱ)时,测定波长为572 nm,而参比波长为558 nm及446 nm,两元素的线性范围均为(1.0～20.0 μg)/25 mL.应用此方法测定了味精和松花皮蛋两种样品中的锌量和铅量,所得测定值与原子吸收光谱法的测定结果相符.在此样品的基础上,加入锌及铅的标准溶液作回收试验,测得锌及铅的回收率依次在96.5%～104.2%之间和95.0%～103.7%之间.     

高效液相色谱法测定烟草中二甲基二硫代氨基甲酸酯类杀菌剂

建立了高效液相色谱法测定烟草中二甲基二硫代氨基甲酸酯类农药方法,优化了烟草样品的前处理方法、样品提取溶剂和提取时间等参数。利用三氯甲烷可提取出烟草中的福美双,福美锌和福美铁通过碱性乙二胺四乙酸二钠盐提取后经碘甲烷衍生化后直接高效液相色谱分析,高效液相色谱流动相比例为甲醇:水=48:52(V/V),紫外检测波长为235 nm和270 nm。方法的平均回收率范围为80%~97%,相对标准偏差范围为1.1%~6.4%,福美双的检出限为10 ng/g,福美锌和福美铁的检出限为1 ng/g。方法适合烟草中二甲基二硫代氨基甲酸酯类杀菌剂的定性和定量分析。     

偏最小二乘紫外分光光度法同时测定甲基苯甲醛三种同分异构体

将偏最小二乘法(PLS)用于紫外分光光度数据的解析,建立了同时测定甲基苯甲醛3种同分异构体的模型。在230～304 nm范围内,将测得的48个样品的吸光度值作为校正集,另18个样品的吸光度值作为预测集用于建模。所建立的邻、间、对甲基苯甲醛模型的平均回收率分别为101.2%、100.2%和98.9%;均方根误差(RMSE)分别为0.2667、0.3853和0.2118;预测浓度范围分别为4.6～16.2μg/mL、5.8～17.4μg/mL和6.5～20.6μg/mL。讨论了混合物中3种同分异构体浓度比例对测定结果的影响,并确定了最佳的浓度比例范围。对模拟样品进行加标回收率试验。并通过与顺、反丁烯二酸两种同分异构体测定结果的比较,得出了有意义的结论。     

微分脉冲溶出伏安-偏最小二乘法同时测定代森锌和代森锰

采用循环伏安法讨论了两种常用的杀菌剂代森锰和代森锌在汞电极上的电化学还原反应机理,发现它们均具有良好的的伏安还原峰.采用微分脉冲溶出伏安法研究本体系时,获得的代森锰和代森锌的线性范围分别为0.005～0.07 mg/L和0.02～0.24 mg/L;检出限分别为4.10和12.8μg/L.由于这两种杀菌剂的分子结构很相似,它们的伏安波谱峰重叠严重,采用常规方法很难对它们分别进行测定.为解决波谱重叠的问题,本研究采用主成分回归和偏最小二乘法对波谱进行解析.结果表明,偏最小二乘法能得到较好的定量结果.利用本方法对几种蔬菜和水果样品进行分析,三氯甲烷作萃取剂的萃取率最大,回收率在95.5％～103％之间.     

动力学分光光度法结合化学计量学同时测定农药杀线威和抗蚜威

本文采用动力学分光光度法结合化学计量学方法对水样中的两种氨基甲酸酯类农药杀线威和抗蚜威进行测定.该方法基于酸性条件下,Cu(Ⅱ)能催化H2O2氧化罗丹明B而使其褪色,杀线威或抗蚜威存在时能使该反应速率降低,而且两者对反应速率的影响存在一定差异.实验对硫酸浓度、Cu(Ⅱ)浓度、罗丹明B浓度、H2O2的质量分数以及温度等条件进行考察.在选定实验条件下,杀线威和抗蚜威测定的线性范围分别为2～16μg·mL-1和1～15μg·mL-1,检测限分别为0.65μg·mL-1和0.41 μg·mL-1.实验采集波长554 nm处和反应时间0～600 s范围内动力学吸光度数据,并分别采用偏最小二乘法(PLS)和主成分回归法(PCR)处理,建立了定量回归模型并对合成样品进行测定以验证模型.该方法可应用于实际水样中杀线威和抗蚜威的同时测定.     

化学计量学-同步荧光光谱法同时测定速灭威、残杀威和呋喃丹

在pH 4.0的B-R缓冲溶液中,速灭威、残杀威和呋喃丹能够产生内源荧光,但光谱严重重叠。当波长差Δλ=30 nm时,加入一定量的β-环糊精,3种农药的荧光强度均有不同程度的加强,且荧光强度与农药的浓度呈良好的线性关系,速灭威、残杀威和呋喃丹单组分的测量线性范围分别为0.2~2.0、0.02~0.38和0.04~0.56μg/mL;检出限分别为0.083、0.015和0.020μg/mL。应用多种化学计量学方法,如经典最小二乘(CLS)、主成分回归(PCR)和偏最小二乘(PLS)对同步荧光光谱严重重叠的3种农药混合体系合成样进行光谱解析并比较其分析能力。结果表明,PLS预报各组分的结果较好,采用该模型分析了一些实际食品样品,获得满意的结果。     

酸性铬兰K褪色分光光度法测定罐头中的铅

在H2SO4介质中,以2,2'联吡啶为活化剂,铅能灵敏地催化KIO4氧化酸性铬兰K的褪色反应,据此建立了测定痕量铅的催化动力学分光光度法.最大吸收波长位于526 nm,线性范围为0.002～0.006 μg/mL,检出限为2.0×10-4μg/mL.且大多数常见离子不干扰测定,可用于罐头中痕量Pb(Ⅱ)的测定.     

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%.     

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.