表面活性剂增敏硝普钠分光光度法测定甲硝唑

本文建立了十四烷基二甲基苄基铵增敏作用下硝普钠分光光度法测定甲硝唑的方法.研究表明:在碱性条件下,甲硝唑与硝普钠反应生成化学计量比为1:1的红褐色产物,其最大吸收波长λmax=500nm,表观摩尔吸光系数为ε=9.8×103L·mol-1·cm-1.甲硝唑在0.70～30μg·mL-1浓度范围内与吸光度成良好线性关系,...     

硝普钠分光光度法测定头孢他啶

建立了硝普钠分光光度法测定头孢他啶的方法。实验结果表明,在碱性条件下,头孢他啶与硝普钠以1∶2的化学计量比反应形成一种红褐色产物,其最大吸收波长为528 nm。 头孢他啶在2.50~810 mg/L浓度范围内与吸光度呈良好线性关系,线性回归方程为A=0.02704+0.00218ρ(mg/L),线性相关系数r＝0.9987,表观摩尔吸收系数ε528=1.2×103 L/(mol·cm),检测限(3σ/k)为1.38 mg/L。 本方法操作简便、快速,成功用于药品中头孢他啶含量的测定。     

硝普钠分光光度法测定头孢噻肟钠

建立了测定头孢噻肟钠的新方法,碱性溶液中硝普钠与头孢噻肟钠生成了化学计量比为2∶1的产物,其最大吸收波长λmax=525 nm,表观摩尔吸光系数3.9×103L.mol-1.cm-1。头孢噻肟钠在0.91~200μg/mL浓度范围内与吸光度呈现良好线性关系,线性回归方程A=0.010+0.00816ρ(μg/mL),线性相关系数r=0.9994,检出限(3σ/k)为0.62μg/mL。方法可用于药物样品和血清中头孢噻肟钠含量的测定。     

硝普钠和盐酸二甲双胍分光光度法相互测定

建立了硝普钠(SNP)和盐酸二甲双胍(MET)分光光度法相互测定的新方法。在碱性条件下,MET与SNP以1:1的化学计量比生成了一种酒红色的物质,其最大吸收波长为524 nm。当固定SNP(6.0×10-3mol/L)为5.00 m L时,吸光度和MET的浓度呈现良好的线性关系,线性回归方程为A=0.008+0.449cM ET(mmol/L),相关系数为0.9997,检出限(3σ/k)为0.02 mmol/L。当固定MET(6.0×10-3mol/L)为5 m L时,吸光度与SNP的浓度呈现良好的线性关系,线性回归方程为A=0.005+0.436cSNP(mmol/L),相关系数为0.9992,检出限(3σ/k)为0.01 mmol/L。方法可用于分别测定药物样品中MET和SNP含量。     

硝普钠分光光度法测定对乙酰氨基酚

建立了硝普钠分光光度法测定对乙酰氨基酚的方法。研究表明:在碱性条件下,对乙酰氨基酚与硝普钠以1∶2的化学计量比反应形成一种绿色产物,其最大吸收波长为698nm。对乙酰氨基酚在1.7～102μg·mL-1浓度范围内与吸光度成良好线性关系,线性回归方程为A=0.02804+0.02285c(μg·mL-1),线性相关系数r=0.9986,表观摩尔吸收系数ε698=3.5×103L·mol-1·cm-1,检测限(3s·k-1)为1.42μg·mL-1。本方法成功应用于药物样品中对乙酰氨基酚含量的测定,回收率在97.6%～102.0%,结果满意。     

硝普钠分光光度法测定头孢克肟

研究了硝普钠(SNP)与头孢克肟(CEF)之间的显色反应机理,确定了最佳反应条件,建立了一种测定CEF的新方法。结果表明:在NaOH溶液浓度为0.17mol/L的碱性介质中,控制温度40℃,反应30min,CEF与SNP以1∶2化学计量比生成一种含亚硝基的红褐色化合物,最大吸收波长为530nm,表观摩尔吸光系数ε=1.96×103L/(mol·cm)。CEF的浓度在0.8~400μg/mL范围内服从比耳定律,线性相关系数为0.9991,检测限(3σ/k)为0.48μg/mL。     

荧光检测海水介质中的一氧化氮

基于2,3-二氨基萘(DAN)与一氧化氮(NO)在海水介质中生成荧光性2,3-萘酚三唑(NAT)来测定海水中NO.确定了荧光法测定NO的条件(λex=383 nm,λem=410 nm)、温度和时间对DAN捕集NO的影响,以及DAN溶液对捕集NO的影响.测得NO浓度与其荧光强度之间呈线性关系,线性范围1.4～1400 nmol/L, r=0.9985,P<0.0001;检出限1 nmol/L (S/N=3);相对标准偏差1.63%(14 nmol/L NO);不存在介质干扰.同样条件下与NaOH为介质的荧光法相比,本方法将检出限提高了1个数量级.结合吹扫-捕集检测出青岛石老人(36°05′46″ N; 120°29′40″ E)海水中NO浓度为(0.12±0.01) nmol/L,可用于监测硝普钠在海水中释放NO的规律.     

1,2-萘醌-4-磺酸钠体系分光光度法测定磺胺甲噁唑

采用1,2-萘醌-4-磺酸钠体系分光光度法测定磺胺甲噁唑(SMZ)。磺胺甲噁唑与1,2-萘醌-4-磺酸钠在pH=10.0的缓冲溶液中发生亲核取代反应生成橙红色的产物,组成比为1:1,最大吸收波长λ=476 nm;表观摩尔吸光系数ε=6.44×103L/(mol.cm);SMZ浓度在0.2~60 mg/L范围内呈良好的线性关系;线性回归方程为A=0.02452 0.02301C(mg/L),线性相关系数r=0.9991;检出限为0.08 mg/L;RSD为0.25%(20 mg/L,n=11);平均回收率为98.7%以上。优化了对磺胺甲噁唑的测定条件。初步探讨了反应机理,应用拟定的方法测定磺胺甲噁唑的含量,与药典法相比,结果满意。     

硝普钠褪色分光光度法测定硼

在碱性条件下,硼酸与硝普钠能够形成二亚硝铣铁氢化硼,最大褪色波长为459 nm。硼的浓度在0.6~120.1μg·m L~(-1)范围内与吸光度降低的程度成良好线性关系,线性回归方程为A=-0.0165-0.0077C(μg·m L~(-1)),线性相关系数为0.9991,检测限为0.36μg·m L~(-1)。此外,还详细讨论了硼酸与硝普钠的反应机理。该方法用于药物样品中硼含量的测定,结果满意。     

液相色谱串联质谱法测定水果中复硝酚钠残留量

以甲醇提取样品,采用超高效液相色谱串联质谱法(UPLC–MS/MS)测定水果中复硝酚钠的残留量。以甲醇–10 mmol/L乙酸铵水溶液(体积比为60∶40)为流动相,质谱采用电喷雾负离子MRM检测模式。对硝基苯酚钠和5-硝基愈创木酚钠的线性范围为0.05~2.00 mg/L,检出限为0.01 mg/kg,邻硝基苯酚钠的线性范围为2.5~100.0 mg/L,检出限为0.5 mg/kg,线性相关系数均大于0.995。实际样品中对硝基苯酚钠、邻硝基苯酚钠和5-硝基愈创木酚钠的加标回收率分别为83.0%~93.4%,81.0%~87.4%,83.0%~91.8%,测定结果的相对标准偏差小于7%(n=6)。该法操作简单、快捷,精密度、准确度高,适用于水果中复硝酚钠的残留分析。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.