紫外分光光度法间接测定果冻中甜蜜素

提出了紫外分光光度法间接测定食品中甜蜜素的方法。考察了酸性介质的种类,亚硝酸钠与碘化钾浓度、用量及反应时间对测定的影响。在优化的试验条件下,甜蜜素在1.0～14.0mg·mL-1范围内遵守比耳定律,检出限(3S/N)为0.3mg·mL-1。用此方法测定果冻中甜蜜素含量,加标回收率为102.6%～103.3%,相对标准偏差(n=5)为0.7%～1.3%。     

柱前衍生-高效液相色谱法快速测定膨化食品中的甜蜜素

建立了一种柱前衍生-高效液相色谱法快速测定膨化食品中甜蜜素的方法.用水直接提取膨化食品中的甜蜜素,在强酸环境中用次氯酸钠衍生处理,生成具有较强紫外吸收的N,N-二氯环己胺,通过HPLC,在C18柱上用V(乙腈):V(水)=70:30为流动相,在314 nm处,外标法定量.在1～100 μg/mL范围内线性良好.在0.1,0.2和0.4 mg/g 3个添加水平下回收率95.4%～118.8%之间,RSD%在0.96%～4.2%之间.     

气相色谱法测定水果罐头中甜蜜素

在硫酸介质中将添加在水果罐头中的甜蜜素利用次氯酸钠中的有效氯转化为N,N-二氯环己胺,经正己烷萃取,用气相色谱法(GC/ECD)检测各种水果罐头中的甜蜜素,用DB1701为色谱柱(30 m×0.32 mm,0.25μm),并用气质联用仪对产物进行了定性分析和确认。采用外标法定量,样品中甜蜜素的浓度在5~200 mg.kg-1范围内呈良好的线性关系,r为0.999 2,回收率在96.2%~102.0%;RSD在0.26%~2.47%,检出限为2.5 mg.kg-1,最低定量限为5 mg.kg-1。     

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.     

气相色谱法测定果汁中甜蜜素的含量

建立了气相色谱法测定果汁中甜蜜素含量的分析方法.采用HP-5石英毛细管柱(30 m×0.32 mm,0.25μm)和氢火焰离子化检测器测定,甜蜜素标准溶液制作浓度范围在0.1～0.3 mg/L之间的校正曲线,相关系数为0.9999.样品加标回收率为≥95%,相对标准偏差为0.05%.     

基于灿烂绿与甜蜜素的显色反应测定饮料中甜蜜素

建立了测定饮料中甜蜜素的吸收光谱法。在弱酸性溶液中,甜蜜素与灿烂绿反应生成离子缔合物,在608 nm和636 nm处产生2个较强的正吸收峰,甜蜜素的质量浓度在0.05～3.6 mg/L范围内服从朗伯-比尔定律,表观摩尔吸光系数(κ)为5.12×10~4L/(mol·cm)(608 nm)和4.11×10~4L/(mol·cm)(636 nm),检出限为0.038 mg/L(608 nm)和0.041 mg/L(636 nm),定量限分别为25.2和27.2 mg/L。若将608 nm和636 nm叠加测定,表观摩尔吸光系数(κ)为9.23×10~4L/(mol·cm),检出限和定量限分别为0.02和13.3 mg/L,此法用于实际样品中甜蜜素的测定,加标回收率(n=5)和相对标准偏差(RSD,n=5)分别为97.7%～102%和1.0%～2.0%。该法适于苏打、果味及碳酸饮料中甜蜜素的测定。     

气质联用法测定含蛋白食品中的甜蜜素

建立了一种用于检测含蛋白食品中甜蜜素的方法.用三氯乙酸对样品进行蛋白变性,次氯酸钠作衍生剂将甜蜜素定量转化为N,N-二氯环己胺,正己烷萃取与基体分离后由气相色谱-质谱联用技术进行测定.在2～50 μg/mL范围内方法的线性良好,5,10和25mg/kg等3个添加水平下,回收率稳定在75.0%～100.0%之间,RSD≤12.1%,灵敏度高,检出限为1.0 mg/kg.     

液相色谱-串联质谱法测定水产加工品中的甜蜜素

建立了液相色谱-串联质谱法测定水产加工品中甜蜜素的测定方法。样品用水提取,正己烷净化后,以0.1%甲酸-甲醇为流动相,C18色谱柱分离,在负离子模式下用配有电喷雾离子源的液相色谱-串联质谱测定。甜蜜素含量1~200 ng/m L范围内,线性关系良好(r~2=0.9999);方法定量限5μg/kg(S/N≥10)。甜蜜素在5μg/kg和50μg/kg添加水平下,平均回收率为81.0%~88.4%,相对标准偏差为4.0%~6.4%。方法适合水产加工品中甜蜜素的测定。本文根据甜蜜素的性质,选取水为提取剂,并对净化方法进行了研究,通过正已烷液-液萃取和冷冻方式去除了提取液中的油类物质和水溶性蛋白,确保了分析结果的稳定性和准确性。该技术的建立为水产加工品中甜蜜素监管提供技术支撑。     

光度法间接测定环己基氨基磺酸钠

提出在 0 .0 3mol·L- 1磷酸介质中和 80℃的反应温度下 ,定量的溴与环己基氨基磺酸反应 2 0min后 ,比色法测余溴间接测定环己基氨基磺酸钠的新方法。在测定条件下 ,方法的线性范围为 0～ 0 .5 0mg·ml- 1,检出限为 0 .0 5mg·ml- 1,RSD小于 6 .0 % (n =6 ) ,加标回收率为 90 0 %～99.7%。用于食品添加剂甜蜜素和食品样品的测定 ,结果满意     

毛细管柱气相色谱法测定白酒中的甜蜜素

建立了毛细管色谱柱气相色谱法测定白酒中甜蜜素的方法。在国标方法的基础上增大取样量,水浴蒸干浓缩,减少衍生后的萃取液体积,增加浓缩倍数,降低方法检出限。甜蜜素浓度在0.02～0.40 g/L范围内与其峰面积呈良好的线性关系,线性相关系数r=0.9998,方法检出限为0.1 mg/kg。该方法适用于白酒中甜蜜素的检测,加标回收率在88%~96%之间,同一样品测定结果的相对标准偏差为4.06%(n=6)。该方法检测结果与高效液相色谱–质谱法测定结果的相对偏差为3.3%~8.3%。     

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.