流动注射激光诱导荧光光度法测定食品中的铁

将流动注射与CCD阵列检测激光诱导荧光装置联用 ,形成连续自动荧光光谱分析系统 ,建立了在 1× 1 0 -3 mol L的HCl溶液中 ,Fe3 催化H2 O2 氧化罗丹明B(RhB)的催化荧光光度测定铁的新方法 ,对反应条件及流动注射各实验参数进行了优化 ,用于食品样品中铁的测定 ,测定结果与原子吸收分光光度法有一致性 ,方法的相对标准差不大于 8.0 % ,加标回收率为 95 .9%～ 1 0 6%。     

CCD阵列检测-激光诱导荧光光度法测定食品中锌

利用自行组装的激光诱导荧光 CCD阵列检测器 计算机联用装置 ,建立了测定食品中锌的灵敏方法。在乙酸 乙酸铵缓冲溶液 (pH 4 )中 ,Zn(Ⅱ )与SCN- 、若丹明B(RhB)反应生成Zn SCN RhB配合物 ,经乙醚萃取后 ,在激发波长 5 32nm和发射波长 5 80nm进行荧光强度测定。研究了表面活性剂对Zn SCN RhB配合物荧光强度的影响 ,优化了荧光反应及食品样品的处理条件 ,并用于食品试样中锌的测定。方法的检出限为 4ng·ml- 1,加标回收率为 90 .0 %～ 110 .0 % ,相对标准偏差为 2 .0 %～ 9.7% ,能满足食品卫生检验的要求。     

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     

单波长X射线荧光光谱法测定加氢催化剂中磷

建立了单波长X射线荧光光谱法测定加氢催化剂中磷含量的方法。将干燥催化剂样品粉末0.200 0 g置于银坩埚中,加入10 mL 0.67 g·mL~(-1)氢氧化钠溶液,加热微沸20 min,趁热转移至250 mL烧杯中,加入10 mL 50%(体积分数)硫酸溶液调节体系酸度,加热至样品完全溶解,冷却后,定容至250 mL。取上述待测液6 mL,采用Phoebe型单波长X射线荧光磷含量分析仪测定其中的磷含量,测量时间600 s。结果表明,磷的质量分数在0.006%内与其对应的荧光强度呈线性关系,检出限(3s/k)为0.4μg·g~(-1)。按标准加入法进行回收试验,回收率为93.0%～120%,测定值的相对标准偏差(n=7)均小于5.0%。方法所得测定结果与经典的分光光度法的一致。     

槲皮素铝的络合反应及槲皮素的荧光光度测定

槲皮素铝配合物在紫外光照射下产生荧光 ,其荧光强度与槲皮素的浓度呈线性关系。据此能测定槲皮素含量 ,线性范围为 2 .5× 10 - 6 ～ 4× 10 - 5mol·L- 1。该方法成功用于槐米提取物中槲皮素的测定。回收率在 97.8%～ 10 0 .0 %。     

高效液相色谱法同时测定食品中安赛蜜、糖精、苯甲酸、山梨酸和咖啡因

用KromasilC1 8柱 ,以甲醇 :0 .5g/L柠檬酸铵 (42 5 :5 75 )为流动相 ,在波长 2 1 5nm ,柱温 40℃下测定了食品中的安赛蜜、糖精、苯甲酸、山梨酸和咖啡因。方法RSD 0 .6 2 %～ 1 48% ,回收率 1 0 0 .7%～ 1 0 3 % ,相关系数r>0 .9998;应用于可乐、汽水、果奶等测定。     

冷蒸气发生原子吸收光谱法测定食品中痕量镉

为建立食品中痕量镉的测定方法 ,研究了用硼氢化钾 盐酸 铁氰化钾 盐酸羟胺发生挥发性镉蒸气的反应体系 ,将发生器表面及玻璃导气管进行硅烷化处理 ,提高了灵敏度并明显改善测定精密度。在最佳条件下 ,该法测定镉的线性范围为 0 .0 11～ 2ng·ml-1,检出限为 11pg·ml-1。运用此法测定了小米等 6种食品 ,相对标准偏差在 5 .35 %～ 6.4 4 %范围内。加标回收率在 86.3%～10 8.4 %之间 ,结果满意     

柱前荧光衍生-高效液相色谱法测定尿中雌二醇

建立了对硝基苯甲酰氯柱前荧光衍生 高效液相色谱法测定尿中 1 7α 和 1 7β 雌二醇的方法。尿样经盐酸水解、固相萃取柱浓缩、净化分离后 ,在无水条件下与对硝基苯甲酰氯反应生成荧光产物 ,再用高效液相色谱 荧光检测器测定。流动相为乙腈 水 (5 5∶45 )。线性范围为 7.0× 1 0 - 3～ 1 0mg L ,检出限均为 7.0× 1 0 - 3mg L,相对标准差分别为 0 .93 %～ 1 .5 %和 0 .88%～ 1 .3 %。平均回收率分别为 83 .5 %和 88.2 %。     

铽-钛铁试剂络合物荧光猝灭法测定磷酸盐

研究Tb3 + 钛铁试剂 (TR)络合物荧光猝灭法测定无机磷酸盐的新方法 ,并讨论采用荧光光谱法测定时的最佳条件 :pH 6 .9六次甲基四胺 HCl缓冲溶液 ,1.2× 10 -6mol/LTb3 + ,4 .0× 10 -6mol/LTiron ,λex=317nm ,λem=5 4 6nm。该方法简便 ,灵敏度高 ,线性范围为 0 .0 0 5～ 30mg/L ,检测限为 4 .1μg/L。直接用于尿样中无机磷酸盐的加入回收测定 ,标准加入回收率为 93%～ 98% ,相对标准偏差为 3.5 %。     

钒—钼酸铵比色法测定食品中总磷

食品中的磷具有营养学意义.常用的定量方法有钼蓝比色法和重量法,钼蓝比色法测定食品中的总磷,酸度对测定结果的影响比较大,方法的重现性差;重量法仅适用于磷的含量较高的食品.本文参照文献,用钒-钼酸铵比色法测定食品中总磷,试液酸度对吸光度几乎没有影响,磷含量在0.5～10mg·L~(-1)范围内呈良好的线性关系,相关系数r=0.9998,相对标准偏差<3%,加标回收率在97.6%～103.7%之间.     

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.