火焰原子发射光谱法直接测定蜂蜜中钾钙

建立了火焰原子发射光谱法测定蜂蜜中钾、钙的快速分析方法。用硝酸 (1+ 1)微热溶解蜂蜜样 ,可获得均匀透明的溶液。为消除干扰 ,取适量样品溶液 ,加入消电离剂NaCl溶液 (测定钾 )或释放剂La(Ⅲ )溶液 (测定钙 )配制成试液 ,以空白为参比 ,用工作曲线法测定。RSD小于1 0 % ,加标回收率为 98.4 %～ 10 3.7% ,检出限钾为 0 .0 12mg·L- 1,钙为 0 .0 30mg·L- 1。     

电位溶出法间接测定血清中钙镁

利用钙置换Zn EGTA中锌 ,镁置换Zn EDTA中锌 ,采用计时电位溶出法间接地测定血清中钙镁含量。血清用量仅为 2 0 μl,且不必消化 ,钙的线性范围为 0～ 4 80 μg·L- 1,检出限为 2 μg·L- 1,相关系数为 0 .9976 (n =6 ) ,镁的线性范围为 0～ 2 88μg·L- 1,检出限为 1μg·L- 1,相关系数为0 .9984 (n =6 )。用模拟血清测定钙的平均回收率为 99.4 % ,镁的平均回收率为 10 0 .1%。     

原子吸收光谱法同时测定铅钙锡铝合金中钙和锡

铅钙锡铝合金广泛用于全密封免维护铅蓄电池极板的生产。合金中微量钙的测定有汞分离ＥＤＴＡ容量法[1] ,氯化铅 铜试剂分离ＥＤＴＡ容量法[2 ] ,原子吸收光谱法[3 ] 。锡的测定通常采用邻苯二酚紫 十六烷基三甲基溴化铵吸光光度法[4 ] 。而用原子吸收光谱法测定铅钙锡铝合金中钙和锡的方法还未见报道。科研所研制生产的铅钙锡铝合金中含钙0 0 75 %～ 0 .12 % ,含锡 0 .4 %～ 0 .6 % ,含铝 0 .0 2 %～ 0 .0 3% ,余量为铅。本文用原子吸收光谱法同时测定其中的钙和锡 ,吸收波长分别为 4 2 2 .7和2 86 3ｎｍ。为了防止铅钙锡铝合金中锡水…     

EDTA作基体改进剂火焰原子吸收法直接测定植酸中钙

植酸中钙含量一般在千分之几至万分之几之间.目前测定植酸中钙含量的方法有:草酸铵沉淀法、ICP-AES法、原子吸收分光光度法等.草酸铵沉淀法分析手续冗繁、耗时;ICP-AES法仪器昂贵;原子吸收法因植酸中含有大量的磷(11%～20%),在乙炔-空气火焰中与钙生成耐熔性化合物,不易原子化,即使加入相当量的锶和镧,也难以全部消除这种干扰,使得钙的测定结果严重偏低.本文采取直接稀释植酸,加入EDTA作基体改进剂,用乙炔-空气火焰原子吸收法测定植酸中钙含量,取得满意的效果,回收率为101%,与ICP-AES法测定比较,结果吻合.     

双波长吸光光度法同时测定饮用水中钙和镁

研究了以偶氮胂Ⅲ作显色剂 ,用双波长吸光光度法同时测定水中钙和镁的最佳条件。测定钙和镁的最佳波长对分别为 6 5 0～ 5 93nm和 6 15～ 6 6 5 .5nm ,服从比耳定律的线性范围分别为0～ 12 μg/ 2 5ml和 0～ 18μg/ 2 5ml,检出限分别为 0 .0 1和 0 .0 18μg·ml- 1,加标回收率分别在 97 2 %～ 10 4 .5 %和 89.8%～ 92 .8%之间。将此法应用于饮用水中钙和镁的测定 ,结果满意。     

偶氮氯膦Ⅰ光度法测定铅钙锡铝合金中微量钙

铅钙锡铝合金广泛应用于全密封免维护铅蓄电池极板的生产.铅钙锡铝合金中微量钙的测定有汞分离EDTA容量法、氯化铅-铜试剂分离EDTA容量法等.本文研究了用偶氮氯膦Ⅰ(CPAⅠ)光度法测定铅钙锡铝合金中的微量钙,在测定条件下,合金元素锡、铅分别以β-偏锡酸和硫酸铅沉淀分离,共存元素用三乙醇胺、邻菲罗啉掩蔽.测定结果的准确度和精密度令人满意.     

EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

火焰原子吸收光谱法连续测定蘑菇中钙镁

钙、镁是人体所必需的常量元素 ,一旦缺乏 ,人体的生命活动就会发生障碍 ,引起某些疾病。蘑菇是生活中常用的食品 ,研究钙和镁的含量具有实际意义。本文用火焰原子吸收光谱法在同一体系中完成了对钙和镁的连续测定 ,方法简单、快速 ,精密度和准确度高 ,结果满意。1　试验部分1 .1　主要仪器与试剂AAS950 2 C型原子吸收光谱仪钙和镁标准储备液 :均为 1 mg·ml-1镧盐溶液 :1 0 0 g· L-1试剂为光谱纯、优级纯 ,水为去离子水。1 .2　试样制备将新鲜蘑菇用水洗净 ,再用水冲洗 ,放入洁净容器中 ,于 1 0 5°C恒温烘干 ,取出研成粉末 ,置于干燥…     

EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

硅钡钙联合测定

硅钡钙是炼钢中很好的新型脱氧剂 ,并且有很好的脱硫、磷能力 ,对冶炼含硫、磷较低的钢种起着非常重要的作用 ,在特钢系统有着广阔的应用前景。本文提出了硅钡钙联合测定分析方法 ,该法快速、准确、简便、易掌握。1　试验部分1 .1　试剂混合熔剂 :无水碳酸钠 硼砂 过氧化钠 =2 0 1 0 3,硼砂在 350°C马弗炉中烘去结晶水分。NH4 CNS:50 g· L-1Ag NO3溶液 :1 0 g·L-1(NH4 ) 2 SO4 溶液 :1 0 0 g·L-1Ba Cl2 溶液 :1 0 0 g·L-1KOH溶液 :40 0 g·L-1EDTA标准溶液 :0 .0 2 mol· L-1,称取 EDTA基准试剂 7.4452 g溶于水中 ,用…     

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.