用4,4′-二硝基重氮氨基苯分光光度测定微量镉

4,4′-二硝基重氮氨基苯(DNAAB)曾用于光度测定微量汞。DNAAB的苛性钾溶液呈洋红色,亦可被镉(Ⅱ)减褪,借此可测定微量镉,具有很高的灵敏度。本文研究了用DNAAB分光光度测定微量镉的条件、干扰以及在测定条件下的Cd(Ⅱ)-DNAAB之化合比;矿石和废水浓集液中的微量镉,经适当分离后用本法测定,结果满意。     

巯基棉富集分离3,5-diBr-PADAP——乳化剂OP分光光度法测定微量镉

本文提出了巯基棉分离,用3,5-diBr-PADAP-乳化剂OP光度法测定微量镉的新方法,本法灵敏度高,ε=1.3×10~5,是目前在水相中测镉的高灵敏方法之一,用本法测定了水样中的微量镉。     

镉基体中微量锌的富集与分离研究

提出了一种用于富集分离镉基体中的微量锌的分离体系,研究了从镉基体中富集分离微量锌的可行性——采用二安替比林甲烷(DAM)作为络合剂,与硫氰酸铵、锌在盐酸介质中形成三元离子缔合物,用三氯甲烷作为萃取剂,最后用氨水作为反萃剂将有机相中的锌洗脱出来与镉分离。试验发现,当15%的硫氰酸铵用量为1.5mL,DAM的用量为1.5mL,加入20mL4mol/L的盐酸时,用20mL的三氯甲烷萃取两次,10mL1:3的氨水反萃两次,锌的回收率达到95%以上,相对误差小于0.5%。     

活性炭分离富集水体中痕量镉

建立了以PAN为吸附辅助剂,以活性碳为吸附剂,结合火焰原子吸收法测定地表水中痕量镉的方法.研制了以微量过滤器和医用注射器组成的分离富集装置;探讨了镉吸附解吸的最佳试验条件,并应用于实际环境水样中痕量镉的测定,回收率为98.25%～105.0%.该方法简化了分离富集程序,操作简单,迅速,能同时进行6～8个样品的分析测定,具备一定实用性.     

四-(对-三甲铵苯基)卟啉光度法测定微量镉

伊藤纯一等研究了镉与四-(对-三甲铵苯基)卟啉(简称TAPP)在100℃时的反应。我们进一步研究了用TAPP光度法测定微量镉的反应条件。经试验发现在强碱性介质中,8-羟基喹啉和溴化十六烷基吡啶在室温下对镉与TAPP的反应有良好的催化作用。干扰离子采用阴离子交换树脂分离。用制定的方法测定天然水中微量镉,结果较为满意。     

DDTC—Cd萃取分离火焰原子吸收光谱法测定电镉中微量铅

微量铅在电镉中是必须测定的有害杂质。早期电镉中微量铅的测定常采用 Pb SO4 和 Cs O4 共沉淀与基体镉分离 ,然后将沉淀转化为碳酸铅沉淀或用Fe(OH) 3作载体在氨性溶液中富集铅与基体镉分离后 ,沉淀用盐酸溶解 ,双硫腙比色法或火焰原子吸收光谱法测定铅[1] 。此方法手续繁锁 ,流程长、精确度差 ,且使用巨毒试剂氰化钾 ,给分析者带来不便。本文在文献 [2 ,3]基础上 ,在 p H9～ 1 1的氨性溶液中 ,用二乙基二硫代氨基甲酸镉 (DDTC- Cd)萃取铅与基体镉分离。稀盐酸反萃铅至水相 ,再用火焰原子吸收光谱法测定。试验表明 ,该方法简便快速准…     

5—Br—DMPAP—OP双波长吸光光度法测定微量锌镉

本文采用OP为胶束增溶增敏稳定剂,5-Br-DM-pap双波长吸光光度法同时测定微量锌、镉尚未见文献报道。利用等吸收法进行波长对的粗选和精选,并对各种干扰离子进行试验,提出使用合适的掩蔽剂可降低某些离子的干扰,从而避免了繁琐的分离手续。选锌波长对为524/569 nm,镉波长对为512.5/568.5nm。锌、镉的线性范围分别为0～16μg/25ml、0～12μg·ml~(-1),本法应用于废水中微量锌和镉的测定,结果令人满意。     

石墨炉原子吸收光谱法测定三氧化钨和钨酸中微量铝和镉

石墨炉原子吸收光谱法测定铝和镉的灵敏度较高,但它们受基体的影响比较严重,测定钨酸和三氧化钨中微量铝尚有文献报导,测定微量镉还未见到有关文献。本文采用国产仪器,全热解石墨管,对石墨炉原子吸收光谱法测定钨酸及三氧化钨中微量铝和镉进行了实验。选择了最佳条件,对基体元素钨及其在溶样过程中所要接触到的干扰因素进行了考查。提出了消除干扰的措施,选择了合适的溶样方法。采用悬浮液进样解决了因钨酸析出而必须化学分离的困难。样品分解后直接用标准曲线     

荧光分光光度法测定废液中微量镉

１引言荧光法测定微量镉，常用的试剂有８－羟基喹啉－５－磺酸、硫基喹啉和桑色素等，但选择性欠佳。本文应用８－羟基喹啉－５－磺酸，加入溴代十六烷基三甲胺，由于表面活性剂的增敏效应，使灵敏度提高２～３倍。用ＨＣＩ作浓度梯度淋洗的阳离子交换法预处理，使镉与共存离子获得满意分离，消除了干扰。器壁吸附会导致微量镉的损失，采用玻璃器皿硅烷化处理后效果显著。该方法的线性工作范围为５～１００μｇ／Ｌ，相对标准误差为±４．９％，可应用于各种水样，尤其是大体积水样中微量锅的分析测定。２实验部分２．１试剂与仪器　镉标准…     

黄原酯棉富集分离金属离子的研究及金属镍中铅和镉的测定

用黄原酯棉对铜、锌、铅、镉、铋、铁、钴、镍等金属离子进行了吸附试验，探索了分离富集条件，给出了５种元素的吸附曲线、脱附曲线和吸附试验结果。作者经过系统的试验，将黄原酯棉用于金属镍及其纯盐类中微量铅、镉的同时分离和测定，获得成功。     

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%.     

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.     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.