二氧化碳溶剂浮选光度法测定高碘蛋总碘量

浮选法是二氧化碳气氛中,以溴化十六烷基三甲基铵(CTMAB)为捕收剂,用溶剂浮选吸光光度法对离子缔合物(CTMA~ I_3~-)的组成进行测定。试验表明,方法有较高的灵敏度,较好的准确性和重现性。     

离子液体双水相溶剂浮选法分离/富集桑黄黄酮类成分

将亲水性离子液体氯化-1-丁基-3-甲基咪唑([C4mim]Cl)和K2HPO4形成的双水相体系与溶剂浮选结合,建立了分离/富集桑黄中总黄酮类成分的方法。考察了分相盐的种类和用量、样品量、溶液pH值、浮选时间和氮气流速对浮选效果的影响,并与双水相萃取进行比较。当浮选分相盐K2HPO4的质量浓度为50%、溶液pH=9.53、离子液体的用量为3 mL、浮选时间为50 min、氮气流速为30 mL/min时,浮选效率最佳,达到85.31%,富集倍数为8.59。离子液体双水相溶剂浮选法浮选效率高,富集倍数大,为中草药有效成分分离/富集提供了新方法。     

有機陽離子用作分析試劑的研究Ⅰ.碘化(N,N-二甲基)氫化吡啶鹽用作钯的定性分析試劑

1.碘化(N,N-二甲基)氢化吡啶盐可以用作二价钯离子的定性分析试剂,灵敏度在点滴板上为0.2γ(1:200,000),在纸上为0.006γ(1:200.000)。 2.铂离子与试剂生成类似的棕色沉淀,但可以用加入大量的磷酸根除去其干扰。铋和汞(Ⅱ)离子与试剂生成红色沉淀,但可以用加入浓盐酸以消除之。Ag~+,Pb~(++),Cu~(++),Fe~(3+),Tl~(+),Sb~(3+)的干扰比例限度及灵敏度也测定过。 3.用点滴色层分析法,可以在包含二十五种阳离子(包括铋,汞(Ⅱ),铂(Ⅳ))的混合物中直接检出0.006γ(1:180,000)的钯(Ⅱ)离子,各离子对钯的浓度比例界限皆为1:50。     

溴化钾-四丁基溴化铵体系浮选分离钯(Ⅱ)

在pH 2的水溶液中,钯(Ⅱ)与溴化钾和四丁基溴化铵(TBAB)形成不溶于水的三元离子缔合物,此三元配合物浮于盐水相上层形成界面清晰的液-固两相,当溶液中溴化钾和四丁基溴化铵的浓度分别为1.5×10-2,2.0×10-3mol·L-1,酸度为pH 2.0时,钯(Ⅱ)被定量浮选.汞(Ⅱ)、铅(Ⅱ)、钨(Ⅵ)和钒(Ⅴ)离子在该体系中不被浮选,实现了钯(Ⅱ)与这些离子的定量分离.对合成水样中100μg钯(Ⅱ)进行了定量浮选分离和测定,结果表明此方法的浮选率达99.7%.     

离子液体溶剂浮选-光度法测定水中痕量四环素类抗生素

将离子液体应用于气浮溶剂浮选分离/富集四环素类抗生素(TCs),建立了一种离子液体1-丁基-3-甲基咪唑六氟磷酸盐(\PF6)取代传统有机溶剂气浮溶剂浮选分离/富集四环素类抗生素的新方法.TCs与镧能形成疏水性络合物,易于浮选至离子液体相,考察了在离子液体中加入有机溶剂的种类和体积,试液的pH值、La的加入量、气体流速、浮选时间以及共存物质对浮选效率的影响,优化了浮选条件,与溶剂萃取方法相比,离子液体溶剂浮选四环素类抗生素富集倍数高,且无毒,无污染,试剂用量少,实测了鱼塘水和辽河水样,RSD分别为3.0%和4.3%(n=5),回收率为97%.本方法适合于环境水样中痕量四环素总量的分析检测.     

微量胺乙基硫代磷(膦)酸酯的荧光法测定

胺乙基硫代磷(膦)酸酯类化合物常用作农药中的杀虫剂。其残留量分析,可采用气液色谱法或比色法。但是灵敏度或排除杂质干扰方面仍不够理想。荧光法测定,灵敏度高,方法简便。我们利用离子交换法和离子交换柱上化学反应相结合的技术,富集与分离试样。此类化合物被吸附在柱上,它与银、氟离子作用生成氟磷(膦)酸酯后,再用去离子水洗脱。此氟磷(膦)酸酯与过氧化物反应生成的过氧磷(膦)     

在二氧化碳气氛中溶剂浮选高碘蛋总碘量的吸光光度法

浮选法是在二氧化碳气氛中,以溴化十六烷三甲基铵（ＣＴＭＡＢ）为捕收剂,用溶剂浮选吸光光度法,对离子缔合物（ＣＴＭＡ＾＋Ｉ３＾－）的组成进行测定。试验表明,方法有较高的灵敏度,较好的准确性和重性现。     

用改进的玫瑰红酸钠法检定水中钡离子

可溶性钡盐毒性较大,人的口服致死量约为0.8g.我国有的地区自然水中含有可溶性钡盐,食用过量会引起中毒。为了确保野外工作人员的饮水安全,需要一种灵敏、简便的钡离子检定方法。我们经过研究建立了一种改进的玫瑰红酸钠检定饮水中钡离子的方法,灵敏度可达2μg/ml,能满足实际需要,方法灵敏、可靠,操作简便、快速。其原理系水中的钡离子在弱酸溶液中同玫瑰红酸钠生成玫瑰红酸钡沉淀,然后用氯仿作为浮选剂进行浮选、浓缩,则在水溶液与有机溶剂的界面间形成一层红色的玫瑰红酸钡薄膜,可目视直接观察。本文用酷酸代替矿物酸,严格限制反应液的pH值;用固体玫瑰红酸钠代替本试剂的溶液,提高了灵敏度。     

阳极溶出伏安法测定水中溶解氧

测定水中溶解氧的方法很多。本文提出用阳极溶出伏安法(以下简称溶出法)测定水中溶解氧,其原理为:金属铊与水中溶解氧按下式定量地反应生成亚铊离子,4Tl+O_2+2H_2O→4Tl~++4OH~-然后用溶出法测定亚铊离子的浓度,间接求出水中溶解氧的含量。操作分为三步:(1)电解制备金属铊;(2)借金属铊的氧化固定水中溶解氧,(3)亚铊离子的溶出测定。使用883型极谱仪和银基汞膜球电极,测定亚铊离子的浓度范围为10~(-5)M～10~(-7)M,可测溶氧的浓度范围为10~(-3)M～2.5×10~(-8)M。测定氧的灵敏度可达2.5×10~(-8)M(相当于0.8ppb氧)。     

IO_3~--I~--吖啶红-聚乙烯醇体系分光光度法测定环境水样中溶解氧

1 引言 溶解氧(Dissolved oxygen,DO)是指溶解于水中的分子态氧,是环保、油田井下注水、工业锅炉用水、生物养殖用水和科研用水的重要检测指标之一.目前,测定溶解氧常用的方法有碘量法(即Winkler法)、氧电极法、水相化学发光法和分光光度法等.本方法依据碘量法中可以析出与溶解氧相当的I_2,利用I_3~-与吖啶红(AR)在H_2SO_4-聚乙烯醇(PVA)介质中反应生成离子缔合物,采用光度法测定水体中溶解氧,本方法以基准物KIO_3为溶解氧标准溶液,灵敏度高,克服了原有碘量法中Na_2S2O_3为溶解氧标准溶液不稳定的不足.由于试剂便宜易得,无污染,适用于大批试样的测定.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.