灿烂甲酚蓝萃取光度法快速测定冷饮中糖精钠

食品中糖精钠的测定,在国家标准规定的三种方法中,薄层层析法仅能作半定量分析,紫外光度法和酚磺酞比色法都有繁杂的样品前处理(提取、分离)过程,且易受食品成份等多种因素影响,回收率差。Cordoba等曾用尼罗蓝-糖精离子缔合物萃取光度法测定了牙膏和冷饮中糖精钠,方法快速灵敏,但标准曲线的线性范围(10～35μg/10mL)较窄。作者经实验发现,灿烂甲酚蓝、亚甲蓝等染料均与尼罗蓝具有相似结构,在一定条件下可与糖精发生离子缔合反应,形成憎水性离子缔合物。实验表明,在氢离子浓度为4×10~(-2)mol/L的硫酸介质中,糖精与灿烂甲酚蓝形成蓝色离子缔合物,可被氯仿定量萃取,其λ_(max)=620nm,ε_(620nm)=2.0×10~4L·mol~(-1)·cm~(-1)。糖精钠在0～0.10mg/50mL范围内符合比尔定律。所拟方法快速     

丽春红S分光光度法快速测定硫酸链霉素含量

在pH值为4.0～5.0的条件下,丽春红S与硫酸链霉素(Streptomycin sulphate)反应生成缔合比为1∶1的缔合物,使丽春红S溶液褪色并产生新峰,最大褪色峰谷波长位于537nm,新吸收峰波长位于575 nm.利用最大褪色峰峰谷与新吸收峰峰高的高度差,进行硫酸链霉素含量的测定,其表观摩尔吸光系数(ε)为1.25×104L.mol-1.cm-1,硫酸链霉素的浓度在1.46～58.30 mg.L-1范围内符合比耳定律,方法检出限为0.91 mg.L-1.该法用于硫酸链霉素针剂中硫酸链霉素含量的测定,平行6次测定相对标准偏差1.20%～1.82%,回收率95.6%～102%,结果满意.     

苯胺蓝-溴酸钾体系催化分光光度法测定水中痕量亚硝酸盐

在硫酸介质中,亚硝酸盐对溴酸钾氧化苯胺蓝褪色反应有明显的催化作用,据此提出了测定痕量亚硝酸盐催化分光光度方法。优化的试验条件如下:1 1.0mol·L-1硫酸溶液的用量为1.8mL;2 3×10-4 mol·L-1苯胺蓝溶液用量为1.5mL;3 0.02mol·L-1溴酸钾溶液用量为1.1mL;4反应温度为30℃。该方法的线性范围分别为0.01~0.2mg·L-1和0.2~1.0mg·L-1,检出限(3s/k)为4.6×10-6g·L-1。方法用于水样的分析,回收率在96.0%~104%之间,测定值的相对标准偏差(n=6)在1.6%~2.3%之间。     

马来酸噻吗洛尔的CTAC逆胶束介导化学发光法测定

在酸性条件下,马来酸噻吗洛尔分子中氮原子被质子化后与阴离子AuCl4-形成离子缔合物,该缔合物被三氯甲烷带入鲁米诺的氯化十六烷基三甲基铵(cetyltrimethylammonium chlorine,CTAC)逆胶束中(三氯甲烷-环己烷(体积比3∶7)-H2O(0.3 mol.L-1Na2CO3缓冲溶液,pH11.5)),离解出来的AuCl4-立即与鲁米诺产生化学发光。在0.01~20 mg.L-1范围内,发光强度与马来酸噻吗洛尔的含量成线性关系,从而间接测定马来酸噻吗洛尔的含量。检出限(3δ)为0.5μg.L-1,对质量浓度为1.0 mg.L-1的马来酸噻吗洛尔进行11次平行测定,其RSD为1.8%。该法已成功用于片剂和滴眼液中马来酸噻吗洛尔的测定。     

磷铋钼蓝分光光度法测定水果、蔬菜及饮料中L-抗坏血酸

Bi~(3+)与Mo(Ⅵ)和PO_4~(3-)在硫酸介质中反应生成黄色的磷铋钼杂多酸,然后被L-抗坏血酸还原为磷铋钼蓝,据此建立了分光光度法测定水果、蔬菜及饮料中L-抗坏血酸的方法。优化的试验条件如下:(1)测定波长为710nm;(2)1.95×10~(-2) mol·L~(-1)磷酸二氢钾溶液的用量为3.0mL;(3)6.51×10~(-2) mol·L~(-1)钼酸铵溶液的用量为4.0 mL;(4)2.06×10~(-4) mol·L~(-1)硝酸铋溶液的用量为1mL;(5)硫酸的浓度为0.16mol·L~(-1);(6)反应温度为室温。L-抗坏血酸的质量浓度在4~120mg·L~(-1)内与其对应的吸光度呈线性关系,表观摩尔吸光率为3.59×10~3L·mol~(-1)·cm~(-1),检出限(3s/k)为0.2 mg·L~(-1)。方法用于水果、蔬菜及饮料样品的分析,加标回收率为98.0%~102%,测定值的相对标准偏差(n=11)为1.1%~2.3%。     

分光光度法测定青霉胺药片中青霉胺含量

青霉胺的巯基具有还原性,可将Fe(Ⅲ)还原Fe(Ⅱ),Fe(Ⅱ)能与2,2′-联吡啶形成桔红色的配合物,其最大吸收波长为524nm,据此提出了分光光度法间接测定青霉胺药片中青霉胺含量的方法。优化的试验条件如下:①pH 4.5的0.2 mol·L-1乙酸-乙酸钠缓冲溶液用量为2.5mL;②0.2g·L-1氯化铁溶液用量为2mL;③1g·L-1 2,2′-联吡啶溶液用量为2.5mL;④显色时间为5min。青霉胺的质量浓度在26mg·L-1以内间接地与吸光度呈线性关系,检出限(3S/N)为0.01mg·L-1。采用此法测定了青霉胺药片中青霉胺含量,所得测定值与标示量相符,测定值的相对标准偏差(n=5)为2.4%。     

涂丝型聚氯乙烯膜-硫酸沙丁胺醇电极的研制与应用

采用电位分析法测定猪肉中硫酸沙丁胺醇的含量。以硫酸沙丁胺醇与四苯硼钠形成的缔合物为电活性物质制备了涂丝型硫酸沙丁胺醇选择电极,并对其各项性能进行测定。结果表明:电极对硫酸沙丁胺醇有很好的能斯特响应。电极响应的范围为1.0×10-5~1.0×10-1 mol·L-1,级差电位为31mV·pc-1,测定下限(10S/N)为6.5×10-6 mol·L-1。用该电极对猪肉中硫酸沙丁胺醇的含量进行测定,测定结果与标准方法测定值相符。     

曲利本蓝共振瑞利散射法测定苹果中钙北大核心CSCD

采用曲利本蓝共振瑞利散射法测定苹果中钙的含量。在pH 6.50的三羟甲基氨基甲烷-盐酸缓冲溶液中,曲利本蓝与钙(Ⅱ)及阳离子表面活性剂十六烷基三甲基溴化铵反应生成一种三元离子缔合物,使体系的共振瑞利散射(RRS)信号显著增强,最大共振瑞利散射峰位于波长348nm处。优化的试验条件如下:(1) pH 6.50的三羟甲基氨基甲烷-盐酸缓冲溶液的用量为2.00mL;(2)1.0×10^(-4) mol·L^(-1)曲利本蓝溶液的用量为2.50mL;(3) 4.00×102 mg·L^(-1)十六烷基三甲基溴化铵溶液的用量为0.40 mL;(4)反应时间为25 min。钙的质量浓度在0.007 0～0.080 0mg·L^(-1)内与体系的RRS增强程度(ΔIRRS)呈线性关系,检出限(3s/k)为0.001 3mg·L^(-1)。方法用于苹果样品的分析,加标回收率为98.3%～102%,测定值的相对标准偏差(n=6)为1.8%～2.3%。     

基于磷钼蓝反应测定钴-钼催化剂浸渍液中钼离子含量

基于磷钼蓝反应测定钴-钼催化剂浸渍液中钼离子含量。建立了一个流动注射-磷钼蓝分光光度法测定高浓度钼离子的含量,优化后的条件为:1酸度调节剂为0.5mol·L-1硫酸溶液;2载流为超纯水;3反应试剂为120g·L-1磷酸二氢钾、100g·L-1抗坏血酸及0.3mol·L-1硫酸的混合液;4总流量为2.8 mL·min-1;5酸度调节盘管长度为20cm;6反应盘管长度为250cm。三氧化钼的质量浓度在10.0~300.0g·L-1范围内与峰高呈线性关系,检出限(3s/k)为2.0g·L-1。方法用于钴-钼催化剂钼浸渍液的分析,回收率在99.7%~105%之间,测定值的相对标准偏差(n=11)小于1%。     

阻抑动力学光度法测定痕量钌

在硫酸介质中,钌(Ⅲ)对高碘酸钾氧化甲基绿褪色反应具有显著的阻抑作用,从而提出了一种阻抑动力学光度法测定痕量钌(Ⅲ)的方法。优化的试验条件如下:①0.01mol.L-1高碘酸钾溶液用量为1.40mL;②1×10-3 mol.L-1甲基绿溶液用量1.50mL;③反应温度为80℃;④反应时间为10min。钌(Ⅲ)的质量浓度在0.04～64μg.L-1范围内与ΔA呈线性关系,检出限(3s/k)为8.5ng.L-1。方法用于活性炭和分子筛中痕量钌(Ⅲ)的测定,测定值的相对标准偏差在1.6%～2.2%之间,加标回收率在98.6%～100%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%.     

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.     

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.     

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.