中孔分子筛P123-SH分离富集-火焰原子吸收法测定水样中镉

利用自制的中孔分子筛P123-SH作为镉的分离富集新材料,探讨了中孔分子筛P123-SH吸附镉的原理,优化了测定镉最佳条件。在pH6.5,室温下恒温振荡15min,镉可被该材料定量吸附,其静态吸附容量为9.52mg/g。吸附的镉可用2mol/LHCl洗脱,用火焰原子吸收法测定洗脱下来的镉。该方法线性范围为0.80～120μg/L;检出限为0.12μg/L,对50μg/LCd2 溶液平行测定7次,RSD=2.1%。此法已成功地应用于环境水样中痕量镉的测定。     

三聚氰胺修饰玻碳电极用于溶出伏安法测定水样中痕量银

用电化学沉积法将三聚氰胺修饰在玻碳电极上,应用此三聚氰胺修饰玻碳电极测定银时,试液在pH 4.6的乙酸-乙酸钠缓冲溶液中,在—0.45V处还原60 s,然后在0～+0.6V范围内扫描,使银离子从修饰电极上溶出,实现了水样中银离子的溶出伏安法测定,在+0.27V处可得银离子的氧化峰电位,银的浓度在6.0×10~(-9)～5.0×10~(-7)mol·L~(-1)范围内与其峰电流呈线性关系,检出限(3S/N)为1.0×10~(-9)mol·L~(-1)。方法用于实际水样中痕量银的测定,加标回收率在90.0%～96.0%之间。     

中孔分子筛Ti-MCM-48的合成及其对痕量银(Ⅰ)的吸附性能研究与应用

以正硅酸乙酯、钛酸丁酯为原料,十六烷基三甲基溴化铵为表面活性剂合成中孔分子筛Ti-MCM-48。研究了中孔分子筛Ti-MCM-48分离富集材料对银(Ⅰ)的吸附性能,优化了影响其吸附和解吸的主要条件。结果表明,在pH=3.0的柠檬酸-柠檬酸钠缓冲溶液中,恒温35℃振荡25min时,银(Ⅰ)能被该材料吸附完全,其静态饱和吸附容量为2.96mg/g。吸附在中孔分子筛Ti-MCM-48上的银(Ⅰ)可用5mL 0.5mol/L HNO3-0.1mol/L硫脲洗脱液完全洗脱。采用火焰原子吸收光谱法(FAAS)测定洗脱液中银(Ⅰ)的方法检出限(3σ)为21.39ng/mL,线性范围为0.02～5.0μg/mL(r=0.9995),相对标准偏差(RSD)为1.25%,加标回收率在96%～102%之间。方法可用于实际样品中痕量银的测定。     

大孔硫脲螯合树脂吸附银的研究

本文研究了大孔硫脲螯合树脂对银(I)的吸附行为.结果表明:硫脲树脂对银离子的吸附在pH5.0 的HNO3-柠檬酸钠介质中最佳,静态饱和吸附容量为402mg·g-1树脂,用5～10%硫脲-1.0mol·L-1HCl溶液作解吸剂,二次累计解吸率达到92%;等温吸附服从Freundlich经验式;表观吸附速率常数k298=1.64×10-5s-1;吸附反应的△H=41.6kJ·mol-1;吸附物中树脂功能基与Ag(I)的配位比约为1∶ 1.     

嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法分析痕量铬的形态

研究了嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法对尿中痕量铬的形态分析方法,探讨了嵌段分子筛聚合材料P123-SH吸附铬的原理和最佳条件。在pH 7.0、常温下,Cr3+和Cr(Ⅵ)被很好的分离,且Cr3+可被该材料定量吸附,其吸附容量为6.15 mg/g。吸附的Cr3+可用2 mol/L的HCl洗脱,用石墨炉原子吸收法测定洗脱下来的Cr3+,往溶液中加入0.1%抗坏血酸将Cr(Ⅵ)还原为Cr3+测总铬,Cr(Ⅵ)含量为总铬减去Cr3+,方法测定Cr3+的检出限为0.011μg/L(3σ,n=11),线性范围为0.1～10μg/L,加标回收率在94%～106%之间,对0.50μg/L的Cr3+溶液平行测定7次,RSD为3.6%。方法可应用于生物样品和环境样品中痕量铬的形态分析。     

线性扫描极谱法测定消旋山莨菪碱

用线性扫描极谱法和循环伏安法研究了消旋山莨菪碱在0.3mol·L~(-1)磷酸氢二钠-磷酸二氢钾缓冲溶液(pH 6.70)中的电化学行为。消旋山莨菪碱于-1.095V(vs.SCE)处产生一灵敏的吸附波,消旋山莨菪碱质量浓度在0.10～10.0mg·L~(-1)范围内与其一次微分线性扫描峰电流i_p呈线性关系,检出限(3S/N)为0.06mg·L~(-1)。对5.0mg·L~(-1)消旋山莨菪碱溶液进行6次平行试验,相对标准偏差为0.34%,该方法用于片剂中消旋山莨菪碱含量的测定,测定值与标示值相符。     

有机-无机介孔材料分离富集痕量铅及其火焰原子吸收光谱法测定

以正辛胺及γ-巯丙基三乙氧基硅烷在氯化钾溶液中反应,制得一种有机-无机介孔材料,并应用于分离富集痕量铅,试验了溶液pH值、温度、洗脱条件及干扰离子对铅(Ⅱ)分离富集的影响,结果发现该材料对铅(Ⅱ)的吸附具有较高的选择性和较大的吸附容量。在pH 6.0、试验温度为(20±1)℃条件下,铅(Ⅱ)可被该材料定量吸附。其静态饱和吸附容量为26.37 mg·g~(-1)。吸附的铅(Ⅱ)可用0.2 mol·L~(-1)硝酸-0.5 mol·L~(-1)乙酸混合酸溶液洗脱,再用火焰原子吸收光谱法测定。该方法测定铅(Ⅱ)的检出限(3s/k)达到1.5μg·L~(-1),线性范围在0.80 mg·L~(-1)以内。此法应用于环境水样中痕量铅的测定,加标回收率在96.7%～105.0%之间。测定值的相对标准偏差(n=7)在1.66%～2.05%之间。     

藻红B分光光度法测定罗红霉素胶囊中罗红霉素

在乙酸介质中,罗红霉素与藻红B反应生成电荷转移络合物,其最大吸收波长为520nm,采用分光光度法测定罗红霉素胶囊中罗红霉素的含量。优化的试验条件如下:①4.0×10~(-4)mol·L~(-1)的乙酸溶液作为反应介质;②反应温度为25℃;③反应时间为20min;④2.0×10~(-4)mol·L~(-1)藻红B溶液的用量为1.2mL。罗红霉素的质量浓度在0.020～0.500mg·L~(-1)内与反应体系的吸光度差值呈线性关系,检出限(3s/k)为0.014mg·L~(-1)。方法用于罗红霉素胶囊样品的分析,加标回收率为101%～107%,测定值的相对标准偏差(n=5)为0.84%～1.6%。     

流动注射-催化光度法测定痕量草酸根

在1.8×10~(-2)mol·L~(-1)硫酸介质中,于30℃加热160s时,草酸根对重铬酸钾、碘化钾和罗丹明6G之间的褪色反应具有显著的催化作用。结合流动注射技术,提出了一种催化光度法测定痕量草酸根的方法。草酸根的线性范围为0.10～1.20mg·L~(-1),检出限(3s/k)为0.03mg·L~(-1),进样频率18次·h~(-1)。对0.30及0.80mg·L~(-1)草酸根标准溶液进行平行测定,其相对标准偏差(n=11)分别为2.7%和1.6%。该方法用于菠菜、尿液中草酸根含量的测定,并以此样品为基体进行回收试验,测得回收率在93.3%～96.7%之间。     

镉—8—羟基喹啉络合物吸附波的研究

8-羟基喹啉(HOx)是许多金属有效的络合剂,其与金属络合物的极谱行为已有报道.镉的络合物吸附波体系已有不少报道,但镉与8-羟基喹啉络合物的极谱波尚未见报道.我们在试验中发现,镉在5×l0~（-2）mol·L~(-1)HCl-9.4×10~(-2)mol·L~(-1)HOAc-9.0×10~(-2)mol·L~(-1)NaOAc-5.O×10~（-4）mol·L~(-1)HOx溶液中,于-0.69V(vs.SCE)处出现一灵敏的络合物吸附波,峰电流与镉浓度在2.7×10~(-8)～8.9×10~(-6)mol·L~(-1)范围内呈线性关系.检测下限为1.8×1O~(-8)mol·L~(-1).用极谱直线法求得Cd(Ⅱ)与HOx络合物的络合比为1:1.本法用于河水及污水中痕量镉的测定,效果理想,回收率在95%～104%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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.