高效液相色谱法同时测定甜瓜样品中的抑霉唑和噻菌灵

提出了一种用高效液相色谱法 (HPLC)同时测定甜瓜样品中的抑霉唑和噻菌灵残留量的方法。用乙酸乙酯作提取剂提取甜瓜样品 ,通过一个净化步骤分离样品中共提取组分。采用InertsilC8 3色谱柱 (15 0mm× 4 .6mm ,5 μmi.d ,) ,流动相为乙腈∶水 =75∶2 5 ,外标法定量 ,方法的检出限噻菌灵为 0 .70ng ,抑霉唑为1.5 3ng ;回收率为 87.5 %～ 98.0 % ;相对标准偏差为 1.5 %～ 4 .2 %。本法用于甜瓜样品中抑霉唑、噻菌灵含量的测定 ,获得了满意的结果。     

荔枝中抑霉唑和嘧霉胺残留量的超高效液相色谱-串联质谱法同时测定

建立了超高效液相色谱-串联质谱法同时测定荔枝中抑霉唑和嘧霉胺的方法,对提取试剂、流动相、质谱条件进行了研究,并对抑霉唑和嘧霉胺可能的断裂机理进行了推测。待测样品直接用乙腈提取,采用电喷雾离子源(ESI)、多反应监测正离子模式扫描,外标法定量。抑霉唑、嘧霉胺的质量浓度在1.00～20.0μg/L范围内与峰面积呈良好线性,方法的检出限为0.005mg/kg;添加水平为0.005、0.010、0.020mg/kg时抑霉唑和嘧霉胺的平均回收率分别为91%～96%和83%～90%,相对标准偏差分别为6.5%～8.4%和9.5%～11.1%。该方法快速、简便、准确,可用于荔枝中抑霉唑和嘧霉胺残留量的定性与定量检测。     

凝胶渗透色谱净化-气相色谱-质谱法测定柑橘及其制品中抑霉唑的残留量

提出了气相色谱-质谱法测定柑橘及其制品中抑霉唑保鲜剂残留量的方法。样品用乙酸乙酯-环己烷(1+1)混合溶剂提取,所得提取液须经凝胶色谱净化去除大分子干扰物质。采用气相色谱分离后,选择离子监测模式下质谱法进行测定。方法检出限(3S/N)为0.02mg.kg-1,测定下限(10S/N)为0.05mg.kg-1。在3个标准加入水平下进行了回收试验,所得回收率在79.0%～92.1%之间,相对标准偏差(n=6)小于10%。     

粮谷中抑霉唑残留的气相色谱法测定

报道了气相色谱法测定粮谷中抑霉唑残留的方法.选取稻谷、小麦、燕麦和黍(大黄米)4种粮谷产品为研究对象,考察了不同类型检测器、不同提取体系、不同淋洗曲线和不同离心时间的破乳效率对抑霉唑测定的影响.试样以正己烷-乙酸乙酯(体积比1 ∶ 1 )提取,经毛细管气相色谱柱HP-5(30 m×0.25 mm×0.25 μm)分离, μ-ECD检测器测定.方法检出限为0.005 mg/kg (S/N=3).添标水平为0.01、0.05、0.25和0.50 mg/kg时平均回收率为82% ～111%,相对标准偏差为5.5% ～11.5%.线性范围为0.05 ～1.0 mg/L(r2=0.999 4).该方法快速、灵敏、准确,适合粮谷中抑霉唑残留的测定.     

液液提取-固相萃取-气相色谱法测定牛肉中蝇毒磷残留量的研究

建立了液液提取-固相萃取-气相色谱火焰光度法(LLE-SPE-GC-FPD)测定牛肉中蝇毒磷的残留量.优化了气相色谱分离条件,研究了样品基质对蝇毒磷测定的影响,考察了Florisil固相萃取小柱和ODS固相萃取小柱的萃取效果,并选择乙酸乙酯为洗脱剂,考察了液-液提取和固相萃取的回收率.将该方法用于牛肉中蝇毒磷的测定,其检出限为0.02 μg/mL,回收率高于83%,相对标准偏差13.7%.使用气相色谱质谱仪(GC-MS)对样品中的蝇毒磷进行定性分析,其特征离子和相对丰度为362(100)、226(55)和210(40).     

离心破乳-气相色谱法测定黑米中残留抑霉唑的研究

报道了离心破乳-气相色谱法测定黑米中残留抑霉唑的方法. 考察了不同离心速率、不同离心时间的破乳效率. 试样以V(正己烷):V(乙酸乙酯)＝1:1提取, 经毛细管气相色谱柱HP-5 (30 m×0.25 mm×0.25 μm)分离, μ-ECD检测器测定. 方法检出限为1.0×10-3 mg/kg (S/N=3). 在添标水平0.05、 0.25和0.50 mg/kg时的平均回收率为92.3%～104.3%, 相对标准偏差为6.9%～9.3%. 线性范围为0.02～1.0 mg/L (r2=0.9994). 方法适合黑米中残留抑霉唑的测定.     

固相分散萃取与气相色谱-负化学离子源质谱联用法测定食品中三唑醇的残留量

建立了食品中三唑醇残留量的固相分散萃取-气相色谱-负化学离子源质谱联用检测方法。样品中三唑醇残留物由正己烷饱和的乙腈(含1%冰醋酸)提取,加入无水硫酸镁与无水醋酸钠振荡促使提取液分层后进行固相分散萃取净化,用气相色谱-负化学离子源质谱法进行测定与确证,外标法定量。方法具有良好的选择性和抗干扰能力,其检出限和定量限分别为0.001 mg/kg和0.003 mg/kg;线性范围为0.050～0.750 mg/L,相关系数为0.9947;在0.005,0.010,0.020 mg/kg共3个添加水平下的平均回收率为70%～110%,相对标准偏差不大于12.0%。该方法适合于多种食品中三唑醇残留量的确证分析。     

植物源食品中6种三唑类杀菌剂残留量的气相色谱法测定

建立了同时测定6种三唑类杀菌剂(四氟醚唑、戊菌唑、氟菌唑、己唑醇、丙环唑、氟环唑)残留量的气相色谱方法.植物源食品采用乙腈溶剂提取,无水硫酸镁、氯化钠盐析,经弗罗里硅土固相萃取柱净化后,用气相色谱/电子捕获检测器(GC/ECD)测定.结果表明:6种三唑类杀菌剂在0.01 ～0.5 mg/L范围内线性关系良好,相关系数均大于0.996,样品添加水平为0.05 ～0.20 mg/kg时的平均加标回收率为87% ～110%,相对标准偏差为3.0% ～5.6%,方法的检出限为0.002 ～0.007 mg/kg.该方法可同时满足植物源食品中多种三唑类杀菌剂残留量的检测需要.     

农产品中甲草胺残留量的气相色谱-质谱检测

建立了玉米、花生、菠菜、柑橘4种不同类型农产品中甲草胺残留量的检测方法。样品先用丙酮-水(体积比为8∶2)提取,经二氯甲烷液-液分配,再用凝胶色谱(GPC)和固相萃取(SPE)去除色素和提取待测物,最后采用气相色谱-质谱测定,外标法定量。甲草胺的添加水平为0.010～0.200 mg/kg时,平均回收率为86.0%～98.2%;相对标准偏差为5.1%～6.7%;方法的测定低限为0.010 mg/kg。     

气相色谱质谱联用法同时测定果蔬中5种防腐杀菌剂

建立了果蔬中5种防腐杀菌荆(噻苯咪唑、邻苯基苯酚、联苯胺、抑霉唑、联苯)同时测定的气相色谱质谱联用法.样品用V(丙酮):V(乙酸乙酯)=50:50超声萃取,脱水,浓缩定容,经GC/MS分析.5种防腐杀菌剂分离良好并排除了样品中杂质峰的干扰,加标平均回收率为96.7%～104.7%之间,相对标准偏差为1.5%～4.25%.检出限0.5～1.5μg/L.     

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.     

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.     

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.     

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%).