顶空气相色谱/质谱法测定卷烟烟丝吸附的甲苯

建立了顶空气相色谱/质谱(HS-GC/MS)法测定卷烟烟丝吸附的甲苯。考察了色谱柱升温程序、顶空平衡温度、顶空平衡时间、传输线温度及样品环温度、样品加入量、基质校正剂加入量对分析结果的影响,确定的最优分析条件为:顶空平衡温度140℃,顶空平衡时间45min,样品环温度190℃,传输线温度210℃,样品加入量为1.0g,不添加基质校正剂。结果表明,方法相对标准偏差(RSD)为2.76%,检出限为0.013μg/g,定量限为0.043μg/g。该方法简便、快速、重现性好,可用于卷烟烟丝吸附的甲苯的测定。     

顶空进样气相色谱-质谱法测定山葵中异硫氰酸酯

建立了山葵中异硫氰酸酯的测定方法。样品装入顶空进样瓶中,加热平衡后顶空进样,经HP-5MS毛细管柱分离,质谱测定。传输线温度250℃,离子源温度230℃,顶空瓶平衡温度60℃,平衡时间15min。通过计算机检索与NIST库中标准质谱图比较定性。在山葵样品中分离鉴定出8种异硫氰酸酯。方法具有操作简单、快速等特点。     

顶空-气相色谱法测定水中三氯甲烷和四氯化碳方法的改进

改进了顶空-气相色谱法测定水中三氯甲烷和四氯化碳的方法,对平衡温度和平衡时间进行了优化,对不同溶剂配制的标准使用液和不同方法制作的工作曲线对测定结果的影响进行了比较.试验结果表明,样品最佳平衡温度和时间分别为50℃和35 min.采用甲醇代替标准中规定的纯水配制标准使用液,采用微量进样针取样到预先密封的顶空瓶中,三氯甲...     

顶空-毛细管气相色谱法测定印刷品中15种痕量挥发性有机物

采用顶空-气相色谱法对印刷品中的挥发性有机物(苯、甲苯、乙苯、二甲苯、乙醇等15种)进行分析,研究了不同升温程序、顶空平衡温度、平衡时间等对分析结果的影响,优化的实验参数为:进样口温度:200℃;检测器温度:250℃。升温程序:初始温度40℃,保持5 min;以20℃/min速率升温至200℃,保持3 min。以高纯氮气作为载气,流速为8.0 mL/min保持5 min,再以0.2 mL/min的速率降至5.0 mL/min(分流比5:1);顶空条件:进样瓶平衡温度为90℃,平衡时间30 min,顶空进样体积1.0 mL。本方法线性关系良好,15种挥发性有机物的相关系数均大于0.9998,高、中、低3个浓度的回收率为77.8%~100.6%;相对标准偏差均低于6.0%(n=6)。方法可用于印刷品中挥发性有机物的分析。     

顶空气相色谱法测定水中的1，2-环氧丙烷

采用顶空-气相色谱法分析水中的1,2-环氧丙烷,研究了不同色谱柱、取样体积、平衡温度、平衡时间对1,2-环氧丙烷测定结果的影响．结果表明最佳分析条件为取25mL水样子45mL顶空瓶中,于40℃平衡25min后,用HP-1（60m×0．53mm×5μm）色谱柱60℃测定．线形范围0．20-40．0mg／L,相关系数0．9995,检出限0．05mg／L,方法灵敏度高,干扰少．     

卷烟烟丝香气成分的固相微萃取-气相色谱-质谱法分析

采用固相微萃取顶空取样和气相色谱－质谱法对３种名牌卷烟烟丝的香气成分进行了对比分析。探讨了最佳的取样条件（包括不同极性涂层的纤维头、样品量、平衡温度、平衡时间等）。结果表明,５ｇ烟丝在７０℃下平衡１４ｈ以上,然后用固相微萃取纤维头顶空取样６０ｍｉｎ,可获得较高的灵敏度。６５ｕｍＣＷ－ＤＶＢ纤维头对强极性的香气成分（如低级脂肪酸类、芳香酸类、醇和二醇类、甘油及其衍生物类、芳香醇类、酚类、含氮和含氧杂     

顶空-气相色谱质谱法测定水中10种氯苯类化合物

文文建立了不同水体中10种氯苯类化合物的顶空-气相色谱质谱的检测方法;优化了10种氯苯类化合物的最佳顶空条件,10种氯苯类化合物的最佳顶空条件为水样pH5～6,氯化钠加入量为4.0g,顶空加热平衡温度55℃,加热平衡时间20min,震荡,在此顶空条件下,可以获得满意的10种氯苯类化合物的响应值和回收率.10种氯苯类化合...     

顶空-气相色谱法快速测定化工固体废物中16种挥发性有机物

采用顶空-气相色谱法快速测定化工固体废物中16种挥发性有机物的含量。顶空加热平衡温度为80℃,顶空加热平衡时间为30min。用HP-FFAP色谱柱(30m×0.32mm,0.25μm)分离,氢火焰离子化检测器检测。16种挥发性有机物的的质量浓度在一定范围内与其对应的峰高呈线性关系,方法的检出限为0.001～0.009mg·L~(-1)。方法用于化工固体废物样品的分析,加标回收率为82.5%～115%,测定总量的相对标准偏差(n=6)为1.9%～9.1%。     

顶空气相色谱-质谱法测定土壤和地下水中的甲基叔丁基醚

建立顶空–气相色谱–质谱法测定土壤和地下水中甲基叔丁基醚的检测方法。对顶空萃取进样器的工作条件进行优化,确定了最佳的顶空萃取条件:顶空平衡温度为85℃,顶空瓶恒温时间为30 min,平衡时间为1 min,传输线温度为110℃,进样针温度为90℃,进样时间为0.2 min,拔针时间为0.4 min。甲基叔丁基醚的质量浓度在10～200μg/L范围内与响应值呈良好的线性关系,线性相关系数r~2≥0.990。土壤和地下水中甲基叔丁基醚的检出限分别为1.2μg/kg,1.0μg/L,加标回收率分别为80.0%～94.8%,86.0%～100.5%,测定结果的相对标准偏差分别为2.35%～13.2%,2.84%～9.53%(n=6)。该方法具有良好的精密度与准确度,适用于土壤和地下水中甲基叔丁基醚的分析检测。     

顶空气相色谱法测定食用植物油中苯、甲苯和二甲苯

建立顶空气相色谱法测定食用植物油中苯、甲苯和二甲苯的残留量的分析方法。样品采用自动顶空进样技术，经TG-624型毛细管色谱柱（30 m×0.25 mm,1.4μm）分离后，用氢火焰离子化检测器检测。采取分流进样，分流比为25∶1；色谱柱程序升温，初温温度为40℃，保持1 min，以10℃/min升温至100℃，保持1 min，再以40℃/min升温至250℃，保持1 min；顶空平衡时间为30 min，顶空平衡温度为70℃。苯、甲苯和二甲苯的标准曲线相关系数为0.998～0.999 5，方法检出限为0.07～0.18 mg/kg，回收率为90.4%～104%，相对标准偏差为1.5%～4.2%(n=7)。该方法能够满足食用植物油中苯、甲苯和二甲苯的残留量检测。     

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.