分散液相微萃取-气相色谱联用测定葡萄中百菌清、克菌丹和灭菌丹残留

采用分散液相微萃取与气相色谱-电子捕获检测联用技术建立了测定葡萄样品中百菌清、克菌丹和灭菌丹农药残留的新方法.对影响萃取和富集效率的因素进行了优化.萃取条件选定为在10 mL带塞离心试管中加入 5.0 mL葡萄样品溶液,并加入1.0 mL丙酮(分散剂),振荡摇匀后以5000 r/min离心5 min,然后将上层清液转移至另一离心试管中,加10.0 μL氯苯(萃取剂),分散混匀后再以5000 r/min离心5 min,萃取剂氯苯相沉积到试管底部,吸取1.0 μL萃取相直接进样分析.在优化的实验条件下,3种杀菌剂的富集倍数可达788～876倍;检出限在6.0～8.0 μg/kg(S/N=3∶ 1)范围内.以α-六六六为内标,测定3种杀菌剂的线性范围为10～150 μg/kg,线性相关系数在0.9990～0.9995范围内.本方法已成功应用于葡萄样品中百菌清、克菌丹和灭菌丹残留的测定,平均加标回收率在92.3%～106.1%范围内;相对标准偏差在4.5%～7.2%之间,结果令人满意.     

分散液液微萃取-气相色谱/质谱法测定水中多环芳烃

用分散液液微萃取-气相色谱/质谱法测定水样中的16种多环芳烃(PAHs)。通过实验确定最佳萃取条件为:20μL四氯化碳作萃取剂,1.0 mL乙腈作分散剂,超声萃取1 min。在优化条件下,多环芳烃的富集倍数达到216～511,方法在0.05～50μg/L范围内呈良好的线性关系,相关系数(R2)在0.9873～0.9983之间,检出限为0.0020～0.14μg/L。相对标准偏差(RSD)在3.82%～12.45%(n=6)之间。该方法成功用于实际水样中痕量多环芳烃的测定。     

超声波辅助分散液相微萃取-气相色谱联用分析菌核净

将超声波萃取(USE)与分散液-液微萃取(DLLME)联合,利用气相色谱-电子捕获检测(GC-ECD),建立了一种高灵敏度检测水体中菌核净的新方法。对萃取的条件进行优化,选定萃取条件为:在5 mL样品中,注入1 mL丙酮和0.1 mL的四氯化碳混合液,20 Hz超声10 min,振荡混匀后高速离心5 min,移出下层溶剂低温吹干以丙酮定容自动进样分析。在优化条件下,样品的富集倍数可达50倍,检出限为0.001μg/mL,对采于蔬菜地边的水样进行加标回收率实验,平均回收率在81%以上,相对标准偏差在4.3%~7.6%之间,方法可满足水样中菌核净农药残留的检测要求。     

分散液液微萃取-高效液相色谱法测定水样中痕量2-萘酚

建立了分散液液微萃取-高效液相色谱法测定水样中2-萘酚的分析方法。对萃取剂、分散剂的种类和体积、萃取时间、离心时间、盐浓度等影响萃取效率的因素进行了优化。在优化后的萃取条件下(30μL氯苯作为萃取剂、0.8 mL乙腈作为分散剂、萃取时间为2 min、3000 rpm离心时间为5 min、不加盐)方法的线性范围为0.2~1000μg/L(r=0.9998),检出限为0.05μg/L(S/N=3)。2-萘酚质量浓度为100μg/L时,方法的萃取率为91.4%~105.4%,相对标准偏差为4.7%(n=11)。采用该方法对4种实际水样中的2-萘酚进行了测定,加标回收率在85.5%~104.4%之间,相对标准偏差在2.3%~12%之间(n=3)。本方法可用于环境水样中的痕量2-萘酚的检测。     

分散液液微萃取-气相色谱法测定水中苯、甲苯和二甲苯

以CHCl3为萃取剂,丙酮为分散剂,建立了基于分散液液微萃取(DLLME)结合气相色谱测定水样中苯、甲苯和二甲苯含量的新方法。实验对影响萃取效率的因素进行优化,萃取条件为:在1.0mL含有50g/LNaCl的样品溶液中加入40.0μLCHCl3和0.16mL丙酮,振荡分散均匀后,以400r/min离心5min,取萃取溶剂1.00μL直接进样分析。本方法线性范围为0.8～200μg/mL,相关系数r0.9980,检出限为0.1μg/mL,回收率分别在93.5%～102.1%之间。将该方法与液液萃取法、单滴微萃取相比较,具有操作简单、富集效率高和灵敏度高等特点。     

分散液液微萃取-气相色谱法快速测定水中15种硝基苯类物质

建立了分散液液微萃取-气相色谱电子捕获检测器测定水中15种硝基苯类物质的方法.筛选出了具有高密度且能够适用于电子捕获检测器的萃取剂.优化了色谱条件,对萃取剂种类及用量、分散剂种类及用量、萃取时间、萃取温度等条件进行了优化.DB-35毛细管柱对15种硝基苯类物质具有最好的分离效果.使用程序升温,初始80℃ 保持2 min,以5℃/min速率升温至180℃,可以在22 min内完成分离.以100μL氯苯作为萃取剂、400μL甲醇作为分散剂,对5.00 mL水样在室温下进行萃取,仅需30 s即可达到萃取平衡,15种目标物的萃取率均可达到90%以上,富集倍数达到45.0~48.8.离心分离,取下层沉积相进行气相色谱测定,使用电子捕获检测器检测,方法的定量限为0.03~0.15μg/L,线性范围为0.20~50.0μg/L,相关系数不低于0.998.方法的相对标准偏差在3.3%~8.9%之间,加标回收率在86.0%~103.5%之间.     

分散液液微萃取-气相色谱法测定水样中甲基环硅氧烷

将分散液液微萃取与气相色谱法技术相结合,建立了测定水样中3种甲基环硅氧烷残留的方法.重点探讨了萃取剂的种类和用量、分散剂的种类和用量、萃取时间及盐浓度等对样品萃取效率的影响.结果表明在优化条件下,待测物在5～100μg/L范围内线性良好(r＞0.99),检出限在2～4μg/L之间,富集倍数可达165～170倍,相对标准...     

蔬菜中甲胺磷等5种有机磷农药残留量的分散液-液微萃取/气质联用技术检测

建立了分散液-液微萃取/气相色谱质谱(DLLME/GC-MS)联用技术分析蔬菜样品中甲胺磷、甲拌磷、甲基对硫磷、毒死蜱和乐果5种有机磷农药残留的新方法。优化后的萃取条件:10μL氯苯为萃取剂,1.0 mL丙酮为分散剂,萃取时间为3 m in。5种有机磷农药均具有良好的线性关系,相关系数不低于0.995,加标回收率为60%~95%,相对标准偏差为2.8%~9.1%,检出限为0.001~0.140 mg/kg。应用于蔬菜中有机磷农药残留的检测,结果满意。     

表面活性剂辅助分散液相微萃取-气相色谱法分析蔬菜水果中有机磷类农药残留

建立了测定蔬菜水果中有机磷类农药残留的表面活性剂辅助分散液相微萃取-气相色谱法。优化的萃取条件为:在5.0 mL样品溶液中加入50.0μL三氯甲烷和0.5mL 0.04 mmol·L-1的N-十二烷基-β-氨基丙酸盐表面分散剂,分散混匀后,以5 000r·min-1离心5min,吸取三氯甲烷相直接进样分析。在最优化条件下,8种有机磷类农药在0.02~0.50μg·mL-1范围内具有良好的线性关系,相关系数在0.9948~0.9985之间;检出限为0.0056~0.0110μg·mL-1。有机磷类农药的富集倍数高达264~537倍。方法应用于蔬菜水果中的有机磷类农药分析,加标回收率在82.4%~114.5%之间;相对标准偏差(RSD)在4.9%~13.7%之间。该方法具有操作简单、富集效率高和灵敏度高等特点,可满足蔬菜水果中有机磷类农药残留的检测。     

低温富集液液萃取-气相色谱-串联质谱法测定水样中15种农药残留

利用低温冷冻条件下农药在水相和有机相之间达到新的传质平衡,建立了低温富集液液萃取-气相色谱-三重四极杆串联质谱法同时测定水样中15种有机磷、有机氯及菊酯类农药的方法。通过对样品前处理中的溶剂选择、冷冻温度及冷冻时间的优化,最终确定的样品前处理条件为:萃取溶剂为甲苯2.0 mL;冷冻温度-40℃;冷冻时间1h。15种农药的检出限(3S/N)在0.005~0.02μg·L-1范围,测定下限(10S/N)为0.02~0.07μg·L-1。方法用于水样中农药的分析,加标回收率在78.8%~124%之间,测定值的相对标准偏差(n=5)在0.9%~9.1%之间。     

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.     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.