固相微萃取衍生化与GC-MS测定水中痕量路易氏剂的方法研究

采用固相微萃取衍生化和气相色谱．质谱（GC-MS）监测技术，对水中痕量路易氏剂进行了测定，考察了衍生化试剂、萃取纤维、萃取时间等因素对方法灵敏度的影响。测定路易试剂的线性范围为1．1—220ng／mL，检出限为0．0001mg／L，相对标准偏差为3．4％，回收率为93．2％～104．4％。     

固相微萃取-高效液相色谱联用测定环境水样中双酚A的自由溶解态浓度

应用可忽略耗损固相微萃取与高效液相色谱联用技术测定了环境水样中双酚A的自由溶解态浓度。为了获得高的灵敏度并减小环境因素（如温度和搅拌等）的影响，采用商品化固相微萃取纤维CW／TPR进行平衡采样。在环境水样常见pH（5～8）、缓冲容量（5～200mmol／L）和盐度（0～500mmol／L）条件下，4h可以达到萃取平衡。100mL样品足以避免样品耗损。以配制在250mmol／L NaCl和125mmol／L磷酸盐溶液（pH6．4）中的双酚A标准溶液进行校准，可以将缓冲液（0～200mmol／L）、盐度（0～500mmol／L）和pH（5．7～8．5）的影响控制在15％偏差范围以内。如需更准确的测定，也可以对样品pH值的影响加以校正。pH为6．4时，方法的线性范围为0．1～250μg／L，检出限为0．03μg／L，相对标准偏差（5μg/L，n=3）为1．1％。采用本方法测定了污水处理厂排水口的双酚A的自由溶解态浓度。     

固相微萃取-气相色谱法测定水中的甲基膦酸

报道了应用固相微萃取-气相色谱法测定水中甲基磷酸的方法,研究了不同固相微萃取纤维、萃取温度和时间、解吸时间、pH值等萃取条件和衍生化温度和时间、衍生化程序等衍生条件对测定效果的影响;结果表明该法简便、快速、有效,其检出限为0．03mg/L。     

微波辅助萃取-固相微萃取联用气相色谱-质谱法测定土壤中的扑草净

研究了微波辅助萃取-固相微萃取联用、气相色谱-质谱联用测定土壤中除草剂扑草净的分析方法。采用正交设计实验优化了萃取溶剂种类和体积、微波辐射时间和微波功率等微波辅助萃取条件;研究了SPME萃取涂层、搅拌速度、萃取时间和解吸时间等对萃取效率的影响。方法的检出限为0．01ng／g;线性范围为0．2—200μg／L。在优化的条件下测定了5和50ng/g的合成土壤样品,回收率分别为90．1％和91.6％;相对标准偏差分别为9．4％和8．8％(n=6)。本法综合了微波辅助萃取和固相微萃取的优点,操作简便．灵敏度高,特别适合于固体样品中痕量有机物的萃取分离。     

分散液液微萃取-柱前衍生-高效液相色谱法测定水样中双酚A

建立了分散液液微萃取-柱前衍生-高效液相色谱法测定水样中双酚A的分析方法.通过交互正交试验和混合型优化实验设计对影响因素(萃取剂体积、分散剂类型及其体积、水样体积、pH值及离子强度)进行了优化.优化后的分散液液微萃取条件为:60 μL萃取剂,0.4 mL分散剂(甲醇),pH 4.0;优化后的柱前衍生化条件:0.1 mL 2.0 g/L衍生剂(对硝基苯甲酰氯)、衍生化时间30 min;方法的线性范围:0.002～0.2 mg/L(r=0.9997),检出限0.007 μg/L(S/N=3);不同浓度双酚A的萃取率为59.0%～63.0%,相对标准偏差(RSD)2.5%～9.2%(n=5);水样中双酚A的加标率为86.5%～107.1%,RSD为4.0%～11.9%(n=5),其它雌激素(雌酮、雌二醇、雌三醇和17α-乙炔基雌二醇)对双酚A的测定无干扰.本方法可以对水环境中的痕量BPA进行检测,具有操作简便、快速等优点.     

表面活性剂辅助-凝固-漂浮分散液液微萃取/高效液相色谱法测定环境水样中酚类化合物

建立了表面活性剂辅助-凝固-漂浮分散液液微萃取(SA-DLLME-SFO)/高效液相色谱法同时测定环境水样中4种酚类化合物的分析方法。SA-DLLME-SFO实验中选用十二醇为萃取剂,Tween 20为分散剂,考察了萃取剂和非离子表面活性剂的体积、萃取时间、离心时间和盐效应等因素对萃取效率的影响。结果表明:对硝基苯酚、对甲酚、对溴酚和双酚A的检出限分别为0.13,0.13,1.02,0.25 ng/m L;对硝基苯酚、对甲酚和双酚A的线性范围为2~4 000 ng/m L,对溴苯酚的线性范围为10~4 000 ng/m L;加标浓度为0.2,0.8μg/m L时,4种酚类化合物的回收率为96.6%~105%,相对标准偏差(RSD,n=5)为1.9%~4.9%。该方法可用于池塘水和湖水等天然水体中对硝基苯酚、对甲酚、对溴酚和双酚A的测定。     

固相微萃取-脉冲火焰光度法测定大气及水中的路易氏剂

建立了固相微萃取（SPME）与气相色谱/脉冲火焰光度检测器（GC／PFPD）联用测定大气和水中路易氏剂及其水解产物的方法。探讨了影响SPME萃取效率的萃取头类型、萃取时间、解吸时间等因素。优化了PFPD的条件参数、衍生化试剂及衍生条件。在优化的条件下，路易氏剂衍生产物的响应值与浓度有良好的线性关系。本方法对水中路易氏剂及其水解产物的检出限为0．1μg/L；气体中路易氏剂的检出限为10ng／m^3；水样的加标回收率为96．7％-102．1％；气体样品的加标回收率为94．9％-103．0％；RSD为2．06％。     

固相微萃取-高效液相色谱法测定垃圾渗滤液中的双酚A

本文应用固相微萃取一高效液相色谱法(SPME—HPLC)分析了垃圾渗滤液中的痕量双酚A。对SPME的条件如测定模式、pH值、萃取时间、解吸方式、解吸溶剂、解吸时间和HPLC条件进行了优化。建立了SPME—HPLC分析垃圾渗滤液中痕量双酚A的方法。方法的线性范围为12．8～192μg／L,相关系数为0．9975,检出限为3．25μg／L(3σ,n=11)。以12．8μg／L的双酚A标准溶液平行测定11次,相对标准偏差(RSD)为4．4％,回收率为94．5％～103．3％。将其用于分析具有垃圾填埋场的渗滤液实际水样,结果十分满意。该方法具有快速、灵敏、简单、无溶剂的特点,适合于环境水样中痕量双酚A的分析。     

顶空固相微萃取-气相色谱-质谱测定水中异味化合物

采用顶空固相微萃取-气相色盐／质谱联用测定了水中常见的3种异味化合物，即2-甲基异茨醇、土腥素和β-柠檬醛。研究并讨论了纤维头的类型、盐的种类和浓度、温度、萃取时间、搅拌和解吸时间等因素对异味化合物萃取量的影响。结果表明：在水样中加入30％（W／V）的NaCl溶液，采用65μm PDMS／DVB纤维头，在搅拌的条件下，于60℃顶空萃取40min为异味化合物固相微萃取的最佳条件。在优化的条件下，使异味化合物吸附于纤维涂层后，将其在250℃高温下解吸，再用GC—MS分析。土腥素、β-柠檬醛、2-甲基异茨醇的检出限依次为1．0、1．3和1．7ng／L；其相对标准偏差分别为4．9％、8．4％和6．2％：3种异味化合物在5～1000ng／L的范围内线性关系良好，相关系数均大于0．997。因此，用该方法分析水中痕量（ng／L级）的异味化合物，结果满意。     

超声辅助提取–固相萃取净化–高效液相色谱法测定灰渣和污泥中11种双酚类及烷基酚类化合物

建立同时测定灰渣和污泥中11种双酚类及烷基酚类化合物(双酚F、双酚A、4-叔丁基苯酚、4-丁基苯酚、4-戊基苯酚、4-己基苯酚、4-叔辛基苯酚、4-庚基苯酚、壬基酚、4-辛基苯酚和4-壬基苯酚)的超声辅助提取–固相萃取净化–高效液相色谱法.以二氯甲烷–丙酮(体积比为1:1)为提取溶剂,提取时间为20 min,提取温度为...     

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.     

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%).     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.