吹扫捕集-气相色谱-质谱法测定地下水中挥发性有机物

应用吹扫捕集-气相色谱-质谱联用法测定地下水中54种挥发性有机污染物(VOC′s)含量.选定在40℃条件下吹扫捕集11 min,取样品溶液10 mL于吹扫瓶中,利用PTA 3000型吹扫捕集器直接进样,经DB-5MS毛细管色谱柱分离,电子轰击电离(EI)全扫描检测,选用特征离子,以内标法进行定量测定;54种VOC′S样品加标回收率在83.2%～115.5%之间,相对标准偏差在0.85%～3.88%之间,方法的检出限范围在0.03～0.12μg·L-1之间.     

稳定性同位素内标-吹扫捕集-气相色谱-质谱联用分析水中硫化物

建立稳定性同位素内标-吹扫捕集-气相色谱-质谱联用法(GC-MS)分析多种水体中硫化物,为预警异味水质突发事件和开展相关研究奠定基础。水样脱氯过滤后,加入同位素内标与氯化钠,吹扫捕集装置40℃氮气吹扫10 min,200℃脱附2 min,吹扫流量40 mL/min。色谱柱:DB-624,进样口温度270℃,分流比20∶1,载气高纯He,流速3.8 mL/min。升温条件:35℃(5 min),6℃/min升至120℃,20℃/min升至210℃。传输线(AUX)温度为280℃。质谱条件:离子源温度230℃,四极杆温度150℃,电子能量70 eV。以保留时间和质谱全扫描方式进行定性分析,质量范围m/z 45~450;选择离子监测定量;基质加标验证方法的准确度与精密度。乙硫醇、二甲基硫和二甲基二硫在0.6~21.3μg/L范围内线性良好。ET,DMS和DMDS的检出限分别为0.088,0.13和0.10μg/L。5种水体高、低浓度加标,回收率为90.7%~118.0%,RSD为2.7%~9.8%。本方法采用稳定同位素内标法,具有较好的准确性、稳定性和实用性,可用于地表水、地下水和生活饮用水等多种水体中含硫嗅味物质的分析。     

吹扫捕集-气相色谱-质谱法快速测定同序列地下水和土壤中的37种挥发性有机物

建立了吹扫捕集-气相色谱-质谱法(GC-MS)测定同序列地下水和土壤样品中37种挥发性有机物(VOCs)含量的方法。分别采集地下水、土壤样品并封装于40 mL棕色吹扫瓶中,采用全自动固液一体吹扫捕集装置,于20℃吹扫11 min,于250℃脱附1.7 min,于280℃烘烤8 min,将分离后的VOCs利用气相色谱-质谱联用仪进行分析,采用内标法定量。结果显示:目标物的相对响应因子(RRF)的相对标准偏差(RSD,n=8)小于11%,校准曲线相关系数大于0.998 0;对地下水和土壤样品分别进行3个浓度水平的加标回收试验,所得的回收率分别为75.5%～112%和82.0%～115%,测定值的RSD(n=7)分别为0.85%～11%和0.81%～7.9%。     

吹扫捕集-气相色谱-质谱法测定土壤和地下水中四氢呋喃

建立吹扫捕集-气相色谱-质谱法测定土壤和地下水中四氢呋喃。最佳的吹扫捕集条件:吹扫温度为40℃,吹扫时间为15 min,脱附温度为250℃,脱附时间为2 min。四氢呋喃的质量浓度在10～200μg/L范围内与色谱峰面积线性关系良好,相关系数不小于0.990。土壤和地下水中四氢呋喃的检出限分别为1.5、1.4μg/L,标准样品平均加标回收率分别为84.5%、77.2%,测定结果的相对标准偏差分别为3.3%、5.8%(n=6)。该方法适用于土壤和地下水中四氢呋喃含量的检测。     

吹扫捕集-气相色谱-质谱法同时分析饮用水源水中9种氯苯系化合物

建立了饮用水源水中氯苯、二氯苯、三氯苯和四氯苯等共9种氯苯系化合物同时测定的吹扫捕集-气相色谱-质谱法(P&T-GC- MS).优化了吹扫捕集时间及解析时间,采用质谱的选择离子监测模式和内标定量法进行定量分析.在优化的吹扫捕集条件下,线性回归方程的相关系数均大于0.999 8;氯苯、二氯苯、三氯苯和四氯苯的方法检出限(...     

稳定性同位素稀释吹扫捕集-气质联用法测定水中典型臭味物质

采用稳定性同位素稀释吹扫捕集-气相色谱/质谱联用法测定水中典型臭味物质土臭素(GSM)和2-甲基异莰醇(MIB).研究了特征离子、升温程序、样品吹扫温度及盐浓度等因素对臭味物质萃取过程的影响.本实验测定臭味物质的最佳条件为:盐浓度20%(m/V),样品吹扫温度60℃,程序升温速率5℃/min.通过加人同位素内标d5-G...     

常温吹扫捕集-气相色谱法测定海水中氧化亚氮

建立了海水中氧化亚氮的常温吹扫捕集-气相色谱检测方法。对吹扫捕集系统的条件进行了考察,优化结果如下:捕集温度30℃,脱附温度250℃,吹扫时间10min,吹扫气流速20mL/min。等实验条件进行了优化。本方法操作简单、灵敏、重现;检出限达2.8×10-10mol/L,标准工作曲线的线性相关系数大于0.9995(n=5);曲线斜率的相对标准偏差为2.8%(n=5);回收率为93.93%±3.1%(n=5)。用此方法测定了厦门近海表层海水样品中氧化亚氮的浓度。     

吹扫捕集-气相色谱-质谱法测定水和土壤中的甲基叔丁基醚含量

提出了测定水和土壤中甲基叔丁基醚(MTBE)的吹扫捕集-气相色谱-质谱法。水和土壤样品按相关标准采集后于25℃保存,吹扫捕集参数选定如下:1吹扫时间为11min;2脱附时间和温度分别为190℃,2min。经气相色谱分离后采用电子轰击离子源和选择离子扫描模式进行质谱分析。在水和土壤样品中MTBE的质量浓度在一定范围内与其峰面积呈线性关系,MTBE在上述2种样品中的检出限(3S/N)分别为0.10μg·L~(-1),0.26μg·kg~(-1)。按标准加入法进行回收试验,测得回收率在87.6%~103%之间,测定值的相对标准偏差(n=5)在2.3%~7.2%之间。     

吹扫捕集-气相色谱-质谱法测定海岸带表层沉积物中挥发性有机物

应用吹扫捕集-气相色谱-质谱法测定海岸带表层沉积物中28种挥发性有机物的含量。选定在40℃条件下吹扫捕集11min,取样品于吹扫瓶中,利用PTA 3000吹扫捕集仪直接进样,经J&W DB5-MS毛细管色谱柱分离,电子轰击电离全扫描检测,内标法进行定量测定。28种挥发性有机物的方法检出限在0.16～0.38μg.kg-1之间,样品加标回收率在70.7%～115.5%之间,相对标准偏差(n=7)在1.7%～7.8%之间。     

吹扫捕集-气相色谱/质谱联用测定土壤中挥发性石油烃

建立了吹扫捕集-气相色谱/质谱联用测定土壤中挥发性石油烃的分析方法。实验优选出了NaHSO_4作为样品的保存试剂,优化了吹扫-捕集条件和气相色谱质谱条件;GC条件:色谱柱60 m×0.32 mm×1.8μm RTX-502.2,进样口温度190℃,分流比20:1,程序升温;MS条件:EI源,离子源温度200℃,接口温度220℃,扫描范围40~350 amu/s。方法的线性范围为0.20~300 ng/g,相关系数均在0.995以上,检出限为0.03~0.38 ng/g。方法标准添加样品回收率为90.3%~108%;RSD为1.8%~8.8%。该方法适合于土壤样品中挥发性石油烃的分析检测。     

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%.     

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.     

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.     

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.     

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.     

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.     

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.