大气环境中挥发性有机化合物的测定

 参考美国环保局大气中挥发性有机化合物 (VOCs)的标准分析方法TO14A和TO15 ,采用预浓缩器与气相色谱联用 ,以质谱或氢火焰离子化检测器检测 ,建立了 5 6种VOCs(主要是臭氧前体物 )的快速分析方法。该方法在同一台仪器上采用单柱、单检测器 ,准确测定了高浓度CO2 下的VOCs。方法检出限为 0 1μg·m-3 ,相对标准偏差(RSD)为 2 5 7%～ 9 82 %。用该法分析了实际大气样品中的VOCs,结果令人满意。     

便携式气相色谱–质谱法现场测定有组织排放废气中VOCs

建立便携式气相色谱-质谱仪现场测定有组织排放废气中VOCs的方法。针对固定污染源有组织废气排放的特点,对升温程序、扫描方式、采样方式、进样体积进行了讨论优化,提出了对高、低浓度废气样品测定的解决方案,分析了气袋本底的干扰和去除方式。用所建方法对TO-14标准气体进行测定,各组分的含量在0.02~1.00μL/L范围内线性关系良好,相关系数均大于0.990,各组分检出限为0.004~0.014μL/L。测定结果的相对标准偏差为2.4%~15.3%(n=6),加标回收率为73.3%~109%。该方法检测时间短,具有良好的精密度和准确度,适用于有组织排放废气中VOCs测定。     

热脱附-气相色谱-质谱法测定稀土萃取分离车间固定污染源废气中18种挥发性有机化合物的含量北大核心CSCD

提出了热脱附-气相色谱-质谱法测定稀土萃取分离车间固定污染源废气中18种挥发性有机化合物(VOCs,包括1,1-二氯乙烷、1,2-二氯乙烯、1,1,2-三氯乙烷、甲苯、1,2,4-三甲基苯、苯、三氯乙烯、四氯乙烯,C_(7)~C_(16)等10种正构烷烃)含量。将采样器与2只串联的吸附管(装载有2种石墨化碳黑和1种碳分子筛)连接,于固定污染源排气口以50~65 mL·min^(-1)采样速率采集样品50 mL,密封吸附管,置于热脱附仪上,按照优化的仪器工作条件测定收集的气体中的18种VOCs含量(苯和四氯乙烯含量为2只吸附管吸附量的加和)。吸附管和聚焦冷阱的脱附温度均设置为350℃,脱附时间均设置为10 min。结果显示,10种正构烷烃标准曲线的线性范围为50.0~400 ng,其他8种VOCs的质量在20.0~300 ng内与其对应的峰面积与内标物峰面积的比值呈线性关系,检出限(3s)为0.0015~0.026 mg·m^(-3)。对空白样品进行3个浓度水平的加标回收试验,18种VOCs的回收率为73.5%~110%,测定值的相对标准偏差(n=5)为1.2%~22%。4家实验室同时采用以上方法分析空白加标样品,偏差的绝对值均小于参考HJ 168-2010计算所得的再现性限。     

热脱附-气相色谱-质谱法应用于工业源废气中挥发性有机物的目标和非目标筛查

建立了固相吸附热脱附-气相色谱-质谱(TD-GC-MS)综合筛查工业源废气中挥发性有机物(VOCs)的方法。对两种型号的固相吸附管进行了比较,最终选择使用Tenax SS TD Tubes吸附管。气体样品以恒定流速通过吸附管,富集分析物,经热脱附后,用GC-MS进行检测,目标化合物以内标法定量,非目标化合物的含量以甲苯的响应系数计算。方法检出限为1.06~5.44 ng,以采样体积300 mL计算,目标化合物的检出限为0.004~0.018 mg/m~3。吸附管平均加标回收率为78.4%~89.4%,相对标准偏差为3.9%~14.4%(n=7)。应用该方法对大连市某垃圾焚烧发电厂排放的废气进行VOCs目标及非目标化合物综合筛查,共检出29种VOCs,其中仅5种VOCs为预先设定的目标化合物,另外24种为非目标化合物,5种目标化合物含量仅占所有检出物总量的26.7%。证明了工业源废气VOCs分析中非目标化合物筛查的重要性,该研究思路对完整测定工业源挥发性有机污染物分布具有一定的借鉴意义。     

电子制冷预浓缩-双柱气相色谱-质谱/氢火焰检测器法测定空气中104种挥发性有机物

基于吸附剂辅助电子制冷预浓缩技术，建立了多维切割双柱气相色谱-质谱/氢火焰离子化检测器（GC-MS/FID）同时测定环境空气中104种挥发性有机物（VOCs）的方法。将采集于苏玛罐中的环境空气样品在配有吸附剂的电子制冷预浓缩系统中富集、脱附、除水、除CO₂和浓缩，然后通过GC-MS/FID的多维切割单元将C₂~C₃组分和C₄~C₁₂组分分别引入PLOT柱和InterCap-624柱进行分离。C₂~C₃组分用FID检测，以保留时间定性、外标法定量；C₄~C₁₂组分采用电子轰击离子源质谱检测，以保留时间和特征离子定性、内标法定量。考察了冷阱吸附剂种类、辅助压力控制单元压力设置、双柱切换时间切割点等参数对分析结果的影响，优化了GC-MS/FID条件，并评估了在此优化条件下的方法性能。104种VOCs在0.0446~0.892 μmol/m³范围内线性关系良好，相关系数（r）为0.9984~0.9999，对0.0446 μmol/m³和0.223 μmol/m³水平的混合标准气体重复6次进样，平均回收率为86.4%~116.1%，相对标准偏差为0.9%~11.3%；方法的检出限为0.145~1.90 μg/m³，定量限为0.435~5.70 μg/m³。该法稳定性好，灵敏度高，操作简便，可用于环境空气中104种VOCs的测定。     

催化光度法测定痕量钒——钒（V）-溴甲酚紫-过氧化氢体系

催化光度法测定钒已有报道[1~3],在0.45 mol·L-1磷酸介质及加热条件下,过氧化氢氧化溴甲酚紫褪色反应非常缓慢,而痕量钒对此反应具有较高的催化活性,且在一定浓度范围内,钒量与褪色反应程度呈线性关系,据此可建立测定痕量钒的方法。方法的检出限为1.9×10-6g·L-1,测定范围为0·003~1.8 mg·L-1。方法操作简便,重现性好,用于钢样中痕量钒的测定,结果满意。1试验部分1.1仪器与试剂721型分光光度计LB801-2型超级恒温器钒(Ⅴ)标准溶液:1.000 0 g·L-1,称取偏钒酸铵0.229 7 g溶于热水中,冷却,定容于100 mL容量瓶中。溴甲酚紫(用R表示)溶液:…     

LC/ESI-MS分离和测定冬虫夏草及其代用品的有效成分

本文报道采用电喷雾离子化(ESI),用高效液相色谱质谱联用法同时分离和测定冬虫夏草及其代用品中主要活性成分尿苷和腺苷的方法。本法使用Shimadzu VP ODS色谱柱,以水甲醇甲酸(90∶9.0∶1.0,V/V)为流动相,2 氯腺苷为内标,选择性离子检测(SIM)模式作定量分析。结果表明:尿苷和腺苷线性范围分别为2.0~110.0μg·mL-1和1.0~120.0μg·mL-1,检出限分别为0.3μg·mL-1和0.2μg·mL-1,标准加入回收率为97.0%~103.3%。该法已成功地用于冬虫夏草及其代用品中尿苷和腺苷的分析。     

褪色光度法测定微量溴酸根

美国国家环保总局(U.S.EPA)对消毒副产物(DBPs)作出了规定———饮用水中消毒副产物的最大污染浓度(MCLs)分别是: BrO3-(潜在致癌物)10μg·L-1; ClO3-1 mg·L-1。从标准可看出BrO3-的浓度限量远低于ClO3-,因此研究BrO3-的测定方法具有重要的意义。目前,测定溴酸根的方法不多,有萃取浮选光度法[1]、DSPCF光度法[2],近几年褪色光度法[3~5]得到广泛应用。试验发现,在室温下,盐酸介质中,溴酸根能显著氧化甲基红褪色,据此建立了测定微量溴酸根方法,检出限为8.76×10-6g·L-1,线性范围为0~1.0 mg·L-1,用于测定化学试剂中微量溴酸根,…     

偶氮胂(Ⅲ)-溴化十六烷基三甲基铵光度法测定高铝矿中的稀土总量

偶氮胂 应用于稀土总量的测定早有报道[1] ,但作者在应用这些方法分析高铝矿时 ,发现铝有严重干扰 ,且灵敏度不高 ,本文采用 1 -苯基 - 3-甲基 -4-苯甲酰基代吡唑酮 ( PMBP)萃取分离。经 8-羟基喹啉 -甲酸反萃后于水相中 [2 ]进行偶氮胂 ( ) ( Ars( ) ) -溴化十六烷基三甲基铵 ( CTMAB)光度法测定。方法已应用于生产。1　实验部分1 .1　主要仪器与试剂镧、铈混合标准溶液 :将 1 .0 mg· m L-1L a3+和 Ce2 + 标准储备液 (金川公司研究所提供 ) ,用1 .0 mol·L-1HCl分别稀释成 5 .0 μg·m L-1,然后按 1 + 1混合成 1 0 μg· m L-1…     

固定源废气中二噁英及多氯联苯、溴代阻燃剂和溴代二噁英的分析

建立了同时分离分析固定源废气中二噁英(PCDD/Fs)、二噁英类多氯联苯(dl-PCBs)、溴代阻燃剂(BFRs)和溴代二噁英(PBDD/Fs)的方法。废气样品经甲苯索氏提取,硫酸处理和多层硅胶柱净化后,应用活性炭分散硅胶翻转淋洗技术分离4类目标物。气相色谱使用耐高温薄膜短色谱柱配合高压进样,高分辨质谱使用低能量电离,一次性测定高/低溴代化合物。方法检出限分别为:PCDD/Fs 0.081~1.2 pg、dl-PCBs0.10~0.32 pg、多溴联苯醚(PBDEs)0.14~12 pg、新型BFRs 0.26~16 pg、四~七溴代PBDD/Fs 0.44~3.6 pg、八溴代PBDD/Fs(OBDD/F)8.2~12 pg。废气空白基质加标回收率(RSD)分别为:PCDD/Fs 88%~115%(2.9%~6.1%)、dl-PCBs 84%~118%(3.2%~10%)、PBDEs 71%~135%(2.1%~18%)、新型BFRs 71%~114%(2.9%~7.4%)、四~七溴代PBDD/Fs 83%~127%(5.2%~10%)、OBDD/F 52%~149%(23%~24%)。将本方法用于废气样品分析,所有质量控制指标均符合相关标准规定。     

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.