顶空固相微萃取气相色谱法测定浓海水中的氯酚

建立浓海水中氯酚的顶空固相微萃取气相色谱法检测方法。采用顶空固相微萃取对海水淡化排放的浓海水样品中2,4,6-三氯酚(2,4,6-TCP)和五氯酚(PCP)进行分离富集,气相色谱-电子捕获检测器(μECD)测定浓海水样品中2,4,6-TCP和PCP的含量。讨论了萃取时间、萃取温度、水样盐度等实验条件对富集效率的影响,确定了萃取时间为40 min,萃取温度为60℃。2,4,6-TCP,PCP的质量浓度在0.500~20.0μg/L范围内与其色谱峰面积呈良好的线性关系,线性相关系数均大于0.999,2,4,6-TCP和PCP的检出限(2S/N)分别为0.055,0.128μg/L,测定结果的相对标准偏差为3.65%~11.4%(n=6),加标回收率为73.5%~119.0%。该方法快速,灵敏度高,适合于浓海水中氯酚的分析。     

氢化物发生-原子荧光光谱法测定大蒜中砷和硒

采用氢化物发生-原子荧光光谱法测定大蒜中砷和硒。样品经硝酸和高氯酸消解,在盐酸(5+95)溶液中,加入溶于50g·L~(-1)氢氧化钠溶液的20g·L~(-1)硼氢化钾溶液,使其与溶液中砷及硒离子反应生成氢化物。分析中采用载气流量依次为800mL·min~(-1),600mL·min~(-1),屏蔽气的流量均为1000mL·min~(-1)。试样溶液中加入硫脲-抗坏血酸混合溶液作为还原剂。于仪器中引入试样溶液0.5mL,按选定的工作条件操作。砷及硒的质量浓度分别在0.04～0.40,1.00～10.0μg·L~(-1)范围内与其荧光强度呈线性关系,方法的检出限(3s/k)砷为0.017μg·L~(-1),硒为0.314μg·L~(-1)。分别加入两元素的标准溶液作回收试验,测得砷和硒的回收率分别在95.3%～104.4%和94.7%～105.2%之间。     

氢化物发生-原子荧光光谱法同时测定饮用水中砷和锑

采用氢化物发生-原子荧光光谱法同时测定饮用水中砷和锑。在盐酸(1+9)溶液中,加入硼氢化钾溶液作还原剂,使其与溶液中砷(Ⅲ)及锑(Ⅲ)离子反应生成氢化物。分析中采用载气及屏蔽气的流量依次为400mL·min~(-1)及800mL·min~(-1)。试样溶液中加入硫脲及抗坏血酸混合溶液作为预还原剂,于仪器中引入1.0mL试样溶液,按所选定的工作条件操作。砷及锑的质量浓度均在10.0μg·L~(-1)以内与其对应的荧光强度呈线性关系,砷和锑的检出限(3S/N)依次为0.087μg·L~(-1)和0.048μg·L~(-1)。应用此法对饮用水进行分析,测得砷和锑的回收率分别在90.5%～93.3%和92.5%～95.3%之间。     

气相色谱-质谱法测定聚对苯二甲酸乙二醇酯瓶装水中乙醛的迁移量

提出了测定聚对苯二甲酸乙二醇酯(PEGTP)瓶装纯水中乙醛迁移量的气相色谱质谱法。水样(100mL)中乙醛用2,4-二硝基苯肼在pH 3柠檬酸盐缓冲溶液10mL中,于40℃水浴上振荡1h加热使之衍生化。冷却后用二氯甲烷萃取3次,每次10mL。萃取液于40℃旋转蒸发至1.0mL,分取1分L进样分析。采用DB-5MS毛细管柱及在70℃～280℃范围内程序升温进行分离。线性范围在300μg·L~(-1)以内,检出限(3S/N)为1μg·L~(-1),加入50μg·L~(-1)及100μg·L~(-1)标准溶液做回收试验及精密度试验,测得平均回收率为88%,相对标准偏差(n=5)依次为5.4%及4.5%。     

气相色谱法快速测定环境水中叔丁醇的含量

提出了气相色谱法快速测定环境水中叔丁醇含量的方法,外标法定量。考察了萃取剂、色谱柱、柱升温程序、载气流量等因素对叔丁醇测定的影响,得到最佳条件为:二氯甲烷作萃取剂,Rtx-Wax色谱柱为分离柱,以5℃·min~(-1)的速率进行程序升温,载气流量为15 mL·min~(-1)。叔丁醇的线性范围为10.0～800μg·L~(-1),方法的检出限(3S/N)为2.65μg·L~(-1),测定下限(10S/N)为10.6μg·L~(-1)。空白加标回收率在82.3%～93.5%内;当叔丁醇的质量浓度不小于50.0μg·L~(-1)时,测定值的相对标准偏差(RSD)均小于10%。     

固相微萃取-气相色谱法测定鱼肉中五氯酚

经匀浆的鱼肉样品置于20 mL顶空瓶中,加入氯化钠3.0 g,水1 mL及pH 2.0硫酸溶液9 mL,于40℃超声萃取30 min。将顶空瓶放入带固相微萃取装置的Combi PAL全自动进样器中,于90℃温度下加热20 min后,用85μm聚丙烯酸酯萃取头固相微萃取10 min,于280℃热解3 min,用HP-5毛细管柱分离后,用气相色谱法(电子捕获检测器)测定五氯酚的含量。五氯酚的线性范围在0.05~100μg.L-1之间,方法的检出限(3S/N)为0.02μg.L-1。在3个浓度水平(1.0,5.0,50.0μg.kg-1)上对方法的回收率进行试验,测得回收率在81.2%~89.4%之间,测定值的相对标准偏差(n=6)在4.2%~7.1%之间。     

固相萃取膜富集-超声解吸-气相色谱法测定地下水中有机磷农药的含量

应用以苯乙烯/二乙烯苯聚合物为吸附剂的固相萃取膜对地下水中6种有机磷农药(OPPs)进行富集。经解吸后所得解吸液直接用气相色谱法进行测定。取水样500mL,加入甲醇2.5mL,逐滴加入20%(体积分数)的盐酸溶液或200g·L~(-1)的氢氧化钠溶液调节水样的酸度至pH 6.0,将此溶液以100 mL·min~(-1)的流量流经SDB-XC固相萃取膜,取下膜片,折叠后置于10mL棕色小瓶中,加入丙酮2.0mL,硫酸钠约0.2g,盖紧瓶塞后于30℃条件下将膜片上吸附的6种OPPs超声解吸(7 min),使其溶于丙酮中。避光静置约5 min后,直接分取丙酮溶液0.50mL,用气相色谱法测定其中OPPs的含量,采用火焰光度检测器。结果表明:6种OPPs的质量浓度在一定范围内与其对应的峰面积之间呈线性关系,其检出限(3S/N)均小于0.01μg·L~(-1)。以空白水样为基质,加入0.10μg·L~(-1)的OPPs的混合标准溶液,按上述方法进行7次平行测定,测定值的相对标准偏差在4.3%～7.6%之间。以3个实际样品为基体,分别加入3个浓度水平(0.050,0.10,0.70μg·L~(-1))的6种OPPs混合标准溶液进行回收试验,测得6种OPPs的回收率均在76.0%以上。     

顶空固相微萃取-气相色谱-质谱法测定苦杏仁中苦杏仁苷含量

采用顶空固相微萃取-气相色谱-质谱法对苦杏仁中苦杏仁苷进行了测定。0.1g苦杏仁样品及4mol·L~(-1)硫酸4mL置于25mL顶空瓶中,于沸水浴水解15min。PDMS/DVB萃取头顶空萃取20min,萃取头于气相色谱进样口解析1 min。采用HP-5MS色谱柱在程序升温条件下进行分离。用氦气为载气,流量为1.0mL·min~(-1),质谱分析中采用电子轰击电离源(230℃,70 eV),并在40～600amu质量数范围内进行全扫描。结果表明:方法在100μg·g~(-1)以内呈线性。采用此法对市售苦杏仁中苦杏仁苷含量测定结果为60.43μg·g~(-1),与分光光度法结果相符。样品5次测定结果相对标准偏差为1.8%;60μg·g~(-1)及20μg·g~(-1)两个水平添加回收率均在90%以上。     

气相色谱-串联质谱法测定动物性食品中的9种N-亚硝胺类化合物

称取样品10.00g,加入100μL由N-二甲基亚硝胺-d6和N-亚硝基二丙胺-d14组成的混合内标溶液(1.00mg·L~(-1)),加入20mL乙腈,涡旋1min,于-20℃冷冻20min,再加入萃取盐(4g硫酸镁、1g氯化钠),迅速振荡30s,以8 000r·min~(-1)在0℃离心10min,取上清液加入10mL乙腈饱和的正己烷,涡旋1min,以6 000r·min~(-1)在0℃离心3min,去除正己烷层,加入净化填料(50mg N-丙基乙二胺、150mg封端十六烷基键合硅胶、900mg Na2SO_4),涡旋1min,以8 000r·min~(-1)在0℃离心5min,取上清液用氮吹浓缩(不吹干),用乙腈定容至1.0mL,采用气相色谱-串联质谱法测定其中的9种N-亚硝胺类化合物。色谱分析中选用VF-WAXms色谱柱(0.25mm×30m,0.25μm),质谱中选择电子轰击离子源和多反应监测模式。9种N-亚硝胺类化合物的质量浓度在5.0～150μg·L~(-1)内与其峰面积呈线性关系,检出限为0.1μg·kg~(-1),测定下限为0.5μg·kg~(-1)。加标回收率在89.0%～117%之间,测定值的相对标准偏差(n=6)在0.6%～8.0%之间。     

顶空-气相色谱-串联质谱法测定水中苯甲醚的含量

采用顶空-气相色谱-串联质谱法测定水中苯甲醚的含量。取10mL水样和氯化钠3g加入于顶空瓶中,于70℃平衡15min,搅拌速率为95r·min~(-1)。气相色谱中采用Rxi-5Sil毛细管色谱柱,质谱中采用电子轰击离子源和多反应监测模式。苯甲醚的质量浓度在0.005~0.1μg·L~(-1)范围内呈线性,检出限(3S/N)为0.001μg·L~(-1),加标回收率在73.7%~92.2%之间,测定值的相对标准偏差(n=6)为3.7%~8.2%。     

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%.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.