中空纤维膜萃取电喷雾电离质谱测定水中的全氟化合物

采用中空纤维膜( HF)做固相微萃取( SPME)材料,与常压离子化质谱( AMS)联用,分析水中全氟庚酸(PFHpA)、全氟辛酸(PFOA)、全氟壬酸(PFNA)、全氟癸酸(PFDA)、全氟辛烷磺酸(PFOS)、全氟十一酸(PFuDA)和全氟十二酸(PFDoA)7种全氟化合物(Perfluorinated compounds, PFCs)。对萃取时间和萃取溶液pH值进行了优化,质谱在负模式下使用选择反应监测扫描( SRM),并使用同位素内标13 C4-PFOS和13 C4-PFOA进行定量分析。结果表明,本方法对7种PFCs均有良好的线性(R2>0.99);除了PFHpA外,其它6种PFCs化合物的检出限为0.8~2.7 ng/L,定量限为2.7~8.9 ng/L;其中5种PFCs的富集倍数超过200倍。实际水样中(自来水和珠江水)7种PFCs均未检出,PFCs加标浓度在40和400 ng/L时,自来水的回收率范围分别为88.5%~108.3%和94.2%~116.7%,珠江水的回收率范围分别为75.0%~102.6%和82.1%~97.6%。     

超高效液相色谱-串联质谱法测定表层水中全氟及多氟化合物

建立了固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)同时测定水中全氟烷基羧酸(PFCAs)、全氟烷基磺酸(PFSAs)、全氟烷基膦酸(PFPAs)、全氟烷基次膦酸(PFPis)和多氟烷基膦酸二酯(di PAPs)等23种全氟及多氟化合物的分析方法。固相萃取柱WAX柱依次用6 m L甲醇(含1%(V/V)NH4OH)、12mL甲醇和12mL超纯水活化,上样后,用6mL乙腈(含0.5%(V/V)NH4OH)、6mL甲醇(含1%(V/V)NH4OH)和6mL乙腈(含1%(V/V)NH4OH)洗脱。样品萃取液分为3份,一份用于分析PFCAs和PFSAs,溶液组成为等体积萃取液与超纯水;一份用于分析PFPAs,溶液组成为等体积萃取液与25 mmol/L四丁基硫酸氢铵;另一份用于分析PFPis和di PAPs,溶液组成为甲醇。结果表明,水中23种全氟及多氟化合物平均加标回收率为55%~125%,相对标准偏差为0.3%~15.0%,方法检出限和定量限分别为0.003~0.215 ng/L和0.010~0.714 ng/L。本方法简便、灵敏度高、重现性好,适用于同时检测水中多类全氟及多氟化合物。     

高效液相色谱-串联质谱法对奶粉、酸奶中全氟化合物的分析

建立了液相色谱-质谱检测奶粉和酸奶中11种全氟化合物(PFCs)的分析方法.分别考察了溶液离子强度和酸碱度对固相萃取效率的影响,结果表明,0.5 ～12.5 mmol/L NaCl溶液的影响很小,且中性和微酸性条件下回收率较好.通过优化和比较,选用等体积的甲醇和0.01 mol/L盐酸的甲醇溶液依次对奶粉中的PFCs进行萃取,对于酸奶则使用甲醇直接萃取,并用WAX柱对萃取液净化.以甲醇(A)和50 mmol/L 醋酸铵(B)为流动相进行梯度洗脱,洗脱时间为10 min(或15 min),流速1 mL/min.内标法定量,奶粉和酸奶中11种PFCs的加标回收率分别为81% ～111%和80% ～118%,方法检出限为2 ～29 ng/L.用该方法对市售国产和进口奶粉及酸奶样品中的PFCs进行了分析.     

固相萃取-液相色谱-串联质谱法同时测定水中14种短链和长链全氟化合物

建立了固相萃取-超高压液相色谱-三重四极杆质谱同时测定水中14种短链和长链全氟化合物（PFCs）的方法。水样经WAX混合型固相萃取小柱富集和净化后,采用BEH C18色谱柱、甲醇和5 mmol/L乙酸铵水溶液作为流动相进行梯度洗脱,质谱采用多反应监测模式,内标法定量分析。14种PFCs在0.1~50 μg/L范围内线性关系良好,相关系数大于0.99,方法检出限和定量限分别为0.09~1.15 ng/L和0.29~3.85 ng/L。在2、10和20 ng/L加标水平下,8种PFCs的平均回收率为85.0%、120.2%和117.4%,平均相对标准偏差为9.2%、9.0%和6.6%,6种PFCs的回收率相对较低,主要由于其在瓶/管壁上的吸附作用导致。应用本方法分析某淡水湖水样,检出4种短链和5种长链PFCs,质量浓度为41.29~49.05 ng/L和98.43~111.02 ng/L。结果表明该方法适用于对环境水体中短链和长链PFCs的同时分析测定。     

大体积全自动固相萃取气相色谱–质谱法测定水中苯并芘

建立了全自动固相萃取–气相色谱–质谱联用测定水中苯并芘的方法。优化了全自动固相萃取条件,选择C8固相萃取柱萃取水样品中的苯并芘,样品中加入甲醇以增强苯并芘在萃取柱上的保留能力,采用正压大体积六通道同时进样,进样体积为1 000 m L,进样流量20 m L/min,使用二氯甲烷为洗脱溶剂,浓缩至0.5 m L。水中苯并芘的质量浓度在10~200μg/L范围内与其质谱响应值线性关系良好,相关系数为0.995,检出限为2 ng/L。在20~200μg/L加标水平上,苯并芘回收率为85.0%~94.5%,测定结果的相对标准偏差均小于6%(n=6)。该方法操作简单、测定结果准确,可用于水中苯并芘的测定。     

碳纳米管复合材料结合分散固相萃取-高效液相色谱-串联质谱法检测环境水样中痕量全氟化合物

以碳纳米管-二氧化硅棒复合材料为吸附剂,基于分散固相萃取法和液相色谱-串联质谱法建立了一种高灵敏、快速分析环境水样中痕量全氟化合物(PFCs)的方法。该研究选择全氟己烷磺酸、全氟庚酸、全氟辛酸、全氟辛烷磺酸、全氟壬酸和全氟癸酸6种全氟化合物为目标分析物。采用单因素优化法对影响萃取效果的重要因素进行了优化。获得的最佳条件为：吸附时间为30 min、吸附剂用量为10 mg、样品溶液pH为6、萃取过程添加NaCl浓度为1.7 mol/L、解吸溶剂为丙酮、解吸时间为4 min、解吸液的体积为4 mL。采用高效液相色谱-三重四极杆质谱联用技术对水样品中全氟化合物进行定量分析。以5 mmol/L乙酸铵和甲醇为流动相进行梯度洗脱,经Kinetex C18色谱柱(100 mm×2.1 mm, 1.7μm)分离,采用电喷雾离子源、负离子扫描模式和质谱多反应监测,实现了环境水样中6种全氟化合物的快速定性和定量分析。在优化条件下,6种全氟化合物在各自的线性范围内线性关系良好,检出限(S/N=3)为0.10～0.26 ng/L。添加500 ng/L 6种PFCs进行重复性实验,日内相对标准偏差(RSD)为2....     

高效液相色谱-串联质谱联用测定人血液中的全氟化合物

采用HPLC-ESI-MS/MS联用技术,建立了分析血样中9种全氟化合物(PFCs)的方法.以13C4标记的PFOS (MPFOS)作为内标物.以C18反相柱为分析柱,甲醇、醋酸铵为梯度洗脱淋洗液,9种分析物包括全氟己烷磺酸(PFHxS)、全氟庚酸(PFHpA)、全氟辛酸 (PFOA)、全氟辛烷磺酸(PFOS)、全氟壬酸(PFNA)、全氟癸酸(PFDA)、全氟十一酸(PFUnDA)、全氟十二酸(PFDoDA)和全氟十四酸(PFTA),在15 min内即可达到良好的分离.在血样前处理中,采用MTBE液-液萃取和固相萃取相结合的方法,进一步净化样品以延长色谱柱寿命;比较了4种固相萃取小柱对全氟化合物的萃取性能,最终选定HLB柱(Waters).本研究还讨论了两种C18反相柱Acclaim 120(50 mm×4.6 mm, 3 μm)和Acclaim120 (250 mm×4.6 mm, 5 μm)(Dionex) 对PFCs的分析性能,在本实验条件下,两种色谱柱具有相似的分离性能及检出限,线性范围在0.1～50 μg/L之间 (r≥0.9957);对于血液样品该方法的检出限在0.03～0.8 μg/L之间.本研究将该方法成功地应用于血样实际样品中全氟化合物的测定,加标回收除PFTA较低外,其它化合物均在74.2%～118.1%之间.     

牛奶、母乳中全氟化合物分析方法的研究

建立了HPLC-ESI-MS/MS联用技术测定奶制品中12种全氟化合物(PFCs)的方法.12种全氟化合物包括9种常见PFCs和2种调聚酸及一种全氟磺酰胺.对比了MTBE液-液萃取、甲酸、乙腈和甲醇萃取这4种萃取方法对12种全氟化合物的萃取和回收效果.最终选用甲醇作为萃取溶剂,并选取WAX作为固相萃取柱对萃取的溶液进行净化,方法对12种PFCs的加标回收在83.5%～113.3%之间,检出限0.005～0.092 μg/L.最后完成了对纯牛奶,早餐奶和母乳样品中12种PFCs的分析.     

牛奶中全氟烷基酸的简便萃取与定量研究

采用阴离子交换树脂和硅胶作为混合填料对牛奶中的全氟烷基酸进行固相萃取,并结合液相色谱质谱联用技术,建立了一种简便的牛奶中21种全氟烷基酸同时定量方法.在牛奶样中加入乙腈析出大量蛋白,萃取液在自制固相萃取小柱采用1.5 mL 80%乙腈水溶液进行洗脱纯化.对纯化液进行液相色谱质谱联用分析,分析条件如下:以乙腈-5 mmol的醋酸铵水溶液为流动相,在XDB-C 18色谱柱上进行梯度洗脱,采用电喷雾负离子模式电离(ESI),质量扫描模式为多反应监测(MRM)模式检测.方法中全氟烷基酸(PFAAs)的检出限为0.01~0.20 ng/mL,定量限为0.03~0.67 ng/mL,方法的线性关系(R2>0.999)和重现性均良好,回收率范围为66%~125%.对13种常见市售牛奶中全氟烷基酸进行分析,主要检出了7种全氟烷基酸,其牛奶质量浓度在2.43~12.00 ng/mL之间.     

固相萃取-超高效液相色谱-电喷雾串联质谱法同时测定地表水中16种全氟有机化合物

建立了固相萃取-超高效液相色谱-电喷雾串联三重四极杆质谱联用技术分析水中16种全氟有机化合物的高通量检测方法。样品经WAX固相萃取柱富集和净化后,采用Waters ACQUITY UPLC^TM BEH C₁₈色谱柱,含2 mmol/L乙酸铵的甲醇和含2 mmol/L乙酸铵的水作为流动相进行梯度洗脱,质谱采用电喷雾负离子电离,多反应监测模式检测。16种全氟有机化合物在0.5~100 μg/L或1.0~100 μg/L浓度范围内线性关系良好,相关系数为0.9987~0.9999,方法的检出限为0.06~0.46 ng/L;高、中、低3个添加水平的回收率为67.6%~103%,相对标准偏差为2.94%~12.0%。结果表明,该方法灵敏、准确且检测范围广,分析速度快,是一种适于实际水样中全氟有机化合物检测分析的方法。     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.