吹扫捕集-气相色谱-质谱法测定土壤中28种挥发性有机化合物的含量北大核心CSCD

以甲醇为提取剂,提出了吹扫捕集-气相色谱-质谱法测定土壤中28种挥发性有机化合物(VOCs)含量的方法。称取土壤样品5.0 g,加入甲醇10 mL,振荡静置后吸取250μL提取液至吹扫瓶中,加入一定量的混合内标溶液,用水定容至10 mL,其中内标质量浓度为10μg·L^(-1)。结果显示:28种VOCs标准曲线的线性范围均为1~100μg·L^(-1),检出限为7.4~15.2μg·kg^(-1);对空白样品进行加标回收试验,回收率为79.8%~108%,测定值的相对标准偏差(n=6)为1.9%~12%。方法用于两份实际土壤样品分析,三氯甲烷的测定值为22.6 mg·kg^(-1)和24.0 mg·kg^(-1),其余27种VOCs均未检出。     

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。     

茶叶中29种挥发性有机物的固相微萃取-气相色谱-质谱法测定及其危害水平评估

建立了固相微萃取-气相色谱-质谱法(SPME-GC-MS)测定茶叶中29种挥发性有机物(VOCs)含量的方法,并对随机选择的100个茶叶样品进行了危害水平评估。在顶空进样瓶中加入茶叶样品和内标物乙酸苯乙酯,采用纤维头DVB/CAR/PDMS在平衡温度60℃下吸附目标化合物30 min,解吸后不分流进样,以HP-FFAP色谱柱为固定相在程序升温条件下分离,分离得到的目标化合物进入配有电子轰击离子(EI)源的质谱仪,在选择离子监测(SIM)模式下进行测定,内标法定量。采用食品安全指数(IFS)评价茶叶中VOCs的危害水平。结果显示:29种VOCs的质量分数在0.05～0.50 mg·kg~(-1)内和内标物的质量分数之比与两者对应的峰面积之比呈线性关系,检出限(3S/N)为0.001 6～0.031 6 mg·kg~(-1);对实际样品进行加标回收试验,所得回收率为74.4%～86.6%,测定值的相对标准偏差(n=6)为2.4%～8.9%;100份茶叶样品中均有VOCs的检出,VOCs总检出量为0.035～0.113 mg·kg~(-1),所得的IFS最大值为2.79×10~(-3),远低于1,说明茶叶中的VOCs对人体潜在危害水平是可以接受的。     

同位素稀释气相色谱-质谱法快速测定酱油中3-氯-1,2-丙二醇量

采用同位素稀释气相色谱-质谱联用(GC-MS)法,快速测定酱油中3-氯-1,2-丙二醇(3-MCPD)的含量。试样中加入3-氯-1,2-丙二醇的氘代同位素作为内标,经超声混匀后加入到自行填装的弗罗里硅土柱中,以乙醚洗脱,洗脱液经氮气吹干后在正己烷溶剂中进行衍生化,衍生化试剂采用七氟丁酰咪唑。GC-MS采用选择离子监测(SIM)模式进行定性定量分析。结果表明,本方法的添加回收率为95.0%~101.0%;相对标准偏差为3.2%~4.8%;检出限达到0.010mg/kg。本方法步骤简单,溶剂用量少,定性定量准确可靠。可快速测定酱油等调味品中3-氯-1,2-丙二醇的含量。     

同位素稀释-气相色谱-质谱法测定白酒中23种邻苯二甲酸酯类化合物

提出了同位素稀释-气相色谱-质谱法测定白酒中23种邻苯二甲酸酯类化合物含量的方法。样品用正己烷-乙酸乙酯(1+1)混合液提取后,经DB-5MS毛细管色谱柱分离,采用电子轰击离子源选择离子反应监测模式进行质谱测定,同位素内标法进行定量分析。23种邻苯二甲酸酯类化合物的线性范围在0.2~3.0mg·L-1之间,测定下限(10S/N)在0.05~0.1mg·kg-1之间。加标回收率在73.2%~122%之间,相对标准偏差(n=6)在0.49%~11%之间。     

电感耦合等离子体质谱法测定烟用接装纸中砷时内标法和标准加入法的比较

对内标法和标准加入法在电感耦合等离子体质谱法测定烟用接装纸中砷含量的效果进行了比较研究。内标法的检出限为11.10ng·L-1,相对标准偏差(n=6)为3.4%,加标回收率在94.3%~104%之间;标准加入法的检出限为14.70ng·L-1,相对标准偏差(n=6)为3.2%,加标回收率在91.4%~98.2%之间。配对T检验结果表明,两种不同分析方法测定的实际样品结果间无显著性差异。当待测样品中纸张添加剂成分较为简单时,宜采用内标法进行测定;当基体较为复杂,尤其当施加二氧化钛和云母混合物的烟用接装纸样品时,宜采用匹配基体效果更好的标准加入法。     

同位素稀释-气相色谱-串联质谱法测定植物油中的15种欧盟优控多环芳烃

建立了凝胶渗透色谱(GPC)净化、气相色谱-串联质谱(GC-MS/MS)同时测定植物油中15种欧盟优控多环芳烃(PAHs)残留的分析方法。植物油样品加入同位素内标混合溶液后经乙腈-丙酮(体积比为60:40)混合提取、GPC净化,GCMS/MS采用选择反应监测模式(SRM)采集数据后进行定性/定量分析;优化了影响分析结果的仪器条件。采用内标法定量,植物油样品中添加回收率在70.3%~123.5%之间,相对标准偏差为1.5%~9.9%,定量限为0.276~0.436μg/kg,相关系数均大于0.9985。     

高效液相色谱-串联质谱内标法测定乳品中左旋肉碱含量

建立了高效液相色谱-串联质谱内标法测定乳品中左旋肉碱含量的方法。样品经0.1 mol/L HCl溶解,采用乙腈溶液沉淀蛋白,以HILIC色谱柱分离待测物,采用鞘流电喷雾离子化,正离子多反应监测模式(MRM)检测,内标法定量。在3个加标水平下,左旋肉碱的平均加标回收率为85.2%~102.0%,相对标准偏差(RSD,n=6)为7.6%~14.3%,方法检出限(LOD)为50μg/kg,定量下限(LOQ)为200μg/kg。运用该方法对20个乳品样品中的左旋肉碱含量进行测定,检出含量为68~165 mg/kg,与样品标签的符合率达95%。该方法快速、简便、准确,适用于乳品中左旋肉碱含量的测定。     

超高效液相色谱-串联质谱内标法同时测定地表水中7种微囊藻毒素

建立了超高效液相色谱-串联质谱(UPLC-MS/MS)内标法同时测定地表水中7种微囊藻毒素。样品经0.22μm滤膜过滤后直接进样分析,采用亮氨酸脑啡肽作为内标物,7种目标物在相应浓度范围内线性相关系数在0.997以上,方法检出限为0.143~0.468μg/L;在3个添加浓度水平下的回收率为88.1%~104.0%,相对标准偏差为2.15%~7.63%。7种微囊藻毒素在4min内即可完成含量的测定。该方法快速、简便、重复性好,满足日常对微囊藻毒素检测的要求,适合藻毒素污染的应急突发事件的快速定性定量测定。     

气相色谱-串联质谱法测定卷烟滤嘴中18种邻苯二甲酸酯的含量

取2支卷烟滤嘴称重,经水20mL浸润之后,加入乙醇20mL和10.0g·L~(-1)内标溶液50μL,超声提取30min,取上清液2mL经正己烷5mL萃取,所得溶液采用气相色谱-串联质谱法(GC-MS/MS)测定其中18种邻苯二甲酸酯的含量,内标法定量。质谱分析中采用电子轰击离子源和多反应监测模式。18种邻苯二甲酸酯的线性范围均为0.20~10mg·L~(-1),检出限(3S/N)为0.03~0.50 mg·kg~(-1)。按标准加入法进行回收试验,回收率为86.8%~107%,相对标准偏差(n=6)均小于7.0%。     

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.     

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.     

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.     

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.