加速溶剂-固相萃取-高效液相色谱法测定土壤及蚯蚓样品中多环芳烃

研究了加速溶剂萃取( ASE)、固相萃取柱净化( SPE)、高效液相色谱( HPLC)联合( ASE-SPE-HPLC)测定土壤及蚯蚓样品中7种多环芳烃(PAHs)的分析方法,确定了以正己烷-丙酮(4∶1, V/V)作为萃取剂,用ASE对土壤及蚯蚓进行萃取,提取液经SPE柱净化(土壤样品用硅胶柱净化,蚯蚓样品用 Al2 O3-硅胶柱净化),正己烷-二氯甲烷(9∶1, V/V)进行洗脱,洗脱体积为10 mL,旋转浓缩蒸干后,乙腈定容,过0.22μm有机滤膜,最后用HPLC对提取液中7种PAHs进行定量的分析方法。土壤样品方法回收率在83.5%~110.2%之间,相对标准偏差为1.0%~4.6%;蚯蚓样品回收率在81.2%~97.1%之间,相对标准偏差为1.6%~4.2%。方法检出限为0.15~0.85μg/kg,且重现性好。可满足样品分析的质量控制要求,表明本分析方法具有良好的准确性与可靠性。     

快速溶剂萃取-气相色谱-质谱法测定土壤中24种半挥发性有机物含量

采用快速溶剂萃取-气相色谱-质谱法测定土壤中24种半挥发性有机物的含量。土壤样品以正己烷-乙酸乙酯(5+1)混合液进行萃取,所得萃取物用弗罗里硅土固相萃取小柱净化。在气相色谱分离中用DB-5MS色谱柱为固定相,在质谱分析中采用选择离子监测模式。24种半挥发性有机物在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限在0.83~4.48μg·kg~(-1)之间,测定下限在3.32~15.8μg·kg~(-1)之间。以空白样品为基体进行加标回收试验,所得回收率在60.4%~123%之间。测定值的相对标准偏差(n=4)在5.2%~19%之间。     

加速溶剂萃取-凝胶渗透色谱法净化-气相色谱-串联质谱法测定农作物土壤中5种有机磷类农药的残留量北大核心CSCD

提出了加速溶剂萃取(ASE)-凝胶渗透色谱法(GPC)净化-气相色谱-串联质谱法(GC-MS/MS)测定农作物土壤中甲基内吸磷、辛硫磷、蝇毒磷、灭线磷和二溴磷等5种有机磷类农药残留量的方法。随机采集农作物土壤样品,去除大颗粒杂质,自然风干,用粉碎机粉碎,过0.3 mm筛网。称取过筛后的土壤样品10 g于加速溶剂萃取池中,加入硅藻土12 g,以体积比为1∶1的丙酮-正己烷混合液为萃取剂,采用ASE反复萃取3次;将收集到的萃取液转移至GPC净化瓶中,经GPC浓缩净化并氮吹至近干,用1 mL甲醇溶解,0.45μm滤膜过滤,滤液供GC-MS/MS分析,外标法定量。结果显示:5种农药的质量浓度在0.02~10.00 mg·L^(-1)内与其对应的峰面积呈线性关系,检出限(3S/N)为1.6~3.2μg·kg^(-1);对阴性样品进行3个浓度水平的加标回收试验,5种农药的回收率为90.0%~101%;对6份阴性样品的加标溶液进行测定,5种农药测定值的相对标准偏差为2.8%~4.2%;方法用于实际农作物土壤样品分析,甲基内吸磷、辛硫磷、灭线磷均被不同程度地检出。     

快速溶剂萃取-气相色谱-串联质谱法测定血中12种催眠类药物

提出了气相色谱-串联质谱法测定血液中12种催眠类药物含量的方法。样品以乙酸乙酯-环己烷-丙酮(2+2+1)混合液为萃取剂,使用氧化铝吸附剂达到在线净化的效果,经快速溶剂萃取仪提取后,提取液用氮气吹干,用甲醇0.5mL溶解,通过VF-5MS色谱柱分离,采用电子轰击离子源多反应监测模式进行测定。12种催眠类药物的质量浓度与其峰面积均在50.0~1 000μg·L-1之间呈线性关系,测定下限(10S/N)在0.02~4.7μg·L-1之间。加标回收率在65.4%~98.2%之间,测定值的相对标准偏差在0.9%~14.8%之间。     

固相萃取-在线凝胶渗透色谱-气相色谱-质谱法测定豆芽中53种农药残留量

采用固相萃取-在线凝胶渗透色谱-气相色谱-质谱法测定豆芽中53种农药残留量。豆芽样品以乙酸-乙腈(1+99)混合液提取,固相萃取小柱净化,采用在线凝胶渗透色谱-气相色谱分离,在质谱分析中采用选择离子监测模式。53种农药的质量浓度均在0.01~1.0mg·L-1范围内与其峰面积呈线性关系,方法的检出限在0.1~6.0μg·kg-1之间。在20,50,100μg·kg-1等3个浓度水平进行加标回收试验,回收率在72.3%~104%之间,测定值的相对标准偏差(n=6)在1.6%~6.6%之间。     

超声萃取-气相色谱法测定土壤中石油烃

采用探头式超声波发生器萃取-气相色谱-火焰离子检测法(GC-FID)测定土壤中33种石油烃(C8~C40)。采用正交试验考察了萃取剂及其用量、超声时间和萃取次数等4个因素对土壤中石油烃的萃取效果的影响,得到最佳萃取条件为:10.00g样品用30mL二氯甲烷超声萃取10min,萃取2次。33种石油烃的线性范围在500mg·L~(-1)内,检出限(3s)为0.10~0.40mg·L~(-1)。加标回收率为83.2%~106%,测定值的相对标准偏差(n=7)为0.80%~5.5%。     

在线净化加速溶剂萃取–气相色谱–质谱法测定土壤中11种半挥发性有机物

采用加速溶剂萃取法对样品进行在线净化和萃取,气相色谱–质谱法测定土壤中11种半挥发性有机物.考察了净化条件、萃取剂、浓缩条件等因素对土壤中11种半挥发性有机物测定的影响,分析了在线净化和离线净化的差异以及在线净化的优势.以弗罗里硅土和石墨化碳黑为净化剂,石英砂为分散剂,土壤样品经快速溶剂萃取仪在线净化萃取,浓缩后采用气...     

加速溶剂萃取-气相色谱法测定岩石中痕量正构烷烃(C21~C40)

建立了气相色谱法结合加速溶剂萃取技术测定岩石中痕量正构烷烃(C21~C40)的方法,对比了超声波萃取、加速溶剂萃取及索氏萃取3种提取方式,研究了提取溶剂及净化方式对正构烷烃测定的影响。实验结果表明:以丙酮-二氯甲烷(1∶1,V/V)为萃取剂,使用硅胶和中性氧化铝进行净化,各物质标准曲线相关系数均大于0.999,检出限为0.01~0.09μg/kg,对3个浓度的空白加标样进行回收实验和精密度实验,回收率在70.7%~91.7%之间,相对标准偏差(RSD)为1.8%~13%。方法可用于实际岩石样品中痕量正构烷烃的测定。     

超声萃取-气相色谱/质谱法同时测定土壤中3种季胺盐化合物

建立了超声萃取-气相色谱/质谱法同时测定土壤中3种典型季胺盐化合物十二烷基三甲基氯化胺(DTAC)、十六烷基三甲基溴化胺(CTAB)、双十二烷基二甲基氯化胺(DDAC)的分析方法。采用电子轰击(EI)-选择离子检测(SIM)进行定量分析,特征离子为m/z 58,212。考察了萃取剂种类、辅助萃取剂直链烷基苯磺酸(LAS)浓度、萃取剂pH值(0.5~7.0)、萃取次数(1,2,3)以及净化柱成分对萃取效率的影响。最佳萃取条件为,以甲醇为萃取剂,以HCl调至pH 3.5,LAS浓度为40μg/L,超声萃取2次,每次10 mL甲醇,20 min,萃取液采用中性氧化铝柱净化。3种目标化合物的线性范围在0.02~2.0 mg/L之间;方法检出限为1.2~4.5μg/kg。以此方法测定南方某矿区尾矿渣及周边水稻土、赤红壤等样品,目标化合物的含量在0.24~0.41 mg/kg之间,不同加标水平(0.2,0.5和1.0 mg/kg)回收率在76%~113%之间,相对标准偏差在1.1%~12.9%之间。     

在线固相萃取-液相色谱-串联质谱法测定动物源食品中阿维菌素和伊维菌素的残留量

利用在线固相萃取系统,通过萃取柱的选择和在线洗脱条件的优化,建立了测定动物源食品中阿维菌素和伊维菌素残留量的在线固相萃取-液相色谱-串联质谱法。2.50g样品经5mL乙腈和5mL的0.15%(体积分数)三乙胺溶液提取,采用HySphere C_(18) HD固相萃取柱对提取液进行在线净化。分析物经ZORBAX SB-C_(18)色谱柱(2.1mm×15mm,1.8μm)分离,采用乙腈和含0.2%(体积分数)甲酸的10mmol·L~(-1)乙酸铵溶液进行梯度洗脱。质谱分析采用电喷雾正离子源和多反应监测模式。阿维菌素和伊维菌素的质量浓度在10μg·L~(-1)内与峰面积呈线性关系,测定下限(10S/N)均为5.0μg·kg~(-1)。在猪肉、牛肉和香肠样品中进行加标回收试验,阿维菌素和伊维菌素的加标回收率在74.8%~96.5%之间,测定值的相对标准偏差(n=6)不大于11%。     

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.     

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.     

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.