在线固相萃取-高效液相色谱法测定人体尿液中的N-乙酰-S-(N-甲基甲氨酰)半胱氨酸

建立了在线固相萃取-高效液相色谱法测定人体尿液中的N-乙酰-S-(N-甲基甲氨酰)半胱氨酸(AMCC)的分析方法。左泵以Amino Pac PA柱作为在线固相萃取柱、5 mmol/L KH2PO4溶液为流动相,将AMCC与样品基质分离;然后通过控制阀切换时间仅将含AMCC的部分样品溶液在线洗脱至Acclaim PAⅡC18分析柱上,右泵以0.1%H3PO4溶液(含5%乙腈)和乙腈为流动相对AMCC进行梯度洗脱分离和分析测定。结果表明,AMCC在1.0~100 mg/L范围内线性关系良好,相关系数r>0.999;上样量为10μL时,方法定量限为0.2 mg/L;回收率在85.9%~82.9%之间;相对标准偏差(n=6)分别为0.2%(保留时间)和4.0%(峰面积)。与传统的离线固相萃取-高效液相色谱法相比,本方法更为简便环保、高效稳定。用本方法测定了7份人体尿液,结果满意。     

在线固相萃取-离子色谱法测定4种芳环磺酸盐中的硫酸根离子

建立一种在线固相萃取-离子色谱测定4种芳环磺酸盐中硫酸根离子含量的新方法。将自装填的多孔石墨化碳固相萃取柱应用于离子色谱系统,对样品进行在线前处理。样品经过多孔石墨化碳固相萃取柱基体消除后进入收集环,通过阀切换方式使待测硫酸根离子转入阴离子分析柱和检测系统。固相萃取流路用1.5 mmol/L碳酸钠以0.8 mL/min的流速对基体在线富集,进样量为20μL,分析柱为SH-AC-3(250 mm×4.0 mm)+SH-AG-3(50 mm×4.0 mm)色谱柱,柱温为35℃,在6 mmol/L碳酸钠-4 mmol/L碳酸氢钠条件下等度洗脱,流速为0.8 mL/min。结果表明:硫酸根离子在0.50~20.00 mg/L范围内呈良好的线性关系,线性相关系数为0.998 3,保留时间、峰高和峰面积的相对标准偏差均在0.28%~2.86%之间,方法检出限为0.010 6 mg/L,回收率为91.01%~109.3%,具有良好的线性关系和重复性。整个在线分析过程在25 min之内完成。该方法进样量少、快速、高效。     

固相萃取-超高效液相色谱串联质谱法测定饮用水中15种邻苯二甲酸酯

建立了饮用水中15种邻苯二甲酸酯的固相萃取超高效液相色谱串联质谱测定方法。样品经C18固相萃取柱富集,以苯基柱分离,以甲醇和水为流动相进行梯度洗脱,正离子模式下质谱多反应监测(MRM)模式检测,外标法定量。结果表明,邻苯二甲酸二丁酯在0.63~1000μg/L,其余14种邻苯二甲酸酯在0.002~500μg/L范围内线性关系良好,相关系数均大于0.9970。本方法对15种邻苯二甲酸酯的定量限为2.2~632 ng/L,回收率在81.3%~109%之间,RSD<14%。     

在线固相萃取/液相色谱-串联质谱法检测饲料中5种喹噁啉药物残留量

建立了在线固相萃取/液相色谱-串联质谱法检测饲料中5种喹噁啉药物的方法。准确称取2 g饲料,用10 m L 0.1%盐酸-甲醇(1∶1)提取,提取液用0.2%甲酸稀释10倍,通过双三元液相色谱采用反相在线固相萃取柱在线富集净化,以0.2%甲酸与乙腈梯度洗脱,同时转移至C18色谱柱上进行分离,串联四极杆质谱检测。实验结果表明,5种喹噁啉药物在50~25 000μg/kg含量范围内线性良好(r0.999);方法的检出限为25μg/kg,定量下限为50μg/kg;方法回收率为72.6%~84.6%,批内和批间相对标准偏差(RSD)均小于10%。本方法较传统固相萃取柱净化法更简捷、经济和稳定。     

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。     

在线固相萃取-高效液相色谱检测饮料中5种食用合成色素

建立了同时测定饮料中5种食用合成色素的在线固相萃取-高效液相色谱-紫外检测(Online-SPE-HPLC-UV)方法。饮料样品用水稀释并经0.45μm微孔滤膜过滤后,在线固相萃取柱(Acclaim 120 C18)净化,反相C18分析柱分离,梯度洗脱,紫外检测器检测。结果表明:5种食用合成色素在0.5~20 mg/L浓度范围内线性关系良好,相关系数(r2)均大于0.999 9,检出限为0.02~0.08 mg/kg,3个水平下的加标回收率为94.5%~103.0%,相对标准偏差为0.4%~2.7%。该研究为快速准确地分离测定饮料中的食用合成色素提供了有效方法。     

在线固相萃取-高效液相色谱-串联质谱法同时检测大豆不同部位的4种植物激素

采用双三元液相色谱(Dual gradient liquid chromatography,DGLC)建立了在线固相萃取技术与电喷雾串联质谱联用方法(Online SPE DGLC-ESI MS/MS),并成功应用于实际样品检测。本方法同时检测大豆不同部位中的4种酸碱性植物激素(赤霉素(GA3)、吲哚乙酸(IAA)、玉米素(ZT)和脱落酸(ABA))。通过考察固相萃取富集柱、分析色谱柱、流动相对植物激素的保留和选择性的影响,获得较高的灵敏度、回收率、稳定性及精密度。大豆样品经液氮低温研磨,以80%甲醇溶液提取,再经离心稀释过滤后,进样分析。进样后样品经在线固相萃取Hypersep Retain AX柱洗脱保留,目标分析物依次转移至分析柱Acclaim PA2色谱柱,并以0.1%甲酸和甲醇溶液作为流动相进行梯度洗脱,采用选择反应监测离子模式(SRM)同时采集正负离子通道进行定性分析,基质标准曲线外标法进行定量分析,GA3,IAA,ZT在0.1~50μg/L范围内线性良好,检出限为0.0002μg/g;ABA在0.5~50μg/L的范围内线性良好,其检出限为0.0010μg/g。以0.8,4.0和40μg/L分别为低、中、高浓度考察4种植物激素的回收率为76.1%~93.5%,RSD为0.8%~6.0%。结果表明,籽粒中含有的ABA浓度明显高于其它部位。本研究为快速准确地分离和测定大豆不同部位内源激素提供了有效方法。     

硅胶固相萃取净化/高效液相色谱-串联质谱法测定海洋生物体中六溴环十二烷

建立了海洋生物体中六溴环十二烷(HBCDs)的硅胶固相萃取净化/液相色谱-串联质谱法。样品采用正己烷提取,经硅胶固相萃取柱净化,液相色谱-串联质谱分析。根据硅胶固相萃取柱的使用特性,对洗脱条件进行优化。在ACQUITY UPLC BEH C18色谱柱上进行分离,流动相为水和甲醇乙腈(V甲醇∶V乙腈=4∶6)混合溶液,梯度洗脱。质谱采用电喷雾负离子电离,多反应监测模式,内标法定量。六溴环十二烷在0.50~100.0μg/L范围内线性关系良好,相关系数(r2)大于0.995,定量下限为0.20μg/kg,回收率为85.6%~97.3%,相对标准偏差为3.9%~8.8%。该方法基质干扰小、重复性好,适用于海洋生物中六溴环十二烷的测定。     

在线固相萃取净化-液相色谱-串联质谱法测定猪肉中10种大环内酯类抗生素

建立了在线固相萃取净化-液相色谱-串联质谱检测猪肉中10种大环内酯类抗生素残留的方法。样品经过乙腈提取,提取液40℃旋蒸至干后,分析物用2 mL磷酸盐缓冲液溶解,溶解液经在线固相萃取柱(HLB柱)富集净化,甲醇洗脱,然后转移至XBridge BEH C18色谱柱上,以10 mmol/L乙酸铵水溶液和乙腈溶液为流动相进行分离,最后用串联四极杆质谱检测。结果表明,10种大环内酯类抗生素在0.1~200μg/L范围内呈现良好的线性关系,相关系数均大于0.990。方法的检出限范围为0.05~0.30μg/kg,定量限范围为0.10~1.00μg/kg;添加水平为0.10~10.0μg/kg时,方法回收率为69.6%~115.2%,相对标准偏差(RSD)10%。该方法可以作为猪肉中大环内酯类抗生素的检测方法。     

基质校正固相萃取液相色谱-串联质谱法测定食用菌中22种农药残留

选择氨基柱为固相萃取净化柱,以电喷雾(ESI)为离子源,正负离子切换多级反应离子检测(MRM)方式,建立了基质校正固相萃取液相色谱-串联质谱法(LC-MS/MS)测定食用菌中22种农药残留的分析方法。研究了不同固相萃取柱和洗脱剂对农药保留行为的影响,优化了净化方法、色谱分离条件和质谱条件。研究了平菇、香菇、杏鲍菇和蟹味菇的基质效应。22种农药在0.05～100μg/L(或0.1～200μg/L)范围内线性相关,相关系数为0.9874～0.9997,方法定量限为0.031～1.76μg/kg。除甲基硫菌灵和克螨特外,20种农药在4种食用菌中3个添加浓度的回收率在54.6%～128.0%,RSD为0.3%～29.0%之间,方法灵敏度高,选择性强。     

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.     

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.     

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.     

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.     

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.