QuEChERS-UHPLC-MS/MS法测定烟草中硝苯菌酯EI北大核心CSCD

建立了Qu ECh ERS-UPLC-MS/MS测定烟草中硝苯菌酯(2,4-DNOPC)残留的方法。烟草样品采用改进的Qu ECh ERS技术提取,在碱性条件下超声水解后进样分析,采用负离子多反应监测(MRM)模式检测,通过测定2,4-DNOPC相应的水解产物2,4-二硝基-6-(1-甲基庚基)苯酚(2,4-DNOP)来计算烟草中硝苯菌酯残留量。结果表明,2,4-DNOPC质量浓度在0.001~0.5 mg/L范围线性关系良好,相关系数(r2)大于0.999,检出限为3μg/kg,2,4-DNOPC在烟草中的回收率为92.4%~100.5%,RSD为2.5%~3.3%。方法适用于烟草中硝苯菌酯残留量的检测。     

QuEChERS-UHPLC-MS/MS法测定烟草中硝苯菌酯

建立了Qu ECh ERS-UPLC-MS/MS测定烟草中硝苯菌酯(2,4-DNOPC)残留的方法。烟草样品采用改进的Qu ECh ERS技术提取,在碱性条件下超声水解后进样分析,采用负离子多反应监测(MRM)模式检测,通过测定2,4-DNOPC相应的水解产物2,4-二硝基-6-(1-甲基庚基)苯酚(2,4-DNOP)来计算烟草中硝苯菌酯残留量。结果表明,2,4-DNOPC质量浓度在0.001~0.5 mg/L范围线性关系良好,相关系数(r2)大于0.999,检出限为3μg/kg,2,4-DNOPC在烟草中的回收率为92.4%~100.5%,RSD为2.5%~3.3%。方法适用于烟草中硝苯菌酯残留量的检测。     

多壁碳纳米管作为吸附剂的QuEChERS-气相色谱-四极杆飞行时间质谱快速筛查淡水产品中145种农药残留

建立了基于多壁碳纳米管(MWCNTs)的新型Qu ECh ERS前处理方法,结合气相色谱-高分辨飞行时间质谱对淡水产品中145种农药残留进行快速筛查。样品采用水和乙腈提取,以MWCNTs为净化吸附剂,用Qu ECh ERS方法处理后,采用气相色谱-四极杆飞行时间质谱(GC-QTOF/MS)检测,外标法定量。研究并优化了提取条件、吸附剂种类及用量、GC-QTOF/MS采集速率及质量提取窗口。在最佳实验条件下,145种农药在5~200μg/kg范围内线性关系良好(r20.98),10,20,100μg/kg 3个添加水平下的回收率为69.4%~114.2%,相对标准偏差(RSD,n=6)为2.2%~13.8%,定量下限为1.1~40.0μg/kg。与传统Qu ECh ERS方法相比,所建立的方法快速、准确,净化效果明显,可显著降低基质干扰。     

气相色谱-质谱法快速检测出口蔬菜中16种保鲜剂残留

采用分散固相萃取(Qu ECh ERS)前处理方法结合气相色谱-质谱法(GC-MS)建立出口蔬菜中16种保鲜剂残留量的快速检测方法。以叶菜类、茄果类、豆类、瓜类和块茎类出口蔬菜为原料,样品经乙腈提取,Qu ECh ERS除杂净化,用GC-MS外标法进行定量分析。16种保鲜剂在0.02~2.0 mg/L范围内线性关系良好,相关系数为0.9990~0.9997,检出限(LOD,S/N=3)在0.004~0.965μg/kg范围内。以0.01,0.02和1.0 mg/kg添加浓度水平进行方法学验证,回收率为76.7%~120.0%,相对标准偏差为2.1%~10.6%。与国标GB/T 19648-2006等方法相比,本方法具有快速、简便、灵敏度高等特点,能满足出口蔬菜中16种保鲜剂残留的检测要求。     

改良的QuEChERS样本前处理/高效液相色谱-串联质谱法检测猪肉中四环素类兽药的残留

采用Agilent公司的增强型脂质去除产品Bond Elut EMR-Lipid,建立了针对猪肉中四环素类药物残留的更快更高效的Qu ECh ERS样品前处理方法。样品经酸化乙腈提取,Bond Elut EMR-Lipid Qu ECh ERS净化后,采用HPLC-MS/MS检测,方法检出限可达5.0μg/kg;四环素、金霉素和强力霉素的回收率为75.6%~89.4%,土霉素的回收率为53.4%~61.0%,相对标准偏差均不大于7.7%。     

QuEChERS-超高效液相色谱-串联质谱法测定荨麻提取物中17种氨基甲酸酯类农药残留量

采用Qu ECh ERS-超高液相色谱-串联质谱技术,建立了荨麻提取物中17种常见的氨基甲酸酯类农药残留量的检测方法。样品用含1%甲酸的乙腈提取,Qu ECh ERS法净化,电喷雾正离子(ESI+)模式电离,多反应监测模式检测,基质匹配标准曲线法定量。17种氨基甲酸酯农药在2.5~50μg/L线性关系良好,相关系数均大于0.9920,加标浓度为10,20,50μg/kg,平均回收率在65.3%~119.2%,相对标准偏差(RSD)均低于11%,检出限在0.12~1.7μg/kg。方法适用于荨麻等植物提取物中氨基甲酸酯类农药残留量的测定。     

SPE和QuEChERS前处理方法结合LC-Q-TOF/MS检测苹果和番茄中282种农药残留对比研究

利用液相色谱-四极杆/飞行时间质谱(LC-Q-TOF/MS)对比研究了固相萃取(SPE)和Qu ECh ERS两种前处理方法在282种农药残留检测上的效果。以苹果和番茄为基质,分别从基质效应、回收率、重复性、线性关系、检出限和定量限等方面进行了考察与比较。SPE法和Qu ECh ERS法在苹果中呈现出弱基质效应的农药占比分别为87.2%和57.1%,在番茄中为65.6%和42.2%。与SPE相比,Qu ECh ERS法干扰物较多,基质效应较强;在5.0μg/kg添加水平下(n=5),SPE和Qu ECh ERS在苹果中平均回收率在70%~120%的农药占比分别为99.3%和86.9%,在番茄中为92.9%和87.9%;在5.0μg/kg添加水平下(n=5),SPE和Qu ECh ERS在苹果中重复性相对标准偏差(RSD)20%(n=5)农药占比分别为98.9%和86.5%,在番茄中为92.9%和87.6%;SPE和Qu ECh ERS两种方法在苹果中定量限≤10μg/kg的农药占比为100.0%和96.1%,在番茄中为100.0%和98.9%。两种前处理方法均能与高分辨质谱技术相结合并应用于果蔬农药残留的日常检测中,其中SPE净化效果较优,定量更为准确,但步骤稍显繁琐费时,而Qu ECh ERS方法简单快速,故在检测时可根据不同需要进行选择。     

液相色谱-串联质谱法测定土壤中19种氨基甲酸酯类农药

建立了液相色谱-串联质谱法(HPLC-MS/MS)快速测定土壤中的19种氨基甲酸酯农药残留。土壤样品用含1%乙酸的乙腈溶液(V/V)提取后,经Qu ECh ERS方法纯化处理,过0.22μm滤膜,以乙腈和含0.1%甲酸的5 mmol/L乙酸铵水溶液为流动相,经Eclipse Plus C18色谱柱(3.0 mm×100 mm,1.8μm)分离,多级反应监测(M RM)正离子模式下扫描分析。结果表明,19种氨基甲酸酯农药在0.5~200μg/L范围呈良好线性,线性相关系数均大于0.99,定量限为2.0~10.0μg/kg。样品在定量限1倍、2倍和10倍3个加标水平下的平均回收率为75.4%~94.8%,相对标准偏差(RSD)为3.5%~15%。方法可用于土壤中19种氨基甲酸酯农药的检测分析。     

改进的QuEChERS方法结合气相色谱串联质谱检测韭菜中的多种农药残留

采用改进的Qu ECh ERS方法结合气相色谱串联质谱(GC-MS/MS)检测韭菜中的多种农药残留。样品经含1%乙酸的乙腈匀质提取,采用分散固相萃取剂净化,在GC-MS/MS多反应监测(MRM)模式下进行测定。对Qu ECh ERS方法的提取和净化条件进行了优化。在优化条件下,44种农药残留在10~500μg/kg范围内呈良好线性关系,相关系数的平方(R~2)在0.9971~0.9999之间。在10μg/kg和100μg/kg添加水平下,44种农药的平均回收率为91.5%~119.6%,日内日间相对标准偏差小于14.1%。将所建立的方法用于实际样品的分析中,取得了较好的效果。     

QuEChERS/高效液相色谱法测定棉花田中吡草醚及其代谢物的残留量

建立了棉花植株、棉籽和土壤样品中吡草醚及其主要代谢物E-1的Qu ECh ERS/高效液相色谱-可变波长紫外检测器(HPLC/VWD)检测方法。样品用乙腈-水混合溶液提取,Qu ECh ERS方法净化,以Ultimate XB-C18色谱柱(250 mm×4.6 mm,5μm)进行HPLC分离,检测波长为246 nm,基质匹配标准品外标法定量。结果表明:吡草醚和E-1在0.01~1.0 mg/L质量浓度范围内呈良好线性关系(r20.999)。在棉花植株、棉籽和土壤中分别进行3个浓度的加标回收实验,吡草醚和E-1在样品中的平均回收率分别为83.5%~106.3%和74.9%~102.3%,相对标准偏差(RSD,n=5)分别为0.5%~5.2%和1.6%~19.2%。吡草醚和E-1的检出限(LOD,S/N3)均为0.1 ng,在棉花植株和棉籽中的定量下限(LOQ)均为0.04 mg/kg,在土壤中的LOQ均为0.02 mg/kg。该方法前处理快速、简单、经济,可用于常规实验室棉花植株、棉籽和土壤样品中吡草醚及其代谢物E-1的残留检测。     

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.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

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.     

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.