气相色谱-三重四极杆串联质谱结合QuEChERS测定三七中有机磷农药残留

建立了改良的QuEChERS样品前处理法,结合气相色谱-三重四极杆串联质谱(GC-MS/MS)同时测定三七中18种有机磷农药残留的方法。样品经1%乙酸-乙腈提取,改良QuEChERS技术净化,利用GC-MS/MS采取多反应离子监测模式测定,基质匹配校准曲线外标法定量。18种有机磷农药残留在2.5~120.0μg/kg范围内线性良好,相关系数(R2)大于0.99;检出限为0.4~1.5μg/kg,定量限为0.8~2.5μg/kg。在3个加标水平(2.5,8.0,60.0μg/kg)下平均回收率为70.5%~118.9%,相对标准偏差为1.0%~9.8%。     

气相色谱-串联质谱法测定茶叶中83种农药残留

建立了气相色谱-串联质谱(GC-MS/MS)测定茶叶中83种农药残留的测定方法。茶叶样品经超纯水浸泡,用正己烷提取,过石墨化炭固相萃取小柱净化,待测农药在气相色谱-串联质谱(GC-MS/MS)上测定,用保留时间和特征离子对定性,外标法定量。在最佳的仪器条件下,待测农药在5～500μg/L线性关系良好,定量离子对的相关系数大于0.999,待测农药的检出限LOD(S/N=3)为2～20μg/kg,定量限LOQ(S/N>10)为5～50μg/kg。在空白茶叶样品中添加83种农药,添加水平分别为50、100、500μg/kg时,回收率范围在70.0%～110.0%,相对标准偏差(RSD)范围为3.2%～11.6%。对实际样品检测结果表明,大部分茶叶均有农药残留检出,主要为戊唑醇、溴虫腈、联苯菊酯、氯氟氰菊酯、氯氰菊酯、苯醚甲环唑、溴氰菊酯、唑虫酰胺,检出浓度集中在10～1 000μg/kg。该方法不但可以有效降低基线,减少杂峰的干扰,而且简单、灵敏、稳定,方法灵敏度满足国内外农药残留监测限量标准要求。     

加速溶剂萃取结合气相色谱-三重四极杆质谱测定枸杞中有机磷农药多残留

建立了加速溶剂萃取与气相色谱-三重四极杆质谱联用(GC-MS/MS)法对枸杞中20种有机磷农药残留进行测定。样品经酸化乙腈-二氯甲烷(体积比4∶1)提取,Cleanert TPH固相萃取柱净化,旋转蒸发浓缩后氮吹至干,采用GC-MS/MS检测,并对萃取溶剂、温度、冲洗体积等实验条件进行了优化。结果表明,20种药物在1～500μg/kg范围内线性良好,相关系数(r~2)为0.999 0～0.999 8;在20、40、100μg/kg 3个加标水平下的回收率为70.0%～82.9%,相对标准偏差(RSD,n=5)为0.6%～8.5%,定量下限为1～15μg/kg。该方法样品前处理简单、定量准确,适用于枸杞中有机磷农药残留的检测。     

蔬菜、水果中16种有机磷类农药多残留GC-MS分析

建立了蔬菜、水果中16种农药的气相色谱-离子阱质谱多残留检测方法。采用乙腈作为提取剂,经过Florisil柱净化,用ITQ700气相色谱-离子阱质谱联用仪进行分析。以保留时间和特征离子定性、峰面积定量,确定了16种有机磷农药的线性回归方程、相关系数及最低检出限。结果表明,16种有机磷农药线性关系良好。农药添加浓度为0.5μg/mL,回收率为70%～120%,相对标准偏差20%,最低检出限在0.0012～0.02μg/g之间,符合农药多残留检测要求。此方法具有良好的回收率、精确度和准确度,干扰少,可用于实际检测。     

气相色谱-串联质谱法同时测定白芍中10种有机磷农药残留

建立了同时测定中药白芍中10种有机磷农药残留含量的气相色谱–串联质谱方法。样品用乙腈超声提取,提取液经凝胶渗透色谱净化后,以VF–5毛细管色谱柱(30 mm×0.25 mm,0.25μm)分离,串联四极杆质谱仪为检测器进行定性、定量分析。10种有机磷农药残留的检出限为0.02～4.0 mg/kg,实际样品的加标回收率为75%～105%,相对标准偏差为4%～10%。该方法能够满足白芍中有机磷农药残留的定性、定量检测要求。     

固相萃取净化-气相色谱/串联质谱法测定茶叶中54种农药残留量

建立了固相萃取净化-气相色谱/串联质谱(SPE-GC-MS/MS)分析茶叶中54种农药残留的方法。样品用乙睛提取,提取液经石墨化炭黑/氨基固相萃取柱净化后,采用气相色谱-串联质谱方法在分时段选择反应监测模式下进行测定,外标法定量。当54种农药加标水平为10、50、100μg/kg时,回收率为60%～150%,方法的相对标准偏差小于16%;定量限(LOQ)均小于10μg/kg;在20～320μg/L范围内线性关系良好。方法已用于同时检测茶叶中农药多残留。     

土壤中多种有机磷及氨基甲酸酯类农药残留量的气相色谱-质谱法测定

建立了气相色谱-质谱法测定土壤中12种有机磷和氨基甲酸酯类农药残留分析方法。以丙酮-石油醚(4∶1,V/V)为提取剂,采用超声波提取土壤中农药残留,经弗罗里土层析柱净化,气相色谱-质谱(选择离子模式)法同时测定了土壤中多种有机磷和氨基甲酸酯类农药。该法对0.1μg/mL和0.5μg/mL两个浓度添加水平的回收率分别为70.1%~119.0%和78.1%~119.1%,相对标准偏差分别为6.30%~9.80%和5.20%~8.23%。     

羟基化多壁碳纳米管分散固相萃取-气相色谱-质谱法测定茶叶中21种有机磷农药

建立了用羟基化多壁碳纳米管(MWCNTs-OH)、N-丙基乙二胺键合固相吸附剂(PSA)和MgSO₄作为吸附剂的改进QuEChERS-气相色谱-质谱快速检测茶叶中21种有机磷农药的方法。茶叶中残留的农药经正己烷-丙酮(2 : 1, v/v)混合溶剂提取,以MWCNTs-OH、PSA和MgSO₄去除杂质,离心、过滤后经气相色谱-电子轰击源质谱测定,外标法定量。结果表明,目标化合物在0.01~0.50 mg/kg范围内的线性关系良好。空白茶叶样品在低、中、高3个添加水平下的平均回收率为81.5%~109.4%,相对标准偏差(n=5)为2.3%~10.6%,定量限为0.001~0.040 mg/kg。该方法操作简单、快速、灵敏、成本低,能满足茶叶中常见有机磷农药残留的检测要求。     

气相色谱-离子阱质谱法测定蔬菜中9种有机磷农药的残留量

建立气相色谱-离子阱质谱法测定蔬菜中9种有机磷农药残留的方法.样品经乙酸乙酯提取、无水硫酸钠脱水、活性炭小柱净化,浓缩后通过气相色谱-离子阱质谱进行测定.9种有机磷农药的浓度在0.05～1.0μg/mL范围内与其对应的色谱峰面积具有良好的线性关系(r＞0.999).在3个不同添加浓度下的平均回收率为76.5%～101.2%,测定结果的相对标准偏差为3.9%～9.4%(n=7).该方法快速、准确、操作简便,能满足蔬菜中有机磷农药残留的检测要求.     

气相色谱-串联质谱多反应监测及同步子离子全扫描定性定量分析蔬菜中287种农药残留

建立了气相色谱-三重四极杆串联质谱(GC-MS/MS)多反应监测(T-SRM)及同步二级全谱同时定性定量检测蔬菜中287种农药残留的方法。基于改进的QuEChERS方式进行样品前处理,使叶绿素在乙腈-水体系中的溶解度降低而析出,经0.2μm有机相滤膜过滤,有效的去除了叶绿素,净化后采用气相色谱-三重四极杆串联质谱在多反应监测(T-SRM)模式下进行外标法定量测定。结果表明287种分析物的浓度在5.0～100μg/L范围内线性关系良好,相关系数均大于0.995,定量限为10μg/kg。进行3个水平(10,20和50μg/kg)的加标回收试验,其回收率为45%～110%,其中277个目标物回收率为60%～110%。方法的相对标准偏差(RDS)小于20%。引入了一种新的MRM监测模式(T-SRM),并且在定量限10μg/kg残留浓度下可同步获得二级全扫描质谱图。该方法已广泛应用于蔬菜中多种农药残留的快速检测与确证的日常检测工作中。     

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.     

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.     

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.     

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.