高效液相色谱-串联质谱法同时测定茶叶中290种农药残留组分

建立了茶叶中290种农药的多残留分析方法。前处理采用改进的QuEChERS方法,样品经乙腈提取,氯化钠和无水硫酸镁盐析后,经N-丙基乙二胺(PSA)、石墨化炭黑和无水硫酸镁混合型固相分散净化,提取液过滤膜后经Thermo Accucore aQ色谱柱(100 mm×2.1 mm,2.6μm)进行高效液相色谱分离,以电喷雾电离串联质谱多反应监测模式(MRM)进行检测,外标法定量。结果表明:290种农药在1.0～200μg.L-1范围内具有较好的线性关系,相关系数均大于0.99。3个添加水平(MRL、2MRL、4MRL)下,290种农药的加标回收率为67%～119%;定量下限(LOQ,S/N≥10)均小于10.0μg.kg-1,低于各国规定的限量要求。该方法样品前处理简单、分析时间短、灵敏、可靠,适用于茶叶中多种农药残留的检测。     

凝胶渗透色谱净化-气相色谱-质谱法同时测定金银花中33种农药残留组分

建立了凝胶渗透色谱(GPC)净化、气相色谱-质谱(GC-MS)同时测定金银花中33种有机氯、有机磷和拟除虫菊酯农药残留的方法.样品中的待测农药组分经乙酸乙酯-环己烷混合溶剂(1∶ 1, V/V)提取、GPC净化去除色素等杂质,GC-MS采用全扫描/选择离子监测模式(Scan/SIM)采集数据后进行定性/定量分析.方法的相对标准偏差(RSD)≤16.70 %(6.9～84.6 ng/g,n=5);5种不同加标浓度下,待测农药的标准加入回收率在57.4%(甲胺磷)～109.9%(马拉硫磷)之间;各农药组分的定性检出限(3σ)为0.10～10.5 ng/g,定量检出限(10 σ)为0.33～20.0 ng/g.     

气相色谱-串联质谱法测定烟草中97种农药残留量

利用气相色谱-串联质谱法(GC-MS/MS)检测烟草中97种农药残留。样品以乙腈为溶剂经加速溶剂萃取(ASE),提取液用Carbon-NH2固相萃取小柱净化后,采用VF-5MS色谱柱分离,用电子轰击离子源-多反应监测模式(EI-MRM)检测。97种农药的质量浓度在20~1 000μg·L-1范围内与其峰面积呈线性关系,方法的测定下限(10S/N)在0.02~22.4μg·kg-1之间;在50,100,500μg·kg-1的加标水平下,测得回收率在67.4%~116%之间,测定值的相对标准偏差(n=6)在1.9%~14%之间。     

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。     

在线凝胶渗透色谱/气相色谱-质谱联用法测定水果中11种苯氧羧酸类农药

建立了水果中11种苯氧羧酸类农药多残留的在线凝胶渗透色谱/气相色谱-质谱(GPC/GC-MS)分析方法。样品经丙酮-正己烷溶液超声提取,提取液浓缩、干燥后用正丁醇-硫酸溶液衍生,再用Florisil固相萃取柱和在线GPC净化,GC-MS选择离子监测模式(SIM)进行检测和确证。结果显示,11种苯氧羧酸类农药在0.01～1.0 mg/L范围内线性关系良好,相关系数为0.998 7～0.999 9;在0.02～0.10 mg/kg加标范围内,回收率为66%～112%,相对标准偏差为3.4%～11.5%,11种苯氧羧酸类农药的定量下限为7～10μg/kg。该方法简便、快速、灵敏、净化效果好,可满足国际上对水果中多种苯氧羧酸类农药残留分析的要求。     

QuEChERS-凝胶渗透色谱/气相色谱-质谱法同时测定降尘中18种有机氯农药

建立了在线凝胶渗透色谱/气相色谱-质谱(GPC/GC-MS)测定大气降尘中18种有机氯农药残留的分析方法。样品经过简化QuEChERS方法处理后,经乙腈萃取,石墨化炭黑(GCB)净化,一步离心后过膜上机检测。采用该方法能在30 min内处理8~10个样品,配合GPC净化,不仅缩短了分析时间,而且提高了工作效率和结果的准确性。检测结果表明,18种有机氯农药在0.025~2.0 mg/L质量浓度范围内线性关系良好,相关系数为0.991 9~0.999 6,样品检出限为3.2~14.6μg/kg,定量下限为10.7~48.7μg/kg。在0.2、1.0 mg/kg 2个加标水平下,18种有机氯农药的平均回收率为78.6%~117.3%,相对标准偏差(RSD,n=5)为1.3%~5.1%。     

气相色谱-质谱法检测中药材中81种农药残留

建立气相色谱-质谱(GC-MS)法测定中药材中81种农药残留的分析方法。样品用含0.1%乙酸的乙腈提取后用GPC或GPC-SPE固相萃取净化,在选择离子监测模式(SIM)下对天麻、杜仲、金银花、山茱萸进行测定。方法在0.01～1.0μg/mL范围内具有良好的线性关系,相关系数均大于0.999,检出限为6.0～31.9μg/kg,加标回收率为60.8%～128.9%,测定结果的相对标准偏差为7.6%～18.9%(n=6)。该方法操作简便,灵敏度、准确度和精密度均符合农药多残留检测技术要求,适用于中药材中81种农药多残留的测定。     

液相色谱-串联质谱法测定果蔬中喹啉铜的残留量

通过优化液-液萃取(LLE)作为前处理手段,依托液相色谱-串联质谱仪器,建立了适用于蔬菜、水果中喹啉铜残留量的检测方法。样品以1%乙酸在超声条件下提取,提取液经PSA和C18净化后,以液相色谱-串联质谱法测定。本方法在0.01～2.0 mg/L范围内,不同基质中线性关系良好(R~20.99),进行了定量限(LOQ)、0.5倍最大允许残留限量(MRL)、1倍MRL和2倍MRL共4个水平的添加回收实验,回收率均介于82.7%～99.7%之间,相对标准偏差(RSD)在1.73%～11.8%之间,LOQ为0.1 mg/kg。本方法稳定、简便、灵敏,能够满足农药残留检测需求。     

高效液相色谱-串联质谱法测定牛羊组织中苯酚类和水杨酸苯胺类抗蠕虫药多残留

建立了高效液相色谱-串联质谱法同时测定牛、羊组织中硝碘酚腈、氯羟柳胺、氯氰碘柳胺、碘醚柳胺4种苯酚类和水杨酸苯胺类抗蠕虫药的多残留检测方法。样品用乙腈-丙酮(60∶40,V/V)(肌肉、肝脏和肾脏组织)或1%三乙胺乙腈(脂肪组织)超声提取,MAX阴离子固相萃取柱净化,液相色谱分离,采用多反应监测负离子模式对4种药物同时进行定性定量分析,在1~100μg/L范围内,4种药物与其对应峰面积的线性关系良好,相关系数均大于0.99。在牛、羊组织中的检出限(LOD)均为1μg/kg,定量限(LOQ)均为2.5μg/kg。在LOQ、0.5倍高残留限量(MRL)、MRL、2倍MRL添加水平下,4种药物的平均回收率在71%~112%之间,日内相对标准偏差(RSD)在1.1%~14.0%之间,日间RSD在6.4%~14.7%之间。采用本方法对市场上动物可食性组织进行抽样检测,共抽检40份样品,2份样品检测出苯酚类和水杨酸苯胺类抗蠕虫药残留。     

优化的QuEChERS/超高液相色谱-串联质谱法测定鲜茶叶中21种氨基甲酸酯类农药残留

本文应用改进的QuEChERS法结合超高效液相色谱-电喷雾电离串联质谱仪,建立了同时检测鲜茶叶中21种氨基甲酸酯类农药残留的测定方法。样品用1%甲酸乙腈提取,经N-丙基乙二胺(PSA)、C18和石墨化碳黑(GCB)3种复合吸附剂净化,采用UHPLC-MS/MS在动态多重反应监测(DMRM)模式下检测,基质匹配外标法定量。结果表明:21种氨基甲酸酯在2~100μg·L-1范围内线性关系均大于0.995,在三个添加水平下(5、10、25μg·kg-1)的回收率为73.6%~105.0%,相对标准偏差(RSD)为1.4%~7.3%,检出限(LOD)为0.018~0.86μg·kg-1,定量限(LOQ)为0.060~2.87μg·kg-1。该方法样品前处理简单快速、分析时间短、准确度和精密度均符合农药多残留检测技术的要求,适用于鲜茶叶中21种氨基甲酸酯类农药的快速筛查和测定。     

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.