气相色谱-电感耦合等离子体质谱联用技术应用于水产品中汞形态分析

对气相色谱(GC)与电感耦合等离子体质谱(ICP-MS)联用的商品化接口进行了改进,并将GC-ICP-MS联用技术应用于水产品中汞的形态分析。在优化条件下,甲基汞(MeHg(Ⅰ))和乙基汞(EtHg(Ⅰ))的检出限(S/N=3)分别为0.5pg和1.0pg,定量限(S/N=8)分别为1.5pg和2.8pg,标准曲线的线性范围为1～1000pg。对三文鱼肉、金枪鱼肉和角鲨鱼肉3种标准物质和市售14种鱼贝类水产品,采用非衍生的样品预处理,进行汞的形态分析。结果表明,采集样品中均检出有甲基汞,未检测出乙基汞,甲基汞的含量在3.7～236.6ng/g(以Hg计)范围,甲基汞的加标回收率为91%～102%。     

超高效液相色谱法快速检测粮食中黄曲霉毒素的含量

建立了免疫亲和柱净化-超高效液相色谱法快速测定粮食中黄曲霉毒素(Aflatoxins,AF)的检测方法.样品经提取后,用免疫亲和柱净化、浓缩,Waters Acquity UPLC BEH C18色谱柱(50 mm×2.1 mm,1.7 um)分离.以甲醇-水(40∶60,V/V)为流动相,流速为0.2 mL/min,进样量为1μL,荧光检测器检测,激发波长为360 nm,发射波长为440 nm,无需衍生.黄曲霉毒素B1,B2,G1,G2的保留时间小于5min,从样品前处理到结果分析整个过程小于45 min.根据3倍信噪比的峰响应值,确定黄曲霉毒素(B1,B2,G1,G2)检出限分别为0.15,0.05,0.40,0.06 pg,4种毒素在0.4 ～ 60.0 pg,0.2～15.0 pg,1.5～ 60.0 pg和0.2～15.0 pg范围内分别呈线性相关,相关系数R2值分别为0.9999,0.9999,0.9998和0.9992;在小麦、玉米、稻谷3类样品中加标回收率为77.4％ ～ 104.2％,精密度为1.8％ ～ 8.9％.本方法无需衍生即可同时测定粮食中4种黄曲霉毒素,适用于粮食中黄曲霉毒素的快速定量测定.     

Nd-Sr-Mn-O钙态矿锰氧化物的低场磁电阻效应

采用固相烧结法和脉冲激光沉积法分别制备了钙态矿型锰氧化物Nd1-xSrxMnO3(x=0．1，0．2，0．3，0．4，0．5)大块多晶和Nd0．7Sr0．3MnO3在(100)LaAlO3基片上的单取向薄膜样品，分别研究了这些样品的磁电阻效应。研究表明，在多晶样品中，x=0．3时具有最大的磁电阻比，其值在240K和1T磁场下可达24．2％。对于同一成分的外延薄膜，发现磁电阻随着沉积时基片温度Ts的升高而下降，当Ts=500℃时的制备态薄膜在同样条件下的磁电阻可达84％，随着外加磁场增大到5T，磁电阻将线性增大到275％。并讨论了造成单取向膜和块材磁电阻不同的原因。     

微晶萘负载PMBP微柱分离预富集与电热蒸发-电感耦合等离子体原子发射光谱联用测定痕量稀土元素

报道了微晶萘负载1-苯基-3-甲基-4-苯甲酰基-5-吡唑酮(PMBP)微型柱分离预富集与电热蒸发-电感耦合等离子体原子发射光谱(ETV-ICP-AES)联用测定痕量稀土元素(Sc,Y,La和Yb)的新方法.试验了影响分离/预富集待测物的各种因素(包括溶液酸度、流速、试样体积、微柱尺寸);研究了吸附有待测物的微晶萘的溶解方法及共存元素对分离/测定的影响.在优化的实验条件下,方法的相对检出限为14pg/mL(Sc),32pg/mL(Y),190pg/mL(La)和26pg/mL(Yb),相对标准偏差(RSD)分别为3.1%,3.5%,4.8%和3.4%(n=9,c=10ng/mL).本法已成功地应用于生物样品中痕量稀土元素(Sc,Y,La和Yb)的测定,结果满意.     

大气样品中氯代和溴代二噁英/呋喃同位素稀释分析方法的建立及应用

本研究结合已有的多氯代二噁英/呋喃(PCDD/Fs)分析方法,建立了多溴代二噁英/呋喃(PBDD/Fs)和PCDD/Fs的同位素稀释高分辨气相色谱-质谱联用(HRGC-HRMS)分析方法。样品抽提液经酸性硅胶床、多段硅胶柱、Florisil柱净化后,分别对其中8种2,3,7,8-PBDD/Fs和17种2,3,7,8-PCDD/Fs进行测定。PBDD/Fs仪器分析条件:EI 模式,选择性离子监测,分辨率10000以上,电子发射能50 eV,灯丝电流0.75 mA;DB-5 MS柱(60 m×0.25 mm i.d.,0.25μm);进样口、离子源及传输线温度分别为250℃、250℃和305℃;载气,He(1.0 mL/min)。结果表明:平行标准样品分析相对标准偏差(RSD)≤10.3%;PBDD/Fs和PCDD/Fs回收率在73%~112%之间;标准参考样品测定平均值与标准值基本符合,平行样RSD≤12.0%。方法检出限:TBDF,0.25 pg/μL;TBDD,0.3 pg/μL;PeBDFs,0.5 pg/μL;PeBDDs,1.0 pg/μL;HxBDD/Fs,1.5 pg/μL;TCDD/Fs,0.5 pg/μL;PeCDD/Fs和HxCDD/Fs,2.5 pg/μL;HpCDD/Fs以及OCDD/Fs,5 pg/μL。测定某地区大气样品颗粒相中PBDD/Fs和PCDD/Fs浓度分别在1.01~2.43 pg/m3和6.19~10.8 pg/m3之间;气相中的浓度为0.036~0.801 pg/m3和1.37~12.1 pg/m3。     

石墨炉原子吸收光谱法测定含盐食品中铅

含盐食品样品经硝酸和过氧化氢加热消解,采用石墨炉原子吸收光谱法测定其中铅的含量。以氯化钯-硝酸铵为混合基体改进剂,灰化温度为1 200℃,原子化温度为1 850℃。铅(Ⅱ)的质量浓度在25μg·L-1以内与其吸光度呈线性关系,检出限(3s/b)为26pg。应用此法分析了酱油样品,加标平均回收率为96.2%,相对标准偏差(n=5)为3.0%。     

同位素稀释的气相色谱／高分辨质谱联用测定食品中二嗯英和共平面多氯联苯

采用HRGC／HRMS和同位素稀释定量技术对样品中17种4～8个氯原子取代的二嗯英和呋喃(PCDDs／Fs)与12种共平面多氯联苯(PCBs)定量分析。样品经索式抽提、FMS Power Prep系统净化、浓缩，利用高分辨气相色谱／高分辨质谱联用仪的多离子检测方式，同位素稀释技术对样品中的目标化合物进行定性和定量。该方法的检出限为pg／g水平。^13同位素内标回收率范围为47％～100％。对3个CRM鱼样中17个PCDDs／Fs和4个PCBs的检测值均在标准定值允许误差范围内。对5个不同的实际样品鱼进行测定表明，样品的回收率在48％～100％之间，回收率的相对标准偏差小于20％；对同一样品进行定量检测的精密度测试结果表明，17种PCDDs／Fs浓度的RSD低于16％，12种PCBs浓度的RSD低于11％。本方法定量分析重现性良好。     

ICP-AES法测定淀粉中的铅、汞、镉、砷

建立了ICP-AES法测定淀粉中铅、汞、镉、砷的方法。用HNO3、HClO4处理样品,然后用ICP-AES法进行测定。加标回收率为98．2％～104．3％,测定结果的相对标准偏差均小于5％(n=5)。     

新型分散液液微萃取-石墨炉原子吸收光谱法测定地质样品中银

采用基于正辛醇为萃取剂的新型分散液液微萃取-石墨炉原子吸收光谱法测定地质样品中银的含量。优化的试验条件如下:(1)萃取剂正辛醇的用量为0.30mL;(2)2g·L~(-1)对称二苯基硫脲(络合剂)乙醇溶液的用量为1.0mL;(3)分散剂乙醇的用量为10mL;(4)样品溶液的pH为3.0~7.0;(5)灰化温度为500℃;(6)原子化温度为1 700℃。银的质量浓度在0.02~0.50μg·L~(-1)内与其对应的吸光度呈线性关系,检出限(3s)为4.7pg。方法应用于地质样品的分析,测定值与认定值相符,测定值的相对标准偏差(n=5)为3.2%~6.8%。     

分散液液微萃取-上浮溶剂固化/高效液相色谱法测定沉积物中的十溴联苯醚

建立了沉积物中痕量十溴联苯醚的分散液液微萃取-上浮溶剂固化-高效液相色谱-紫外法(DLLME-SFO-HPLC-UV)。以正交试验数据为训练样本,采用BP(Back propagation)神经网络模型优化了分散液液微萃取-上浮溶剂固化条件:分散剂为1.00mL甲醇、萃取剂为35.0μL十二醇、NaCl质量浓度为10.00%、萃取时间10min和pH=5,其萃取率(ER)可达62.22%。方法的线性范围为3.5～1400ng/g(r=0.9960),检出限(LOD)和定量限(LOQ)分别为2.3pg/g(S/N=2)和5.6pg/g(S/N=5),实际样品的加标回收率为97.7%～104.2%。本方法集萃取、富集、分离步骤于一体,简化了沉积物中十溴联苯醚的前处理过程。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.