动态液相微萃取-气相色谱法测定水样中残留有机磷农药

应用动态液相微萃取与气相色谱联用技术测定了水样中3种有机磷农药(敌敌畏、甲基对硫磷、对硫磷).考察了萃取溶剂、溶剂体积、萃取次数、水样pH值以及离子强度对液相微萃取的影响.该方法甲基对硫磷、对硫磷的线性范围在30～70μg·L-1之间,敌敌畏的线性范围在40～70μg·L-1之间,回收率在84.9%～103.0%之间,相对标准偏差(n=7)在5.1%～9.4%之间,检出限(3S/N)为26.5～35.7μg·L-1.     

溶剂浮选-石墨炉原子吸收光谱法测定水样中痕量Pb(Ⅱ)、Ni(Ⅱ)和Co(Ⅱ)

本文采用溶剂浮选分离富集,石墨炉原子吸收光谱法测定水样中的痕量Pb(Ⅱ)、Ni(Ⅱ)以和Co(Ⅱ)。以双硫腙为捕集剂,甲基异丁基酮(MIBK)为浮选溶剂,确定了最佳浮选条件。所拟定的方法用于自来水和工业用水中Pb(Ⅱ)、Ni(Ⅱ)和Co(Ⅱ)的测定,金属离子的富集倍数为37,Pb(Ⅱ)、Ni(Ⅱ)和Co(Ⅱ)的检出限分别为0.2μg/L、1.08μg/L和0.38μg/L;样品加标回收率在94.7%~103.2%之间;测定结果的RSD≤4.67%。     

溶剂浮选分离-紫外分光光度法测定环境水样中罗红霉素残留量

采用溶剂浮选法分离富集环境水样中罗红霉素,并利用紫外分光光度法对罗红霉素进行测定。罗红霉素的最佳浮选条件为在磷酸氢二钾溶液中,以异丙醇作浮选溶剂,控制溶液pH为9.0,氮气流量15mL·min~(-1),浮选时间30min。罗红霉素的质量浓度在8.2～40.2mg·L~(-1)范围内与其吸光度呈线性关系,检出限(3S/N)为0.26mg·L~(-1)。在河水及湖水样品中分别加入3个浓度水平的罗红霉素标准溶液做方法的回收试验,测得平均回收率均超过90%。     

离子液体[Bmim]PF_6溶剂浮选分离富集-光度法测定环境中痕量四环素类抗生素的研究

建立了离子液体溶剂浮选四环素类(TCs)抗生素的新方法。以1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF6)和乙酸乙酯(EA)的混合溶剂(V/V=1)为浮选剂,以Al(Ⅲ)为捕集剂,在pH=6.7条件下,分离富集环境水样中四环素(TC)、土霉素(OTC)、金霉素(CTC)三种四环素类抗生素,并用紫外-可见分光光度法测定总含量。方法线性范围为0.2~10.3μg.mL-1,表观摩尔吸光系数3ε80=3.8×105L.mol-1.cm-1,加标回收率达到94.5%~102.2%,相对标准偏差RSD3.76%(n=5)。该方法适合于环境水样中痕量TC、OTC、CTC抗生素总含量的分离分析。     

固相萃取-高效液相色谱法测定水中磺胺类药物

提出了固相萃取-高效液相色谱法测定水中3种磺胺类药物(磺胺甲噁唑、磺胺异噁唑和磺胺间甲氧嘧啶)的方法。水样经自制的阳离子交换固相萃取柱净化和富集后,以C18色谱柱(250mm×4.6mm,5μm)为固定相,以乙腈和2%(体积分数)乙酸溶液以体积比1比5的混合液为流动相进行分离,在波长270nm处用紫外检测器测定。3种磺胺类化合物的质量浓度均在0.005～0.5mg.L-1之间与其峰面积呈线性关系,方法检出限(3S/N)在2.4～3.7μg.L-1之间。方法用于水样中上述3种磺胺类化合物的测定,测定值的相对标准偏差(n=6)在2.6%～4.4%之间,加标回收率在88.6%～103%之间。     

分散液相微萃取-气相色谱联用分析水样中菊酯类农药残留

将分散液-液微萃取(DLLME)与气相色谱-电子俘获检测(GC-ECD)技术相结合,建立了高灵敏度测定水样中7种菊酯类农药残留的新方法。对影响萃取富集效率的因素进行优化,萃取条件选定为:在5.0mL样品溶液中加入10.0μL氯苯和1.0mL丙酮,分散混匀后,以5000r/min离心5min,吸出萃取溶剂氯苯直接进样分析。在优化条件下7种菊酯类农药的富集倍数高达708～1087倍。以α-六六六为内标,7种菊酯类农药在0.8～600μg/L范围内具有良好的线性关系,线性相关系数在0.9990～0.9999之间;检出限为0.04～0.10μg/L(S/N=3)。本方法已应用于自来水、井水及河水等实际水样的分析,平均加标回收率在76.0%～116.0%之间;相对标准偏差在3.1%～7.2%之间。方法具有操作简单、富集效率高和灵敏度高等特点,可满足水样中菊酯类农药残留的检测要求。     

液-液萃取富集-气相色谱法测定水中有机氯农药和多氯联苯

采用正己烷作萃取溶剂提取并富集水样中有机氯农药(OCP's)和多氯联苯(PCB's),所得提取液经浓缩至约0.5mL并定容至1.0mL后,用气相色谱法-电子捕获检测器测定水中有机氯农药和多氯联苯。采用Rtx-5MS和Rtx-1701双柱法根据与标准物质的保留时间相对比进行定性分析;采用Rtx-5MS柱对被测组分按外标法进行定量分析。结果表明:各种农药质量浓度均在0.5～40μg·L~(-1)范围内与峰面积呈线性关系。有机氯农药和多氯联苯的检出限(3s)在0.001 1～0.004 7μg·L~(-1)之间。用标准加入法测得其回收率在83.3%～112.1%之间,相对标准偏差(n=7)在4.4%～9.4%之间。     

磁固相萃取-高效液相色谱法测定环境水样中双酚A

采用磁固相萃取-高效液相色谱法测定环境水样中双酚A的含量。优化的试验条件如下:1 50mL水样中加入20mg磁性微球进行萃取;2水样的pH为3.0;3萃取时间为15min;4解析溶剂为甲醇(80+20)溶液;5解析时间为10 min。采用C18色谱柱为分离柱,以甲醇-水(85+15)混合液为流动相,在检测波长224nm处进行测定。双酚A的质量浓度在5.0~500μg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)为1.0μg·L-1。方法应用于环境水样的分析,加标回收率在81.4%~109%之间,测定值的相对标准偏差(n=6)在5.7%~8.6%之间。     

离子液体溶剂浮选-光度法测定水中痕量四环素类抗生素

将离子液体应用于气浮溶剂浮选分离/富集四环素类抗生素(TCs),建立了一种离子液体1-丁基-3-甲基咪唑六氟磷酸盐(\PF6)取代传统有机溶剂气浮溶剂浮选分离/富集四环素类抗生素的新方法.TCs与镧能形成疏水性络合物,易于浮选至离子液体相,考察了在离子液体中加入有机溶剂的种类和体积,试液的pH值、La的加入量、气体流速、浮选时间以及共存物质对浮选效率的影响,优化了浮选条件,与溶剂萃取方法相比,离子液体溶剂浮选四环素类抗生素富集倍数高,且无毒,无污染,试剂用量少,实测了鱼塘水和辽河水样,RSD分别为3.0%和4.3%(n=5),回收率为97%.本方法适合于环境水样中痕量四环素总量的分析检测.     

气相色谱法测定水样中硝基苯类化合物含量

提出了气相色谱法测定水样中硝基苯类化合物的含量的方法。水样经乙酸乙酯-苯-乙醚(2+1+0.02)混合溶剂提取,采用HP-1701毛细管色谱柱(30m×0.25mm,0.25μm)分离,用微电子捕获检测器测定。9种硝基苯类在11.5min内达到完全分离,其线性范围在质量浓度0.001～5.0mg.L-1之间。方法的回收率在92.0%～108%之间,测定结果的相对标准偏差(n=5)均小于5.0%。     

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.