微波消解-石墨炉原子吸收光谱法测定纳米二氧化钛中痕量砷

建立了微波消解-石墨炉原子吸收光谱法（GF-AAS）测定纳米二氧化钛中痕量杂质元素砷的分析方法。采用由一定浓度和比例的氢氟酸、硝酸组成的混合试剂,结合应用高压密闭微波加热技术快速完全消解纳米二氧化钛样品,优选了最佳微波加热控制程序,不仅解决了二氧化钛难消解和待测元素砷高温消解过程中易挥发损失等难点,而且检测溶液酸度低,避免对GF-AAS石墨管的侵蚀。并且,通过基体效应影响实验,优化选择了石墨管类型、石墨炉升温原子化控制程序以及原子吸收光谱仪检测参数,消除热稳定性强的二氧化钛基体对测定易挥发痕量元素砷的影响。方法检出限为0.02μg/L,加标回收率为93.0%~106.0%,相对标准偏差9.4%,与ICP-MS检测方法结果对照一致。     

微波消解-电感耦合等离子体质谱法测定海洋藻类食品中铅、镉含量

利用微波消解-电感耦合等离子体质谱法(ICP-MS)测定海洋藻类食品中铅、镉的含量。样品经过微波消解,在线加入内标校正基体效应,通过修正方程校正质量数干扰。各元素校正曲线的相关系数均大于0.9998,样品分析结果的相对标准偏差均小于3%(n=6),加标回收率在80.5%~101.5%之间。方法可用于海洋藻类食品中铅、镉含量的测定和监控。     

微波消解-电感耦合等离子体质谱法测定砂仁中的铜、铅、砷、镉

建立了微波消解样品,电感耦合等离子体质谱法(ICP–MS)测定黔西南高砷土壤种植的砂仁中痕量铜、铅、砷、镉的分析方法。对微波消解条件进行了优化。为了避免消解试剂对质谱测定的干扰,选择硝酸–双氧水混合溶液(体积比为3∶1)作为微波消解试剂,采用ICP–MS测定消解液中铜、铅、砷、镉的含量。利用校正方程对砷、镉的质谱干扰进行校正。铜、铅、砷、镉4种元素的线性相关系数均大于0.999 2,检出限分别为0.073,0.048,0.39,0.062μg/L,测定结果的相对标准偏差小于4.5%(n=5)。各元素的加标回收率在96.0%～105.0%之间。该方法样品处理快速、简单,溶解率高,测定结果准确、可靠,适用于成批量砂仁样品中铜、铅、砷、镉微量元素的测定。     

石墨消解-动态反应池模式-电感耦合等离子体质谱法测定烟用香精和料液中5种元素的含量北大核心CSCD

将烟用香精和料液样品0.3 g(精确至0.001 g)置于全自动石墨消解仪消解罐中,分3次加入消解液(共计10 mL硝酸、1 mL高氯酸),在170℃的最高消解温度下,样品消解完全.所得溶液用水定容至50 mL,采用电感耦合等离子体质谱法(ICP-MS)测定其中砷、铅、镉、铬、镍等元素的含量.以铟为内标,铬、镉、镍、铅、砷元素的测量同位素分别为^(52)Cr、^(111)Cd、^(60)Ni、^(208)Pb、^(75)As,使用动态反应池(DRC)模式消除了铬、砷元素的质谱干扰,铬、镉、镍、铅等元素的测定选择氦气碰撞模式,砷元素的测定选择氢气反应模式.结果表明,5种元素的质量浓度在一定范围内与各元素与内标计数值的比值呈线性关系,检出限(3s)为0.016~0.035 mg·kg^(-1).按标准加入法进行回收试验,各元素回收率为91.5%~111%,相对标准偏差(n=6)为0.28%~3.1%.方法用于10个烟用香精和料液样品的分析,铬、砷、镍的检出量分别为0.019~0.061 mg·kg^(-1),0.039~0.061 mg·kg^(-1)和0.022~0.031 mg·kg^(-1),镉和铅未检出.     

电感耦合等离子体质谱(ICP-MS)法检测市售鱿鱼中5种重金属

基于硝酸消解体系,建立了微波消解-电感耦合离子体质谱(ICP-MS)法同时测定市售鱿鱼中铅、砷、镉、汞、铬5种重金属元素的检测方法。样品加入HNO₃进行微波消解,优化ICP-MS 相关检测参数后,进行外标法定量。结果表明,5种重金属在各自浓度范围内线性关系均＞0.999,平均回收率为96%-101%,精密度RSD均小于5%。用该法检测广州市农贸市场随机购买的6个批次冰鲜鱿鱼,结果有1个批次砷含量超标,1个批次镉含量超标。该法前处理简单,检测准确、快速,适用于鱿鱼等水产品中铅、砷、镉、汞、铬等重金属的检测。     

基体分离-电感耦合等离子体质谱法测定高纯硒中13种杂质元素

采用基体分离-电感耦合等离子体质谱法（ICP-MS）测定高纯硒中13种痕量杂质元素含量,优化了试验条件.利用二氧化硒在真空条件下升华温度低的特点挥发基体硒,选择合适的内标元素,考察基体效应的影响.结果表明,选择Cs作为待测元素的内标更合适.测定硒残留量小于100 μg/mL的样品,不影响各待测元素.方法检出限为0.007~0.033 μg/g,RSD为5.7%~19%,加标回收率在90.2%~115%之间,可以满足高纯硒中痕量杂质元素含量的测定.     

电感耦合等离子体质谱法测定高纯镓中痕量杂质

采用电感耦合等离子体质谱（ICP-MS）测定高纯镓中痕量杂质元素,以Rh作为内标补偿校正镓基体的抑制效应,采用异丙醚萃取分离镓与ICP-MS技术联用,拓展分析方法应用范围,可满足99.9999%-99.99999%超高纯镓分析方法要求。方法检出限为0.006-0.062μg/L;加标回收率为86.8%-121.4%之间;RSD为1.1%-8.6%。     

浒苔中有毒有害元素及砷化学形态的研究

建立了微波消解-电感耦合等离子体质谱(ICP-MS)法测定浒苔中Cu、As、Cd、Hg、Pb等元素含量的分析方法,对各元素的线性关系良好(r=0.999 3～0.999 9),检出限为0.28～2.3 μg/L,元素加标回收率为83%～108%,符合痕量分析要求.并利用高效液相色谱(HPLC)与电感耦合等离子体质谱(ICP-MS)联用技术对浒苔样品中的砷化学形态进行了初步探讨,发现其中砷主要以无机As(Ⅴ)和某种未知的砷形态存在,推测该未知砷形态为砷糖类物质.     

微波消解-电感耦合等离子体质谱法测定粮食中12种重金属元素

粮食样品用硝酸-过氧化氢微波消解处理,采用电感耦合等离子体质谱法测定样品溶液中12种重金属元素(砷、铅、镉、硒、铬、铊、锰、镍、铜、铀、钴、钒)的含量。采用内标法消除基体的影响。方法的检出限(3S/N)在0.092~17.5pg·g-1之间。方法的加标回收率在88.1%~118%之间,相对标准偏差(n=5)小于6.0%。方法用于鸡肉标准物质(GBW 10018)中重金属含量的测定,测定值与认定值相符。     

微波消解–电感耦合等离子体质谱法测定酱卤肉中铬、砷、镉、铊、铅

建立微波消解–电感耦合等离子体质谱法测定酱卤肉中铬、砷、镉、铊、铅5种元素含量的检测方法。采用微波消解法处理酱卤肉样品,对预处理条件和仪器工作参数进行了优化,以内标校正法降低基体影响。结果表明,铬、砷、镉、铊、铅5种元素的质量浓度在0.1~50.0 μg/L范围内与质谱响应值具有良好的线性关系,相关系数均大于0.999,方法检出限为0.2~6.2 μg/kg。在3种加标浓度水平下平均回收率为72.4%~113.5%,测定结果的相对标准偏差为3.1%~7.7%(n=6)。该方法简便,快速,高效,准确,可为酱卤肉中铬、砷、镉、铊、铅的测定提供技术支持。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.