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91.
92.
将赣南脐橙经硝酸和高氯酸消化后,在样品中加入氯化镧作为释放剂以消除共存离子的干扰,采用火焰原子吸收光谱法测定了Ca、Mn、Zn、Fe、Cu和Pb元素的含量。结果表明,标准加入法的回收率为.96.58%~104.31%,10次平行测定结果的相对标准偏差RSD均小于2%。该法灵敏度高、操作简便快速,结果准确,重现性好。可见赣南脐橙中各元素含量差异显著,其中ca的含量比较丰富,Mn、Fe和zn的含量中等,含有人体必需的微量元素,而对身体有害的元素如P11含量却相当低,这说明赣南脐橙具有一定的药用和经济价值,为进一步探讨赣南脐橙开发利用提供实际依据。 相似文献
93.
Trifluoromethylation‐Initiated Remote Cross‐Coupling of Carbonyl Compounds to Form Carbon–Heteroatom/Carbon Bonds 下载免费PDF全文
Lin Huang Dr. Sheng‐Cai Zheng Prof. Dr. Bin Tan Prof. Dr. Xin‐Yuan Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6718-6722
By involving the reversal of conventional reactivity expectations without external oxidants, we describe a novel and convenient protocol of remote cross‐coupling of carbonyl compounds with a series of common and simple nucleophiles. This cross‐coupling is triggered by radical trifluoromethylation of alkenes, thereby achieving highly selective remote difunctionalization of alkenes and α‐position of the carbonyl group for facile access to trifluoromethyl α‐halo‐ and α‐cyanocarbonyl compounds. The reaction exhibits a broad substrate scope with excellent functionality tolerance and many different types of nucleophiles; further synthetic applicability of the obtained compounds proved to be suitable, thus showing great potential for synthetic utility. 相似文献
94.
95.
Frontispiece: Mutual Cooperation in the Formal Allyl Alcohol Nucleophilic Substitution and Hydration of Alkynes for the Construction of γ‐Substituted Ketones 下载免费PDF全文
96.
《Journal of Coordination Chemistry》2012,65(5):865-874
Ni(II) complexes with 5,5′-bis(4-halogenphenyl)diazo-dipyrromethane have been synthesized and characterized by X-ray crystallography. All the complexes have similar crystal structures in which Ni(II) is square-planar by coordinating to two pyrrole and two azo nitrogen atoms. The azo-pyrroles of the ligands can be converted to the hydrazone tautomer after complexing nickel. Moreover, the C–H?···?Ni interaction played an important role in directing self-assembly of the complexes. The UV-Vis spectra of the complexes showed great difference with the metal complexes of pyrrol-2-imine. 相似文献
97.
《Journal of Coordination Chemistry》2012,65(11):2021-2027
Results of quantum-chemical calculations of MCl4–C6H5COCl (M=Si, Ge, Sn) systems of 1?:?1 composition using RHF/3-21?G* and MP2/3-21?G* levels as well as those of 1?:?2 composition using the RHF/3-21?G* level have been represented. MCl4?←?C6H5COCl complexes of 1?:?1 composition are energetically more advantageous. They are formed in solid state provided that the M···O distance in individual systems is considerably less than the sum of van der Waals radii of M and O and their total energies are appreciably less than the sum of total energies of components. These conditions are realized only for M=Sn. In systems of 1?:?2 compositions, calculated M···O distances are practically equal to the sum of covalent radii of M and O. Nonetheless, complexes with such composition are not formed in solid state. Total energy of the system which is lower than the sum of its components’ energies is not an indispensable condition for complex formation. The 35Cl nuclear quadrupole resonance (NQR) frequencies and asymmetry parameters of the electric field gradient at the 35Cl nuclei have been evaluated using the results of ab initio calculations. 相似文献
98.
《Analytical letters》2012,45(11):2051-2058
Abstract The use of partial least-squares spectrophotometric calibration for the simultaneous determination of suppositories in a multicomponent formulation is presented. This method is applied to the deternination of acetaminophen and phenobarbital in suppository preparations. The results show that these components in a molar ratio of about 61:1 in suppositories have been determined simultaneously with high precision. 相似文献
99.
《复变函数与椭圆型方程》2012,57(9):753-766
In this article some problems related to the Krzy? conjecture are discussed. In particular, we prove the Krzy? conjecture for the fifth coefficient. 相似文献
100.
《Analytical letters》2012,45(12):1900-1910
Abstract An ultraviolet-derivative spectrophotometric method (UV-D) has been proposed as an alternative to a previously described liquid chromatographic (LC) method for the quantitative determination of ritonavir in soft gelatin capsules. The spectrophotometric method is based on recording the second-derivative spectra for ritonavir at 222.3 nm of its solutions in methanol. The linear dynamic range was 10.0–30.0 µg · mL?1 with a correlation coefficient of 0.9995. Mean recoveries were between 99.2% and 100.2% for the tested capsules samples. Mean intra- and interassay relative standard deviations (RSDs) were less than 2.0%. The statistic analysis showed that LC and UV-D methods were equivalent to assay ritonavir capsules. 相似文献