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91.
The possibility of simultaneous application of an electron capture (ECD) and a flame ionization detector (FID) connected to a glass capillary column for analyzing polynuclear aromatic hydrocarbons (PNA) has been investigated. The ECD/FID ratio is determined for 46 PNA compounds. The ratios vary from 0.02 to 117 with relative standard deviations better than 20 percent determined from 10 replicate analyses. The results suggest that the method may be used for obtaining additional evidence in identifying PNA in environmental samples. Impurities and transformation products in the standard were identified by computerized glass capillary gas chromatography/mass spectrometry. Quinones and diones are responsible for the high EC-response determined in some trace components in the standard. An application of the method is shown for PNA from particulates in urban atmospheres. 相似文献
92.
An adjustable low-mass filter has been developed for an electrospray ionization (ESI) source to block ions associated with unwanted background species from entering the mass spectrometer. The low-mass filter is made by using an adjustable potential energy barrier from the conductance-limiting plate of an electrodynamic ion funnel, which prohibits species with higher ion mobilities from exiting the ESI source. We show that this arrangement provides a linear voltage adjustment for low-mass filtering from m/z 0 to 500. Mass filtering above m/z 500 is also performed; however, higher-mass species are attenuated. The mass filter was tested with a liquid chromatography/mass spectrometry (LC/MS) analysis of a bovine serum albumin (BSA) tryptic digest and resulted in the ability to block low-mass, background species, which accounted for 40-70% of the total ion current immediately behind the ESI source during peak elution and detection. 相似文献
93.
乙酰丙酸是配制酱油的特有成分,在硫酸溶液中,乙酰丙酸可与香草醛反应而呈现蓝绿色。掺有尿素的酱油在与丁二酮肟、磷酸混合后,加热煮沸会呈现红色。用酱色、食盐等配制的劣质酱油可用测定氨基酸态氮和酱色含量的方法进行鉴别。酿造食醋和配制食醋的常用鉴别方法是碘液法和高锰酸钾法。 相似文献
94.
J. Becnel C. Falgeust T. Cavalier K. Gauthreaux F. Landry M. Blanchard M.J. Beck J.N. Beck 《Microchemical Journal》2004,78(2):205-210
To determine if a correlation exists between mercury concentrations in lichens and wood from tree cores, tree core and lichen samples were taken from sites under mercury advisories and analyzed for mercury using a Bacharach 50B Mercury Analyzer System employing the Manual Cold Vapor Atomic Absorption EPA method 7471A. Wood from tree cores was dated using tree ring data. Wood samples from the cores were analyzed for various depths in the tree core (periods of time) to determine if variations occur throughout the cores. Preliminary data indicate that a strong correlation exists between mercury concentrations in tree core and lichen samples. Samples were analyzed for the 6-month period of summer 2003–winter 2004. A correlation coefficient of 0.882 was found between the tree core and lichen data sets. The derived correlations were used to estimate concentrations of mercury in tree rings for sites in lichen samples which were previously analyzed. These predicted values compared favorably to recently determined concentrations of Hg in tree cores. The strong correlation between lichen and tree core Hg concentrations suggests similar uptake mechanism for the two types of biota. 相似文献
95.
Prasain JK Patel R Kirk M Wilson L Botting N Darley-Usmar VM Barnes S 《Journal of mass spectrometry : JMS》2003,38(7):764-771
Electrospray ionization combined with tandem mass spectrometry was applied to a study of some representative chlorinated and nitrated isoflavones-potential metabolites of isoflavones in inflammatory cells. Upon collision-induced dissociation of deprotonated [M - H](-) ions of these compounds, a number of structurally characteristic product ions were produced. The product ion analysis of 3'- and 8-chlorodaidzein in the tandom mass spectra led to ready differentiation of these isomers. 3-Nitro derivatives of both genistein and daidzein have product ions due to the losses of HNO(2) and two OH groups. Chlorinated derivatives of isoflavones were detected in cell-based experiments and their structures were proposed by comparing the tandem mass spectra of their product ions with those of standards. This work provides a suitable analytical basis to aid the characterization of chlorinated and nitrated metabolites in studies in vivo and in vitro. 相似文献
96.
Yoshihiko Ohishi Tomonori Kawabata Tetsuya Shishido Ken Takaki Qinghong Zhang Ye Wang Katsuomi Takehira 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):49-58
M-MCM-41 catalysts (M: V, Cr, Fe, and Ga) prepared by direct hydrothermal synthesis (DHT) have been tested for dehydrogenation of ethylbenzene with CO2. The synthesized materials were characterized by X-ray diffraction (XRD), N2 adsorption (77 K), and diffuse reflectance UV–vis spectroscopic measurements. Cr-MCM-41 showed the highest activity among M-MCM-41 catalysts tested, resulting in the production of styrene with the conversion of 65% and the selectivity above 90%. The rate of styrene formation increased with increasing Cr loading up to 1.7 wt.%. It is suggested that Cr(VI)O4 in tetrahedral coordination is formed as an active monochromate species and reduced to Cr(III)O6 in octahedral coordination as a less active polychromate species during the reaction. Deactivated catalyst was regenerated by a treatment with gaseous oxygen or CO2, during which redistribution as well as reoxidation of polymeric Cr(III)O6 octahedra to monomeric Cr(VI)O4 tetrahedra was observed. The rate of CO formation increased together with that of styrene formation, while the rate of H2 formation decreased, with increasing partial pressure of CO2. It was confirmed that reverse water-gas shift reaction took place over Cr-MCM-41 by a separate experiment. The rate of CO formation during the dehydrogenation of ethylbenzene with CO2 over Cr-MCM-41 was well accounted for by assuming parallel occurrence of two reactions, i.e., direct oxidative dehydrogenation of ethylbenzene with CO2 and simple dehydrogenation of ethylbenzene thermodynamically assisted by reverse water-gas shift reaction. 相似文献
97.
CHU Yongbao GAO Baoyu YUE Qinyan WANG Yan & WANG Shuguang . School of Environmental Science Engineering Shandong University Jinan China . College of Material Environment Qingdao University of Science Technology Qingdao China 《中国科学B辑(英文版)》2006,(4)
Polyaluminum chloride (PAC) coagulant has been developed and widely used in water and wastewater treatment industry since the 1980s[1]. PAC is normally made by partial hydrolysis of acid aluminum chloride solution using slow alkaline titration method. However, this method would result in many different Al species. Among these Al species, it seems that tridecamer (Al13O4(OH) 724 , often denoted by Al13) is the most effective and stable polymeric Al species for water and wastewater treatme… 相似文献
98.
氟钽酸钾中碳存在形式的探讨 总被引:2,自引:0,他引:2
本文从氟钽酸钾(K2TaF6)的生产工艺论述了有机物存在于D2TaF6的可能性。通过K2TaF6低温通氧燃烧前后测定碳的结果比较,以及X射线能谱仪表面分析结果,证实了碳的来源是残留的有机萃取剂。 相似文献
99.
Summary An analytical procedure for the individual determination of ortho and non-ortho PCB congeners in sediments, using high performance liquid chromatography (HPLC) preseparation and gas chromatography/ECD detection, is described. Gas chromatography/FTIR spectrometry (GC/FTIR) and gas chromatography/mass spectrometry (GC/MS) were employed for individual congener identification and determination. Sample extraction, clean-up of extract and selective elution procedures were optimized by using reference certified marine sediment samples. Recovery and precision were typically 83% and 16% respectively at 2 ng/g of total PCB content. The proposed procedure, tested by analyzing real sediment samples, showed a reproducibility better than 20% at 13 ng/g PCB level. 相似文献
100.
Debprasad Patra Poulami Pattanayak Jahar Lal Pratihar Surajit Chattopadhyay 《Polyhedron》2007,26(18):5484-5490
The reactions of HL 1 [where HL is 1N-(2-pyridyl-2-methyl)-2-arylazoaniline and is formulated as ArN = NC6H4N(H)(CH2C5H4N); Ar = C6H5 (for HL1) or p-MeC6H4 (for HL2) or p-ClC6H4 (for HL3)] with K2PtCl4 and Co(ClO4)3 · 6H2O afforded the (L)PtCl and [(L)2Co]ClO4 complexes, respectively. The HL ligands bind the platinum(II) and cobalt(III) centres in a tridentate (N,N,N) fashion, forming new diazoketiminato chelates upon dissociating the amino proton. The X-ray structures of (L3)PtCl and [(L3)2Co]ClO4 were determined. Redox properties of the new complexes have been examined. 相似文献