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61.
Nitrogen-15 labeled pyrroles have been prepared from commercially available 15N glycine or sodium nitrite using the Barton-Zard, Knorr, and Kleinspehn approaches. These pyrroles were used as intermediates in the synthesis of per-15N labeled porphyrins needed for the analysis and assignment of vibrational spectra for sedimentary porphyrins. Etioporphyrin-I was prepared via pyrromethene intermediates, while etioporphyrins II-V and a related tetrahydrobenzoporphyrin were synthesized via stepwise routes involving the copper(II) mediated cyclization of a,c-biladienes as the key step. Detailed analyses of both the proton and carbon-13 NMR spectra provide nitrogen-15 coupling constants for these important structures. 相似文献
62.
Sample preparation in analysis of pharmaceuticals 总被引:1,自引:0,他引:1
Dragana Mutavdi Pavlovi Sandra Babi Alka J.M. Horvat Marija Katelan-Macan 《Trends in analytical chemistry : TRAC》2007,26(11):1062-1075
Sample preparation is a very important and essential step in environmental analysis. This article presents an overview of extraction methods for environmental samples, focusing especially on pharmaceuticals as there is great concern about them as pollutants. 相似文献
63.
倒数示波计时电位法在合金样品测定中的应用 总被引:2,自引:0,他引:2
应用倒数示波计时电位法,在含有吸附络合物的溶液中,采用桂汞电极作为极化电极,测定了Cu^2+、Ni^2+、Cd^2+、Pb^2+等几种金属离子的检测下限,并通过沿(dE/dt)-1 ̄E曲线上的峰高对合金样品进行定量分析,得到满意结果。实现了示波分析由常量到微量的飞跃。 相似文献
64.
A substoichiometric isotope dilution method was developed for the determination of microgram amounts of manganese. The method involves the use of carrier-free 54Mn with Mn(II) carrier and its complexation with 2-thenoyltrifluoroacetone (TTA) at pH 8.5, the complex then being extracted into isobutyl methyl ketone. A minimum of 50 ng of manganese can be determined. The method was applied to the determination of manganese in several standard reference materials and biological samples such as tea leaves, spices and condiments. The method is simple and fast and yields results with high accuracy and precision. 相似文献
65.
N Arnaud 《Analytica chimica acta》2003,476(1):149-157
The luminescent properties of terbium complexes with furosemide (FR), flufenamic (FF) acid, tolfenamic (TF) acid and mefenamic (MF) acid have been investigated in aqueous solutions. For all four compounds, complexation occurs when the carboxylic acid of the aminobenzoic group is dissociated and is greatly favoured in the presence of trioctylphosphine oxide as co-ligand and Triton X-100 as surfactant. Under optimum conditions, luminescence of the lanthanide ion is efficiently sensitised and the lifetime of the resonance level of terbium in the complex is ranging between 1 and 1.9 ms, against 0.4 ms for the aqua ion. The sensitivity of the method for the determination of anthranilic acid derivatives is improved by one to two orders of magnitude with respect to that achieved using native fluorescence or terbium-sensitised luminescence in methanol. The limits of detection are 2×10−10, 5×10−10 and 2×10−9 mol l−1 for flufenamic acid, furosemide and tolfenamic acid, and mefenamic acid, respectively, with within-run RSD values of less than 1%. The method has been applied to the determination of flufenamic acid in spiked calf sera with and without sample pretreatment. Depending on the method and the analyte concentration, the recovery was ranging between 83 and 113% and the lowest concentration attainable in serum samples was close to 1×10−7 mol l−1. 相似文献
66.
J. P. Pérez-Trujillo S. Frías M. J. Sáchez J. E. Conde M. A. Rodríguez-Delgado 《Chromatographia》2002,56(3-4):191-197
Summary A study of different extraction techniques for the determination of a selected group of organochlorine compounds in surface
waters is presented. Comparison of liquid-liquid extraction (LLE) with solid-phase extraction (SPE) and solid-phase microextraction
(SPME) with fibers of different polarity shows that SPME with a recently commercialised fiber of polydimethylsiloxane divinylbenzene
allows these compounds to be determined in surface waters with good extraction efficiencies. Extraction time, effect of temperature,
ionic strength and pH were optimised, allowing quantification in agricultural effluents in the range 1.0–60 ng·L−1. 相似文献
67.
Circular high-performance thin-layer chromatography (HPTLC) has been used to differentiate a series of twelve tricyclic neuroleptics, using both normal phase and reverse phase procedures. The use of normal phase systems also allows the resolution of geometric isomers of chlorprothixene, clopenthixol and flupenthixol. Thirteen sulphonamides and Trirnethoprim may also be distinguished using HPTLC. 相似文献
68.
Thomas F. Brodasky 《Journal of separation science》1978,1(5):239-244
Two new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures. 相似文献
69.
Two different injectors, a split/splitless injector and a programmed temperature vaporizer (PTV) injector were investigated as the interface in on-line supercritical fluid extraction (SFE)-capillary gas chromatography (cGC). The parameters affecting the chromatographic peak shapes as well as the quantitative performance of the interfaces in on-line SFE-cGC were identified and studied. Particular attention was paid to the case where modified extraction fluids were used. Experiments were performed on two different samples. The first sample consisted of PAHs spiked on sand at different concentration levels. The other sample was a polymeric material. 相似文献
70.
Carbon nanotubes and graphitized carbon are investigated as adsorbents for solid phase extraction of dicamba and 2,4,5-T,
two phenoxyalkanoic acid herbicides. These adsorbents have much greater adsorption capability than that of C18 bonded silica, which was also tested for comparison studies. The adsorption capacity increases remarkably at lower pH of
the sample solution. Freundlich isotherms were applied to analyze the data. Our studies suggest that carbon nanotubes have
great potential applications in environmental analysis. 相似文献