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271.
Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 g/ml concentration range; the limit of detection was 5 ng/mL. 相似文献
272.
M. Valkeapää Y. Katsumata T. Motohashi R.S. Liu H. Yamauchi 《Journal of solid state chemistry》2007,180(5):1608-1615
A comparative study on the oxidation and charge compensation in the AxCoO2−δ systems, A=Na (x=0.75, 0.47, 0.36, 0.12) and Li (x=1, 0.49, 0.05), using X-ray absorption spectroscopy at O 1s and Co 2p edges is reported. Both the O 1s and Co 2p XANES results show that upon removal of alkali metal from AxCoO2−δ the valence of cobalt increases more in LixCoO2−δ than in NaxCoO2−δ. In addition, the data of O 1s XANES indicate that charge compensation by oxygen is more pronounced in NaxCoO2−δ than in LixCoO2−δ. 相似文献
273.
Wladyslaw Walkowiak Eok-Giu Jeon Hwang Huh Richard A. Bartsch 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):213-222
The selectivity and efficiency of competitive liquid-liquid extraction of alkali metal cations into organic solvents containingsym-(octyl)dibenzo-16-crown-5-oxyacetic acid (2) andsym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxyacetic acid (3) have been determined. Solvents examined include: dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene,p-xylene, chlorobenzene, 1,2-dichlorobenzene, and 1,2,3,4-tetrahydronaphthalene. The Na+/K+ and Na+/Li+ extraction ratios are highest in chloroform. The extraction selectivity is found to correlate with the diluent parameter (DP) of the organic solvent.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献
274.
Masaru Kojima 《Tetrahedron letters》2007,48(25):4431-4436
A new fluorous benzylidene acetal protecting group was regioselectively introduced into carbohydrates, deprotected under acidic conditions, and reused. Oligosaccharides were synthesized via regioselective conversion of the fluorous acetal group to the benzyl group by traditional reaction conditions. The fluorous compounds were easily separated from non-fluorous by-products by fluorous solid phase extraction. 相似文献
275.
Alessandra Sussulini Jerusa S. Garcia Márcia F. Mesko Diogo P. Moraes Érico M. M. Flores Carlos A. Pérez Marco A. Z. Arruda 《Mikrochimica acta》2007,158(1-2):173-180
Two methods of protein extraction for soybean seeds were evaluated in terms of preservation of the metal ions bound to proteins
after the extraction and separation procedures. The proteins were firstly separated according to their molar masses by polyacrylamide
gel electrophoresis. Then, the protein bands were mapped by synchrotron radiation X-ray fluorescence in order to establish
which metal ions were present in each one. Finally, some mapped protein bands were decomposed by microwave-assisted combustion
and Ca, Cu, K, Mg, Mn, and Zn were quantified by inductively coupled plasma mass spectrometry or inductively coupled plasma
optical emission spectrometry. The extraction methods studied were Method A (based on the treatment of ground soybean seeds with hexane and their extraction with Tris–HCl and β-mercaptoethanol) and
Method B (based on the treatment of ground soybean seeds with petroleum ether and their extraction with Tris–HCl, dithiothreitol,
phenylmethanesulfonyl fluoride, sodium dodecyl sulfate and potassium chloride). The best method was Method B, in which a 78% higher extraction efficiency was obtained when compared to Method A. Additionally, the metal-protein interactions were more appropriately preserved when Method B was applied, where the most affected ions were those that are bound weakly to proteins, such as Ca, K, and Mg. 相似文献
276.
Novel enrofloxacin imprinted polymer applied to the solid-phase extraction of fluorinated quinolones from urine and tissue samples 总被引:1,自引:0,他引:1
A new molecularly imprinted polymer, prepared following a non-covalent approach, was synthesised using enrofloxacin as a template molecule. The imprinting effect of the polymer was verified by chromatographic evaluation and, interestingly, this evaluation also revealed that the imprinted polymer showed a high degree of cross-reactivity for ciprofloxacin, the major metabolite of enrofloxacin. The molecularly imprinted polymer was then applied as a selective sorbent in a two-step solid-phase extraction method focussing upon complex biological matrices, specifically human urine and pig liver. This two-step solid-phase extraction protocol, in which a commercial Oasis HLB cartridge and a molecularly imprinted solid-phase extraction cartridge were combined, allowed enrofloxacin and ciprofloxacin to be determined by liquid chromatography coupled to a UV detector at levels below the maximum residue limits established by the European Union. The quantification and detection limits in tissue samples of enrofloxacin and ciprofloxacin were established at 50 μg kg−1 and 30 μg kg−1, respectively. 相似文献
277.
In the present study a multi-residue analytical method was developed for monitoring some polar pesticides such as acephate,
methamidophos, carbofuran, isoproturon, dimethoate in water with SPE (solid-phase extraction) and LC–MS–MS. Acetochlor was
taken as surrogate, and alachlor as internal standard. SPE with different types of columns was compared with LLE (liquid-liquid
extraction). Further, the breakthrough volume for different pesticides was determined. The results showed that the selected
pesticides can be determined very sensitively with LC–MS–MS. The minimum detectable quantity (MDQ) for each pesticide was
about 1.0 ng. To date, SPE cartridge studies showed that the Oasis HLB cartridges were suitable for further studies. However,
for Oasis HLB cartridge, different pesticide showed different breakthrough volume. The results showed that for acephate and
methamidophos, the breakthrough volume was about 30 mL of water sample, much less than the breakthrough volume of other pesticides
studied. Because of the higher vapor pressure and higher Henry's constant of methamidophos, dimethoate and carbofuran, much
attention should be paid on their losses in the evaporation step of the experiment. This analytical method can be applied
to determine pesticide contamination in environmental water samples.
Revised: 12 September 2005 and 21 October 2005 相似文献
278.
P538 P204及其混合物从盐酸溶液中萃取Fe(Ⅲ)的平衡可分别表达为: P538: Fe~(3 ) 4/j(H_2A)j(o) K′_A Fe(HA)_3·H_2A(o) 3H~ P204: Fe~(3 ) 2H_2B_2(o) K′_B FeB_3·HB(o) 3H~ P538 P204:Fe~(3 ) 2/j(H_2A)j(o) H_2B_2(o) K′_(AB) Fe(HA)_2B·HB(o) 3H~ 其表观萃取平衡常数分别为 lgK_A=4.46±0.09 lgK_B=3.44±0.08 lgK_(AB)=5.47±0.10 等摩尔的P538,P204混合物有最大的协同萃取系数。 相似文献
279.
The leaching of two estrogens, 17β-estradiol and estrone, and two degradation products of non-ionic surfactants, octylphenol and nonylphenol, through a soil column were studied to estimate their transport behavior. Different concentration methods (lyophilization, solid phase extraction, and liquid–liquid extraction) were evaluated for analyzing these compounds in small effluent fractions (30–50 mL) collected. Liquid chromatography-mass spectrometry (LC-MS-MS) and gas chromatography-mass spectrometry (GC-MS) were employed for quantitative analysis of these compounds. After comparison, the lyophilization-LC-MS-MS method was found to be best suited for the analysis of the two estrogen hormones and the liquid–liquid extraction-GC-MS method best for the analysis of the two phenols in small samples in the soil column study. Because of their high sorption capacity, these compounds were mostly sorbed in the upper part of the soil column and were difficult to detect in column effluent. 相似文献
280.
Rainer P. H. Garten 《中国化学会会志》1994,41(3):259-274
Selected prominent problems in the analysis of advanced ceramic materials are surveyed. The importance of reliability of results is discussed in the field of elemental trace- and microanalysis in view of its interaction with economy, power of detection, local resolution and speciation selectivity. Particular problems in the analysis of major constituents, trace components and microlocal distributions are based on the striking propertics of ceramics; they are exemplified. Analytical assistance must start from the beginning of the production processing, in the preparation of the powdered base materials. Determination of the stoichiometry requires high accuracy and differentiation of chemical species in bulk and surface analysis of ceramic base powders. Element trace determination by direct instrumental methods requires standard reference materials for calibration; these are currently inavailable in a sufficient variety. For optimum reliability and power of detection, element traces must be prepared in isolated form in a small excitation volume for analysis. A review on the state-of-the-art of wet-chemical combined procedures is presented. Decomposition position procedures are emphasized, due to their risk of contributing severe systematic error. Combustion in elementary fluorine is presented for decomposition of refractory materials. The performance of some direct procedures is discussed. Very efficient methods are available for element trace determinations in ceramic materials, offering high detection power. Several approaches for high-resolution local microanalysis in non-conductive ceramic materials are identified as the most promising development in the analysis of sintered compact ceramic products and devices. 相似文献