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91.
Quantitation of agmatine by liquid chromatography with laser-induced fluorescence detection 总被引:3,自引:0,他引:3
Shulin Zhao Yangzheng Feng Michael H. LeBlanc John E. Piletz Yi-Ming Liu 《Analytica chimica acta》2002,470(2):155-161
A high performance liquid chromatography (HPLC) method is described for the determination of agmatine, an endogenous neuromodulator. The method involves pre-column derivatization of the sample with a fluorescent tagging reagent, 7-fluoro-4-nitrobenzoxadiazole (NBD-F). The resulting agmatine derivative is stable and can be readily extracted into ethyl acetate at pH 8.5. The extraction enhances the quantification of low level agmatine because it eliminates chromatographic peaks caused by endogenous amino acids. The HPLC separation is carried out on a C8 reversed phase column and completed in less than 10 min. With laser-induced fluorescence (LIF) detection, the detection limit is 5×10−9 M agmatine. Method precision (coefficient of variation) is 5% for agmatine in human plasma at the sub-μM level. This method has been validated by determination of agmatine in biological samples including human plasma and rat brain and stomach tissues. 相似文献
92.
Spevácková V Korunová V Cejchanová M Vobecký M 《Analytical and bioanalytical chemistry》2004,380(2):346-350
A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a 197Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised 197Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na2EDTA (0.05 mol L–1). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period. 相似文献
93.
94.
Summary The role of the volume of the sample and the sample vial in equilibrium headspace-gas chromatography is discussed. A new term, thesample phase fraction (S) is introduced. It is shown that if the value of S is kept constant, the vial's volume has no influence on the sensitivity of the headspace analysis (which is proportional to the concentration of the analyte in the headspace). In a given headspace sampling system, concentration of the compound of interest in the headspace (c
G
*
) at equilibrium is related to the value of S: a higher S will increase c
G
*
. However, the influence is important only in the case of low distribution coefficients: in the case of higher distribution coefficients this influence is negligible. This conclusion is also true for small changes in the sample volume in duplicate analyses: exact reproducibility of the sample volume is important only in the case of low distribution coefficient values. 相似文献
95.
Examples of exact expressions for the moments (mainly of the mean) of functions of sample moments are given. These provide checks on alternative developments such as asymptotic series for n, and simulation processes. Exact expressions are given for the mean of the square of the sample coefficient of variation, particularly in uniform sampling; Frullani integrals studied by G. H. Hardy arise. It should be kept in mind that exact results for (joint) moment generating functions (mgfs) are of interest as they produce a means of obtaining exact results for (cross) moments—including moments with negative indices. Thus an exact expression for the joint mgf of the 1st two noncentral moments can be used to obtain the mean of the (c.v.)2 (but not for the mean of the c..). A general expression is given for the moment generating function of the sample variance. The limitations of Fisher's symbolic formula for the characteristic function of sample moments (or more general statistics) are noted.This research was sponsored by the Applied Mathematical Sciences Research program, Office of Energy Research, U. S. Department of Energy under contract DE-AC0584OR21400 with the Martin Marietta Energy Systems. Inc. 相似文献
96.
自动化样品预处理的一项新技术——吉尔森ASTED系统及其应用(续完)陈小华(华运有限公司香港上环永乐街172—176号永富商业大厦三楼)3应用吉尔森ASTED系统已经被广泛地应用在许多领域,如药理学、药物动力学、药物-蛋白质结合研究、毒理学、临床医学... 相似文献
97.
Summary The effect of silica gel pretreatment and of different bonding techniques, on the chromatographic properties of octadecyl
bonded phases is described. The experiments show that a monomeric octadecyl bonded phase, prepared from silica gel that has
not been treated before bonding, has a poor selectivity towards polycyclic aromatic hydrocarbons (PAHs) and shows high adsorption
of basic components. Silica gel treatment before the bonding of the monofunctional silane does not give a substantial improvement.
Polymeric phases on the other hand show a much better PAH selectivity and a lower adsorptivity towards basic components. Further
improvement can be achieved with the polymeric modification if silica gel treatment is carried out before bonding. 相似文献
98.
《Journal of separation science》2003,26(17):1527-1532
In this paper, a setup called micro‐column solid phase extraction (MicroSPE) was developed to enhance the sensitivity of capillary electrophoresis. The setup consists of a manual pump, several insulin syringes, and a Teflon extraction cartridge. The cartridge was made of 2–4 mm irregular C18 solid phase materials in a Teflon tube (375 μm ID) with glass fiber frits. Two pieces of capillary tubing were connected to both the ends of the cartridge. Using sulindac‐spiked urine as the test sample, the extraction and analytical conditions were investigated in detail. When 1 μL 70/30 methanol/water was applied as the elution solvent, satisfactory results could be obtained. The internal standard method was used to quantitatively determine the compound in urine. The detection limit for sulindac was 2.9 ng/mL and the enrichment factor reaches more than 260. The result illustrates that the MicroSPE setup has a significant concentrating effect and is suitable for preconcentrating and cleaning‐up samples with complex matrices. 相似文献
99.
Nguyen Q. A. Tucker M. P. Boynton B. L. Keller F. A. Schell D. J. 《Applied biochemistry and biotechnology》1998,(1):77-87
Selective thinning of forests in the western United States will generate a large, sustainable quantity of softwood residues
that can be an attractive feedstock for fuel ethanol production. The major species available from thinning of forests in northern
California and the eastern Rocky Mountains include white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii), and Ponderosa pine (Pinus ponderosa). Douglas fir chips were soaked in 0.4% sulfuric acid solution, then pretreated with steam at 200 – 230°C for 1 – 5 min.
After pretreatment, 90 – 95% of the hemicellulose and as much as 20% of the cellulose was solubilized in water, and 90% of
the remaining cellulose can be hydrolyzed to glucose by cellulase enzyme. The prehydrolysates, at as high as 10% total solid
concentration, can be readily fermented by the unadapted yeastSaccharomyces cerevisiae D5A. 相似文献
100.
A simple and fast analytical procedure has been developed for the determination of As, Sb, Se, Te and Bi in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS). Samples were treated with aqua regia for 10 min in an ultrasound water bath and pre-reduced with KBr for total Se and Te determination or with KI and ascorbic acid for total As and Sb, the determination of Bi being possible in all with or without pre-reduction. Slurries of samples, in the presence of antifoam A, were treated with NaBH4 in HCl medium to obtain the corresponding hydrides, and AFS measurements were processed in front of external calibrations prepared and measured in the same way as samples. Results obtained by the developed procedure compare well with those found after microwave-assisted complete digestion of samples. The proposed method is simple and fast, and only 1 ml of milk is needed. The values obtained for detection limit are 2.5, 1.6, 3, 6 and 7 ng l−1 for As, Sb, Se, Te and Bi respectively in the diluted samples, with average relative standard deviation values of 3.8, 3.1, 1.9, 6.4 and 1.2% for three independent analysis of a series of commercially available samples of different origin. Data found in Spanish market samples varied from 3.2±0.3 to 11.3±0.2 ng g−1 As, from 3.1±0.2 to 11.6±0.4 ng g−1 Sb, from 10.7±0.5 to 25.5±0.4 ng g−1 Se, from 0.9±0.2 to 9.4±0.6 ng g−1 Te and from 11.5±0.1 to 27.7±0.4 ng g−1 Bi. 相似文献