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191.
A simple method using solid-phase extraction (SPE) and ultra high-performance liquid chromatography (UHPLC) for the simultaneous determination of β-blockers, isoflavones, and flavonoids in human urine is developed. A statistical central composite design and response surface analysis is used to optimize the separation of the analytes. These multivariate procedures are efficient in determining the optimal separation condition using resolutions and retention time as responses. A gradient elution using a mobile phase consisting of 0.05% trifluoroacetic acid in water and acetonitrile is applied on a Hypersil GOLD column within a short analysis time of 4.5 min. UV detection was used to monitor the analytes. The suggested method was linear in a concentration range from 0.04-20.00 μg/mL, depending on the compound. The limits of detection ranged from 8.9 to 66.2 ng/mL. The precision was lower than 2.74%, and the accuracy was between 0.01-3.65%. The Oasis HLB column, with the highest recoveries, is selected for the pre-concentration step. This present paper reports, for the first time, a method for the simultaneous determination of β-blockers, isoflavones, and flavonoids in human urine samples. Furthermore, the developed method can also be applied to the routine determination of examined compounds concentrations in human urine. 相似文献
192.
The paper focuses on the numerical solution to two-dimensional temperature field of boiling liquid flowing along a vertical, asymmetrically heated minichannel with a rectangular cross-section. One of the walls of a minichannel is DC supplied single-sided enhanced foil with mini-recesses distributed unevenly in the selected area. The parallel walls are made of glass panes for thermal insulation and they are intended for observation of the two-phase flow and the void fraction. The thin layer of thermosensitive liquid crystal paint on the outer side of the foil enabled to record two-dimensional temperature distribution of outer foil surface. The paper described computations based on Trefftz method for finding two-dimensional temperature field of boiling liquid flowing along the minichannel. The presented research is limited only to the liquid phase of the two-phase mixture observed in the minichannel. The velocity of liquid flowing through the minichannel is represented by a piecewise linear approximating function. To solve energy equation for liquid phase, Trefftz functions specially generated for this purpose were employed. Temperature field in the fluid was approximated by a linear combination of Trefftz functions. Equalizing calculus was applied to the Trefftz method to smooth temperature measurements and reduce measurement errors. Temperature at the interface between working fluid and foil amounts to the saturation temperature. Temperature distribution in the foil and the glass pane was also computed using proper Trefftz functions. 相似文献
193.
Sylwia BzdonJacek Góralski Waldemar ManiukiewiczJan Perkowski Jacek RogowskiMagdalena Szadkowska-Nicze 《Radiation Physics and Chemistry》2012,81(3):322-330
Fe-doped TiO2 catalyst was prepared by wet impregnation, using TiO2 P25 Degussa as a precursor and Fe(NO3)3 as a dopant, followed by irradiation with an electron beam or γ-rays. Surface properties of Fe/TiO2 samples were examined by BET, XRD, ToF-SIMS, and TPR methods. The photocatalytic activity towards destruction of the anionic surfactant, sodium dodecylbenzenesulfonate (SDBS), in aqueous solutions was higher for the irradiated Fe/TiO2 catalysts than for bare TiO2 P25 or that calcined at 500 °C. The results show that irradiated catalysts exhibit a more uniform texture with high dispersion of iron species. An enhancement of the activity of irradiated Fe/TiO2 systems can be attributed to the synergetic effects of small crystallite size and homogenous distribution of iron species including FeTiO3 phase. 相似文献
194.
D Bratkowska N Fontanals S Ronka AW Trochimczuk F Borrull RM Marcé 《Journal of separation science》2012,35(15):1953-1958
Two imidazolium supported ionic liquid phases (SILPs) containing different anions, trifluoromethanesulphonate [CF(3) SO(3) (-) ], and tetrafluoroborate [BF(4) (-) ], were synthesized and evaluated as solid-phase extraction sorbents for extracting acidic pharmaceuticals from aqueous samples under strong anion-exchange conditions, which include an effective cleanup of the sample. The best SILP material [MI(+) ][CF(3) SO(3) (-) ] was selected and successfully applied to the determination of acidic pharmaceuticals in different types of water samples (river water and effluent wastewater). The results were then compared to the previously synthesized SILP material based on [MI(+) ][CF(3) COO(-) ] and the commercially available Oasis MAX sorbent. 相似文献
195.
The reaction mechanisms of the enzymatic deamination of tryptamine catalysed by the enzyme monoamine oxidase (MAO, EC 1.4.3.4) were investigated using the kinetic isotope effect and solvent isotope effect methods. The numerical values of these deuterium effects in the (1S) and (1R) positions of tryptamine were determined using the non-competitive spectrophotometry. The deuterium-labelled isotopologue [(1S)-2H]tryptamine was obtained in two steps by enzymatic coupling of indole with S-methyl-l-cysteine in a deuterated medium followed by enzymatic decarboxylation of the resulting [2-2H]-l-tryptophan. [(1R)-2H]tryptamine was obtained by enzymatic decarboxylation of l-tryptophan in the fully deuterated medium. 相似文献
196.
The sensitivity of Lepidium sativum L. germination to three imidazolium ionic liquids was investigated in solutions and soils artificially contaminated with
mixtures of those compounds. In case of aquatic solutions, the toxic character of analyzed compounds is connected with their
hydrophobicity. The seedling growth is increasing with the decrease in ionic liquid hydrophobicity. The novelty of those studies
is the application of high-performance liquid chromatography, which was used for the determination of ionic liquid quantity
absorbed by cress. There was almost linear relationship between decrease in root germination and amount of ionic liquid uptaken
by cress. Furthermore, the systematic studies on the influence of total organic carbon content in soil on the toxicity of
ionic liquids to cress were performed for the first time. Hazardous effects appeared to be closely connected with organic
matter: with the decrease of total organic carbon quantity, the inhibition of plant growth was more significant. Visual effects
of ionic liquid toxic activity to garden cress are similar as in the case of nutrient deficit in plants.
Figure Visual phytotoxicity effects observed during the test; leaf chromatosis: light green and yellow (up photos), violet (lower
photos) 相似文献
197.
Marcin Leszek Marszałł Ryszard Makarowski Sylwia Hinc Wojciech Czarnowski 《Chromatographia》2009,69(9-10):829-835
An isocratic high-performance liquid chromatographic method with coulometric electrochemical detection has been used for analysis of 5-methyltetrahydrofolate (5-MTHF) in human plasma. A 250 mm × 4.6 mm i.d., 5-μm particle, C18 column was used with 12:88 (v/v) acetonitrile ?35 mM sodium phosphate buffer pH 3.8 as mobile phase at a flow rate of 1.0 mL min?1. The method was validated for 5-MTHF plasma concentrations in the range 2.5–100.0 nM. The method was characterized by a good linearity (regression coefficient r ≥ 0.9989) and limits of detection and quantification of 0.72 and 2.16 nM, respectively. Mean recovery at low and high concentrations ranged from 89.1 to 96.3%, respectively, with a relative standard deviation <4.6%. Between-run imprecision (4.2%) was higher than within-run imprecision (3.4%). The proposed separation and detection procedures were successfully applied to analysis of 5-MTHF in human plasma. 相似文献
198.
199.
Zhang J Ma Y Stachura S He H 《Langmuir : the ACS journal of surfaces and colloids》2005,21(9):4180-4184
This paper reports a robust and efficient approach to assemble highly aligned DNA strands onto Si chips. The method combines advantages from molecular combing and microcontact printing to realize controlling both the density and direction of DNA strands on the Si chip. In addition, it also can be utilized to prepare stretched DNA structures on solid surfaces. Compared to approaches that use molecular combing directly on silanated surfaces, the stretched single-chain DNA structures are straighter. Furthermore, by exploiting the hydrophobic property of the intrinsic poly(dimethylsiloxane) stamp, this study also describes a simple way to produce straight bundled DNA arrays on Si and other substrates. 相似文献
200.