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排序方式: 共有811条查询结果,搜索用时 15 毫秒
1.
Elnaz Marzi Khosrowshahi Behnaz Limuie Khosrowshahi Mir Ali Farajzadeh Abolghasem Jouyban Mustafa Tuzen Mohammad Reza Afshar Mogaddam Mahboob Nemati 《Biomedical chromatography : BMC》2022,36(7):e5371
A dispersive solid-phase extraction method based on a new sorbent has been performed on plasma and wastewater samples to determine metoprolol by high-performance liquid chromatography–tandem mass spectrometry. In this study, the analyte was adsorbed from the samples onto microcrystalline cellulose as a green and efficient sorbent and then eluted for use in the determination step. In the mass spectrometer, the analyte was detected in the positive mode and selectivity of the analysis was increased by sequential mass analysis through multiple reaction monitoring. All of the effective parameters in the extraction of metoprolol from plasma and wastewater were optimized. Under optimal conditions the method was linear in the ranges of 1–1,000 and 0.1–1,000 ng/ml in plasma and wastewater samples, respectively. The detection limits of the method were 0.30 and 0.03 ng/ml in plasma and wastewater samples, respectively. The data showed that the method provides low detection limit, wide linear range, good precision and high extraction recovery. Finally several plasma and wastewater samples were successfully analyzed using the method. The use of a small amount of a green and inexpensive sorbent and a low volume of plasma without the need for further pretreatment steps are the main advantages of the method. 相似文献
2.
3.
O.G. Kosareva N.A. Panov N. Akozbek V.P. Kandidov Q. Luo S.A. Hosseini W. Liu J.-F. Gravel G. Roy S.L. Chin 《Applied physics. B, Lasers and optics》2006,82(1):111-122
We demonstrate a three orders of magnitude increase and stability in the backscattered fluorescence signal from nitrogen molecules
by terawatt femtosecond laser pulse induced air filaments using a new method. The method is based on squeezing the initial
beam diameter using a telescope. The effect of laser shot-to-shot fluctuations was included in numerical simulations by a
random distribution of the initial intensity in both squeezed and non-squeezed beams. Statistical processing of the simulation
results shows that the average diameter of plasma channels as well as the total amount of free electrons generated in a bunch
of multiple filaments in air is larger in the squeezed beam. Shot-to-shot stability of the simulated plasma density increases
in the squeezed beam. The change of this plasma density with propagation distance is in good qualitative agreement with the
change of the range-corrected nitrogen fluorescence signal with distance.
PACS 42.65.Jx; 42.60.Jf; 42.68.Ay; 42.68.Wt 相似文献
4.
Several planar waveguides have been fabricated. The waveguides have been polished for determination of their refractiveindex profiles (RIP) by wedge method. The RIP determined by inserting the sample in a Mach-Zehnder interferometer andapplying fringe analysis methods. 相似文献
5.
Headspace solvent microextraction (HSME) into a single drop is developed for the determination of six trihalomethanes, CH2Cl2, CHCl3, C4H9Cl, CCl4, C2HCl3, and C2Cl4, in aqueous solution. A drop of benzyl alcohol containing bromoform, as an internal standard, is used for extraction. The analytes are extracted by suspending a 3-microL drop directly from the needle of a microsyringe. The needle passes through the septum of a vessel, and the needle tip appears above the surface of the solution. After the prescribed extraction time, the drop is drawn back into the syringe. The syringe is then removed, and its content is injected directly into a gas chromatography column for analysis. The main parameters affecting the HSME process, such as stirring speed, microdrop volume, sample solution temperature, microsyringe needle temperature, sample volume, solution pH, extracting solvent, and ionic strength of the solution, are studied. Also, the linear range and precision of the method are examined. 相似文献
6.
Potentiometric determination of ultratrace amounts of fluoride enriched by zirconia in a flow system
A satisfactory method was described for separation and preconcentration of ultratrace amounts of fluoride ions enriched by
zirconia (ZrO2) as an inorganic ion exchanger. Fluoride ions can be adsorbed rapidly and selectively on zirconia from an acidic solution
(pH 4.8) then reversibly desorbed by increasing pH up to 13. A flow system consisting of a column packed with zirconia impregnated
on cellulose fibers and an ion-selective electrode was used for the determination of fluoride. The RSD was found to be 1.6%
and the detection limit defined by S/N = 3 was 3 × 10−9 mol L−1. The interference effects of various ions, such as nitrate, sulfate, halides, alkaline, and alkaline earth ions, which may
be found in the environmental water, were studied, and it was found that they were tolerated even at high concentrations.
The method was applied to determine fluoride in drinking water, which contains ultratrace amounts of fluoride. The concentration
of fluoride was found to be 42 μg L−1, which is confirmed by spiking 2 μmol fluoride to the drinking water with a recovery of 99%.
Published in Russian in Zhurnal Analiticheskoi Khimii, 2006, Vol. 61, No. 2, pp. 179–183.
The text was submitted by the authors in English. 相似文献
7.
Khodayar Gholivand Zahra Hosseini Mehrdad Pourayoubi Zahra Shariatinia 《无机化学与普通化学杂志》2005,631(15):3074-3079
Some new N‐carbonyl, phosphoramidates with formula C6H5C(O)N(H)P(O)R2 (R = NC3H6 ( 1 ), NC6H12 ( 2 ), NHCH2CH=CH2 ( 3 ), N(C3H7)2 ( 4 )) and CCl3C(O)N(H)P(O)R′2 (R′ = NC3H6 ( 5 ), NHCH2CH=CH2 ( 6 )) were synthesized and characterized by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis. The structures were determined for compounds 1 and 2 . Compound 1 exists as two crystallographically independent molecules in crystal lattice. Both compounds 1 and 2 produced dimeric aggregates via intermolecular ‐P=O…H‐N‐ hydrogen bonds, which in compound 2 is a centrosymmetric dimer. In compounds with four‐membered ring amine groups, 3J(P,C)>2J(P,C), in agreement with our previous studies about five‐membered ring amine groups. Also, 3J(P,C) values in compounds 1 and 5 are greater than in compounds with five‐, six‐ and seven‐membered ring amine groups. 相似文献
8.
Solid Phase Extraction and Flame Atomic Absorption Spectrometric Determination of Trace Amounts of Zinc and Cobalt Ions in Water Samples 总被引:1,自引:0,他引:1
A simple and rapid method for the preconcentration of Co2+ and Zn2+ as their 2-guanidino-benzimidazole chelates is proposed using an octadecyl silica cartridge. The retained analytes were recovered with a mixture of 5mL of 0.01M HNO3 and 5mL of methanol. The metal ions in the effluent were determined by flame atomic absorption spectrometry. The effect of different parameters, such as sample matrix, amount of ligand, type of eluent for elution of ions from cartridge, flow rates of sample solution and eluent, breakthrough volume, and limit of detection, were evaluated. The effects of various cationic and anionic interferences on the percent recovery of Co2+ and Zn2+ were also studied. Quantitative extraction efficiencies were obtained by elution of the cartridge with a minimal amount of solvent. Hence, with a typical preconcentration factor of 50, the limits of detections of the proposed method are 0.26 and 1.62ngmL–1 for Zn2+ and Co2+, respectively. The method was applied to the determination of zinc and cobalt ions in different water samples. 相似文献
9.
The stability constants for anion binding by the acyclic hexaamine 1 , its macrocyclic analogue 2 , and the bicyclic compound 3 in their protonated forms are reported. Compound 3 forms stable and selective complexes with halide ions, the stability sequence being I? > Br? > Cl?. Compound 2 forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue 1 and shows a better selectivity pattern. Compound 3 forms stronger complexes with oxalate2? than 2 and shows a remarkably high binding selectivity between oxalate2? and malonate2?. The comparison of the ability of 1–3 to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability and selectivity. 相似文献
10.
This paper reports a simple and highly selective method for the separation, preconcentration, and determination of trace amounts of thorium and uranium in some complex samples via staircase flotation. The method is based on the initial flotation of the Th(IV)‐arsenazo III complex in the presence of U(VI) from a solution of 5 mol dm?3 HCl, then reduction of U(VI) to U(IV) and repetition of the flotation step. In both steps, the floated complex was dissolved in a 5‐mL portion of methanol and its absorbance was measured at 655 nm, spectrophotometrically. For a 30‐mL portion of the sample, Beer's law was obeyed over the concentration ranges of 3.40 × 10?7to 3.06 × 10?6 mol dm?3 for Th(IV) and3.40 × 10?7 to 3.40 × 10?6 mol dm?3 for U(IV) with the apparent molar absorptivity of 4.20 × 105 dm3 mol?1 cm?1 and 3.59 × 105 dm3 mol?1 cm?1, respectively. The RSDs (n = 7) corresponding to 1.7 × 10?6 mol dm?3 of Th(IV) and U(IV) were obtained as 1.7% and 1.87%. The detection limits (7 blanks) for both the metal ions were found to be 1.7 × 10?7 mol dm?3. The important benefit of the method is that the determinations are free from the interference of almost all cations and anions found in the complex matrixes, such as seawater samples. The proposed method was also applied to reference materials, and the determinations were shown to have good agreement with the certified values. 相似文献