We describe a simple and efficient method for solid phase extraction and speciation of trace quantities of arsenic. It is based on the use of functionalized aluminum oxide nanoparticles and does not require any oxidation or reduction steps. The experimental parameters affecting extraction and quantitation were optimized using fractional factorial design methods. Adsorbed arsenic was eluted from the sorbent with 1 M hydrochloric acid and determined by graphite furnace atomic absorption spectrometry. Preconcentration factors up to 750 were achieved depending on the sample volume. Studies on potential interferences by various anions and cations showed the method to be highly selective. Under optimum conditions, the calibration plots are linear in the 5.0 to 280 ng L−1 and 8.0 to 260 ng L−1 concentration ranges for As(III) and total arsenic, respectively. The detection limits (calculated for S/N ratios of 3) are 1.81 and 1.97 ng L−1 for As(III) and total arsenic, respectively. The method was successfully applied to the determination and speciation of arsenic in (spiked) environmental, food and biological samples and gave good recoveries. The method was validated using a certified geological reference material.
A new cobalt (II) coordination compound was synthesized using proton transfer mechanism. The reaction between CoCl2·2H2O, Salicylic acid (H2Sal) and acridine (Acr) gave a new coordination compound formulated as (HAcr)4[Co(Sal)3], which was characterized by elemental analysis, NMR, IR and UV/Vis spectroscopies. The interaction of this complex with DNA has been investigated in vitro using UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis methods. The intrinsic binding constant has been estimated to be 5.8 × 105 M?1 using UV absorption. The interaction of DNA–Co (II) complex caused quenching in fluorescence. The binding constant, the number of binding site and Stern–Volmer quenching constant have been calculated to be 7.7 × 104 M?1, 1.143 and 1.5 × 104 Lmol?1, respectively. The increase in the viscosity of DNA with increasing the concentration of the Co (II) complex and the observations of other experiments suggest that the cobalt (II) complex binds to DNA by partial intercalation binding mode. Furthermore, the interaction of DNA–Co (II) complex was confirmed using gel electrophoresis studies. Moreover, molecular docking technique predicted partial intercalation binding mode for the complex. 相似文献
5-Fluorouracil (5FU) is in clinical use as an antitumor agent for the treatment of several types of solid tumors and cancers. However, development of drug resistance within the tumor cells and side effects has been a major limitation for the clinical use of 5FU. Preparation polymer-5FU conjugation is a promising potential antitumor drug and alternative pathway that could be used to treatment of cancer. For this purpose, water soluble poly(maleic anhydride-alt-N-vinyl pyrrolidone)[Poly(MA-alt-NVP)] is synthesized via charge transfer complex (CTC) copolymerization with benzoyl peroxide as an initiator at 80°C under nitrogen atmosphere. CTC mechanism is formed between through MA and NVP by determined using Uv-vis spectroscopy. Molar absorption coefficient (?AD) and equilibrium constant (KAD) of the complex are determined by Scott equation. The results obtained from indicate that copolymerization of MA:NVP system is preceded via alternating mechanism. The compositions of synthesized copolymers are also investigated by elemental analysis and the reactivity ratios of these monomers are calculated by using the elemental analysis data through Kelen-Tüdös, Mayo-Lewis, Fineman-Ross and Inverted Fineman-Ross equations. For preparation of polymer-drug conjugate, chemical modification is employed between the copolymer and 5FU. Polymer-drug conjugate and conjugation mechanism are enlightened by ATR-FTIR, NMR, HR-Raman and XRD methods. 相似文献
An ultrasound assisted emulsification microextraction (USAEME) is successfully used for extraction and determination of trace amount of iron in water and tea samples, followed by flame atomic absorption spectroscopy (FAAS). In this approach, a new synthetic ligand dimetyl (E)‐2‐[(Z)‐1‐acetyl)‐2‐hydroxy‐1‐propenyl]‐2‐butenedioate (DAHPB) is used as chelating agent and chloroform is selected as an extraction solvent. The factors influencing the complex formation and extraction by USAEME method are optimized. These factors are extraction solvent type as well as extraction volume, time, temperature, pH, and the amount of chelating agent. Under optimum conditions, an enrichment factor of 202.9 is obtained from only 7.1 mL of aqueous phase. The calibration graph using the preconcentration system for iron is linear between 40.0 and 800.0 μg L?1 with a detection limit of 7.4 μg L?1. The relative standard deviation (R.S.D) for ten replicate measurements of 500.0 μg L?1 of iron is 2.5%. 相似文献
Ions undergoing a reaction-diffusion process are susceptible to electric field. We show that a constant external field may induce a kind of instability on the state stabilized by diffusion in a reaction-diffusion system giving rise to formation of pattern even when the diffusion coefficients of the reactants are equal. The origin of the pattern is due to the difference in mobilities of the two species and is thus markedly different from that of deformed Turing pattern in presence of the field. While this differential flow instability had been shown earlier to result in traveling waves, we realize in the context of stationary pattern formation in a typical reaction-diffusion-advective system. Our analysis is based on a numerical simulation of a generic model on a two-dimensional domain. 相似文献
The period of a curve is the smallest positive degree of Galois-invariant divisor classes. The index is the smallest positive degree of rational divisors. We construct examples of genus one curves with prescribed period and index over a given global field, as long as the characteristic of the field does not divide the period. 相似文献
A green and sensitive dispersive liquid-phase microextraction procedure based on room-temperature ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) for preconcentration and determination of total iron in real samples prior to flame atomic absorption spectrometry was developed. 2-Mercaptopyridine-N-oxide (pyrithione) and ethanol were used as complexing agent and dispersive solvent in the proposed method, respectively. The factors influencing the extraction were optimized. Under optimum conditions, the enhancement factor of 15 was obtained from only 11.35 mL of aqueous phase. The linear dynamic range and the detection limit were 10.0–700 and 2.4 μg L?1, respectively. The relative standard deviation (RSD) for ten replicate measurements of 500 μg L?1 of iron is 3.1 %. The developed method has been successfully applied for the determination of iron in water samples, human blood serum and rock certified reference material with high efficiency. 相似文献