Nefazodone, an antidepressant was electrochemically studied in various buffer systems and at different pH using glassy carbon electrode. Nefazodone was electrochemically oxidized at all pH values. According to the linear relation between the peak current and the nefazodone concentration differential pulse (DPV) and square wave (SWV) voltammetric methods for its quantitative determination in pharmaceuticals and human serum were developed. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H2SO4 at 0.99 and 1.03 V for DPV and SWV techniques, respectively. The linear response was obtained in the ranges of 8×10−7 to 6×10−4 M with a detection limit of 2.1×10−7 M for DPV and 1.17×10−7 M for SWV techniques. The repeatability and reproducibility of the methods were within 1.03, 0.81% relative standard deviations (R.S.D.) for peak currents and 0.40, 0.20% R.S.D. for peak potentials, for DPV and SWV, respectively. Precision and accuracy of the developed method was checked by recovery studies. The proposed methods were successfully applied to the individual tablet dosage form and human serum. 相似文献
The oxidation of fluvastatin sodium on a glassy carbon electrode has been studied by use of a variety of voltammetric techniques. Different conditions were investigated to optimize the determination of fluvastatin sodium. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, and nature of the buffer was investigated. Oxidation of fluvastatin sodium was found to be diffusion-controlled and irreversible. The best results for the determination of fluvastatin sodium were obtained by using differential pulse and square-wave voltammetric techniques in Britton-Robinson buffer at pH 10.04. Differential pulse and square-wave voltammetry at a glassy carbon electrode resulted in linear calibration in the range 8x10(-6) to 6x10(-4) mol L(-1) and detection limits of 1.07x10(-6) and 7.99x10(-7) mol L(-1), respectively. The proposed methods were successfully applied to the determination of the drug in capsules and biological fluids. Excipients did not interfere with the determination. Statistical validation revealed that the methods were free from significant systematic errors. 相似文献
Fibrinogen is a major plasma protein. Previous investigations of structural changes of fibrinogen due to adsorption are mostly based on indirect evidence after its desorption, whereas our measurements were performed on fibrinogen in its adsorbed state. Specific enzyme-linked immunosorption experiments showed that the amount of adsorbed fibrinogen increased as the surface became more hydrophobic. Atomic force microscopy (AFM) investigations revealed the trinodular shape of fibrinogen molecules adsorbed on hydrophilic surfaces, whereas all of the molecules appeared globular on hydrophobic surfaces. The distribution of secondary structures in adsorbed fibrinogen was quantified by in situ Fourier-transform infrared (FTIR) analysis. Substrates of identical chemical bulk composition but different surface hydrophobicity permit direct comparison among them. Adsorption properties of fibrinogen are different for each degree of hydrophobicity. Although there is some increase of turn structure and decrease of β-sheet structure, the secondary structure of adsorbed fibrinogen on hydrophilic surface turned out to be rather similar to that of the protein in solution phase with a major -helix content. Hydrophilic surfaces exhibit superior blood compatibility as required for medical applications. 相似文献
In this paper, domain-specificity is presented as an understudied problem in chemical education. This argument is unpacked
by drawing from two bodies of literature: learning of science and epistemology of science, both themes that have cognitive
as well as philosophical undertones. The wider context is students’ engagement in scientific inquiry, an important goal for
science education and one that has not been well executed in everyday classrooms. The focus on science learning illustrates
the role of domain specificity in scientific reasoning. The discussion on epistemology of science presents ideas from the
emerging field of philosophy of chemistry to highlight the much neglected area of epistemology in chemical education. Domain-specificity
is exemplified in the context of chemical laws, in particular the Periodic Law. The applications of the discussion for chemical
education are explored in relation to argumentation, itself an epistemologically grounded discourse pattern in science. The
overall implications include the need for reconceptualization of the nature of teaching and learning in chemistry to include
more particular epistemological aspects of chemistry. 相似文献
The electrooxidative behavior and determination of Tamsulosin HCl (TAM), one of the alpha(1)-adrenoceptor antagonist, on a glassy carbon disc electrode were investigated for the first time by using cyclic, linear sweep, differential pulse (DPV) and square wave voltammetry (SWV). TAM showed an irreversible oxidation behavior at all pH values and buffers studied. From the electrochemical response, the main oxidation step was found to be related to the methoxy group on the phenyl ring. DPV and SWV were used to generate peak current versus concentration curves for TAM. A linear response was obtained in the range comprised between 2x10(-6) and 4x10(-4) M for both techniques with detection limit of 3.34x10(-7) M for DPV and 2.45x10(-7) M for SWV. The methods were proposed for the determination of TAM in dosage forms adopting both DPV and SWV modes. The methods were extended to the in vitro determination of TAM in spiked serum samples. 相似文献
Two organobentonites (ODTMA-B, HDTMA-B) were synthesized using hexadecyltrimethyle ammonium bromide (HDTMAB) and octadecyltrimethyle ammonium bromide (ODTMAB). Synthesized organobentonites were characterized by X-ray diffraction particle size, and surface area analysis. Particle size analyses of the original bentonite and organobentonites showed that the organobentonites contained a greater number of coarse particles than present in the original bentonite. While the basal spacings of the organobentonites increased organic cation, the surface area decreased.
To evaluate the potential use of two modified bentonites in removing organic pollutants such as benzoic acid and hydroquinone from water, adsorption experiments were performed under conditions of varied pH (3, 6 and 11) and temperatures(298 and 313 K). Experimental results showed that the sorption capacities increase with decreasing pH value and increasing temperature. The adsorption equilibrium of benzoic acid and hydroquinone on organobentonites was described by the Langmuir and Dubinin–Radushkevich (D–R) models. It was concluded that the isotherm shapes were not affected by pH and temperature. Adsorption capacity of ODTMA-B for benzoic acid was higher compared to that of HDTMA-B at various pH and temperatures. 相似文献
Adsorptive stripping differential pulse voltammetry (AdSDPV) was applied to the assay of sorafenib in human serum sample. Cyclic voltammetry at a carbon based screen printed electrode (SPE) permitted to detect the irreversible oxidation of SOR with formation of a new compound reversibly oxidized at a lower potential. Quantitative assays were realized using a chitosan/carboxylic acid functionalized multiwalled carbon nanotube modified glassy carbon electrode in 0.1 M phosphate buffer pH 7.0 in the presence of 50 % methanol. The AdSDPV method provided two linear responses within the concentration ranges 1×10?8–8×10?8 M and 1×10?7–8×10?7 M in serum with LOQ and LOD of 3.2×10?9 and 9.6×10?10 of lower linear range, respectively. The recovery of sorafenib in spiked serum was 97.5 %. 相似文献
A series of metal complexes were synthesized from equimolar amounts of Schiff bases: 1,4-bis[3-(2-hydroxy-1-naphthaldimine)propyl]piperazine (bappnaf) and 1,8-bis[3-(2-hydroxy-1-naphthaldimine)-p-menthane (damnaf) with metal chlorides. All of synthesized compounds were characterized by elemental analyses, spectral (UV-vis, IR, (1)H-(13)C NMR, LC-MS) and thermal (TGA-DTA) methods, magnetic and conductance measurements. Schiff base complexes supposed in tetragonal geometry have the general formula [M(bappnaf or damnaf)]Cl.nH(2)O, where M=Cr(III), Co(III) and n=2, 3. But also Fe(III) complexes have octahedral geometry by the coordination of two water molecules and the formula is [Fe(bappnaf or damnaf)(H(2)O)(2)]Cl. The changes in the selected vibration bands in FT-IR indicate that Schiff bases behave as (ONNO) tetradentate ligands and coordinate to metal ions from two phenolic oxygen atoms and two azomethine nitrogen atoms. Conductance measurements suggest 1:1 electrolytic nature of the metal complexes. The synthesized compounds except bappnaf ligand have the antimicrobial activity against the bacteria: Escherichia coli (ATCC 11230), Yersinia enterocolitica (ATCC 1501), Bacillus magaterium (RSKK 5117), Bacillus subtilis (RSKK 244), Bacillus cereus (RSKK 863) and the fungi: Candida albicans (ATCC 10239). These results have been considerably interest in piperazine derivatives due to their significant applications in antimicrobial studies. 相似文献
Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoparticles have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to CdS quantum dots (QDs), reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for DNA recognition. In this method, methacryloylamidohistidine-platinium (MAH-Pt(II)) is used as a new metal-chelating monomer via metal coordination-chelation interactions and guanosine templates of DNA. Nanoshell sensors with guanosine templates give a cavity that is selective for guanosine and its analogues. The guanosine can simultaneously chelate to Pt(II) metal ion and fit into the shape-selective cavity. Thus, the interaction between Pt(II) ion and free coordination spheres has an effect on the binding ability of the CdS QD nanosensor. The binding affinity of the guanosine imprinted nanocrystals has investigated by using the Langmuir and Scatchard methods, and experiments have shown the shape-selective cavity formation with O6 and N7 of a guanosine nucleotide (K(a) = 4.841x10(6) mol L(-1)) and a free guanine base (K(a) = 0.894x10(6) mol L(-1)). Additionally, the guanosine template of the nanocrystals is more favored for single stranded DNA compared to double stranded DNA. 相似文献