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排序方式: 共有235条查询结果,搜索用时 15 毫秒
91.
The oxidative behaviour of pimozide was studied in hydroalcoholic media (10+90 methanol-H2O, pH range 2-7.5) at carbon based electrodes. Pimozide was irreversibly oxidized at high positive potentials, resulting in the formation of a couple with a reduction and re-oxidation peak at much lower potentials. The response was evaluated with respect to pH, scan rate, addition of surfactant and other variables. Using differential pulse voltammetry (DPV), the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 2.1 at +1.1 V (versus Ag/AgCl) on glassy carbon electrode. The process could be used to determine pimozide concentrations in the range 8×10−7-1×10−4 M. Applicability to tablets and human serum analysis was illustrated. Furthermore, a high-performance liquid chromatographic method with electrochemical detection (HPLC-EC) was developed, which allowed pimozide to be detected down to a level of 2.7×10−10 M (0.25 ppb). 相似文献
92.
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
93.
Electrochemical study of fluvastatin sodium – analytical application to pharmaceutical dosage forms, human serum, and simulated gastric juice 总被引:3,自引:0,他引:3
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
94.
A known phenylethanoid glycoside, ehrenoside (1), was isolated together with three new phenylethanoid glycosides, verpectoside A (2), B (3) and C (4) from the aerial parts of Veronica pectinata var. glandulosa. On the basis of spectral analysis (UV, FAB-MS, 1H-, 13C- and 2D-NMR), compounds 2-4 were determined to be 2-(3,4-dihydroxyphenyl)ethyl-O-alpha-L-arabinopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-(4-O-trans-feruloyl)-beta-D-glucopyranoside, 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-glucopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-(4-O-trans-caffeoyl)-beta-D-glucopyranoside and 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-glucopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-(4-O-trans-feruloyl)-beta-D-glucopyranoside, respectively. Isolated phenylethanoid glycosides exhibited potent radical scavenging activity against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. 相似文献
95.
Tunc S Maitz MF Steiner G Vázquez L Pham MT Salzer R 《Colloids and surfaces. B, Biointerfaces》2005,42(3-4):219-225
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
96.
Sibel Erduran 《Foundations of Chemistry》2007,9(3):247-263
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
97.
Merve Yuzbasioglu Baran Zuhal Guvenalp Iclal Saracoglu Cavit Kazaz Bekir Salih L. Omur Demirezer 《Natural product research》2020,34(12):1669-1677
AbstractIn this study, phytochemical composition of Arnebia densiflora (AD) was determined and cytotoxic effects of the n-hexane extract and compounds isolated from this species on various cell lines were investigated. By means of serial chromatographic studies, 6 naphthoquinone derivatives were yielded, which are isovalerylalkannin, α-methyl-n-butyl alkannin, acetylalkannin, β-acetoxy isovalerylalkannin, alkannin and a new compound: 4-hydroxy 4-methyl valeryl alkannin. Structures of the isolated compounds were elucidated using UV, IR, 1D-2D NMR, MS and CD methods. Cytotoxic effects of the extract and isolated alkannins were investigated on L929, HeLa, HEp-2 cells. AD and the isolated compounds demonstrated moderate to strong cytotoxic effects (IC50 range: 4.92-172.35?µg/ml). The results of DNA fragmentation and caspase-3 activity studies on HeLa cells exhibited that AD and the naphthoquinones isolated from it caused cytotoxicity through induction of apoptosis. 相似文献
98.
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
99.
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
100.
Cemil Ibis Sibel Sahinler Ayla Şenol Yavuz Hatice Asar Funda Özkök Hakan Bahar 《Phosphorus, sulfur, and silicon and the related elements》2018,193(6):358-362
In this study, S-, S,S- and S,O-substituted novel nitrodiene compounds were synthesized. Cyclization products were formed when difunctional nucleophiles were used. The stereoisomerism of a heterocyclic nitrodiene is discussed with the help of XRD studies. The structures of all compounds were characterized by spectroscopic methods (FT-IR, 1H NMR, 13C NMR, 19F NMR, MS) and microanalysis. 相似文献