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?engül Dilem Yard?mc? 《Tetrahedron》2006,62(46):10633-10638
The photooxygenation of the 1-methyl-, 2,3-dimethyl-, and 1,4-dimethylcyclohexa-1,4-dienes, which are readily available through Birch reduction, yielded the corresponding ene-products. The formed endocyclic dienes were trapped by the addition of singlet oxygen to give the corresponding bicyclic endoperoxy hydroperoxides. In the case of 1-methylcyclohexa-1,4-diene and 1,4-dimethylcyclohexa-1,4,-diene, the cis-effect determined the product distribution. Photooxygenation of 2,3-dimethylcyclohexa-1,4-dienes gave mainly exocyclic olefin, which was attributed to the lowered rotational barrier of the methyl group and increased reactivity of the methyl groups. 相似文献
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A novel, fast and simple liquid chromatographic method was developed and validated for the simultaneous determination of rosiglitazone and metformin in human plasma. The analysis was performed on a phenyl column (250 mm × 4.6 mm i.d., 5 μm) using a gradient method starting with mobile phase composed of acetonitrile:5 mM acetate buffer pH 5.5 (75:25, v/v). The flow rate was 1 mL min−1. UV detection was performed at 245 nm and verapamil was used as internal standard. The total run time was less than 10 min. Sample preparation included a simple protein precipitation step with acetonitrile. Validation experiments were performed to demonstrate stability, specificity, sensitivity, linearity, accuracy, precision and robustness. The limit of quantification was 100 ng mL−1 for rosiglitazone and 250 ng mL−1 for metformin. The extraction recoveries were 100.02-105.0% for rosiglitazone and 105.64-103.88% for metformin. The method was applied with success to plasma samples obtained from diabetic patients undergoing treatment with rosiglitazone and metformin. 相似文献
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The electrochemical reduction of fenofibrate at a hanging mercury drop electrode (HMDE) was investigated by cyclic voltammetry, square-wave voltammetry, and chronoamperometry. Different buffer solutions were used over a wide pH range (3.0–10.0). The best definition of the analytical signals was found in borate buffer (pH 9.0)–tetrabutylammonium iodide mixture containing 12.5% (v/v) methanol at –1.2 V (versus Ag/AgCl). According to cyclic voltammetric studies, the reduction was irreversible and diffusion controlled. The diffusion coefficient was 2.38×10–6 cm2 s–1 as determined by chronoamperometry. Under optimized conditions of square-wave voltammetry, a linear relationship was obtained between 0.146–4.96 g mL–1 of fenofibrate with a limit of detection of 0.025 g mL–1. Validation parameters such as sensitivity, accuracy, precision, and recovery were evaluated. The proposed method was applied to the determination of fenofibrate in pharmaceutical formulations. The results were compared with those obtained by a published high-performance liquid chromatography method. No difference was found statistically. 相似文献
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A fast and simple micellar electrokinetic capillary chromatographic method was developed for the analysis of piribedil in pharmaceutical formulations. The effects of buffer concentration, buffer pH, sodium dodecyl sulphate (SDS) concentration, organic modifier, applied voltage and injection time were investigated. Optimum results were obtained with a 50 mM borate buffer at pH 8.0 containing 50 mM SDS by using a fused silica capillary (50 m internal diameter, 72 cm effective length). The sample was injected hydrodynamically for 4 s at 50 mbar pressure and the applied voltage was +30 kV. The detection wavelength was set at 205 nm. Diflunisal was used as an internal standard. The analysis was performed at 25 °C and the total run time was 14 min. The method was suitably validated with respect to linearity range, limit of detection and quantification, precision, accuracy, specificity and robustness. The linear calibration range was 5–100 g mL–1 and the limit of detection was determined as 1 g mL–1. The method developed was successfully applied to the determination of piribedil in pharmaceutical formulations. The results were compared with a spectrophotometric method reported in the literature and no significant difference was found statistically. 相似文献
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This study reports the fabrication of an amperometric cholesterol biosensor based on cholesterol oxidase (ChOx), SnO2NPs and Nafion-modified carbon paste enzyme electrodes (CPE/SnO2NPs-ChOx/Naf). The electrochemical characterisations of BCPE and CPE/SnO2NPs were performed using CV and EIS. The determination of cholesterol was carried out by electrochemical oxidation of H2O2 at 0.6 V vs. Ag/AgCl. The CPE/SnO2NPs-ChOx/Naf presented a linear range from 0.20 μ.mol L?1 to 4.95 μmol L?1 with a low limit of detection (0.04 μ.mol L?1). In addition, the optimal values for pH and temperature were found to be 7.5 and 35°C, respectively. The CPE/SnO2NPs-ChOx/Naf was used for the determination of cholesterol in serum samples and good results were obtained. 相似文献
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Batuhan Yardımcı Ferda Dondurmacıoğlu Ayşem Üzer Reşat Apak 《Analytical letters》2019,52(17):2710-2723
AbstractNovel analytical methods were designed for monitoring humic acid photodegradation in environmental waters. Modified CUPric Reducing Antioxidant Capacity (CUPRAC) spectrophotometric and chromatographic methods were used for the determination of dihydroxybenzoate isomers (DHBAs) produced from a salicylate probe, which was hydroxylated by hydroxyl radicals (?OH) produced from the photodegradation of humic acid under ultraviolet A-radiation. The combined use of CUPRAC colorimetry and HPLC was shown to effectively monitor humic acid photodegradation and ?OH generation for the first time. The formation of 2,5-dihydroxybenzoate and 2,3-dihydroxybenzoate, as major and minor products, respectively, from the hydroxylation of a salicylate probe was demonstrated by HPLC and confirmed by a modified CUPRAC method to indicate ?OH formation from humic acid, which acted as both a generator and absorber of hydroxyl radicals. Salicylate hydroxylation showed an increase between 30 and 50?min of illumination, and was affected by the initial concentration of humic acid up to 0.01% but not by solution pH around the neutral values. Traces of Fe(III) and Mn(II) present in natural waters decreased the ?OH production, but EDTA partly restored the probe hydroxylation by chelating these metal cations. Since humic acid-mediated ?OH generation may aid in natural disinfection processes, this work may extend our comprehension of concentration- and time-dependent generation of ?OH in environmental waters and of the possible effects of other antioxidants. 相似文献
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En-Jun?GaoEmail author Shaozhong?Zhang Yang?Meng Fu-Chen?Zhao Xiao-Yu?Ma Hai-Tao?Jin Si-Jia?Liu Jing?Ge Ya-Guang?Sun Wan-zhong?Zhang Ming-Chang?ZhuEmail author 《Journal of fluorescence》2016,26(4):1331-1339
Two new zinc complexes, namely Zn(L1)ClCH2NO(1) and {Zn(L2)CH2NO}n?N(CH3)3?ClO4(2) (L1 = 3,5-di(1H-imidazol-1-yl)pyridine L2 = 1,3,5-tris(1-imidazolyl) benzene), have been synthesized, and characterized by IR spectra, elemental analysis, and a single crystal X-ray diffraction. Fluorescence spectroscopy indicated that two complexes presented strong DNA binding affinity constants to fish sperm DNA (FS-DNA). Gel electrophoresis assay demonstrated the ability of the complex to cleave the HL-60 DNA. Apoptotic study showed the complex exhibited significant cancer cell(KB) inhibitory rate. 相似文献
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In the present study, a novel, fast and simple liquid chromatographic method was developed and validated for the simultaneous
determination of rosiglitazone and metformin in pharmaceutical preparations. The separation was achieved on a phenyl column
(250 × 4.6 mm i.d., 5 μm) using a mobile phase composed of acetonitrile:10.0 mM phosphate buffer pH 5.5 (70:30, v/v). The flow rate was 1 mL min−1. UV detection was performed at 245 nm and verapamil was used as internal standard. The developed method was validated in
terms of stability, specificity, sensitivity, linearity, accuracy, precision and robustness. The limit of quantification was
0.02 μg mL−1 for both drugs. The method developed was successfully applied to the simultaneous determination of rosiglitazone and metformin
in pharmaceutical preparations. The results were compared to two methods reported in the literature and no significant difference
was found statistically. 相似文献
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