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801.
Etofibrate, fenofibrate, and atorvastatin were determined in their pharmaceutical preparations and human plasma using differential pulse polarographic and square wave voltammetric techniques by reduction at a dropping-mercury working electrode versus Ag/AgCl reference electrode. The reversibility of the electrode reactions was tested using cyclic voltammetry, and they were found to be irreversible reduction reactions. Optimum conditions such as pH, scan rate, and pulse amplitude were studied, and validation of the proposed methods was performed. The proposed methods proved to be accurate, precise, robust, and specific for determination of the 3 drugs. The relative standard deviation values were <2%, indicating that these methods are precise. Limits of detection and quantitation were in the ranges of 0.037-0.21 and 0.12-0.71 microg/mL, respectively, indicating high sensitivity. 相似文献
802.
The substituted benzylpiperazines, 3,4-methylenedioxybenzylpiperazine, its regioisomer 2,3-methylenedioxybenzylpiperazine and three isobaric ring substituted ethoxybenzylpiperazines have equal mass and many common mass spectral fragment ions. The mass spectra of the three ethoxybenzylpiperazines yield a unique fragment at m/z 107 that allows the discrimination of the three ring substituted ethoxybenzylpiperazines from the two methylenedioxy isomers. Perfluoroacylation of the secondary amine nitrogen of these isomeric piperazines gave mass spectra with differences in relative abundance of some fragment ions, but acylation does not alter the fragmentation pathway and did not provide additional MS fragments of discrimination among these isomers. Gas chromatography coupled with infrared detection provides direct confirmatory data for the structural differentiation between the five isomers. The mass spectra in combination with the vapor phase infrared spectra provide for specific confirmation of each of the isomeric piperazines. The perfluoroacyl derivatives of the ring substituted benzylpiperazines were resolved on a stationary phase of 50% phenyl and 50% methylpolysiloxane. Gas chromatography coupled with time-of-flight mass spectrometric detection provides an additional means of differentiating between the isobaric compounds 3,4-methylenedioxybenzylpiperazine and 4-ethoxybenzylpiperazine, which have similar nominal masses but are different in their calculated exact masses. 相似文献
803.
Uli Schmidhammer Abdel Karim El Omar Anna Balcerzyk Mehran Mostafavi 《Radiation Physics and Chemistry》2012,81(11):1715-1719
The transient absorption induced by picosecond pulse radiolysis in the windows of a fused silica optical cell is investigated with pump probe techniques in the UV and the visible range. After excitation with an electron pulse of 7 MeV and an effective duration of around 10 ps the absorbance changes during relaxation are recorded up to nanoseconds with a supercontinuum and a single wavelength probe at 263 nm. The complex spectral signatures and kinetics of the empty cell are set into relation with the transient absorption of water radiolysis. Special care is taken to assure equal irradiation conditions for the comparative measurements over the large spectral range. The results reveal clearly that the transient absorption induced in the fused silica cell is not negligible. The transient signals due to the cell should be considered in picosecond pulse radiolysis of solutions in order to avoid important errors on the time dependent yield of transient species, particularly of those absorbing in the UV. 相似文献
804.
Najim A. Al‐Masoudi Basil A. Saleh Nesreen Abdul Karim Ahmed Y. Issa Christoph Pannecouque 《Heteroatom Chemistry》2011,22(1):44-50
A series of new Cu(II), Pt(II), VO(II), Fe(II), and Co(II) complexes ( 1‐‐5 ) with 3‐methyl‐6,7‐diphenyllumazine are described. Similarly, complexes from 2‐thiouracil with Cu(II) ( 6,7 ) and Pt(II) ( 8 ) have been prepared and characterized by spectroscopic methods. All the complexes were assayed for their anti‐HIV‐1 and HIV‐2 activity by examination of their inhibition of HIV‐induced cytopathogenicity in MT‐4 cells. Compound 3 was found to be the most active inhibitor against HIV‐2 in cell culture (EC50 = >18.9 μ g/mL, selectivity index (SI) = 3), which provided a good lead for further optimization. Compounds 6 and 7 exhibited some activity (EC50 = >7.12 μ g/mL and >2.23 μ g/mL) against HIV‐1 and HIV‐2, but no selectivity was observed (SI <1). © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:44–50, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20654 相似文献
805.
Karim Engelmark Cassimjee Sílvia Rodríguez Marín Per Berglund 《Macromolecular rapid communications》2012,33(18):1580-1583
Multifunctional polycationic polyamines, for example, used in drug and gene delivery, have product range limitations in their synthesis methods. Here, we synthesize a polyamine by forming a self‐assembling amino aldehyde from the corresponding amino alcohol with horse liver alcohol dehydrogenase (HLADH), followed by reduction. Circular polyamines were synthesized from 3‐amino‐propan‐1‐ol as starting material, analogous to cyclic polyamines formed from azetidin. The product had an isolated yield of 89.7% or 15.3 g L−1. The predicted range of possible polyamine products by this method is broad since many amino alcohols are putative substrates for HLADH. The enzyme also had activity for 2‐amino‐propan‐1‐ol and 2‐amino‐2‐phenyl‐ethanol, for which the enantioselectivity was 330 (S) and 32 (R), respectively. 相似文献
806.
Sahena Ferdosh Md. Zaidul Islam Sarker Nik Norulaini Nik Abd Rahman Jinap Selamat Md. Rezaul Karim Tariq Abdul Razak Mohd Omar Abd Kadir 《中国化学会会志》2012,59(11):1421-1429
Fish viscera, a waste of fish processing industry, can be exploited as a source of PUFA‐rich fish oil for use in food or pharmaceutical industry and at the same time the environment can be protected from pollution by fish wastes. Fish oil was recovered from viscera of Indian Mackerel (Rastrelliger kanagurta), by different supercritical fluid extraction (SFE) e.g. continuous, co‐solvent, soaking, and pressure swing techniques and the yields were compared with that of the solvent extraction method. The SFE parameters such as pressure, temperature, and CO2 flow rate were optimised by employing Response Surface Methodology (RSM) with a view to maximize the oil yield and minimize CO2 consumption. The central composite rotatable design (CCRD) consisting of three variables provided 20 experimental settings. Multiple regressions determined the coefficients of the second‐order polynomial equation. The optimum parameters for all 4 techniques applied were found to be 35 MPa, 60 °C, and 2 mL min?1 with an Oil recovery ranging from 93 to 99%. The study demonstrated a lower CO2 consumption by the soaking and pressure swing techniques at the optimized conditions. Thus, the soaking and pressure swing techniques were most effective for extracting oil from fish viscera. 相似文献
807.
808.
A simple, sensitive, and selective method for the determination of cerium(IV), based on the oxidative reaction between cerium(IV)
and ascorbic acid, has been described. The fluorescence comes from Ce(III) at λexcitation 298 nm and λemission 358 nm, which, in turn, is obtained from the oxidation of ascorbic acid by Ce(IV) in the presence of sulfuric acid. The optimum
conditions such as concentrations of ascorbic acid, sulfuric acid media and pH of the buffer solution were investigated. The
fluorescent intensity of the system is linear over the range 0.0531 μg/ml to 0.3322 mg/ml Ce(IV) and detection limit and correlation
coefficient are 0.0145 μg/ml and R=0.99987,respectively. 相似文献
809.
A batch type chemiluminescence (CL) determination of enoxacin is described. In this work, it was observed that enoxacin could enhance the chemiluminescence (CL) emission Ru(phen)3
2+–Ce(IV) system and this enhancement effect was dependent on the concentration of enoxacin, based on which, CL system was established for the determination of enoxacin. Under the optimum experimental conditions, the linear range and detection limit are 0.6406–64.06 μg/ml and 0.0210 μg/ml, respectively. The R.S.D. is 1.75%. (n=10). The proposed method has been applied to detect the content of enoxacin in pharmaceutical formulation and human serum with satisfactory results. The possible mechanism of the CL reaction was discussed. 相似文献
810.
Piotto M Bourdonneau M Elbayed K Wieruszeski JM Lippens G 《Magnetic resonance in chemistry : MRC》2006,44(10):943-947
The acquisition time and quality of 1D 13C{1H} spectra can be improved substantially by using a modified driven equilibrium Fourier transform (DEFT) sequence, which is specifically designed to compensate for the effects of B1 inhomogeneity, pulse miscalibration and frequency offsets. The new sequence, called uniform driven equilibrium Fourier transform (UDEFT), returns the carbon magnetization with a high accuracy along its equilibrium position after each transient is complete. Thus, the sequence allows the use of relaxation delays (RD), which are much shorter than the carbon T1 of the molecule, thereby speeding up the acquisition process of 1D 13C{1H} spectra. To achieve this level of performance, UDEFT employs a refocusing element constituted by a composite adiabatic carbon pulse surrounded by two 90 degrees carbon pulses whose phases are designed to compensate for 90 degrees pulse miscalibrations in an MLEV manner (90 degrees+x-tau(FID)-180+y(Adia)-tau-90 degrees+x-180 degrees+x(Adia)). A version of the UDEFT sequence allows recording 1D 13C{1H} spectra devoid of heteronuclear NOE by using a matched adiabatic 1H decoupling scheme where an even number of 180 degrees adiabatic pulses is applied during the UDEFT module. Spectra of a solution of 300 mM camphor that contains some carbon nuclei with very long T1 relaxation times (90 s and 78 s) were acquired with 128 scans in 10 min using a 5 s relaxation delay. 相似文献