Contribution to the alkaline degradation of cefepime

Deviations of the value of the rate constant for borate anions of the first step in the degradation of the antibiotic cefepime from Bronsted relation and deviations from i=f(pH) plots in voltammetric reductions of the oximino group led to investigation of the kinetics of degradation of cefepime in ammonia, borate, CHES and glycine buffers pH 9.3 using UV–visible spectra. Presence of at least two consecutive processes was detected and an interaction of cefepime with glycine has been proved. Identification of intermediates is under investigation.     

Voltammetric behavior and determination of antidepressant drug paroxetine at carbon-based electrodes

Ionics - Simple, rapid, sensitive, and reproducible methods were developed for the assay of paroxetine in tablets. The electrooxidative behavior and determination of paroxetine on boron-doped...     

Intermolecular Magnetic Spin–Spin Interactions in Solution State at 1.53 mT

Overhauser dynamic nuclear polarization (DNP) technique can provide a dramatic increase in the signal obtained from nuclear magnetic resonance experiments owing to the magnetic spin–spin interactions between ¹H nuclei of the solvent and electrons delocalized on the asphaltene in crude petroleum or asphalt. Studies on ¹H Overhauser DNP enhancements at 1.53 mT are reported for benzene solvent medium with three different radical sources: Iran crude petroleum, MC30 liquid asphalt, and MC800 liquid asphalt for a range of radical concentrations. The results show that protons of benzene are good detectors for dipolar coupling.     

A Novel RP-LC Method for Determination of pK a Values of Some Anticancer Agents and Their Assay

A simple, reliable, and rapid RP-LC method has been developed for the determination of some anticancer drugs (daunorubicin, doxorubicin and vincristine sulfate) in their dosage forms and human urine. These compounds are well separated on a C18 column using the mobile phase consisting of a mixture of acetonitrile (50:50; v/v) at a flow rate of 1.5 mL min⁻¹. The analyte peaks were detected at 235 nm for doxorubicin and daunorubicin, and 220 nm for vincristine. Linearity was obtained in different concentration ranges between 0.10 and 12 μg mL⁻¹ for all compounds. Good sensitivity for all analytes was observed with DAD detection. LOD and LOQ of the method were found satisfying. The proposed method has been extensively validated in accordance with ICH guidelines and obtained results proved that the proposed method was precise, accurate, selective, and sensitive for simultaneous analysis of studied compounds. All analytical procedures including sample preparation, flow rate, and run time were at low levels. Also, pK _a values were determined using the dependence of the retention factor on the pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pK _a at different methanol–water mixtures, ranging between 45 and 60 % (v/v).

     

A Novel RP-LC Method for Determination of pK a Values of Some Anticancer Agents and Their Assay

A simple, reliable, and rapid RP-LC method has been developed for the determination of some anticancer drugs (daunorubicin, doxorubicin and vincristine sulfate) in their dosage forms and human urine. These compounds are well separated on a C18 column using the mobile phase consisting of a mixture of acetonitrile (50:50; v/v) at a flow rate of 1.5 mL min^?1. The analyte peaks were detected at 235 nm for doxorubicin and daunorubicin, and 220 nm for vincristine. Linearity was obtained in different concentration ranges between 0.10 and 12 μg mL^?1 for all compounds. Good sensitivity for all analytes was observed with DAD detection. LOD and LOQ of the method were found satisfying. The proposed method has been extensively validated in accordance with ICH guidelines and obtained results proved that the proposed method was precise, accurate, selective, and sensitive for simultaneous analysis of studied compounds. All analytical procedures including sample preparation, flow rate, and run time were at low levels. Also, pK _a values were determined using the dependence of the retention factor on the pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pK _a at different methanol–water mixtures, ranging between 45 and 60 % (v/v).     

A Sensitive and Selective RP-LC Method for the Simultaneous Determination of the Antihypertensive Drugs, Enalapril, Lercanidipine, Nitrendipine and Their Validation

A RP-LC method is presented, which is sensitive and selective for the simultaneous determination of enalapril–lercanidipine and enalapril–nitrendipine binary mixtures in their pharmaceutical dosage forms. The analyte peaks were detected using the LC method with the mobile phase ratio of methanol: water (70:30 v/v, pH 3.0) and a 1.0 mL min^?1 flow rate. The detection wavelength was selected at 210 nm using photo diode array detector and column temperature was optimized to 30 °C. Linearity was obtained at different concentration ranges for all working pharmaceutically active compounds between 0.5 and 25 μg mL^?1. The proposed methods were extensively validated according to USP 27 requirements and ICH guidelines. The methods were applied to the analysis of pharmaceutical dosage forms containing binary mixtures of enalapril–lercanidipine and enalapril–nitrendipine. Moreover, the proposed methods were applied for the degradation studies of the selected compounds. Degradation studies were conducted using stress conditions such as UV light, acidic and alkaline hydrolysis, oxidation and heat in oven, to evaluate the ability of the separation of the response of standard compounds from their degradation products.     

Evolution of magnetic and structural properties of TiO2 with Co-doping

This paper presents the phase formations and magnetic properties of Co-doped TiO₂ synthesized by the colloidal and ammonium nitrate melt techniques (ANMT). The phase formations and ferromagnetic properties were studied with XRD and SQUID magnetometry. Crystallization of the TiO₂ rutile lattice was completed at 1000 °C and that was preserved during annealing up to 1300 °C. For the samples annealed at 1200 °C, elemental analysis has shown that the colloidal technique leads to a single-phase rutile with cobalt concentration of almost nothing even in the initially 0.5 mol Co-added samples. Further increase of annealing temperature results in the appearance of other Ti-phases in addition to the rutile. On the other hand, it is quite interesting that these samples show ferromagnetic behavior. The samples synthesized by the ANMT method contain larger amounts of Co compared to the colloidal technique.     

New exact solutions to the space–time fractional nonlinear wave equation obtained by the ansatz and functional variable methods

In this paper, the ansatz method and the functional variable method are employed to find new analytic solutions for the space–time nonlinear fractional wave equation, the space–time fractional Kadomtsev–Petviashvili–Benjamin–Bona–Mahony equation and the space–time fractional modified Korteweg–de Vries–Zakharov–Kuznetsov equation. As a result, some exact solutions are obtained in terms of hyperbolic and periodic functions. It is shown that the proposed methods provide a more powerful mathematical tool for constructing exact solutions for many other nonlinear fractional differential equations occurring in nonlinear physical phenomena. We have also presented the numerical simulations for these equations by means of three dimensional plots.