Co. SEP - Academia.edu (original) (raw)

Papers by Co. SEP

New, accurate, sensitive and economical non‐aqueous volumetric method for the determination of pr... more New, accurate, sensitive and economical non‐aqueous volumetric method for the determination of pregabalin in raw material has been developed. The titrimetric method involves the reaction of perchloric acid with pregabalin and crystal violet was used as indicator to detect the end of the titration. The method was validated by following the analytical performance parameters suggested by the International Conference on Harmonization (ICH). The calibration curve was linear from 80 to 120 % with r = 0.9994. Statistical treatment of the experimental results indicated that the method is precise and accurate. The proposed method can be used for quality control assay of pregabalin in bulk drug.

The present manuscript describes simple, sensitive, rapid, accurate, precise and economical ratio... more The present manuscript describes simple, sensitive, rapid, accurate, precise and economical ratio spectra derivative method for the simultaneous determination of Cefixime and Dicloxacillin sodium in tablet dosage form. The method is based on the use of the first derivative of the ratio‐spectra obtained by dividing the absorption spectrum of binary mixtures by a standard spectrum of one of the compounds. The cefixime was estimated directly at the 289 nm (λ‐max of cefixime) without any interference of dicloxacillin sodium. The first derivative amplitudes at 227.2 nm was selected for estimation of dicloxacillin sodium. The wavelength interval (Dl) was selected as 8 nm. Methanol was used as the solvent. Both the drugs showed linearity in the range of 3‐16 μg/ml. The method was successfully applied for the determination of these two drugs in tablet dosage form. No interference was observed from excipients present in the tablet. The suitability of this method for the quantitative determination of Cefixime and Dicloxacillin sodium was proved by validation. The proposed method was found to be simple and sensitive for the routine analysis of these two drugs in tablet dosage form. The results of analysis have been validated statistically by recovery studies.

A simple, rapid, accurate and economical spectrophotometric method has been developed for estimat... more A simple, rapid, accurate and economical spectrophotometric method has been developed for estimation of Naftopidil from bulk and pharmaceutical formulation. Materials and methods: The λmax of Naftopidil in methanol and water was found to be 281 nm. The drug followed linearity in the concentration range 10‐45 μg/ml with correlation coefficient value 0.998. The proposed method was applied to pharmaceutical formulation and % amount of drug estimated 99.58 % was found in good agreement with the label claim. The accuracy of the method was checked by recovery experiment performed at three different levels i.e., 80%, 100% and 120 %. The % recovery was found to be in the range 98.8%– 99.06%. The low values of % R.S.D. were indicative of the accuracy and reproducibility of the method. The precision of the method was studied as an intra‐day, inter‐day variations and repeatability. The % R.S.D. value less than 2 indicated that the method was precise. Ruggedness of the proposed method was studied with the help of two analysts. The above method was a rapid and cost‐effective quality‐control tool for routine analysis of Naftopidilin bulk and in pharmaceutical dosage form.

The modified epoxy acrylate resin‐based monolith was prepared by in situ free‐radical polymerizat... more The modified epoxy acrylate resin‐based monolith was prepared by in situ free‐radical polymerization. The morphology and pressure drop of the monolith has been characterized. The results showed that the monolith had high permeability. Then, felodipine, lercanidipine and nimodiping were enriched by using the prepared monolith as solid phase extraction (SPE) sorbent and tested quantitatively when connected with RP‐C18 column. The linear calibration curves were obtained over a range of 2‐500 ng/mL (r 2 ≥0.998). Precision for intra‐day and inter‐day assay showed acceptable results for quantitative assay with relative standard deviation (RSD) less than 12%. The accuracy and recovery were found to be within the range of 89%‐101%and 89%‐102%. The proposed method was successfully applied to simultaneously screen felodipine, lercanidipine and nimodiping in river water.

This study aims to understand how substrate electrode surface morphology affects the drug releasi... more This study aims to understand how substrate electrode surface morphology affects the drug releasing capacity of the overlaying conducting polymer film. Fluorescein was used as a model drug to dope the conducting polymer polypyrrole (PPy). To examine the effects of electrode surface morphology, gold electrodes were electrodeposited for increasing periods of time with platinum, effectively increasing the surface roughness of the electrode. Equivalent circuit analysis and cyclic voltammetry further suggested the increase in surface area as Pt deposition time increased. Polypyrrole films doped with fluorescein were then electropolymerized on the platinized electrode surfaces. An increase in electrically stimulated fluorescein release from the electrode surface was observed with increasing substrate roughness. Subsequently, an increase in release per charge accumulation used during electropolymerization was also observed, indicating that releasable drug occupies a higher fraction of the polymer film deposited on rougher surface. Finally, the release per charge injected during electrical stimulation also increased as the substrate surface area increased, suggesting increased release efficiency from rougher electrode substrates. To our knowledge, this is the first time the relationship of increased drug release and release efficiency from rougher substrates has been experimentally verified.

Heat generation of cement mixtures of various compositions was measured with the calorimetric met... more Heat generation of cement mixtures of various compositions was measured with the calorimetric method during hardening of solutions, which simulated liquid medium‐level wastes (MLW) from the radiochemical plant and distillation residues obtained from evaporation of Nuclear Power Plant (NPP) liquid radioactive wastes. Thermal capacity was determined and heat generation was calculated for the processes of hydration and solidification of cement mixtures. Impact of dry mixture and solution compositions on heat generation was determined, as well as that of the solution‐cement ratio. A scaled‐up experiment was carried out to solidify a 4 m 3 block of compound using the developed cement mixture with reduced heat generation. It was found that at hardening, the temperature in the specimen didn't exceed 57ºС. This fact confirmed the efficiency of the measures undertaken to decrease heating up of the compound in the course of hardening. Applicability of the cementation technology was considered in relation to NPP distillation residues with subsequent storage of the obtained compound in pour‐ type compartments. It was demonstrated that the developed dry mixture compositions ensured compliance of the cement compound with the respective process and regulation requirements during NPP distillation residues hardening. Results of the study will help verify and, if necessary, adjust the mathematical model used in preliminary calculations to describe the process of storage compartment heating. It will allow developing a safe mode of filling compartments of the storage facility with the cement compound containing solidified MLW.

The kinetics of oxidation of theophylline (TP) by diperiodatoargentate (III) (DPA) in aqueous alk... more The kinetics of oxidation of theophylline (TP) by diperiodatoargentate (III) (DPA) in aqueous alkaline medium at a constant ionic strength of 0.31 mol dm −3 was studied spectrophotometrically. The reaction between TP and DPA in alkaline medium exhibits 1:2 stoichiometry. The reaction is of the first order with respect to [DPA] and has a zero order in [TP] and unit order in [alkali]. The main oxidation product was identified as 3‐methyl‐2,6‐dioxo‐2,3dihydro‐6H‐purine‐1(7H)‐carbaldehyde by spot test, FT‐IR and LC‐MS spectral studies. A probable mechanism was proposed; the activation parameters were computed and discussed.

The oxidation of erythritol (ERT) by permanganate ion (-4 MnO) in aqueous alkaline medium and a c... more The oxidation of erythritol (ERT) by permanganate ion (-4 MnO) in aqueous alkaline medium and a constant ionic strength of 6.0×10 ‐2 mol dm ‐3 were studied spectrophotometrically at 25 o C. The reaction between erythritol and-4 MnO in alkaline medium exhibits 1:4 stoichiometry. The product, 2, 3, 4‐ trihydroxybutanoic acid, was isolated and identified with the help of TLC and characterized by FT‐IR and GCMS. The other product MnO4 2‐ was confirmed by UV‐Vis spectral studies. The order of the reaction with respect to-4 MnO and ERT concentrations were found to be unity and less than unity respectively. The rate of the reaction increased with increase in [  ]. The effect of ionic strength, dielectric constant and added product on the rate of reaction was also studied. Based on the experimental results, the probable mechanism was proposed. The activation parameters with respect to slow step of the mechanism were computed and discussed. Thermodynamic quantities were also calculated.

A systematic B3LYP/6‐311++G**//B3LYP/6‐31+G* calculations of GIAO/CSGT‐NMR (σd, σp, σii and ∆χani... more A systematic B3LYP/6‐311++G**//B3LYP/6‐31+G* calculations of GIAO/CSGT‐NMR (σd, σp, σii and ∆χanis) and AIM ( , 2   and ε) are performed on some X‐substituted six‐membered ring carbenes (3a/3b, 4a/4b/4c, and 5a/5b; X=amino and cyclopropyl). The findings confirm the interaction of divalent centers with neighboring attached groups, either amino or cyclopropyl, but have a much more pronounced impact for the former. The N–Ccarbene bonds of all singlet carbenes are stronger than their corresponding triplets and the π‐components also bring about higher charge transfer contributions as compared with the corresponding triplets. The large chemical shielding anisotropy at the Ccarbene could mainly be related to a low‐lying n→π* transition, σxx,p. The extent of paramagnetic contribution is generally proportional to the inverse of singlet‐triplet gaps ΔEs‐t. Calculated 13 Ccarbene chemical shifts for singlet states are significantly more downfield as compared with their corresponding triplets. Calculated σiis at the Ccarbene show that the amino and cyclopropyl groups have the same behavior in the polarization of the X–Ccarbene bond toward X, but the amino group has a more π back‐donation ability. In the singlet carbenes, the absolute values of paramagnetic components decrease in the order of σxx,p > σyy,p > σzz,p, but in the triplet carbenes the order is almost reverse. The calculated ∆χanis values show that the electron delocalization to carbene center of all triplet carbenes is less than the corresponding singlet states.

The present review article reports on the recent developments on the determination and analysis o... more The present review article reports on the recent developments on the determination and analysis of the electrochemical and photoelectrochemical properties of p‐type semiconducting materials, namely nickel oxide (NiO), prepared with different modalities of deposition and thermal treatment. All these electrodic materials possess a mesoporous morphology as required by the specific application of the dye‐sensitized solar cell (DSC), or Grätzel's cell. In particular, NiO thin film electrodes prepared with the methods of screen‐printing, spray deposition and sintering under various thermal conditions have been reviewed for the elevated reproducibility of their photoelectrochemical behavior, and the possibility offered by these methods of being scalable. The performance of these electrodes as photoactive cathodes of p‐DSCs has been compared with the performance of the NiO samples obtained via other methods of sysnthesis/deposition. The choice of the dye sensitizers for p‐ DSCs has been confined to those colorants that have been purposely designed for p‐type semiconductors, i.e. erythrosine b as benchmark, P1 and perylenemonoimides as highly performing hole photoinjectors, fast green and squaraines. The latter class of dyes is particularly useful for the envisage of tandem DSCs due to their red shifted main absorption with respect to traditional organometallic dye‐sensitizers (characteristic of optical complementarity). The recent review of Daeneke et al. (ref. 53 in the following) analyzed systematically all the factors influencing negatively the poor performances of p‐DSCs. They reached the important conclusion that the energy conversion losses of p‐DSCs were mainly associated to the low fill factors expressed by the JV curves of these photoelectrochemical cells. The content of this review differs from that of the work of Daeneke et al. since it will be here shown that the photoelectrochemical performances of nanostructured NiO films are heavily determined by the capacitive behavior of NiO. This correlation has been evidenced by the fact that NiO acts as charge storing system in both forward and reverse bias with the retention of ionic charge either on the surface or within the open structure. Adsorption and/or intercalation phenomena in NiO will depend on the nature and size of the ions compensating the electronic charge injected in NiO either electrochemically or photoelectrochemically.

Improved electrochemical oxidative determination of riboflavin (RF) at a thin graphene film modif... more Improved electrochemical oxidative determination of riboflavin (RF) at a thin graphene film modified glassy carbon electrode (GF‐GCE) has been established using cyclic and differential pulse voltammetric techniques. The graphene was characterized by SEM, TEM and electron diffraction studies. The surface area calculated for modified electrode was higher than the glassy carbon electrode which is responsible for more catalytic activity in the present system. Cyclic voltammetry was employed to unveil the electrocatalytic performance of graphene and two redox peaks were observed for RF with good intensity. The redox voltammetric behavior of RF at the sensor was quasi‐reversible involving two electrons‐two protons. At the surface of modified electrode, the redox reaction was adsorption‐controlled. A probable electro‐redox mechanism was proposed. Under the optimum conditions, a calibration curve of longer linearity for peak current and RF concentration in the range from 1.0 nM to 1.5 × 10 ‐8 M was obtained with a detection limit of 1.0 × 10 ‐10 M. The present method was applied to riboflavin determination in pharmaceutical and real samples with good recovery. There was no interference from any excipients, which indicates the specificity of the composite electrode. Furthermore, the fabricated RF chemical sensor exhibited excellent stability, remarkable catalytic activity and reproducibility towards RF determination. The method finds applications in clinical laboratory.

Direct electrochemistry of perazinedimaleate (PDM) was performed at a graphite pencil electrode u... more Direct electrochemistry of perazinedimaleate (PDM) was performed at a graphite pencil electrode using cyclic and differential pulsevoltammetryover a wide range of pH. The oxidation of PDM is an irreversible process, pH dependent, and involves the charge transfer of twoelectrons. The results enabled themeasurement of the oxidation peak current to be used as the basis for a simple, accurate and rapid method for determining the investigated compounds, within a concentration range of 1.5 × 10 ‐7 M to 13.0 × 10 ‐5 M. The limits of detection (LOD) and quantification (LOQ) calculated from the results obtained at this pH are 8.53 × 10 −9 M and 2.84 × 10 −8 M, respectively. Promising results were obtained for PDM determination in real samples, without separation from the matrix.

This article is to introduce the main functions of intelligent traffic information management sys... more This article is to introduce the main functions of intelligent traffic information management system based on mass rule parallel processing technology, and the key technologies thereinto, including mass rule description model, mass rule network and optimization, mass rule processing measure and mass rule parallel processing mechanism.

Representations of thermodynamic properties (e. g. pressure, Helmholtz Free energy, Gibbs Free en... more Representations of thermodynamic properties (e. g. pressure, Helmholtz Free energy, Gibbs Free energy, enthalpy, internal energy) as a sum of two constituents: internal and thermal, were reviewed. General form of thermodynamic relationships between internal and thermal components of caloric properties was derived. It is shown that existence of ideal curves on thermodynamic surface is result of a mutual indemnification of internal and thermal contribution in thermodynamic properties. Dependence of the behavior of thermal and internal components on features of intermolecular interactions is considered.

Synthesis of cobalt oxide nanostructures using a facile route still remains a challenge. Herein, ... more Synthesis of cobalt oxide nanostructures using a facile route still remains a challenge. Herein, we propose a simple, economical and 'green' route for the synthesis of cobalt oxide nanostructures by using a two step microwave assisted solvothermal route. Binary solvent system of water and ethylene glycol (EG) was used as a medium for solvothermal heating in a household microwave oven. We studied the effect of change of microwave power on the morphological properties of the resultant nanostructures. The physico‐chemical investigations reveal formation of nanostructures having faceted growth with different shapes. These nanostructures might prove useful for catalytic and gas sensor applications.

The solubility of thiourea in triglycol + water mixture has been determined with the mass fractio... more The solubility of thiourea in triglycol + water mixture has been determined with the mass fraction of triglycol (ω) being 0.63, 0.72, 0.82, and 0.91. The experimental data have been correlated with the modified Apelblat equation. The dissolution enthalpy and dissolution entropy have been calculated from the experimental data. The mutual interactions between solvent and solute have been discussed in brief.

The solubilities of thiourea in methanol were correlated with the modified Apelblat equation. The... more The solubilities of thiourea in methanol were correlated with the modified Apelblat equation. The dissolution enthalpy and dissolution entropy were calculated from the experimental data. The mutual interaction between solvent and solute were discussed in brief. The data can be used for the synthesis of isopropyl mercaptan.

Hindered phenol AO‐80/polyacrylate rubber (AO‐80/ACM) damping hybrids were prepared to investigat... more Hindered phenol AO‐80/polyacrylate rubber (AO‐80/ACM) damping hybrids were prepared to investigate the influence of the content of hindered phenol AO‐80 on the thermal and damping properties. Meanwhile, molecule dynamics (MD) simulation, a molecular‐level method, was applied to elucidating the microstructure and mechanism of the hybrids. The computed results revealed that three types of hydrogen bond, namely, type A (AO‐80) ‐OH • • • OC‐ (ACM), type B (AO‐80) ‐OH • • • OC‐ (AO‐80), and type C (AO‐80) ‐OH • • • OH‐ (AO‐80), were formed in the AO‐80/ACM hybrids. Moreover, the experiment was highly consistent with the MD simulation results in showing that the introduction of AO‐80 improved the damping properties.

A series of hierarchical pores Cu–BTC membrane was obtained by electrochemical method when copper... more A series of hierarchical pores Cu–BTC membrane was obtained by electrochemical method when copper foams with different pore‐density were used as the electrodes. Scanning electron microscope (SEM) and X‐ray diffraction (XRD) were used to characterize the morphology and structure of the coating; while their specific surface areas were obtained by nitrogen adsorption. Key factors in the process of electrochemical synthesis such as current intensity, temperature, time and ligand concentration were investigated systematically to find out the optimal conditions based on synthesis yield and morphology of the samples. The mechanisms of Cu‐BTC formed on the surface of copper foams were discussed. The effective thermal conductivity of Cu‐BTC/Cu‐Foam film was higher than that of pure Cu‐BTC. This paper provides a simple and reproducible way to construct hierarchical pores membrane for potential industrial applications on separation and adsorption.