We investigated crystal formation process and crystal structure on a surface or in a bulk medium in gaseous solution system, using maleimide as solute gas and air or air/MeOH as solvent gas. In the air solvent, some of the gaseous maleimide molecules aggregated to form small crystal in the bulk medium and fell down on a surface without any orientation formation. Maleimide molecules which did not fell down was adsorbed on a surface with the orientation in such a way that the pyrrole ring was parallel to the surface. In the air/MeOH mixture solvent, strong correlation was observed between maleimide and MeOH. The maleimide crystal changed its orientation together with that of MeOH with the passage of time. The C-O axis of MeOH was perpendicular to the surface at the final stage. On vaporization of these MeOH molecules, maleimide crystallization proceeded further to form complete crystal so that the molecular plane
Aim: To conduct a comparative study between the smart novel ratio difference spectrophotometric method (RDSM) versus four spectrophotometric methods: first derivative spectrophotometry (D1), first derivative of the ratio spectra (1DD), isoabsorpative point (Aiso), ratio subtraction (RS), and two chemometric techniques based on principal component regression (PCR) and partial least-squares (PLS-1) for the determination of a binary mixture of Ofloxacin (OFX) and Dexamethasone (DXM).
Study Design: The results obtained from the proposed methods were statistically compared to the reported HPLC method using student’s t-test, F-test and One way ANOVA.
Methodology: (OFX) was determined by the application of direct spectrophotometry, by measuring its zero-order (D0) absorption spectra at its λmax = 296.6 nm. (DXM) was determined by (D1) at 227.1 nm. By applying (1DD), (DXM) was determined at 237.3. The total concentration of both (OFX + DXM) was determined at their isoabsorpative point λiso= 238.3 nm, then the concentration of (DXM) in mixtures were calculated by subtraction. (DXM) was determined using the (RS) method at its λmax = 239 nm. (DXM) was determined using (RDSM) by measuring amplitude difference at two selected wavelengths (248.4 and 290 nm). A concentration of 10 µg.mL-1 of OFX was used as a divisor. The linearity range was found to be (1-10 µg.mL-1) and (2-14 µg.mL-1) for OFX and DXM respectively.
Results: The recovery percentage for OFX was found to be 100.07 ±0.65 and for DXM was found to be 100.41 ±0.84, 100.15 ±0.97, 100.14 ±0.91, 100.54 ±0.75 and 100.11 ±.66 for the five methods, respectively.
Conclusion: The novel method showed advantages over the other proposed methods regarding simplicity, minimal data manipulation and maximum reproducibility and robustness; which enabled the analysis of binary mixtures with overlapped spectra for routine quality control testing with quite satisfactory and in lower cost.
The main aim of this research was to prepare nanoparticles of nickel oxide through a new mixed reverse microemulsion route. Quaternary microemulsion (water/surfactant/co-surfactant/oil-phase) was used to synthesize nickel oxide nanoparticles. The microemulsion was prepared by Tween-80, Aerosol-OT, n-Propanol, Cyclohexane, and Nickel Chloride. Previously nickel oxide nanoparticles were synthesized by reverse microemulsion method but the novelty of the process lies in the fact that conventionally either cationic or anionic or non ionic surfactants are used for the synthesis of nickel oxide nanoparticles.Whereas in the present developed novel process preparation of nickel oxide nanoparticles has been carried out using a unique blend system consisting of Tween-80 and AOT. The average particle size of as synthesized nickel oxide powder, calculated by Scherrer equation, is observed to be 14 nm. The X-ray diffraction pattern confirms the presence of pure bunsenite phase with FCC Scanning Electron Microscopy (SEM) shows that particles have spherical morphology.
Aim: To develop and validate a sensitive method for the determination of rapeprazole (RPZ) and omeprazole (OPZ) in bulk and formulations based on nucleophilic substitution reaction of RPZ and OPZ with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium.
Study Design: All variables were studied to optimize the reaction conditions and the reaction mechanism was postulated.
Place and Duration of Study: Department of Chemistry, Faculty of Science, Aleppo University, Aleppo, Syria between December 2011 and December 2012.
Methodology: The colored products were measured spectrophotometrically at 453 nm using double beam UVD-2960 (Labomed, INC., U.S.A) ultraviolet-visible spectrophotometer with matched 1-cm quartz cells. The reaction time and temperature were 20 min and 25ºC for RPZ and OPZ. As per ICH guidelines, the proposed method was validated. The developed method was successfully applied for the estimation of RPZ and OPZ in tablets and capsules and results were compared statistically with the official methods.
Results: The developed method showed a linear Beer's law range from 0.26 to 12.0 and from 0.49 to 12.0 μg mL-1 with limit of detection values of 0.181 and 0.187 μg mL-1 for RPZ and OPZ, respectively. The calculated molar absorptivity values are 7.7×104 and 3.8×104 L mol−1 cm−1 for RPZ-NQS and OPZ-NQS, respectively. The proposed methods were successfully applied to the determination of RPZ and OPZ in formulations and the results tallied well with the label claim.
Conclusion: The developed method was linear, sensitive, selective, precise, accurate and robust, being suitable for routine quality control analyses of RPZ and OPZ.
The adsorption behavior of the antihypertensive and antianginal agent amlodipine besylate onto a Hanging Mercury Dropping Electrode (HMDE) was explored by square wave and cyclic voltammetry. The drug accumulated at HMDE and a well-defined peak was obtained at –1.73V versus Ag/AgCl (saturated KCl) in phosphate buffer at pH 7. A validated simple, rapid and sensitive square-wave voltammetric procedure was described for direct determination of the authentic cited drug. The optimum procedure conditions were accumulation potential Eacc. = –1.1V, accumulation time tacc. = 60s, wave amplitude = 100mV, wave increment = 12mV and frequency = 100 Hz. Limits of detection (LOD) and quantification (LOQ) of 3.61×10–11M and 1.2×10–10M were achieved, respectively. The developed method was standardized for the determination of the drug in pharmaceutical formulation (amlodipine and myodura tablets) for quality control purposes. The observed data were subjected to statistical analysis, which revealed high reliability and precision. The intra-day relative standard deviation RSDs ranged from 0.331 to 0.418% at three different concentrations and inter-day RSDs ranged from 0.055 to 0.271%. The procedure was successfully applied to the quantification of the drug in human urine and serum samples. The mean percentage recoveries were 99.5±0.58 and 99.7±0.96 in human urine and serum sample, respectively. The proposed method was found to be suitable for the assay of amlodipine besylate in the presence of some common excipients and hence it can be consider specific.
In order to obtain further insights into the mode of protection afforded by conversion coatings on aluminium substrates, Scanning and Transmission Electron microscopy techniques and potential measurements was employed to monitor variously treated aluminium specimens in chloride environments. Examinations revealed that conversion coated aluminium with top lacquer coatings and subsequently subjected to Chloride environments prevented pitting of the substrate. However, pits were observed on ‘bare’ aluminium and those with top lacquer coatings after being exposed to similar environments. The ‘bare’ chromate coated specimen revealed pits plugged by corrosion products suspected to be hydrated Cr III oxide and/or hydroxide formed through the reduction of Cr VI species present in the coating. Such a capability was not observed for the ‘bare’ chromate-phosphate specimen.