H.A. Dessouki

Utility of oxidation/reduction reaction for the determination of ranitidine hydrochloride in pure form, in dosage forms and in the presence of its oxidative degradates

Three simple, accurate and sensitive colorimetric methods (A, B and C) for the determination of ranitidine HCl (RHCl) in bulk sample, in dosage forms and in the presence of its oxidative degradates are described. The first method A is based on the oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measurement of the decrease in absorbance of amaranth dye (AM) at a suitable lambda(max)=520 nm. The methods B and C involve the addition of excess Ce(4+) and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable lambda(max)=528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable lambda(max)=526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2-3.6, 0.1-2.8 and 0.1-2.6 microg ml(-1) for methods A, B and C, respectively. The apparent molar absorptivity. Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.3-3.4, 0.2-2.6 and 0.2-2.4 microg ml(-1) for methods A, B and C, respectively. Analyzing pure and dosage forms containing RHCl tested the validity of the proposed methods. The relative standard deviations were </=1.38 with recoveries 98.9-101.0%.

Synthesis and spectral characterization of CoxMg1−xAl2O4 as new nano-coloring agent of ceramic pigment

New nano-blue ceramic pigments of Co(x)Mg(1-x)Al(2)O(4) (0< or =x< or =0.1) have been prepared by co-precipitate-combustion as a hybrid method using urea as a fuel at 500 degrees C in open furnace in air atmosphere. The structure of pigment is assigned based on TGA/DTA/DrTGA analyses, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Also, electronic spectra, infrared (IR) and diffuse reflectance spectroscopy (DRS) using CIE L*a*b* parameter measurement techniques were used. The results revealed that the nano-particle size of pigments were obtained in the range 30-38 nm as well as the varying colors and particle size as a result of different calcinations temperatures within the range of 500-1200 degrees C for 2h.

Relation between molecular structure and spectral characteristics of some chelating mono-azo dyes based on o-hydroxy aryl aldehydes and carboxylic acids

Abstract The electronic absorption spectra of some chelating mono-azo compounds have been studied in some organic solvents of varying polarities. The u.v. bands in ethanol and cyclohexane are assigned in the light of electronic transitions. The effect of microscopic and macroscopic solvent polarity parameters are also discussed. The i.r. spectra of the solid compounds as KBr discs as well as the 1 H NMR spectra have also been assigned and discussed in relation to molecular structure. The azo ⇌ hydrazone tautomerism in some of these compounds is assured. The study indicated that the colour of the materials depends on the polarity and the formation of intermolecular H-bonds with the solvent molecules.

Spectrophotometric methods for sertraline hydrochloride and/or clidinium bromide determination in bulk and pharmaceutical preparations

A spectrophotometric procedure for the determination of sertraline hydrochloride (Sert) and/or clidinium bromide (Clid) in bulk sample and in dosage forms was developed. The purpose of this work was to develop a rapid, simple, inexpensive, precise, and accurate visible spectrophotometric method. The procedure is based on formation of an ion-pair complex by their reaction with bromocresol green (BCG), bromophenol blue (BPB), and bromothymol blue (BTB) in buffered aqueous solution at pH 3. The colored products are extracted into a polar solvent and measured spectrophotometrically at the optimum λmax for each complex. Optimization of different experimental conditions is described. Regression analysis of Beer-Lambert plots showed good correlation in the concentration range of 1–30 µg mL−1. The apparent molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. For more accurate analysis, Ringbom optimum concentration range of 2–27 µg mL−1 was used. The developed methods were successfully applied for the determination of sertraline hydrochloride and clidinium bromide in bulk in pharmaceutical formulations without any interference from common excipients. The procedure has the advantage of being highly sensitive and simple for the determination of the studied drugs, weak UV-absorbing compounds.

Synthesis, thermal and spectral characterization of nanosized NixMg1−xAl2O4 powders as new ceramic pigments via combustion route using 3-methylpyrozole-5-one as fuel

New Ni(x)Mg(1-x)Al(2)O(4) nanosized in different composition (0.1≤x≤0.8) powders have been synthesized successively for first time by using low temperature combustion reaction (LTCR) of corresponding metal chlorides, carbonates and nitrates as salts with 3-methylpyrozole-5-one (3MP5O) as fuel at 300°C in open air furnace. Magnesium aluminate spinel (MgAl(2)O(4)) was used as crystalline host network for the synthesis of nickel-based nano ceramic pigments. The structure of prepared samples was characterized by using different techniques such as thermal analysis (TG-DTG/DTA), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). UV/Visible and Diffuse reflectance spectroscopy (DRS) using CIE-L*a*b* parameters methods have been used for color measurements. The obtained results reveal that Ni(x)Mg(1-x)Al(2)O(4) powder of samples is formed in the single crystalline and pure phase with average particle size of 6.35-33.11 nm in the temperature range 500-1200°C. The density, particle size, shape and color are determined for all prepared samples with different calcination time and temperature.

Spectrophotometric quantification of fluoxetine hydrochloride: Application to quality control and quality assurance processes

Simple and rapid spectrophotometric methods have been developed for the microdetermination of fluoxetine HCl. The proposed methods are based on the formation of ion-pair complexes between fluoxetine and bromophenol blue (BPB), bromothymol blue (BTB), bromocresol green (BCG), and bromocresol purple (BCP) which can be measured at optimum λmax. Optimization of reaction conditions was investigated. Beerșs law was obeyed in the concentration ranges of 0.5–8.0 μg mL−1, whereas optimum concentration as adopted from the Ringbom plots was 0.7–7.7 μg mL−1. The molar absorptivity, Sandell sensitivity, and detection limit were also calculated. The most optimal and sensitive method was developed using BCG. The correlation coefficient was 0.9988 (n = 6) with a relative standard deviation of 1.25, for six determinations of 4.0 μg mL−1. The proposed methods were successfully applied to the determination of fluoxetine hydrochloride in its dosage forms and in biological fluids (spiked plasma sample) using the standard addition technique.

Facile colorimetric methods for the quantitative determination of tetramisole hydrochloride

A facile, rapid and sensitive methods for the determination of tetramisole hydrochloride in pure and in dosage forms are described. The procedures are based on the formation of coloured products with the chromogenic reagents alizarin blue BB (I), alizarin red S (II), alizarin violet 3R (III) and alizarin yellow G (IV). The coloured products showed absorption maxima at 605, 468, 631 and 388 nm for I-IV, respectively. The colours obtained were stable for 24 h. The colour system obeyed Beers law in the concentration range 1.0-36, 0.8-32, 1.2-42 and 0.8-30 microg ml(-1) respectively. The results obtained showed good recoveries with relative standard deviations of 1.27, 0.96, 1.13 and 1.35%, respectively. The detection and determination limits were found to be 1.0 and 3.8, 1.2 and 4.2, 1.0 and 3.9 and finally 1.4 and 4.8 ng ml(-1) for I-IV complexes, respectively. Applications of the method to representative pharmaceutical formulations are represented and the validity assessed by applying the standard addition technique, which is comparable with that obtained using the official method.

Electronic absorption spectra of some azo compounds with condensed ring systems in non-aqueous and mixed buffer solvents

Abstract The electronic absorption spectra of eight substituted phenylazo derivatives of α-and β-naphthol, 9-phenanthrol and 5- and 6-chrysenol were studied in different organic solvents. The assignment of the spectral bands obtained and also the effect of organic solvents on the colour of the compounds was investigated. The spectra in buffer solution over the pH range 2–14 were recorded and explained; also the pKa values were determined.

Solvolysis rates and activation parameters of phenylchloroformate in water―tetrahydrofuran and water―dioxane mixed solvents

Abstract The rates of hydrolysis of phenylchloroformate were measured over the temperature range 30–55 °C in water-tetrahydrofuran and water-dioxane mixtures of different compositions. The influence of solvent variation on reaction rate was examined in terms of changes in the activation parameters. The activation parameters Δ H ★ and Δ S ★ for the solvolysis reaction showed minima at a water mole fraction of about 0.5 in water-tetrahydrofuran solvent mixtures, whereas these parameters increased continuously with increasing concentration of water in water-dioxane solvent mixtures. The results are discussed in terms of the polarity of the medium and the change in the solvent structure.

Structural investigation of isatin-β-arylhydrazone derivatives by u.v., i.r., 1HNMR spectra and PPP CI calculations☆

Abstract The electronic absorption spectra, i.r. and 1 HNMR spectra of isatin-β-arylhydrazone derivatives are investigated and correlated with the proposed structural formula. The experimental data of these compounds show that they are present in a mixture of keto-enol forms. The spectra in buffer solutions containing a percentage of ethanol or dioxane are studied and the ionization constant values are determined. The experimental data were rationalized quantitatively by means of M.O. calculations in the framework of PPP CI model-trends and correlations were observed. Tautomeric structures in correlation with intramolecular charge transfer are demonstrated.