Azza A. Moustafa

Spectrophotometric methods for the determination of lansoprazole and pantoprazole sodium sesquihydrate

Spectrophotometric procedures for determination of two irreversible proton pump inhibitors, lansoprazole (I) and pantoprazole sodium sesquihydrate (II) are presented. Two methods were based on charge transfer complexation reaction of these drugs, where they act as n-donors, with either pi acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and with sigma acceptor as iodine. A third method was also investigated depending on ternary complex formation with eosin and copper (II). The colored products were quantified spectrophotometrically using absorption bands at 457 nm for DDQ (method A) at 293 and 359 nm for iodine (method B) and at 549 nm using ternary complex formation (method C), for both drugs. The molar combining ratio and the optimum assay conditions were studied. These methods determined the lansoprazole in concentration ranges from 10 to 90, 1.48 to 6.65 and 3.69 to 16.61 microg ml(-1) with mean percentage recovery 99.63% for DDQ, 99.71%, 99.18% for iodine and 99.76% for ternary complex and with relative standard deviation 0.11, 0.24, 0.13 and 0.36%, respectively. For pantoprazole, the concentration ranges were 10-60, 17.7-141.6 and 4.3-25.9 microg ml(-1) with mean percentage recovery 99.51, 98.97, 99.84 and 99.46% and relative standard deviation 0.53, 1.21, 0.65, 0.81% for the three mentioned methods, respectively. Investigation of the formed complexes was made with respect to its composition, molar ratio of the reaction, association constant K(C)AD, molar absorptivity epsilon(lambda)AD and free energy change deltaG for methods (A) and (B). The proposed methods have been applied successfully to the analysis of the cited drugs either in pure form or in pharmaceutical formulations, with good accuracy and precision, compared statistically with those given by the reported methods. They are recommended for quality control and routine analysis.

Stability-indicating methods for the determination of doxazosin mezylate and celecoxib

Two stability-indicating methods were developed for the determination of doxazosin mesylate (I) and celecoxib (II) in the presence of their degradation products. The first method depends on the use of first derivative spectrophotometry (D(1)) at 256, 269 nm for (I) and (II), respectively. This method determines (I) and (II) in concentration ranges of 0.8-12 and 1-20 microg ml(-1) with mean percentage accuracies of 99.21+/-0.88 and 99.59+/-1.67% for (I) and (II), respectively. The second method depends on the quantitative densitometric evaluation of thin-layer chromatography of (I) and (II) in the presence of their degradation products without any interference. Methylisobutyl ketone-glacial acetic acid-water (20:10:10) was used as a mobile phase for (I) and cyclohexane-dichloromethane-diethyleamine (50:40:10) for (II). The chromatograms were scanned at 248 and 253 nm for (I) and (II), respectively. This method determines (I) and (II) in concentration ranges of l-4 microg per spot for both drugs with mean percentage accuracies of 100.19+/-0.95 and 99.91+/-1.95% for (I) and (II), respectively. The suggested methods were used to determine doxazosin mesylate and celecoxib in bulk powder, laboratory-prepared mixtures and pharmaceutical dosage forms (cardura tablet and celebrex capsule). The results obtained by applying the proposed methods were statistically analysed and compared with those obtained by the reported methods.

Rapid and Highly Sensitive HPLC and TLC Methods for Quantitation of Amlodipine Besilate and Valsartan in Bulk Powder and in Pharmaceutical Dosage Forms and in Human Plasma

Two simple, sensitive, and specific high-performance liquid chromatography and thin-layer chromatography methods were developed for the simultaneous estimation of Amlodipine besilate (AM) and Valsartan (VL). Separation by HPLC was achieved using a xTerra C18 column and methanol /acetonitrile /water/ 0.05% triethylamine in a ratio 40:20:30:10 by volume as mobile phase, pH was adjusted to 3 ± 0.1 with o-phosphoric acid. The flow rate was 1.2 mL min−1. The linearity range was 0.2 to 2 µg mL−1 for amlodipine besilate and 0.4 to 4 µg mL−1 for Valsartan with a mean percentage recovery of 99.59 ± 0.523% and 100.61 ± 0.400% for amlodipine besilate and valsartan, respectively. The TLC method used silica gel 60 F254 plates; the optimized mobile phase was ethyl acetate/ methanol / ammonium hydroxide (55:45:5 by volume). Quantitatively, the spots were scanned densitometrically at 237 nm. The range was 0.5–4.0 µg spot−1 for amlodipine besilate and 2.0–12.0 µg spot−1 for valsartan. The mean percentages recovery was 99.80 ± 0.451% and 100.61 ± 0.363% for amlodipine besilate and valsartan, respectively. The HPLC method was found to be simple, selective, precise, and reproducible for the estimation of both drugs from spiked human plasma.

Determination of zolpidem hemitartrate by quantitative HPTLC and LC.

Two methods are described for the determination of zolpidem hemitartrate in presence of its degradation product. The first method was a TLC-UV densitometric one in which the mobile phase methanol: water (20:80) was used for developing the TLC plates. The R(f) of zolpidem hemitartrate was found to be 0.29+/-0.01 and that of its degradation product was 0.59+/-0.01. Linearity range was 0.5-4 microg/spot with mean recovery percentage (99.98+/-0.988)%. The second method was an HPLC method. HPLC was performed on a Bondapack C(18) column. The mobile phase was composed of a mixture of acetonitrile-0.01 M KH(2)PO(4) (40:60). The pH was adjusted to 3.5+/-0.1. Flow rate was 1.2 ml/min. Calibration graphs were linear in the range of 0.5-5 microg/ml with UV detection at 245 nm. Both methods have been successfully applied to pharmaceutical formulations. The results obtained were statistically compared with those obtained by applying the reported methods.

Spectrophotometric methods for simultaneous determination of ternary mixture of amlodipine besylate, olmesartan medoxomil and hydrochlorothiazide.

Four, accurate, precise, and sensitive spectrophotometric methods are developed for the simultaneous determination of a ternary mixture containing amlodipine besylate (AM), olmesartan medoxomil (OL) and hydrochlorothiazide (HZ), where AM is determined at its λ(max) 364.6 nm ((0)D), while (OL) and (HZ) are determined by different methods. Method (A) depends on determining OL and HZ by measuring the second derivative of the ratio spectra ((2)DD) at 254.4 and 338.6 nm, respectively. Method (B) is first derivative of the double divisor ratio spectra (D-(1)DD) at 260.4 and 273.0 nm for OL and HZ, respectively. Method (C) based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method then measuring OL and HZ at their isoabsorptive point at 260.0 nm, while HZ is measured using the amplitude of first derivative at 335.2 nm. Method (D) is mean centering of the ratio spectra (MCR) at 252.0 nm and 220.0 nm for OL and HZ, respectively. The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs and their combined dosage form. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p=0.05.

Novel strategy for online monitoring of the degradation kinetics of propantheline bromide via a calixarene-based ion-selective electrode.

Propantheline bromide (PB) is a hydrolysable anti-cholinergic drug. A novel strategy for the online monitoring of PB degradation kinetics catalysed by hydroxyl ions is presented. This is achieved by the incorporation of an on-site PB-selective electrode constructed using as an ionophore. This sensor was used to track the hydrolysis of PB by continuous measurement of the decrease in the produced emf over time. The use of this new technique provides real-time observation and yields a continuous profile of the hydrolysis behaviour of PB under various pH conditions as well as the temperature dependency of each reaction. Moreover, a great advantage of this proposed on-line system is its higher accuracy for rate constant estimation relative to other off-line methods. This kinetic data analysis permitted the determination of the hydrolysis activation energy and prediction of the drug shelf life. The estimated activation energy from Arrhenius plot was 20.77 kcal mol(-1).

Stability-indicating methods for the determination of sumatriptan succinate

Four stability-indicating methods were developed for the determination of sumatriptan succinate in the presence of its degradation products. The first method depends on the quantitative densitometric evaluation of thin-layer chromatography of sumatriptan succinate in the presence of its degradation products without any interference. Cyclohexane-dichloromethane-diethylamine (50:40:10 v/v/v) was used as a mobile phase and the chromatogram was scanned at 228 nm. This method determines sumatriptan succinate in the concentration range l-8 microg per spot with mean percentage recovery 100.52+/-1.23%. The second and third methods depend on the use of first-derivative (D(1)) and second-derivative (D(2)) spectrophotometry at 234 and 238 nm, respectively. These methods determine the drug in the concentration range 1.25-10 microg x ml(-1) with mean percentage recovery 99.91+/-1.01% and 99.96+/-1.13% for (D(1)) and (D(2)), respectively. The fourth method depends on the use of ratio derivative spectrophotometric technique. The amplitude in the first derivative of the ratio spectra at 235 nm was selected to determine the cited drug in the presence of its degradation products. Calibration graph is linear in the concentration range 1.25-10 microg x ml(-1) with mean percentage recovery 100.19+/-1.19%. The suggested methods were successfully applied for determining sumatriptan succinate in bulk powder, laboratory-prepared mixtures and pharmaceutical dosage forms (Imigran tablet) with good accuracy and precision. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method.

Determination of imipramine in presence of iminodibenzyl and in pharmaceutical dosage form.

Two spectrophotometric methods for the determination of imipramine in presence of iminodibenzyl as an impurity are described. The first method is a ratio-spectra first derivative spectrophotometry, the signals were measured at 240.2 nm for imipramine. Calibration graph was found linear in the range 5-30 microg ml(-1). The second method is based on the reaction of imipramine base, being an electron donor, with p-chloranilic acid, being pi acceptor, to form a purple colored charge transfer complex. The absorbance was measured at 520.5 nm without interference with iminodibenzyl. Both methods are rapid, simple and do not require any preliminary separation or treatment of the samples. Furthermore, the two methods were applied to pharmaceutical dosage form.

Evaluating the efficiency of spectral resolution of univariate methods manipulating ratio spectra and comparing to multivariate methods: An application to ternary mixture in common cold preparation

Simple, accurate, and selective methods have been developed and validated for simultaneous determination of a ternary mixture of Chlorpheniramine maleate (CPM), Pseudoephedrine HCl (PSE) and Ibuprofen (IBF), in tablet dosage form. Four univariate methods manipulating ratio spectra were applied, method A is the double divisor-ratio difference spectrophotometric method (DD-RD). Method B is double divisor-derivative ratio spectrophotometric method (DD-RD). Method C is derivative ratio spectrum-zero crossing method (DRZC), while method D is mean centering of ratio spectra (MCR). Two multivariate methods were also developed and validated, methods E and F are Principal Component Regression (PCR) and Partial Least Squares (PLSs). The proposed methods have the advantage of simultaneous determination of the mentioned drugs without prior separation steps. They were successfully applied to laboratory-prepared mixtures and to commercial pharmaceutical preparation without any interference from additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with the official methods where no significant difference was observed regarding both accuracy and precision.

Stability-Indicating Assay of Secnidazole in the Presence of Its Degradation Products

Abstract Four new selective, precise, accurate and rapid first derivative spectrophotometric, RP-HPLC, TLC densitometric and colorimetric methods are described for the determination of secnidazole in the presence of its degradation products, 2 - methyl - 5- nitroimidazole and hydroxyl propanol. (Method A) is applying the first derivative spectrophotometry at 296 nm. (Method B) is RP- HPLC based on using 30% methanol as a mobile phase at a flow rate of 1.0 ml/min. and 5 μ Bondapak C18 column (5 micron, 150 × 4.6 mm) as a stationary phase Detection was earned out using a diode detector at 319 nm (Method C) is densitometry using ethyl acetate as mobile phase and the spot was scanned with a spectrodensitometry at 311 nm. (Method D) is colorimetry based on diazotization of sulfanilamide with the nitrite ions liberated by alkaline hydrolysis of secnidazole and subsequent coupling of the diazonium salt with N-1-(nantuhyl)- ethylenediamine dihydrochloride. Regression analysis of a Beers plot showed good correlat...