Fathy M. Salama

Validated spectrofluorimetric method for the determination of atorvastatin in pharmaceutical preparations

A rapid, sensitive and simple spectrofluorimetric method was developed for the estimation of atorvastatin. In this method, the native fluorescence characteristics of atorvastatin have been studied in both acidic and basic media. High sensitivity was obtained with 5% acetic acid at 389 nm using 276 nm for excitation. Regression analysis showed a good correlation coefficient (r=0.9995) between fluorescence intensity and concentration over the range of 1.5–4 μg/mL with detection limit of 0.012 μg/mL. The proposed method was successfully applied to the analysis of atorvastatin in pure and pharmaceutical dosage forms with average recovery of 100.29±0.47%. The results were compared favorably with those of the reported method.

Spectroflurimetric estimation of the new antiviral agent ledipasvir in presence of sofosbuvir

A spectroflurimetric method has been developed and validated for the selective quantitative determination of ledipasvir in presence of sofosbuvir. In this method the native fluorescence of ledipasvir in ethanol at 405nm was measured after excitation at 340nm. The proposed method was validated according to ICH guidelines and show high sensitivity, accuracy and precision. Furthermore this method was successfully applied to the analysis of ledipasvir in pharmaceutical dosage form without interference from sofosbuvir and other additives and the results were statistically compared to a reported method and found no significant difference.

Application of TLC Densitometric Method for Simultaneous Estimation of the Newly Co-formulated Antiviral Agents Ledipasvir and Sofosbuvir in Their Tablet Dosage Form

Abstract Ledipasvir (LED) and Sofosbuvir (SOF) are newly approved antiviral agents co-formulated for treatment of hepatitis C virus. In the present work; an accurate and precise TLC densitometric method has been developed for simultaneous determination of LED and SOF in their bulk and dosage form. The proposed method based on determination of the UV-visualized bands after TLC separation of LED and SOF. The studied drugs were quantitatively separated on 60 F254 silica gel plates using mobile phase consists of (90% ethyl acetate: 9% hexane: 1% tri ethylamine by volume) with UV detection at 250 nm. The studied drugs were satisfactorily resolved with retention factor (Rf) values of 0.09 ± 0.005 and 0.23 ± 0.01 for LED and SOF, respectively. The proposed method has been validated according to ICH guidelines and show high sensitivity, accuracy and precision and the results were statistically compared to reported method.

Different chromatographic methods for the simultaneous determination of vitamin E and vinpocetine in their combined dosage form and in the presence of the alkaline-induced degradation product of vinpocetine

Accurate, selective, and sensitive thin-layer chromatography (TLC)—densitometry and reversed-phase high-performance liquid chromatography (RP-HPLC) methods have been developed and validated for the simultaneous determination of vitamin E (VIT E) and vinpocetine (VINP) in the presence of the alkaline-induced degradation product of vinpocetine (DEG). The proposed TLC—densitometric method depends on the separation and quantitation of VIT E, VINP, and VINP alkaline-induced degradation product on TLC silica gel 60 F254 plates, using methanol—chloroform—ethyl acetate—glacial acetic acid—ammonia solution (6:2:2:0.5:0.1, by volume) as the developing system followed by densitometric measurement at 235 nm. The studied components were well resolved from each other with significantly different RF values of 0.81, 0.62, and 0.41 for VIT E, VINP, and DEG, respectively. On the other hand, the developed RP-HPLC method was based on the separation of the studied components using 0.05 M KH2PO4 (adjusted to pH = 3) and methanol in gradient elution mode on C8 column at a flow rate of 1.5 mL min−1 and ultraviolet (UV) detection at 235 nm. The studied components were well resolved from each other with significantly different Rt values of 10.90, 2.89, and 1.90 min for VIT E, VINP, and DEG, respectively. The developed methods were validated according to the International Conference on Harmonization (ICH) guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by the reported method, and no significant difference was found. The developed methods are the first developed stability-indicating assay methods (SIAMs) for the analysis of the studied binary mixture.

Stability Indicating Spectrophotometric Methods for Determination of Vitamin E and Vinpocetine in Their Combined Dosage Form

Abstract Stability indicating spectrophotometric methods have been developed and validated for determination of Vitamin E (VIT E) and Vinpocetine (VINP) in presence of alkaline induced degradation product of Vinpocetine (DEG) without prior separation. In method (A), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the other drugs. Absorbance difference between 217.4 and 234.4 nm were used to determine VIT E while difference between 250.4 and 314.0 nm were selected for VINP determination and the difference between 258.6 and 312.0 nm were selected to determine DEG. In method (B), area under the curve method (AUC) was used for measuring VINP concentration by direct measuring AUC in the range of 330-350 nm, at which no interference from other components. While for determination of VIT E and DEG, the ternary mixture was divided by standard spectrum of 6 μg/mL VINP, in the obtained ratio spectra VIT E and DEG has been directly determined at 210.0 and 230.0 nm, respectively. In method (C), VIT E and DEG were determined by second derivative of ratio spectra (2DD) method by measuring their peak amplitudes at 215.2 and 237.2 nm, respectively, using 6 μg/mL standard spectrum of VINP as a divisor, while the absorbance at isoabsorptive point (λiso=264.4 nm) was used to determine the total concentration of VINP and DEG (where no contribution from VIT E) in the mixture and then by subtraction, VINP concentration could be obtained. The developed methods were validated according to ICH guidelines revealing good accuracy and precision. The results obtained by the proposed methods were statistically compared with those obtained by the reported HPLC methods and no significant difference was obtained. These methods are the first developed SIAM ones for analysis of the studied components.

A comparative study of different aspects in manipulating ratio spectra used for the analysis of cefradine in the presence of its alkaline degradation product

Six stability-indicating UV-spectrophotometric methods manipulating ratio spectra were utilized for the analysis of cefradine in presence of its alkaline degradate. These methods are different forms of transformations; ratio difference, mean centering, derivative ratio using numerical differentiation, derivative ratio using Savitsky-Golay filter, continuous wavelet transform and derivative continuous wavelet transform. Water was used as a solvent and the linearity ranges were 6-26 μg/mL. Determination of accuracy and precision for the suggested procedures were executed. Assessment of specificity was run through analyzing laboratory prepared mixtures containing cefradine and its alkaline degradate. The suggested methods were useful for cefradine estimation in tablets. Statistically, the outputs obtained from the recommended and published methods reveal no significant differences.

First derivative synchronous fluorescence spectroscopy for the determination of Gatifloxacin in presence of its oxidative degradation product: Application to pharmaceutical preparation

A highly accurate and precise spectrofluorimetric method was established for quantitation of Gatifloxacin in pure material, pharmaceutical formulations and in the existence of its oxidative degradation product. The emission was recorded at 487 nm after the excitation at 290 nm. Using micelle, sodium dodecyl sulphate (SDS), enhanced fluorescence intensity of Gatifloxacin-SDS complex. The optimization of numerous experimental conditions was carried out. The improved emission showed a suitable linear correlation between derivative synchronous fluorescence power and concentration of Gatifloxacin over the range of 10 to 100 ng/mL with a determination coefficient equals 0.9996. Studying cytotoxicity and antimicrobial susceptibility for oxidative degradation product of Gatifloxacin was carried out using Gatifloxacin as a control. In comparison, the proposed method presented a superior sensitivity and enhanced stability over the reported method.

Disposable gold nanoparticle functionalized and bare screen-printed electrodes for potentiometric determination of trazodone hydrochloride in pure form and pharmaceutical preparations

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride. The sensors were based on the use of a tetraphenylborate ion association complex as an electroactive material in screen-printed electrodes with dioctyl phthalate (DOP) as a solvent mediator modified with gold nanoparticles which improve the electrode conductivity and enhance the surface area. The sensors displayed a stable response for 5, 6 and 7 months with a reproducible potential and linear response over the concentration range 1 × 10−5–1 × 10−2 mol L−1 at 25 ± 1 °C with Nernstian slopes of 57.50 ± 0.66, 58.30 ± 0.45 and 59.05 ± 0.58 mV per decade and detection limits of 7.9 × 10−6, 7.6 × 10−6 and 6.8 × 10−6 mol L−1 for sensor 1, 2 and 3 respectively. The analytical performance of the screen printed electrodes in terms of selectivity coefficients for trazodone hydrochloride relative to the number of potentially interfering substances was investigated. The proposed method has been applied successfully for the analysis of the drug in its pure and dosage forms and there is no interference from any common pharmaceutical additives.

RP- HPLC and TLC- densitometric methods for determination of oxfendazole in the presence of its alkali -induced degradation product

Oxfendazole chemically known as: [5-(Phenylsulfinyl)-1Hbenzimidazol-2-yl] carbamic acid methyl ester1 Figure 1. It is a benzimidazole carbamate anthelmintic used in veterinary medicine.2 Different analytical techniques were applied for quantitative estimation of oxfendazole including potentiometric titration,3,4 radio immunoassay,5 spectrophotometric methods6 and HPLC methods even alone or in presence of other compounds.7–17 Oxfendazole is an amide group containing compound that made it highly sensitive to hydrolytic degradation in basic conditions with the production of the degradation product 2-amino-5-Phenylsulfinyl benzimidazole. There is no stability indicating analytical methods were reported for determination of oxfendazole in presence of its degradation product. The aim of this work is to develop and validate simple, sensitive and selective chromatographic methods for the determination of oxfendazole in presence of its alkali-induced degradation product (2-amino-5-Phenylsulfinyl benzimidazole) without preliminary separation. The proposed methods were found to be fast and simple and can be used for its routine analysis in quality control laboratories.

Application of HPLC-DAD and spectrophotometric continuous wavelet transform methods for simultaneous determination of amoxicillin and diclofenac in their pure and capsule dosage forms

Two methods have been developed and validated for simultaneous determination of amoxicillin sodium and diclofenac sodium in their pure and combined pharmaceutical dosage forms. The first method was HPLC-DAD; the chromatographic separation and resolution has been carried out using a reversed phase BDS Hypersil C18 column with a mobile phase consisting of methanol : acetonitrile : water : orthophosphoric acid (60 : 30 : 9 : 1 by volume), at a flow rate of 1 mL minute−1 and UV detection at 250 nm. The retention times were found to be 3.906 and 6.997 minutes for amoxicillin and diclofenac respectively. The second method was continuous wavelet transform (CWT), which is based on derivative calculation of spectrophotometric spectral data of both drugs in their binary mixture, and the zero crossing point for amoxicillin and diclofenac was found to be at 233 and 247 nm, respectively. The results obtained were statistically compared to reference methods and there were no significant differences between the proposed methods and the reference methods regarding the accuracy and precision. The method was validated according to ICH guidelines and the results were satisfactory.