Fardous A. Mohamed

Selective spectrophotometric determination of p-aminophenol and acetaminophen

A specific spectrophotometric method was developed for the determination of p-aminophenol and acetaminophen. The method is based on the reaction of p-aminophenol at ambient temperature with sodium sulphide in presence of an oxidant to produce a methylene blue-like dye. Different oxidizing agents were tried, e.g. Ce(IV) and Fe(III). The colour developed within 10 min and remained stable for at least 3 h. The method was applied successfully to the determination of p-aminophenol in the presence of acetaminophen without prior separation. The method was also applied to the analysis of various commercially available acetaminophen dosage forms and excellent recoveries were obtained comparable to those obtained by official procedures. The reaction product was isolated and a possible reaction mechanism was suggested.

Analysis of cephalosporin antibiotics

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.

Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent.

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80-400 microg mL(-1) for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.

Spectrophotometric determination of epinephrine and norepinephrine with sodium periodate

A simple and accurate spectrophotometric method is described for the determination of epinephrine (EP), norepinephrine (NE) and their bitartrate salts. The method is based on the development of a red colour (lambda(max) 490 nm) with sodium periodate in aqueous alcoholic medium. The colour is stable for at least 1 hr. The molar reacting ratio of EP or NE to periodate is 1:2. The proposed method is particularly suitable for routine analysis of EP and NE injections. The interference due to the sodium metabisulphite normally used as antioxidant can be overcome by addition of acetone. Results for analysis of bulk drugs and injections agree well with those of official methods.

Utility of quercetin for determination of some tertiary amine and quaternary ammonium salts

A simple and sensitive spectrophotometric method for the assay of eight drugs containing quaternary ammonium or tertiary amine moieties is described. The method is based on the interaction of these drugs with quercetin after its oxidation with N-bromosuccinimide (as counter ion) to give highly colored ion-pairing complexes extractable with organic solvents. The absorbances of the colored complexes are measured in the range of 528-560 nm. Beers law is obeyed for the studied drugs in the range 5-30 mug ml(-1). The method is successfully applied to the analysis of the studied drugs in commercial dosage forms.

An efficient hydrophilic interaction liquid chromatographic method for the simultaneous determination of metformin and pioglitazone using high-purity silica column.

Hydrophilic interaction liquid chromatography (HILIC) provides a feasible approach to effectively separate polar compounds in complex matrices. Herein, a simple, reproducible and efficient HILIC method was developed for the simultaneous determination of pioglitazone. HCl (PIO) and metformin HCl (MET) in rabbit plasma. High-purity silica column was used for rapid and efficient separation of these co-administered drugs. The chromatographic parameters were optimized for best separation. The proposed HILIC system provides high separation efficiency with good peak shape compared to reversed phase (RP) chromatography. Additionally, a simple isocratic elution mode with a mobile phase composed of a mixture of methanol and 10mM phosphate buffer (pH 3.0) (94:6, v/v) was used and the effluent was monitored at 230nm. The method was validated in accordance with the requirements of US-FDA guidelines and was found to behave efficiently for the intended purpose. The correlation coefficient of 0.9992 was obtained in the concentration ranges of 0.5-100μgmL(-1). The limits of detection (S/N=3) and quantification (S/N=10) were 0.16 and 0.5ngmL(-1), respectively. The retention times were 3.4 and 5.0min for PIO and MET, respectively. Plasma levels were successfully determined in rabbit with satisfactory precision and accuracy. In addition, the stability tests in rabbit plasma proved reliable stability under the experimental conditions. The developed HILIC method was applied successfully to study the pharmacokinetic behaviors of the studied analytes in rabbit plasma after a single oral dose containing PIO and MET.

Salting‐out thin‐layer chromatography and computational analysis of some oral hypoglycemic drugs

A quantitative structure-retention relationship study of some oral hypoglycemic drugs was carried out using a salting-out thin-layer chromatographic technique. Aqueous solution of ammonium sulfate and acetonitrile was used as a mobile phase. It was established that the applied mobile phase has different effects on retention of the studied oral antidiabetic drugs. The factors that affect the salting-out process were determined. In this study a good correlation between the structures of the investigated drugs with the retention data and molecular descriptors was established throughout computational analysis and using molecular operating environment software, focusing on octanol/water partition coefficient, molar refractivity, total hydrophobic surface area, hydrophobic volume, Van der Waals energy and solvation energy. Quantitative structure-retention relationship modeling for the separation of the investigated drugs was carried out, validated and evaluated.

The use of separation techniques in the analysis of some antiepileptic drugs: A critical review

ABSTRACT In the last few decades, many new antiepileptic drugs came out to medicine world, and their use was expanded over a wide range of cases. Analysts from all over the world developed many different separation methods for the determination of these drugs in a quantitative way either in pharmaceutical dosage forms or in biological fluids. In this review article, a summation of previously published separation methods including high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and electrophoresis used for the determination of eslicarbazepine acetate, levetiracetam, lacosamide, oxcarbazepine, pregabalin, and retigabine are presented. These six drugs are the most commonly used drugs for the treatment of patients diagnosed with partial onset seizures. This article can help researchers and analysts to build upon this knowledge and add further methods of analysis in the future. GRAPHICAL ABSTRACT

New Salting Out Stability-Indicating and Kinetic Thin Layer Chromatographic Method for Determination of Glimepiride and Metformin HCl Binary Mixture.

A simple, selective salting out and stability-indicating thin layer chromatographic (SOTLC) technique was developed for determination of two antidiabetic drugs; glimepiride and metformin HCl in pure and in tablets as a binary mixture. Separation was performed on silica gel 60 F254 plates using aqueous ammonium sulfate and acetonitrile (7:3, v/v) as a mobile phase. The Rf values were 0.26 ± 0.02 and 0.73 ± 0.02 for glimepiride and metformin HCl, respectively. The separated bands were scanned at λ 237 nm using CAMAG TLC scanner III. The proposed method focusing on study of all the factors that play important role in the mechanism of salting out process. The proposed method was validated according to ICH guidelines and complied with USP31-NF26 validation guidelines. The correlation coefficients of calibration curves were 0.996 and 0.997 for glimepiride and metformin HCl, respectively, in the concentration range of 60-1,400 ng/band for both drugs. The investigated drugs were also subjected to acidic, basic, oxidative and photo-degradation and kinetic study was carried out.

A rapid spectrophotometric method for determination of piperazine.

A spectrophotometric method has been developed for the determination of piperazine and its salts (citrate, phosphate, and tartrate) without prior separation, based on the interaction of piperazine or any of its salts with phenothiazine and N-bromosuccinimide in aqueous methanol. The products exhibit absorption maxima at 448, 595 and 645 nm. Measurements are made at 595 nm. Beers law is obeyed in the concentration range 0.5-5 mug/ml for piperazine salts and 0.5-3 mug/ml for piperazine hexahydrate. The method is rapid, simple and successful for analysis of some pharmaceutical preparations.