Rim S. Haggag

The utilization of copper(II) phosphate for the anodic stripping voltammetric assay of alendronate sodium, desferrioxamine mesylate and lisinopril.

A sensitive differential pulse anodic stripping voltammetric method is described for the determination of alendronate sodium, desferrioxamine mesylate and lisinopril. The procedure is based on the formation of labile drug-copper(II) complex when shaking with copper(II) phosphate suspension. The voltammetric peaks, which correspond to the reduction of the copper(II) moiety of the formed complexes are obtained at -153, -74 and -111 mV, respectively. The different experimental parameters have been carefully studied. The method has been fully validated. The limit of detection was as low as 8.6 ng ml(-1). The method has been applied successfully for the determination of the drugs in plasma and in their pharmaceutical preparations. The obtained results were compared statistically with those obtained from a published method, in case of AS, or the official USP methods, for the other two drugs.

Gradient HPLC-DAD stability indicating determination of miconazole nitrate and lidocaine hydrochloride in their combined oral gel dosage form.

The pharmaceutical combination of miconazole nitrate (MZ) and lidocaine hydrochloride (LD) is used in the curative and prophylactic therapy of the oral and gastro-intestinal infections caused by Candida albicans. To the best of our knowledge, no attempts have yet been made to assay this combination by any analytical method. A simple and selective high-performance liquid chromatography-diode array detection (HPLC-DAD) stability-indicating method was developed for the simultaneous determination of MZ and LD in their combined formulation. Effective chromatographic separation was achieved using a Zorbax SB-C8 column with gradient elution of the mobile phase composed of 0.05 M phosphoric acid and acetonitrile. The gradient elution started with 25% (by volume) acetonitrile, ramped up linearly to 65% in 6 min, then kept constant until the end of the run. The mobile phase was pumped at a flow rate of 1 mL/min. The multiple wavelength detector was set at 215 nm and analytes were quantified by measuring their peak areas. The retention times for LD and MZ were approximately 4.1 and 8.4 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, ranges, precision, accuracy, selectivity, robustness, detection and quantification limits. Calibration curves were linear in the ranges of 5-100 µg/ml for both drugs with correlation coefficients > 0.999. Both drugs were subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The proposed method proved to be stability-indicating by the resolution of the two analytes from the related substance and potential impurity (2,6-dimethylaniline) and from the forced-degradation products. The validated HPLC method was applied to the analysis of MZ and LD in the combined oral gel preparation, in which the two analytes were successfully quantified and resolved from the pharmaceutical additives. The proposed method made use of DAD as a tool for peak identity and purity confirmation.

Gradient HPLC–DAD Determination of Two Pharmaceutical Mixtures Containing the Antihistaminic Drug Ebastine

This work describes the development, validation and application of a simple and reliable high-performance liquid chromatography-diode array detection (HPLC-DAD) procedure for the analysis of two pharmaceutical mixtures. The first mixture contains the antihistaminic drug ebastine (EBS) and the famous sympathomimetic drug pseudoephedrine hydrochloride (PSD), and the second mixture is composed of EBS and another sympathomimetic agent, phenylephrine hydrochloride (PHR). Effective chromatographic separation of EBS, PSD and PHR was achieved using a Zorbax SB-C8 (4.6 × 250 mm, 5 μm) column with gradient elution of the mobile phase composed of 0.05M phosphoric acid and acetonitrile. The gradient elution started with 20% (by volume) acetonitrile, ramped up linearly to 90% in 5 min, then kept constant until the end of the run. The mobile phase was pumped at a flow rate of 1 mL/min. The multiple wavelength detector was set at 254 (for EBS and PSD) and 274 nm (for PHR) and quantification of the analytes was based on measuring their peak areas. The retention times for PHR, PSD and EBS were approximately 2.5, 2.9 and 7.1 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, ranges, precision, accuracy, selectivity, robustness and detection and quantification limits. Calibration curves were linear in the ranges 5-100, 100-1,000 and 10-200 µg/mL for EBS, PSD and PHR, respectively, with correlation coefficients > 0.9996. The validated HPLC method was applied to the analysis of the two pharmaceutical mixtures in laboratory-made tablets in which the analytes were successfully quantified with good recovery values and no interfering peaks were encountered from the inactive ingredients. Finally, the proposed method made use of DAD as a tool for peak identity and purity confirmation.

Green chemistry: Analytical and chromatography

ABSTRACT Nowadays, the environment protection and the personal health and safety are given more consideration in the field of chemistry, thus resulting in an increased number of published researches about how to work according to green instructions, to follow up the recommendations of environmental agencies and to obtain better clean handling of chemistry. In this review, green chemistry definition, importance, principles, and some recent applications in the field of green chemistry were discussed. In addition, the review summarizes the evolution of green analytical chemistry (GAC) with its specific principles and how to make the analytical process more environmentally benign with special emphasis on recent applications of GAC. Moreover, the green chromatography, its methods, and some of its applications were outlined. Finally, different techniques available up till now for the assessment of greening of the methods were also presented. GRAPHICAL ABSTRACT

KINETIC INVESTIGATION OF PENTOXIFYLLINE BASED ON NONPARAMETRIC LINEAR REGRESSION OF DERIVATIVE AND CONVOLUTED DERIVATIVE CHROMATOGRAPHIC AND SPECTROPHOTOMETRIC RESPONSES

A novel application of chemometrics to the chromatographic peak responses in the kinetic investigation of Pentoxiphylline was introduced using nonparametric linear regression method as the statistical method of analysis. The kinetic study of Pentoxiphylline was conducted under two different stress conditions using DAD-HPLC. The chemometric methods were applied to the HPLC and spectrophotometric data of the kinetic study of Pentoxiphylline. First and second derivative treatment of chromatographic and spectrophotometric response data were followed by convolution of the resulting derivative curves using 8-points sin xi polynomials (discrete Fourier functions). The study also presents a comparison between parametric and non-parametric regression methods of analysis. Moreover, application of Arrhenius equation to the determination of the half life of Pentoxiphylline in alkaline condition was studied before and after the chemometric treatment of the data. The results obtained indicated that chemometric treatment of data with the application of non-parametric method enhances the linearity parameters obtained during the kinetic investigation. These linearity parameters were further used to estimate the degradation rate constant (K) and half life of the drug at room temperature which is very important for the estimation of the stability of the drug on shelf with accuracy and with minimum experimental work and errors.

Stability-Indicating HPLC–DAD Determination of Ribavirin in Capsules and Plasma

A simple, selective and stability-indicating high-pressure liquid chromatographic method was developed for the analysis of ribavirin. Chromatographic separation was achieved by using a CPS Hypersil cyano column (4.6 × 250 mm, 5 µm particle size) with isocratic elution of the mobile phase, which was composed of 50 mM phosphate buffer, adjusted at pH 4 with phosphoric acid. The mobile phase was pumped at a flow rate of 0.8 mL/min. The detector was set at 240 nm and quantification of the analyte was based on peak area measurement. The method was validated with respect to linearity, range, precision, accuracy, selectivity, robustness, limit of detection and limit of quantitation. The calibration curve was linear in the range of 5-200 µg/mL with correlation coefficient > 0.999. Ribavirin was subjected to forced degradation studies under two conditions: mild and extensive stress testing. These studies included the effects of hydrolysis (neutral, acidic and alkaline) and oxidation, photolysis and dry heat). The proposed method was proved to be stability-indicating by the resolution of the drug from its forced degradation products, making use of the diode array detector as a tool for confirmation of peak identity and purity. Moreover, the kinetics of alkaline degradation of ribavirin were investigated, an Arrhenius plot was constructed and the activation energy was calculated. The developed method was also extended to analyze ribavirin in capsules and in human plasma with good recovery values.

Extraction-spectrophotometric determination of phenytoin in capsules and plasma using potassium permanganate/dicyclohexano-24-crown-8

An extraction-spectrophotometric method for the determination of phenytoin in capsules and plasma is presented. The method is based upon oxidation of phenytoin using alkaline potassium permanganate solubilized in chloroform/cyclohexane (1:1) after crowning with dicyclohexano-24-crown-8 (DC-24-C-8). The formed benzophenone being soluble in the oxidation reaction medium was directly measured at 238 nm. The optimum conditions for the reaction were studied and the detection limit was found to equal 1.2 mg/100 ml. The developed method was applied to the determination of the drug in capsules and plasma. The method is simple, accurate and avoids laborious multistep extraction procedures.

Green gas chromatographic stability-indicating method for the determination of Lacosamide in tablets. Application to in-vivo human urine profiling

A direct, eco-friendly, stability-indicating GC method was developed for the determination of Lacosamide (LCM) in tablet dosage forms in presence of its degradation products as well as in human urine in presence of the co-administered drug Zonisamide (ZON). The assay method in tablets was validated according to the ICH guidelines, while the method for determination of LCM in urine was validated according to FDA; Bioanalytical Method Validation guidance. Linear response (r = 0.9998) was observed over the range of 20-280 μg/mL of LCM, with detection and quantitation limits of 5.871 and 19.57 μg/mL, respectively for the tablet assay method. While (r = 0.9999) was observed over the range of 0.5-20 μg/mL of LCM, with detection and quantitation limits of 67 and 233 ng mL-1, respectively for the urine analysis method. Under various stress conditions, the investigation of LCM forced degradation behaviour was carried out. Furthermore, monitoring of the drug in urine followed by construction of its urine profile was done after the administration of 50 mg tablet of LCM to three healthy volunteers so as to prove the ability of the method to be applied in assaying LCM in human urine. The method showed also successful separation of LCM and the co-administered drug ZON in urine. Finally, the greenness of the method was assessed using National Environmental Methods Index label and Eco scale methods.

Development of a green stability-indicating HPLC–DAD method for the determination of donepezil hydrochloride in the presence of its related substance and degradation products

ABSTRACT A simple, eco-friendly, stability-indicating HPLC method was developed for the determination of donepezil hydrochloride (DH) in tablet dosage form in the presence of its pharmacopoeia-related compound (donepezil-related compound A) and its different degradation products. The chromatographic conditions were optimized to achieve the highest performance parameters using Zorbax Eclipse Plus C18 rapid resolution column (4.6 × 100 mm, 3.5 µm), with a mobile phase composed of 72.5% acetate buffer pH 5.5 and 27.5% ethanol, flowing at 1 mL min−1. The diode array detector (DAD) was set at 315 nm and the column oven was adjusted at 45°C. Linear response (r = 0.9999) was observed over the range of 2–28 µg mL−1 of donepezil, with detection and quantitation limits of 0.031 and 0.103 µg mL−1, respectively. Forced degradation studies were performed on standard DH and test Demepezil® 5-mg tablets under various conditions and the method was found to be stability indicating. The purity of DH peak was confirmed using the DAD. In the developed method, two principles of green chromatography were adopted (reduce and replace) by reducing solvent consumption through the utilization of a short column (10 cm) with a smaller particle size (3.5 µm) instead of a normal 25 cm with a 5 µm particle size and by replacing hazardous solvents of the official United States Pharmacopoeia method as acetonitrile with ethanol. Furthermore, the greenness of the method was assessed using three assessment tools. GRAPHICAL ABSTRACT

Spectrophotometric and spectrofluorimetric determination of mesna, acetylcysteine and timonacic acid through the reaction with acetoxymercuri fluorescein

Simple, sensitive and specific spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed for the determination of three sulfur-containing drugs: mesna (MSN), acetylcysteine (ACT) and timonacic acid (TMN). The methods are based on the suppressive effect of the drugs on the absorbance and the fluorescence intensity of 2′,7′-bis(acetoxymercuri)fluorescein (AMF) in 0.05 M borate buffer. In Method I the decrease in AMF absorbance was measured at 497 nm, while in Method II the fluorescence quenching of the reagent was measured at λem 520 nm (λex 497 nm). All the experimental parameters affecting this reaction were studied and optimized. The selectivity and the stability-indicating aspect of the methods were confirmed and no interference was detected from the oxidation products of the quantified drugs or from other co-administered drugs. Method I was applicable over the concentration ranges 0.5–3, 0.5–2.75 and 0.25–2.75 μg mL−1 for MSN, ACT and TMN, respectively. The reaction sensitivity was enhanced by Method II where the linearity ranges were found to be 0.6–7.2, 0.7–7 and 0.8–10.4 ng mL−1 for MSN, ACT and TMN, respectively. Both methods were applied for the determination of the three drugs in bulk form and in their pharmaceutical preparations without interference from common excipients. The percentage recoveries were satisfactory and they were statistically compared with those obtained from previously reported methods. Moreover, Method II was extended to analyze the drugs in spiked human plasma, by virtue of its high sensitivity.