Mohamed M. El-Wekil

Spectrodensitometric determination of some pharmaceutical mixtures containing proton pump inhibitors

Two ultraviolet (UV)—spectrodensitometric methods were proposed for the separation and determination of binary and ternary mixtures containing proton pump inhibitors (PPIs). Method A was developed for the assay of omeprazole, panoprazole, rabeprazole, and lansoprazole in binary mixtures with domperidone (DOM) using their isoabsorptive points. Method B was developed for the determination of a ternary mixture containing omeprazole, tinidazole, and clarithromycin. It depends on using malonic acid–acetic anhydride as a spraying reagent to form yellow color (for omeprazole) and dark brown color (for clarithromycin) that are measured at λmax = 350 nm and λmax = 492 nm, respectively, while tinidazole was measured by UV at λmax = 310 nm. For method A, Beer’s law was obeyed for all studied PPIs and domperidone in the concentration range of 180–1440 and 120–720 ng spot−1, respectively. The detection limits for proton pump inhibitors and domperidone were 48.05–73.45 and 30.74–32.50 ng spot−1, respectively, and the quantitation limits were 145.59–222.47 and 93.14–98.48 ng spot−1, respectively. For method B, Beer’s law was obeyed for omeprazole, clarithromycin, and tinidazole in the concentration range of 180–480, 2250–6000, and 30–180 ng spot−1, respectively. The detection limits for omeprazole, clarithromycin, and tinidazole were 20.36, 272.60, and 2.05 ng spot−1, respectively, and the quantitation limits were 61.7, 825.9, and 6.2 ng spot−1, respectively, for the investigated drugs.

A facile synthesis of 3D NiFe2O4 nanospheres anchored on a novel ionic liquid modified reduced graphene oxide for electrochemical sensing of ledipasvir: Application to human pharmacokinetic study

Novel and sensitive electrochemical sensor was fabricated for the assay of anti-HCV ledipasvir (LEDV) in different matrices. The designed sensor was based on 3D spinel ferromagnetic NiFe2O4 nanospheres and reduced graphene oxide (RGO) supported by morpholinium acid sulphate (MHS), as an ionic liquid (RGO/NSNiFe2O4/MHS). This sensor design was assigned to synergistically tailor the unique properties of nanostructured ferrites, RGO, and ionic liquid to maximize the sensor response. Electrode modification prevented aggregation of NiFe2O4, increasing electroactive surface area and allowed remarkable electro-catalytic oxidation of LEDV with an enhanced oxidation response. Differential pulse voltammetry was used for detection LEDV in complex matrices whereas; cyclic voltammetry and other techniques were employed to characterize the developed sensor properties. All experimental factors regarding sensor fabrication and chemical sensing properties were carefully studied and optimized. Under the optimum conditions, the designated sensor displayed a wide linear range (0.4-350 ng mL-1) with LOD of 0.133 ng mL-1. Additionally, the proposed sensor demonstrated good selectivity, stability and reproducibility, enabling the quantitative detection of LEDV in Harvoni® tablets, human plasma and in a pharmacokinetic study. Our findings suggest that the developed sensor is a potential prototype material for fabrication of high-performance electrochemical sensors.

Enhanced dispersive solid phase extraction assisted by cloud point strategy prior to fluorometric determination of anti-hepatitis C drug velpatasvir in pharmaceutical tablets and body fluids

An innovative spectrofluorometric method was developed for the analysis of a recently FDA approved anti-hepatitis C velpatasvir (VELP). The developed method was relied on dispersive solid phase extraction (dSPE) using synergistic effect of reduced graphene oxide (RGO) and cobalt hydroxide nanoparticles (CHNPs) in addition to cloud point extraction (CPE) using polyethylene glycol 6000 (PEG 6000) as non-ionic surfactant. This method combines the merits of preconcentration and interferences elimination achieved by dSPE and CPE, respectively. All relevant parameters such as surfactant concentration, ionic strength, pH, incubation time and others were thoroughly investigated and optimized. Fluorometric detection of VELP was carried out at excitation wavelength of 350 nm and emission wavelength of 415 nm. Under the optimum conditions, a linear calibration curve was achieved in the range of 0.5–45 ng mL−1. Limits of detection (LOD) and quantification (LOQ) based on three and ten times the standard deviation of the blank were 0.040 and 0.112 ng mL−1, respectively. This method was successfully applied for determination of VELP in real samples such as tablets, human plasma and urine samples with good recoveries.

Simultaneous voltammetric analysis of anti-ulcer and D2-antagonist agents in binary mixture using redox sensor and their determination in human serum

Pencil graphite electrode was successfully modified with a thin film of poly (eriochrome black T) and applied for the sensitive and selective voltammetric simultaneous determination of pantoprazole sodium and domperidone in a binary mixture. The preparation and basic electrochemical behavior of poly (eriochrome black T) film on the Pencil graphite electrode were investigated. The modified electrode has exhibited very high electro-catalytic activity towards the cited mixture. The anodic peaks of the both species were well defined with enhanced oxidation peak currents. Under the optimum conditions, the linearity ranges were 0.4-55×10-7M and 0.1-34×10-7M for pantoprazole sodium and domperidone, respectively with detection limits of 0.12×10-7M and 0.04×10-7M for pantoprazole sodium and domperidone, respectively. The proposed sensor has been successfully applied in the analysis of pantoprazole sodium and domperidone in synthetic binary mixtures and human serum.

Synthesis of Fe3O4 nanobead-functionalized 8-hydroxyquinoline sulfonic acid supported by an ion-imprinted biopolymer as a recognition site for Al3+ ions: estimation in human serum and water samples

Herein, a novel “turn on” ion-imprinted chemosensor for highly sensitive and selective detection of Al3+ ions in complex matrices has been developed. The method was based on using chitosan (CHIT) biopolymer/magnetite nanoparticles (MGNPs) functionalized with 8-hydroxyquinoline sulfonic acid (8-HQS) in the presence of Al3+ ions to synthesize a magnetite ion non-imprinted biopolymer (MGINIBP) chemosensor. This newly developed chemosensor was synthesized via polymerization of CHIT with [3-(2,3-epoxypropoxy)-propyl]trimethoxysilane [EPPTMS] in the presence of magnetite nanoparticles, 8-HQS, and an Al3+ ion template. The template was then removed from the sensor using 0.5 M NaF to form new recognition sites for Al3+. The newly developed chemosensor was termed as a magnetite ion-imprinted biopolymer (MGIIBP). Exposure of Al3+ ions to the developed system embedded with 8-HQS resulted in the formation of a fluorescent polymer, and emission maximum was obtained at 500 nm after excitation at 365 nm. Furthermore, with the increasing Al3+ ion concentration, the fluorescence intensity increases within the range 0.081–9.0 × 10−8 M with a limit of detection (LOD) of 0.027 × 10−8 M. In addition, the synthesized chemosensor was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and Fourier-transform infrared spectroscopy (FTIR). The proposed MGIIBP sensor was successfully applied to the determination of Al3+ ions in water and human serum samples as model examples of complex natural matrix media.

Development of a novel and cost-effective redox sensor for voltammetric determination of pantoprazole sodium during pharmacokinetic studies

A pencil graphite electrode modified with poly (bromocresol green (BCG)) was prepared by electro-polymerization process for the determination of pantoprazole sodium. The surface morphology and structure of poly (BCG) film were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The determination of pantoprazole sodium in Britton–Robinson buffer (pH 7.0) was carried out by square wave adsorptive stripping voltammetric technique. Under optimum conditions, the linear response of the peak with concentration of the cited drug was in the range of 6.6–360 × 10−8 M with limit of detection of 2.2 × 10−8 M. Moreover, the poly (BCG)-modified electrode has been successfully applied to determine pantoprazole sodium in tablets, vials and during pharmacokinetic studies.

Highly sensitive and selective complexation based voltammetric methods for the analysis of rabeprazole sodium in real samples

The effect of adding transition metals to the electrolyte containing proton pump inhibitors, such as rabeprazole sodium (RAB sodium), on the voltammetric response of pencil graphite electrode was studied. Both square-wave adsorptive stripping voltammetry (SWAdSV) and cyclic voltammetry (CV) were utilized to elucidate and confirm the possible complexation reaction that could occur between RAB sodium and cobalt as a transition metal. The current signal due to the oxidation process was a function of the concentration of RAB sodium, pH of the medium, cobalt concentration, scan rate, frequency, and deposition time at the electrode surface. This phenomenon could be used for the determination of RAB sodium using CV and SWAdSV. The oxidation peak current linearly varied with the concentration over the range of 0.05–9 × 10−9 M and 0.2–8.5 × 10−7 M for SWAdSV and CV, respectively. The limits of detection were found to be 0.015 × 10−9 M and 0.06 × 10−7 M for SWAdSV and CV, respectively. The validity of using these methods for the determination of RAB sodium in its pharmaceutical formulation and human urine samples was evaluated.

Different Chromatographic and Electrophoretic Methods for Analysis of Proton Pump Inhibitors (PPIs): A Review

A systematic comprehensive review of literature for the analysis of the most recent antiulcer drugs and proton pump inhibitors (PPIs) by different chromatographic and electrophoretic methods are presented. The review includes literature from 1985 until 2015 on eight proton pump inhibitors; namely: omeprazole (OMZ), lansoprazole (LAN), pantoprazole (PAN), rabeprazole (RAB), esomeprazole (EMZ), dexlansoprazole (DLAN), dexrabeprazole (DRAB), and tenatoprazole (TNB). The investigated literature survey covers most chromatographic and electrophoretic methods used for the assay of these drugs in pure forms, in combined mixtures, in pharmaceutical dosage forms, and in biological fluids.

A rapid Fourier transform infrared spectroscopic method for analysis of certain proton pump inhibitors in binary and ternary mixtures

A simple and non-destructive FTIR method was used to determine certain proton pump inhibitors (PPIs) in binary and ternary mixtures. Proton pump inhibitors (PPIs); omeprazole (OMZ), esomeprazole (EZM), lansoprazole (LAN), pantoprazole sodium (PAN sodium) and rabeprazole sodium (RAB sodium) in binary mixture with domperidone (DOM) and ternary mixture of OMZ, clarithromycin (CLM) and tinidazole (TNZ) were determined in the solid-state by FTIR spectroscopy for the first time. The method was validated according to ICH-guidelines where linearity was ranged from 20 to 850μg/g and 20-360μg/g for PPIs and DOM, respectively in binary mixtures and 10-400, 100-8000 and 150-14,000μg/g for OMZ, CLM and TNZ, respectively. Limits of detection were found to be 6-100 and 9-100μg/g for PPIs and DOM, respectively and 4, 40 and 50μg/g for OMZ, CLM and TNZ, respectively. The method was applied successfully for determination of the cited drugs in their respective pharmaceutical dosage forms.

Spectrodensitometric simultaneous determination of esomeprazole and domperidone in human plasma

Abstract A simple, rapid, cost-effective, and sensitive TLC-spectrodensitometric method for simultaneous determination of esomeprazole and domperidone was developed and tested in human plasma. Ethyl acetate: methanol: benzene: acetonitrile (5: 4: 8: 3, v/v/v/v) mobile phase was used for separation on TLC plates detected at 286 nm. The linearity ranges were 5-1200 and 2-600 ng/ spot for esomeprazole and domperidone, and limits of detection were 1.73 and 0.59 ng/spot. The effects of four variables affecting Rf were evaluated by fractional factorial design. The benzene volume and saturation time had significant effects.