Ramadan, N. K., H. A. Merey, S. S. Diab, and A. A. Moustafa, "In-Line Green Potentiometric Monitoring of Dissolution Behavior of Losartan Potassium Versus Pharmacopeial Methods: A Comparative Study", Analytical Chemistry letters, vol. 12, 2022. Abstract

Green electro-analytical method was developed and validated for quantitative determination and monitoring of the dissolution behavior of Losartan potassium tablets by in-line potentiometric measurement system with no need for pre-treatment or derivatization of the sample. A sensor was fabricated for in-line determination of Losartan potassium LOS in its dissolution medium utilizing polyvinyl chloride (PVC) based membrane and nitrophenyl octyl ether (NPOE) as a plasticizer. Tetraheptyl ammonium bromide (THAB) was employed as anion exchanger for the first sensor, while cetyltrimethylammonium bromide (CTAB) was used in the second sensor. The proposed method showed fast, stable near Nernstian responses across a relatively wide LOS concentration range (1.0 × 10-5 to 1.0 × 10-2 mol/L) in the case of THAB-based sensor while LOS concentration range was (1.0 x 10-4 - 1.0 x 10-2 mol/L) in case of CTAB-based sensor. The dissolution method
was developed according to FDA regulations using USP apparatus II, 50 rpm rotation speed, at 37.0 ± 0.5°C and 900 mL of deareated double distilled water as the dissolution medium. Dissolution profile was generated over 45 min and compared to those obtained by the official spectrophotometric and HPLC methods. The developed method can be efficiently applied as benchtop real-time in-process analysis of LOS concentration. Greenness assessment using Analytical Eco-scale, National Environmental Method Index (NEMI), Green Analytical Procedure Index (GAPI) and Analytical Greenness (AGREE) calculator was conducted to evaluate and compare the proposed method with the official ones.

Elmasry, M. S., M. A. Hasan, W. S. Hassan, H. A. Merey, and I. M. Nour, "Flourimetric study on antidiabetic combined drugs; empagliflozin and linagliptin in their pharmaceutical formulation and human plasma.", Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, vol. 248, pp. 119258, 2021. Abstract

Empagliflozin and linagliptin are newly approved FDA combination that used for the treatment of type 2 diabetes mellitus (T2DM) under trade name Glxambi. Two spectroflourimetric methods were developed for simple quantitative determination of empagliflozin and linagliptin in their pharmaceutical formulation and human plasma without need any tedious processing operations. Empagliflozin has a native fluorescence nature, therefore can be directly determined by measuring emission peak at 305 nm after excitation at 234 nm. There is no any interference from linagliptin at this emission wavelength. On the other hand, linagliptin is a very weak florescent compound that needs to react with fluorogenic reagent to be quantitatively determined without any reaction of empagliflozin. So, quantitative analysis of linagliptin was achieved by coupling with NBD-Cl which is an electro active halide reagent (targeting only Linagliptin with no effect on empagliflozin). Dark yellow fluorophore with high fluorescence is a result of this reaction and can be measured at emission wavelength 538 nm after excition at wavelength 469 nm. Experimental conditions of the suggested methods were well checked and optimized. The regression plots were found to be linear over the range of 40-1200 ng/mL and 3-700 ng/mL for empagliflozin and linagliptin, respectively. The obtained results by the suggested methods were statistically compared with those obtained by the reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Elmasry, M. S., W. S. Hassan, H. A. Merey, and I. M. Nour, "Simple mathematical data processing method for the determination of sever overlapped spectra of linagliptin and empagliflozin in their pure forms and pharmaceutical formulation: Fourier self deconvulated method.", Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, vol. 254, pp. 119609, 2021. Abstract

A new and simple spectrophotometric method was developed for the simultaneous determination of a new antidiabetic mixture of linagliptin and empagliflozin namely fourier self deconvulated method. The developed method based on minimal mathematical data processing on the zero order spectrum for solving sever overlapping spectra of the mentioned drugs in their pure forms and pharmaceutical dosage form. The zero order spectra of linagliptin and empagliflozin were deconvulated using Fourier transforms function. The peak amplitudes at 232 nm were selected for linagliptin and at 239 nm for empagliflozin. The constructed calibration graphs were linear over the range (5-30 µg/mL) and (2-12 µg/mL) for empagliflozin and linagliptin, respectively. The adopted method was simple, accurate, precise and validated according to the ICH guidelines.

Ibrahim, H., A. M. Hamdy, H. A. Merey, and A. S. Saad, "Simultaneous Determination of Paracetamol, Propyphenazone and Caffeine in Presence of Paracetamol Impurities Using Dual-Mode Gradient HPLC and TLC Densitometry Methods.", Journal of chromatographic science, vol. 59, issue 2, pp. 140-147, 2021. Abstract

Two chromatographic methods were validated for the determination of the widely prescribed analgesic and antipyretic drug combination of paracetamol (PC) (recently integrated into the supportive treatment of COVID-19), propyphenazone (PZ) and caffeine (CF) in the presence of two PC impurities, namely 4-aminophenol and 4-nitrophenol. A "dual-mode" gradient high-performance liquid chromatography method was developed, where the separation was achieved via "dual-mode" gradient by changing both the ternary mobile phase composition (acetonitrile: methanol: water) and the flow rate. This enables a good resolution within a relatively shorter analysis time. The analysis was realized using Zorbax Eclipse XDB column C18, 5 μm (250 × 4.6 mm) and the UV detector was set at 220 nm. The other method is a thin-layer chromatography densitometry method, where the separation was achieved using a mobile phase composed of chloroform: toluene: ethyl acetate: methanol: acetic acid (6: 6: 1: 2: 0.1, by volume). Densitometric detection was performed at 220 nm on silica gel 60 F254 plates. The developed methods were fully validated as per the ICH guidelines and proved to be accurate, robust, specific and suitable for application as purity indicating methods for routine analysis of PC in pure form or in pharmaceuticals with PZ and CF in quality control laboratories.

Ibrahim, H., A. M. Hamdy, H. A. Merey, and A. S. Saad, "Dual-Mode Gradient HPLC and TLC Densitometry Methods for the Simultaneous Determination of Paracetamol and Methionine in the Presence of Paracetamol Impurities.", Journal of AOAC International, vol. 104, issue 4, pp. 975-982, 2021. Abstract

BACKGROUND: Paracetamol (PC) is one of the most widely used analgesic and antipyretic drugs and has recently been integrated into the supportive therapy of COVID-19. Pharmaceuticals containing methionine (MT) with PC may contribute to avoid hepatotoxicity and eventual PC overdose-dependent death.

OBJECTIVE: The current work purposes to develop and validate two chromatographic methods for the simultaneous determination of MT and PC in the presence of two PC impurities (4-nitrophenol [NP] and 4-aminophenol [AP]).

METHOD: Two chromatographic methods were established and validated according to the International Conference on Harmonization guidelines. The first one was an RP-HPLC/UV method based on applying a "dual-mode" gradient elution. The separation was realized via varying both the composition of the ternary mobile phase (acetonitrile-methanol-water) and its flow rate. This strategy enabled a relatively rapid analysis with a satisfactory resolution, although the investigated compounds exhibit a significant difference in lipophilicity. The second one relied on TLC-densitometry, where the optimum separation was realized using a quaternary mobile phase system composed of butanol-dioxane-toluene-methanol (8:2.5:3.5:0.3, by volume). Both methods were monitored at 220 nm.

RESULTS: The developed methods were proven to be robust, accurate, specific, and appropriate for the routine analysis of PC in its pure form or in pharmaceutical formulations with MT in quality control laboratories.

CONCLUSIONS: The corresponding methods are suitable to determine MT and PC in the presence of PC impurities.

HIGHLIGHTS: The study achieves the analysis of MT and PC in the presence of PC impurities via the application of HPLC and TLC-densitometry methods.

Alamein, A. A. A. M., H. A. Merey, R. E. A. Kalla, and A. E. E. Gendy, "Validated Spectrophotometric Methods for Simultaneous Determination of Sulphadoxine and trimethoprim in a Veterinary Pharmaceutical Dosage Form", Research J. Pharm. and Tech. , vol. 13, issue 11, pp. 5151-5157, 2020.
H. A. Merey, N. K.Ramadan, S. S. Diab, and A. A. Moustafa, "Green spectrophotometric methods for the determination of a binary mixture of lidocaine hydrochloride and cetylpyridinium chloride in the presence of dimethylaniline", Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 242 , pp. 118743, 2020. Abstract

Three green, simple, precise, accurate and sensitive spectrophotometric methods were developed for the determination
of a binary mixture of lidocaine hydrochloride (LDC) and cetylpyridinium chloride (CPC) in the presence
of dimethylaniline (DMA). In the three methods, the interference of DMA spectrum is eliminated using
the ratio subtraction method. Method (A) depended on determining LDC and CPC by measuring the first derivative
of the ratio spectra (1DD) at 271.0 and 268.4 nm, respectively. Method (B) was the ratio difference (RD),
based on dividing the absorption spectrum of the binary mixture by a standard spectrum of CPC or LDC, then
measuring the amplitude difference of the ratio spectra (ΔP) between 231.2 and 240.0 nm for LDC and between
242.8 and 258.0 nm for CPC. Method (C) based on the application of dual wavelength coupled with the
isoabsorptive point method. This was achieved by measuring the absorbance difference (ΔA) between 243.0
and 268.6 nm for the determination of LDC, followed by application of isoabsorptive point method comprised
ofmeasurement the total content of the mixture of LDC and CPC at their isoabsorptive point at 240.0nm. The content
of CPCwas obtained by subtraction. The specificity of the developed methods was investigated by analyzing
laboratory prepared mixtures containing different ratios of LDC and CPC in presence of DMA. The proposed
methods displayed useful analytical characteristics for the determination of LDC and CPC in bulk powder and
their combined dosage form. The obtained results were statistically comparedwith those obtained by the official
methods, showing no significant difference with respect to accuracy and precision.

H. A. Merey, S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Green monitoring of bromhexine oxidative degradation kinetics", Microchemical Journal, vol. 152, pp. 104378, 2020. Abstract

Kinetics studies are important in quality control to assure the safety and efficacy of the pharmaceutical compounds.
Recently, potentiometric ion-selective electrodes (ISEs) breakthrough kinetics study due to their ability
to provide real-time measurements which meet “green analytical chemistry” (GAC) principles. A polyvinyl
chloride (PVC) matrix membrane was fabricated to monitor bromhexine (BR) oxidative degradation kinetics
using tetraphenylborate as a cation exchanger. At-line monitoring of the oxidative degradation kinetics of BR was
performed; by continuous measuring the decrease in the sensor potential over time. So a real-time observation
and a continuous profile were obtained for the oxidation of BR under various H2O2 concentrations and temperature.
This kinetic study determines the oxidation activation energy that was 6.4 kcal mol−1. To expand the
application of this sensor, BR was determined in bulk powder and dosage form in the presence of both coformulated
drug (acefylline piperazine) and dosage form additives. The proposed sensor had been characterized
according to IUPAC recommendations and a linear dynamic range was 5×10−6 to 1×10−3M and other sensor
parameters had been calculated.

H. A. Merey, S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Validated eco--friendly spectrophotometric methods for the determination of acefylline piperazine and bromhexine hydrochloride in the presence of dosage form additives", Journal of Applied Spectroscopy, vol. 87, issue 1, pp. 159-168, 2020.
Merey, H. A., S. S. El-Mosallamy, N. Y. Hassan, and B. A. El-Zeany, "Validated Chromatographic Methods for Simultaneous Determination of Calcipotriol Monohydrate and Betamethasone Dipropionate in the Presence of Two Dosage Form Additives.", Journal of chromatographic science, vol. 57, issue 4, pp. 305-311, 2019. Abstract

Two chromatographic methods were developed, optimized and validated for simultaneous determination of calcipotriol monohydrate (CPM) and betamethasone dipropionate (BMD) in the presence of two dosage form additives named; butylated hydroxytoluene (BHT) and alpha-tocopherol (TOCO). The proposed methods were accurate, sensitive and specific. The first method based on using aluminum thin-layer chromatographic plates precoated with silica gel GF254 as a stationary phase and chloroform-ethyl acetate-toluene (5:5:3, by volume) as a developing system. This was followed by densitometric measurement of the separated bands at 264 nm. Whereas the second method is RP-HPLC where OnyxMonolithic C18® column was used with a gradient profile using methanol, water and acetic acid at flow rate 2.0 mL min-1. Detection was carried out at 264 nm. The methods were validated according to ICH guidelines. The specificity of the developed methods was investigated by analyzing the pharmaceutical dosage form. The validity of the proposed methods was assessed using the standard addition technique. The obtained results were statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision at P = 0.05.

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